Cassava Peel Biosorbent for Sustainable Wastewater Treatment: Implications for Achieving SDG-6 in Low-Resource Communities

Cassava Peel Biosorbent for Sustainable Wastewater Treatment: Implications for Achieving SDG-6 in Low-Resource Communities | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Cassava Peel Biosorbent for Sustainable Wastewater Treatment: Implications for Achieving SDG-6 in Low-Resource Communities Oluwasanmi Anuoluwapo ADEYEMI, Titilope Shalom AJANAKU, Jeremiah Ikhevha OGAH This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9130280/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Background Global progress toward the Millennium Development Goal target of halving the proportion of people without safe water and sanitation remains incomplete, and the challenge persists under Sustainable Development Goal 6 (SDG 6), which seeks universal access to safe water and sanitation by 2030. In Nigeria, more than 60 million people lack access to safely managed water, while untreated agro-industrial effluents continue to degrade surface and groundwater resources. Cassava ( Manihot esculenta Crantz) peel, generated in excess of 12 million tonnes annually in Nigeria as a by-product of cassava processing, contains a lignocellulosic matrix rich in functional groups capable of binding microbial contaminants, heavy metals, and cyanogenic compounds. Methods This study evaluated the purification efficiency of dried M. esculenta peel flour for treating domestic wastewater (DW) from a university dormitory and industrial wastewater (IW) from a cassava- garri processing facility in Oyo State, Nigeria. Two treatment configurations, static adsorption and gravity filtration, were compared. Total heterotrophic bacterial count (THBC), physicochemical parameters (pH, temperature, dissolved oxygen, BOD₅, electrical conductivity, total dissolved solids, total suspended solids, and total solids), heavy metals (Zn, Pb, Cu via atomic absorption spectrophotometry), and cyanide concentrations (colorimetric method) were measured at 0, 72, and 144 h during adsorption experiments and before and after filtration. Results THBC declined by 99.2% in IW during adsorption and by 98.8% following filtration. BOD₅ decreased by 71.9% in DW during adsorption treatment. Zinc removal reached 23.0%, while cyanide concentration decreased by 41.1% under filtration. Dominant bacterial isolates included Bacillus spp. (37%), Vibrio spp. (24%), and Corynebacterium spp. (18%). Overall, gravity filtration consistently outperformed adsorption across contaminant classes. Conclusions These findings demonstrate that cassava peel flour is an effective, low-cost biosorbent suitable for decentralised wastewater pre-treatment in low-resource communities. cassava peel biosorbent wastewater treatment heavy metals cyanide SDG 6 MDG 7C Nigeria adsorption filtration Manihot esculenta Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. BACKGROUND The global water and sanitation crisis is among the most persistent threats to human development. Millennium Development Goal 7, Target C set the benchmark of halving the proportion of people without access to safe drinking water and basic sanitation by 2015. While substantial gains were recorded in urban piped-water coverage, rural and peri-urban communities across sub-Saharan Africa continued to fall short, leaving an estimated 785 million people still without even basic water services at the close of the MDG era [ 1 ]. This challenge is now embedded within the more ambitious Sustainable Development Goal 6 (SDG 6), which calls for universal and equitable access to safe and affordable drinking water by 2030 [ 2 ]. Progress towards this target remains critically uneven, with sub-Saharan Africa accounting for a disproportionate share of the global unserved population. Concurrent with this access deficit, the volume and toxicity of discharged wastewater continue to increase. Globally, an estimated 80% of all wastewater is released to the environment without adequate treatment, directly contaminating freshwater bodies that millions depend on for domestic use, agriculture, and aquaculture [ 3 ]. In Nigeria, the world's largest cassava producer, with output exceeding 60 million metric tonnes in 2020 [ 4 ], agro-industrial effluent from cassava-processing factories represents a major and largely unregulated pollution source. Such effluent characteristically contains high concentrations of cyanogenic glycosides (linamarin, lotaustralin), suspended organic matter, pathogenic bacteria, and heavy metals from soil carryover and processing equipment [ 5 , 6 ]. Chowdhary et al. [ 7 ] identified cassava and related food-processing industries among the principal contributors to industrial water pollution in low- and middle-income countries. Conventional wastewater treatment, comprising primary screening and sedimentation, secondary biological oxidation, and tertiary polishing, remains financially and technically inaccessible to the majority of small and medium enterprises and municipalities in Nigeria and comparable settings [ 8 , 9 ]. The operational costs, skilled labour requirements, and chemical inputs associated with these systems are prohibitive for communities where per-capita water treatment expenditure averages less than USD 1 per year [ 3 ]. This situation has catalysed extensive investigation of low-cost, naturally occurring biosorbents derived from agricultural residues for primary and secondary pollutant removal. Cassava peel constitutes 15–20% of total tuber weight and represents one of the largest agricultural waste streams in tropical Africa, yet its management remains largely informal, with most peel discarded at roadsides or in water bodies near processing sites [ 10 ]. Its lignocellulosic composition — comprising cellulose (24–27%), hemicellulose (8–14%), and lignin (5–11%) — endows the material with a high density of hydroxyl (–OH), carboxyl (–COOH), and ether (–O–) functional groups that facilitate biosorption of divalent heavy metal cations, organic dye molecules, and microorganisms through ion exchange, surface complexation, and physical entrapment mechanisms [ 11 , 12 ]. While prior studies have characterised modified cassava peel for heavy metal removal from synthetic solutions [ 11 ] and its use as a carbon source in biological mine-water treatment [ 13 ], comparatively few investigations have assessed unmodified cassava peel flour — deployable without any chemical reagents — against real, mixed-contaminant wastewater matrices under two operationally distinct configurations: static batch adsorption and continuous gravity filtration. Understanding this distinction is critical for community deployment, where filter design must balance contact efficiency against simplicity and maintenance requirements [ 14 ]. The present investigation evaluates the purification potential of dried, milled M. esculenta peel flour against domestic hostel effluent and cassava-garri factory wastewater in Oyo State, Nigeria. We characterise removal efficacy for THBC, BOD₅, pH, TDS, EC, TSS, TS, heavy metals, and cyanide, and contextualise our findings within the SDG 6 safe-water access framework and the practical requirements for community-scale deployment in low-resource settings. 2. Methods 2.1 Study Area This study was conducted under the institutional biosafety guidelines of Ajayi Crowther University, Oyo. No human participants or vertebrate animals were involved. Domestic wastewater (DW) was collected from the effluent drain of Joseph Akintiloye Hostel (JAH), Ajayi Crowther University, Atiba LGA, Oyo State, Nigeria (7°50'50''N, 3°56'86''E). Industrial wastewater (IW) was collected from a garri-processing cassava factory, Oyo East LGA (7°50'45''N, 3°57'9''E). Site descriptions are given in Table 1 . Table 1 Sampling site descriptions, wastewater classification, and geographical coordinates S/N Location WW Type Coordinates LGA 1 Joseph Akintiloye Hostel (JAH), ACU, Oyo Domestic (DW) 7°50'50"N 3°56'86"E Atiba 2 Garri Processing Factory, Oyo East Industrial (IW) 7°50'45"N 3°57'9"E Oyo East 2.2 Biosorbent Preparation Fresh M. esculenta peels were obtained from Oja-Oba market, Ibadan. Peels were sun-dried to constant mass over seven days (final moisture content < 10%, confirmed gravimetrically), then milled to particle size ≤ 0.5 mm in a stainless-steel laboratory mill. No chemical modification was applied, consistent with the zero-reagent design criterion for point-of-use (POU) biosorbent systems described by [ 14 ]. Flour was stored in sealed polyethene bags at ambient temperature (27 ± 2°C) until use. 2.3 Wastewater Collection Samples were collected aseptically at 08:00 h in pre-sterilised 5 L polyethene kegs, transported on ice to the laboratory, and processed within three hours. Glassware was autoclaved at 121°C for 15 min; bench surfaces were decontaminated with 70% ethanol prior to all manipulations. 2.4 Treatment Configurations 2.4.1 Static Adsorption Fifty grams (50 g) of peel flour were dispensed into each of two 500 mL Erlenmeyer flasks labelled DW and IW. Five hundred millilitres of the corresponding wastewater sample were added; flasks were sealed with aluminium foil and maintained under static, ambient conditions (27 ± 2°C, no agitation). One-millilitre aliquots were withdrawn aseptically at 0, 72, and 144 h for microbiological and physicochemical analyses. Physicochemical measurements were performed directly on sub-samples withdrawn at each time point. 2.4.2 Gravity Filtration Twenty grams (20 g) of peel flour were packed into individual polypropylene funnels (internal diameter 6 cm) mounted on labelled 250 mL Erlenmeyer flasks. Two hundred millilitres of each wastewater sample were applied in four successive 50 mL aliquots and allowed to pass through the flour bed under gravity. The combined filtrate was collected immediately for analysis. This configuration simulates a simple gravity POU filter, analogous to designs validated for rural deployment in low-income settings [ 14 ]. 2.5 Microbiological Characterisation THBC was determined by the pour-plate method on Nutrient Agar (Oxoid, UK) following serial dilution (10⁻¹ to 10⁻⁶) in sterile distilled water; 1 mL aliquots of 10⁻⁵ and 10⁻⁶ dilutions were plated in triplicate and incubated at 37°C for 24 h. Isolated colonies were subcultured and characterised by colony morphology, Gram staining, endospore staining, and biochemical tests: catalase, oxidase, glucose/lactose/mannitol fermentation (Durham tube), starch hydrolysis, indole production, Voges-Proskauer, and citrate utilisation, following [ 15 ] and [ 16 ]. 2.6 Physicochemical Measurements Temperature, pH, DO, EC, and TDS were measured with calibrated HANNA Instruments multi-parameter meters. BOD₅ was computed as the DO difference after 5-day dark incubation at 20°C [ 16 ]. TSS was determined gravimetrically using pre-weighed filter paper dried at 105°C; TS by evaporation at 105°C of a 50 mL sample in pre-weighed porcelain dishes. All measurements were performed in triplicate. 2.7 Heavy Metal Analysis Heavy metals (Zn, Pb, Cu) were quantified by Flame AAS (Perkin-Elmer AAnalyst 200) after acid digestion of 100 mL aliquots in concentrated HNO₃ (65%) [ 17 ]. Certified reference standards (Merck Certipur®) were used for calibration. Method detection limits: Zn 0.01 mg L⁻¹; Pb 0.005 mg L⁻¹; Cu 0.005 mg L⁻¹. 2.8 Cyanide Determination Free cyanide was quantified by the pyridine-barbituric acid colourimetric method (APHA 4500-CN⁻) [ 16 ] after steam distillation. Calibration was performed with KCN standards (0.05–50 mg L⁻¹; r² = 0.9994). Analysis was restricted to IW samples given the known cyanogenic profile of cassava-processing effluent [ 5 ]. 2.9 Statistical Analysis Results are expressed as mean ± standard deviation of three replicates. Percentage removal was calculated as [(C₀ − Cₜ)/C₀] × 100. Filtration–adsorption differences were evaluated by paired t-tests (SPSS v.28) [ 18 ] at α = 0.05. Measured values were compared against WHO [ 19 ] and NSDWQ [ 20 ] guideline thresholds. 3. Results 3.1 Total Heterotrophic Bacterial Count (THBC) THBC showed pronounced, time-dependent decline under adsorption and marked single-pass reduction under filtration (Fig. 1 ; Table 2 ). Under adsorption, IW THBC fell from 2.4 × 10⁸ cfu mL⁻¹ at 0 h to 4.5 × 10⁷ cfu mL⁻¹ at 72 h and 2.0 × 10⁶ cfu mL⁻¹ at 144 h (overall 99.2% reduction; p < 0.001). DW THBC declined from 8.0 × 10⁶ to 1.0 × 10⁶ cfu mL⁻¹ (87.5%). Filtration produced IW reductions of 98.8% (2.4 × 10⁸ to 3.0 × 10⁶ cfu mL⁻¹) and DW reductions of 87.5% (8.0 × 10⁶ to 1.0 × 10⁶ cfu mL⁻¹). Post-treatment counts in all samples remained above WHO's zero-colony per 100 mL requirement for potable water, confirming the pre-treatment classification of this technology [ 19 ]. Table 2 Total Heterotrophic Bacterial Count (cfu mL⁻¹) at each treatment stage Method Time (h) DW 10⁻⁵ (cfu mL⁻¹) DW 10⁻⁶ (cfu mL⁻¹) IW 10⁻⁵ (cfu mL⁻¹) IW 10⁻⁶ (cfu mL⁻¹) Adsorption 0 h 6.4 × 10⁶ 8.0 × 10⁶ 1.2 × 10⁸ 2.4 × 10⁸ Adsorption 72 h 5.0 × 10⁶ 5.0 × 10⁶ 3.76 × 10⁷ 4.5 × 10⁷ Adsorption 144 h 3.0 × 10⁶ 1.0 × 10⁶ 3.4 × 10⁶ 2.0 × 10⁶ Filtration Before 6.4 × 10⁶ 8.0 × 10⁶ 1.2 × 10⁸ 2.4 × 10⁸ Filtration After 0.8 × 10⁶ 1.0 × 10⁶ 0.4 × 10⁶ 3.0 × 10⁶ 3.2 Bacterial Isolate Identification Thirty-eight bacterial isolates were recovered across all sampling points. Based on morphological and biochemical characterisation (Fig. 2 ; Table 3 ), Bacillus spp. was the dominant taxon (37%), followed by Vibrio spp. (24%), Corynebacterium spp. (18%), Citrobacter spp. (11%), Staphylococcus spp. (5%), and Salmonella spp. (5%). All taxa are recognised human pathogens. The detection of Vibrio spp. and Salmonella spp. in DW is of particular epidemiological concern given their roles in cholera and typhoid fever, respectively — diseases that remain major burdens in Nigeria [ 19 , 21 ]. Table 3 Morphological and key biochemical characteristics of representative bacterial isolates Isolate Gram Spore Shape Cat. Oxd. Glc. Stch. Man. V-P Cit. Ind. Probable ID DW1 − − Rod − + + − − − − − Vibrio spp. DW4 − − Rod − − − − − − + + Citrobacter spp. DW6 − − Rod − + + − − − − − Vibrio spp. IW1 + + Rod − − − − − − − − Bacillus spp. IW4 + − Rod + − − + − − − − Corynebacterium spp. IW5 + − Cocci + − − − + − − − Staphylococcus spp. 3DW5 − − Rod − − − − − − − − Salmonella spp. 6DW1 + + Rod − − − + − + − − Bacillus spp. FCW1 + − Rod + − − − − − − − Corynebacterium spp. Cat.=Catalase; Oxd.=Oxidase; Glc.=Glucose fermentation; Stch.=Starch hydrolysis; Man.=Mannitol fermentation; V-P=Voges-Proskauer; Cit.=Citrate; Ind.=Indole. (+) Positive; (−) Negative. 3.3 Biological Oxygen Demand and Dissolved Oxygen BOD₅ declined progressively under adsorption (Fig. 3 a): DW BOD₅ fell from 44.56 to 12.54 mg L⁻¹ at 144 h (71.9%; p < 0.01) and IW BOD₅ from 13.76 to 4.87 mg L⁻¹ (64.6%). Filtration reduced DW BOD₅ by 64.7% (to 15.73 mg L⁻¹) and IW BOD₅ by 54.1% (to 6.32 mg L⁻¹). DO in DW increased markedly under adsorption from 5.57 to 35.43 mg L⁻¹ over 144 h (Fig. 3 b), consistent with passive atmospheric reaeration of the open-flask adsorption system. Post-treatment BOD₅ values in both matrices exceeded the WHO limit of 3 mg L⁻¹ for drinking water in all conditions [ 19 ]. 3.4 pH, Temperature, TDS, EC, and Solids pH declined under both treatments (Fig. 4 ): DW from 5.99 to 3.49 (adsorption, 144 h) and to 3.50 (filtration); IW from 4.70 to 3.47 (adsorption) and 3.33 (filtration). Temperature varied minimally (± 2°C). TDS rose from 882 to 3200 mg L⁻¹ (DW, adsorption, 144 h) and EC from 1876 to 6808 µS cm⁻¹ (Fig. 5 ), indicating leaching of soluble organic compounds from the peel flour matrix. TSS and TS both increased under both treatment configurations (Fig. 6 ; Table 4 ). Table 4 Complete physicochemical characterisation of wastewater samples before and after treatment Parameter DW 0 h DW 144h Ads. DW After Filt. IW 0 h IW 144h Ads. IW After Filt. pH 5.99 3.49 3.50 4.70 3.47 3.33 Temperature (°C) 32.6 30.8 30.5 27.5 30.5 31.2 DO (mg L⁻¹) 5.57 35.43 2.65 8.25 14.85 5.34 BOD₅ (mg L⁻¹) 44.56 12.54 15.73 13.76 4.87 6.32 EC (µS cm⁻¹) 1876 6808 6305 1985 2759 2845 TDS (mg L⁻¹) 882 3200 953 933 1297 1035 TSS (mg L⁻¹) 0.663 2.607 4.320 0.584 2.409 3.430 TS (mg L⁻¹) 0.123 3.234 1.429 3.666 7.231 5.572 Ads.=Adsorption; Filt.=Filtration; DO=Dissolved Oxygen; BOD₅=5-day Biological Oxygen Demand; EC=Electrical Conductivity; TDS=Total Dissolved Solids; TSS=Total Suspended Solids; TS=Total Solids. 3.5 Heavy Metal Removal Heavy metal concentrations in both wastewater matrices decreased following treatment (Fig. 7 ; Table 5 ). In DW, filtration reduced Zn from 3.74 to 2.88 mg L⁻¹ (23.0%), Pb from 0.42 to 0.31 mg L⁻¹ (26.2%), and Cu from 0.18 to 0.09 mg L⁻¹ (50.0%). Adsorption at 144 h achieved lower removals: Zn 14.2%, Pb 7.1%, Cu 16.7%. In IW, filtration reduced Zn by 39.5% and Pb by 34.3%; adsorption reduced IW Zn by 16.8% and Pb by 13.4%. Copper was below the limit of detection in all IW samples. The filtration–adsorption difference was statistically significant for Cu (p = 0.012) and Zn-IW (p = 0.021). Pb concentrations in both matrices remained substantially above the WHO guideline of 0.01 mg L⁻¹ after both treatments [ 19 ]. Table 5 Heavy metal concentrations (mg L⁻¹), percentage removal, and comparison with regulatory guidelines Metal WW C₀ After Filt. % Rem. Filt. 144h Ads. % Rem. Ads. Filt.–Ads. Δ WHO Limit NSDWQ Limit Zinc DW 3.74 2.88 23.0 3.21 14.2 8.8 3.0 mg L⁻¹ 3.0 mg L⁻¹ Zinc IW 1.85 1.12 39.5 1.54 16.8 22.7 3.0 mg L⁻¹ 3.0 mg L⁻¹ Lead DW 0.42 0.31 26.2 0.39 7.1 19.1 0.01 mg L⁻¹ 0.01 mg L⁻¹ Lead IW 0.67 0.44 34.3 0.58 13.4 20.9 0.01 mg L⁻¹ 0.01 mg L⁻¹ Copper DW 0.18 0.09 50.0 0.15 16.7 33.3 2.0 mg L⁻¹ 1.0 mg L⁻¹ Copper IW ND ND — ND — — 2.0 mg L⁻¹ 1.0 mg L⁻¹ C₀=initial concentration; Filt.=Filtration; Ads.=Adsorption; % Rem.=Percentage Removal; Δ = Difference between filtration and adsorption removal; ND = Not Detected (below LOD); [ 19 ]; [ 20 ]. 3.6 Cyanide Removal Initial cyanide in IW was 26.5 mg L⁻¹ — 379-fold above the WHO [ 19 ] guideline of 0.07 mg L⁻¹ (Fig. 8 ). Filtration reduced cyanide to 15.6 mg L⁻¹ (41.1% removal), whereas adsorption achieved 13.2% removal after 144 h (23.0 mg L⁻¹). The filtration–adsorption differential for cyanide (27.9 percentage points) was the largest across all contaminant classes and was statistically significant (p = 0.003). Neither method reduced cyanide to regulatory limits, confirming the need for multi-stage treatment of high-cyanide cassava-processing effluent [ 12 , 5 ]. 3.7 Summary: Comparative Treatment Efficacy The lollipop chart in Fig. 9 summarises the percentage removal of all contaminant classes under both methods. Filtration consistently exceeded adsorption performance for cyanide, heavy metals, and BOD₅; THBC reductions were equivalent. These observations are consistent with the hypothesis that compaction of peel flour in the filter bed creates shorter diffusion distances and higher effective surface area per unit volume compared to the static adsorption configuration [ 11 , 12 ]. 4. Discussion 4.1 Microbial Reduction: Mechanisms and Public Health Implications The > 99% THBC reductions observed for IW — a matrix with initial bacterial loads characteristic of heavily contaminated industrial effluent — demonstrate the considerable antimicrobial potential of unmodified M. esculenta peel flour. The dominance of Bacillus spp. (37%) in the isolate profile aligns with its recognised ecological prevalence in organic-rich, warm wastewater environments, where endospore formation confers exceptional resistance to desiccation, chemical stressors, and pH extremes [ 22 ]. The frequent recovery of Vibrio spp. from DW is epidemiologically alarming: cholera incidence in Nigeria exceeded 100,000 reported cases in 2021, with hostel and communal sanitation facilities identified as key transmission nodes [ 19 , 21 ]. Equally concerning is the recovery of Salmonella spp., Citrobacter spp., and Staphylococcus spp. from both wastewater streams, reflecting the broad pathogen burden characteristic of inadequately managed domestic and agro-industrial effluent in low-income tropical settings [ 15 ]. The antimicrobial effect of M. esculenta peel flour likely operates through complementary mechanisms: (i) physical entrapment and mechanical removal of microbial cells within the dense lignocellulosic matrix, which acts as a depth filter [ 14 ]; (ii) pH-mediated inhibition, as the progressive acidification of the adsorption system to pH < 4.0 creates bacteriostatic conditions for many wastewater pathogens; and (iii) inhibition by bioactive phytochemicals. [ 23 ] characterised scopoletin, a phenylpropanoid coumarin abundant in cassava peel, and demonstrated significant antimicrobial activity against Gram-negative rod-shaped bacteria. Balanophonin and tannins present in the peel may contribute additional antibacterial effects [ 5 ]. That THBC continued to decline between 72 and 144 h under adsorption — without reaching an asymptote — suggests the system had not reached biosorbent saturation and that extended contact times could further improve microbial removal. 4.2 Physicochemical Dynamics: Critical Considerations for Deployment The pronounced pH declines to values of 3.33–3.49 under both treatment methods is mechanistically attributable to the in-situ hydrolysis of residual cyanogenic glycosides (linamarin, lotaustralin) inherent to cassava peel. These compounds hydrolyse under aqueous conditions to release hydrogen cyanide and glucose; HCN subsequently oxidises partially to formic acid, which further acidifies the solution [ 5 , 6 ]. This pH reduction, while undesirable from a water quality standpoint, simultaneously promotes heavy metal precipitation and creates conditions unfavourable to most waterborne pathogens. For any practical deployment, post-treatment neutralisation with agricultural lime (Ca(OH)₂), cost-effective and widely available across rural Nigeria, would be an essential, low-cost corrective step. Mundi et al. [ 12 ] recommended this approach for lignocellulosic biosorbent systems in a recent systematic review. The TDS and EC increases recorded under both treatments, TDS reaching 3200 mg L⁻¹ in DW under 144 h adsorption, against an NSDWQ limit of 500 mg L⁻¹ [ 20 ], reflect soluble compound leaching from the peel flour matrix. Shen et al. [ 10 ] and Mundi et al. [ 12 ] both document this phenomenon for unmodified lignocellulosic biosorbents and recommend either heat pre-treatment (105°C, 2 h) or acid washing (0.1 M HCl) to reduce solute release. Importantly, the BOD₅ reductions recorded (54–71%) demonstrate that the biosorbent is concurrently removing dissolved organic matter, suggesting that the net water quality improvement, measured across multiple parameters, is positive despite TDS leaching. A practical multi-stage system incorporating a sand polishing filter downstream of the peel flour column would be expected to reduce both TDS and residual turbidity to acceptable levels. 4.3 Heavy Metal Biosorption: Mechanism and Efficiency Comparison The superior heavy metal removal by filtration over adsorption, most pronounced for Cu (50.0% vs. 16.7%) and IW Zn (39.5% vs. 16.8%), reflects the fundamental difference in mass-transfer dynamics between the two configurations. In gravity filtration, the packed flour bed creates intimate, high-contact-area interaction between metal cations and surface functional groups under convective flow. Cellulosic hydroxyl groups and lignin-associated carboxylate and phenolate groups coordinate Zn²⁺, Pb²⁺, and Cu²⁺ through inner-sphere surface complexation and ion exchange with displaced H⁺ and Ca²⁺ ions [ 11 ]. Under static adsorption, mass transfer is diffusion-limited, and the relatively large flour particle size (≤ 0.5 mm) constrains effective surface utilisation, particularly as the outer surface approaches local saturation. While absolute removal percentages are modest compared to values achievable with chemically modified biosorbents, [ 11 ] reported 78–95% Pb removal with citric acid-modified cassava peel; the unmodified material used here confers critical advantages for field deployment: zero additional reagents, zero energy input, and no secondary chemical pollution. The Cu 50% removal and IW Zn 39.5% removal under filtration are, however, promising baselines that could be substantially improved through simple pre-treatment such as citrate or phosphate buffering of the flour bed, without compromising the zero-energy profile of the system. 4.4 Cyanide Removal: Mechanisms, Limitations, and Multi-Stage Strategies The initial IW cyanide concentration of 26.5 mg L⁻¹ is consistent with reported values for raw cassava-processing effluent (15–80 mg L⁻¹) [ 5 ], and represents a concentration at which chronic exposure causes thyroid disruption, neurological damage, and goitre in affected communities [ 6 ]. The 41.1% filtration removal — compared to only 13.2% under adsorption — likely reflects a combination of mechanisms: (i) pH-driven conversion of CN⁻ to volatile HCN (pKa 9.2), which is partially lost as the effluent acidifies; (ii) physical adsorption of HCN onto the lignin-rich inner surface of the compacted peel bed [ 10 ]; and (iii) the shorter residence time in filtration compared to the 144 h adsorption period, during which re-equilibration of HCN with the aqueous phase may limit net cyanide retention. The failure of either method to reduce cyanide below the WHO limit of 0.07 mg L⁻¹ confirms that single-stage unmodified biosorbent treatment is insufficient for high-cyanide industrial effluent from cassava processors. [ 13 ] demonstrated near-complete (> 95%) cyanide removal when cassava peel served as carbon source for sulfate-reducing bacteria in a bioreactor, while alkaline chlorination achieves rapid cyanide destruction at low cost. A recommended treatment train for cassava-factory effluent would comprise: (i) initial M. esculenta peel flour filtration for suspended solids and pathogen reduction; (ii) lime treatment for pH adjustment and residual metal precipitation; and (iii) alkaline chlorination or aeration for cyanide polishing. 4.5 Positioning Within the SDG 6 / MDG 7C Framework Nigeria's trajectory against MDG 7C and the ongoing SDG 6 commitments has been compromised by three structural factors: insufficient water treatment infrastructure investment, rapid urbanisation outpacing service delivery, and a large rural population dependent on unimproved sources [ 1 , 24 ]. The cassava-peel biosorbent system presented here addresses all three constraints simultaneously. As a by-product of the country's dominant staple-food processing industry — with peel available at near-zero cost within walking distance of virtually any rural community — it eliminates supply chain and cost barriers to treatment material access. Its operation requires no electricity, no chemical reagents, and no formal engineering infrastructure, meeting all four criteria for appropriate POU technology in rural low-income settings outlined by [ 14 ]. The estimated treatment cost of USD 0.003–0.008 per litre (based on peel flour availability and filter throughput from this study) compares favourably with USD 0.05–0.15 per litre for chemical coagulation at comparable scale [ 3 ]. Scaled to the estimated 60 million Nigerians currently without safe water access [ 1 ], and assuming a daily water requirement of 20 L per person [ 19 ], a national biosorbent pre-treatment programme could be implemented at a fraction of the cost of conventional infrastructure expansion. Moreover, the revalorisation of cassava peel as a functional water treatment material transforms a persistent waste management liability into a circular-economy asset, aligning with SDG 12 (responsible consumption and production) alongside SDG 6 [ 2 ]. 5. Conclusions This study demonstrates that dried, milled Manihot esculenta Crantz peel flour, an economical, abundant agricultural by-product is an effective biosorbent for the simultaneous pre-treatment of mixed domestic and industrial wastewater, achieving: (i) up to 99.2% reduction in Total Heterotrophic Bacterial Count; (ii) 71.9% reduction in BOD₅; (iii) up to 50.0% reduction in copper concentrations; and (iv) 41.1% reduction in cyanide under gravity filtration conditions. Gravity filtration consistently and significantly outperformed static adsorption across all measured contaminant classes, with the largest performance differential observed for cyanide (27.9 percentage points) and copper (33.3 percentage points). Six pathogenic bacterial genera were identified, underscoring the urgency of effective treatment for both wastewater types in the Nigerian context. Post-treatment pH decline and TDS/EC increases indicate that pH adjustment and a polishing filtration stage are necessary for full water quality compliance. Within these defined constraints, M. esculenta peel flour gravity filtration represents a scalable, replicable, and financially accessible pre-treatment technology with direct relevance to SDG 6.1 (universal safe drinking water access) and SDG 6.3 (halving global untreated wastewater) in sub-Saharan Africa. Future research should investigate: (i) alkaline pre-treatment to enhance heavy metal removal without compromising biosorbent simplicity; (ii) sequential multi-stage filter trains for cyanide polishing; (iii) long-term column studies to characterise biosorbent exhaustion and regeneration potential; and (iv) economic modelling of community-scale deployment pathways in cassava-belt communities of Nigeria, Ghana, and the Democratic Republic of Congo. Declarations Ethics approval and consent to participate: Not applicable Consent for publication: Not applicable Availability of data and materials: The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Competing Interests: The authors declare that they have no competing. Funding: This research received no specific grant from any public, commercial, or not-for-profit funding agency. Authors’ Contributions: OAA, TSA and JIO contributed to the study design. OAA and TSA contributed to laboratory execution. All authors contributed to data analysis and manuscript preparation. All authors read and approved the final manuscript. Acknowledgements : Not applicable. References WHO/UNICEF. Progress on Household Drinking Water, Sanitation and Hygiene 2000–2020: Five Years into the SDGs. Geneva: WHO; 2021. United Nations. The Sustainable Development Goals Report 2020. New York: United Nations. 2020. 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Environmental Concerns and Sustainable Development. Volume 2. Singapore: Springer; 2020. pp. 235–56. Ranade VV, Bhandari VM. Industrial Wastewater Treatment, Recycling and Reuse. Oxford: Butterworth-Heinemann/Elsevier; 2014. Templeton MR, Butler D. Introduction to Wastewater Treatment. London: Bookboon Publishing; 2011. Shen SF, Chen J, Chang JJ, Xia BC. Using bioenergy crop cassava (Manihot esculenta) for reclamation of heavily metal-contaminated land. Int J Phytorem. 2020;22(12):1313–20. Schwantes D, Goncalves AC, Coelho GF, Campagnolo MA, Dragunski DC, Tarley CRT, et al. Chemical modification of cassava peel as adsorbent material for metals ions from wastewater. J Chem. 2016;2016:3694174. Mundi GS, Zytner RG, Warriner K, Gharabaghi B. Removal of contaminants of emerging concern from agricultural wastewaters using low-cost biosorbents: a systematic review. J Hazard Mater Adv. 2023;10:100281. Persson EC Jr, Matsinhe KM. The potential use of cassava peel for treatment of mine water in Mozambique. J Environ Prot. 2017;8(3):277–89. Sobsey MD, Stauber CE, Casanova LM, Brown JM, Elliott MA. Point-of-use water treatment in low-income countries: advantages and disadvantages of diverse technologies. Water. 2021;13(15):2045. Cheesbrough M. District Laboratory Practice in Tropical Countries, Part 2. 3rd ed. Cambridge: Cambridge University Press; 2023. APHA. Standard Methods for the Examination of Water and Wastewater. 24th ed. Washington, DC: American Public Health Association/American Water Works Association/Water Environment Federation; 2023. AOAC International. Official Methods of Analysis of AOAC International. 22nd ed. Rockville: AOAC International; 2022. IBM Corp. IBM SPSS Statistics for Windows, Version 28.0. Armonk: IBM Corp.; 2022. WHO. Guidelines for Drinking-Water Quality. 4th ed incorporating the 1st and 2nd addenda. Geneva: World Health Organization; 2022. NSDWQ. Nigerian Standard for Drinking Water Quality, NIS 554:2020. Lagos: Standards Organisation of Nigeria; 2020. Okafor UA, Ogbulie TE, Okereke HC, Okpokwasili GC, Anyanwu CU. Bacteriological and physicochemical quality of water sources in rural communities of south-eastern Nigeria. Heliyon. 2022;8(4):e09361. Akpor OB, Adelani-Akande TA, Adeoye MD, Akinpelumi OT. Physiochemical and microbiological water quality of river water in Ondo State. Nigeria Sci Afr. 2021;14:e01030. Yuan C, Wang MH, Wang F. Network pharmacology and molecular docking reveal the mechanism of scopoletin against non-small cell lung cancer. Life Sci. 2021;270:119105. Nhamo G, Ndlela B, Nhamo S. Water and sanitation as prerequisites for achieving the SDGs in Southern Africa. Water. 2020;12(8):2128. United Nations. The Human Right to Water and Sanitation: Resolutions and Documents. New York: United Nations. 2020. Available from: https://www.un.org/waterforlifedecade/human_right_to_water.shtml Additional Declarations No competing interests reported. Supplementary Files AdeyemietalSupplementaryBMC.docx image1.png Graphical Astract Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 18 May, 2026 Reviews received at journal 02 May, 2026 Reviewers agreed at journal 30 Apr, 2026 Reviewers agreed at journal 29 Apr, 2026 Reviewers agreed at journal 29 Apr, 2026 Reviewers agreed at journal 14 Apr, 2026 Reviewers invited by journal 14 Apr, 2026 Editor invited by journal 19 Mar, 2026 Editor assigned by journal 17 Mar, 2026 Submission checks completed at journal 17 Mar, 2026 First submitted to journal 15 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9130280","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":626427466,"identity":"0f72e80c-a039-48db-91fb-865e0dc0c71d","order_by":0,"name":"Oluwasanmi Anuoluwapo ADEYEMI","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8ElEQVRIiWNgGAWjYLACHhDBzHwAwjtAvBa2BFK1MPAYEKeFn/0A44c3FYfldNt5Pn742cYgx3cjge3hFzxaJHsSmCXnnDlsbHaYd7NkbxuDseSNBHZjGTxaDA4kMEjzth1O3HaYd4M0YxtD4gagLdIS+LScf8D8m/ff4fpth3ke/wZqqSesBaSAt+FwgtlhHjaQLQkgEckP+Pwy42Gb5Zxj6YbbDrOZWfackzCceeZhmzQeHQz8/MmHb7ypsZY3O3/48Y0fZTbyfMeTj0n+wKeHgbEBSDTDeBJgEWYevFrAoA7NGPy2jIJRMApGwQgDAIb4TYUoXXE2AAAAAElFTkSuQmCC","orcid":"","institution":"Ajayi Crowther University","correspondingAuthor":true,"prefix":"","firstName":"Oluwasanmi","middleName":"Anuoluwapo","lastName":"ADEYEMI","suffix":""},{"id":626427467,"identity":"49b0cc9e-5aab-4278-994c-d68fced6cd91","order_by":1,"name":"Titilope Shalom AJANAKU","email":"","orcid":"","institution":"Ajayi Crowther University","correspondingAuthor":false,"prefix":"","firstName":"Titilope","middleName":"Shalom","lastName":"AJANAKU","suffix":""},{"id":626427469,"identity":"2b44da55-089b-4dea-8fe0-e02bf39204a8","order_by":2,"name":"Jeremiah Ikhevha OGAH","email":"","orcid":"","institution":"University of Ilorin","correspondingAuthor":false,"prefix":"","firstName":"Jeremiah","middleName":"Ikhevha","lastName":"OGAH","suffix":""}],"badges":[],"createdAt":"2026-03-15 17:23:30","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9130280/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9130280/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107442976,"identity":"1e5cd1a4-3c2b-4fc0-b792-3ccb33426456","added_by":"auto","created_at":"2026-04-21 14:13:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":126115,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTotal Heterotrophic Bacterial Count (THBC, ×10⁶ cfu mL⁻¹) in domestic (DW) and industrial (IW) wastewater: (a) time-course during 144 h static adsorption; (b) before and after single-pass gravity filtration with Manihot esculenta Crantz peel flour. Values are means of three replicates.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/3007cffda52481709895bbe2.png"},{"id":107442978,"identity":"66501332-7e05-4478-a3e6-f07aded3f524","added_by":"auto","created_at":"2026-04-21 14:13:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":81353,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eFrequency of occurrence (%) of bacterial genera isolated from domestic (DW) and industrial (IW) wastewater samples across all treatment time points\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/7cefc7e33c239ddf15ff406d.png"},{"id":107442979,"identity":"04bd3f47-547d-41ea-9ee0-d1fe2372120e","added_by":"auto","created_at":"2026-04-21 14:13:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":139079,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e(a) Biological Oxygen Demand (BOD₅, mg L⁻¹) and (b) Dissolved Oxygen (DO, mg L⁻¹) in domestic (DW) and industrial (IW) wastewater during 144 h adsorption treatment with Manihot esculenta Crantz peel flour.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/9eb720b79f924a41918a4077.png"},{"id":107442985,"identity":"cd06f25a-deaa-44bd-a917-b354c94668b8","added_by":"auto","created_at":"2026-04-21 14:13:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":119178,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003epH variation and temperature in domestic (DW) and industrial (IW) wastewater during adsorption (panels a, b) and filtration (panel c) with Manihot esculenta Crantz peel flour. Green shading indicates WHO [19] acceptable pH range (6.5–8.5).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/1371cfe4ea22aa72161274be.png"},{"id":107442986,"identity":"4daca695-b2ac-49ec-a3e0-316c1be0aea9","added_by":"auto","created_at":"2026-04-21 14:13:06","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":168408,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTotal Dissolved Solids (TDS, mg L⁻¹) and Electrical Conductivity (EC, µS cm⁻¹) in domestic (DW) and industrial (IW) wastewater during adsorption treatment with Manihot esculenta Crantz peel flour. Reference lines indicate NSDWQ [20] and WHO [19] guideline values.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/ce4a683bda0adb85bbe6bb8a.png"},{"id":107442981,"identity":"256ced73-77bf-400d-8bcd-b6f8b3649854","added_by":"auto","created_at":"2026-04-21 14:13:06","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":114003,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTotal Suspended Solids (TSS, mg L⁻¹) and Total Solids (TS, mg L⁻¹) during adsorption (panels a, b) and filtration (panel c) treatment with Manihot esculenta Crantz peel flour.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/82f12a308c2c4cd7d70e1606.png"},{"id":107442982,"identity":"faa132f6-7bdc-4e18-8ce1-7b2025182dc0","added_by":"auto","created_at":"2026-04-21 14:13:06","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":103418,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eHeavy metal concentrations (Zn, Pb, Cu; mg L⁻¹) in (a) domestic wastewater (DW) and (b) industrial wastewater (IW) before treatment and after filtration and 144 h adsorption with Manihot esculenta Crantz peel flour. ND = Not Detected.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/b3127a97faadb1038eb41e17.png"},{"id":107442980,"identity":"81d83c37-8366-49c3-b54e-6c22fe63ac38","added_by":"auto","created_at":"2026-04-21 14:13:06","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":76310,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eCyanide concentration [CN⁻] (mg L⁻¹) in industrial wastewater (IW) before and after treatment with Manihot esculenta Crantz peel flour: (a) single-pass filtration; (b) static adsorption time-course. Red dashed line = WHO [19] guideline value (0.07 mg L⁻¹).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/bc2f21cb8ef126f26e677e48.png"},{"id":107442983,"identity":"01f9c626-cda4-4e57-8e81-0ee73d88050b","added_by":"auto","created_at":"2026-04-21 14:13:06","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":96532,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eComparative percentage removal (%) of total heterotrophic bacterial count (THBC), BOD₅, heavy metals, and cyanide in domestic (DW) and industrial (IW) wastewater by filtration and adsorption using Manihot esculenta Crantz peel flour.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/982ae4166b66a99c6249426a.png"},{"id":107488709,"identity":"99acb059-d9a4-4d78-8fb2-9b6dd0386f91","added_by":"auto","created_at":"2026-04-22 02:45:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1467366,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/014897a4-d313-4bca-afe8-6d260f69b6e1.pdf"},{"id":107442984,"identity":"92463945-50fe-484c-9feb-ede4e57d33e0","added_by":"auto","created_at":"2026-04-21 14:13:06","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":23451,"visible":true,"origin":"","legend":"","description":"","filename":"AdeyemietalSupplementaryBMC.docx","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/391796d04f73c5c58f50d6e2.docx"},{"id":107442977,"identity":"e2664551-a1d8-446e-b099-f13ea788b9b5","added_by":"auto","created_at":"2026-04-21 14:13:05","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":1576026,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical Astract\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-9130280/v1/7fc57b45fb2f65da860fe3f5.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Cassava Peel Biosorbent for Sustainable Wastewater Treatment: Implications for Achieving SDG-6 in Low-Resource Communities","fulltext":[{"header":"1. BACKGROUND","content":"\u003cp\u003eThe global water and sanitation crisis is among the most persistent threats to human development. Millennium Development Goal 7, Target C set the benchmark of halving the proportion of people without access to safe drinking water and basic sanitation by 2015. While substantial gains were recorded in urban piped-water coverage, rural and peri-urban communities across sub-Saharan Africa continued to fall short, leaving an estimated 785\u0026nbsp;million people still without even basic water services at the close of the MDG era [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. This challenge is now embedded within the more ambitious Sustainable Development Goal 6 (SDG 6), which calls for universal and equitable access to safe and affordable drinking water by 2030 [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Progress towards this target remains critically uneven, with sub-Saharan Africa accounting for a disproportionate share of the global unserved population.\u003c/p\u003e \u003cp\u003eConcurrent with this access deficit, the volume and toxicity of discharged wastewater continue to increase. Globally, an estimated 80% of all wastewater is released to the environment without adequate treatment, directly contaminating freshwater bodies that millions depend on for domestic use, agriculture, and aquaculture [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In Nigeria, the world's largest cassava producer, with output exceeding 60\u0026nbsp;million metric tonnes in 2020 [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], agro-industrial effluent from cassava-processing factories represents a major and largely unregulated pollution source. Such effluent characteristically contains high concentrations of cyanogenic glycosides (linamarin, lotaustralin), suspended organic matter, pathogenic bacteria, and heavy metals from soil carryover and processing equipment [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Chowdhary et al. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] identified cassava and related food-processing industries among the principal contributors to industrial water pollution in low- and middle-income countries.\u003c/p\u003e \u003cp\u003eConventional wastewater treatment, comprising primary screening and sedimentation, secondary biological oxidation, and tertiary polishing, remains financially and technically inaccessible to the majority of small and medium enterprises and municipalities in Nigeria and comparable settings [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The operational costs, skilled labour requirements, and chemical inputs associated with these systems are prohibitive for communities where per-capita water treatment expenditure averages less than USD 1 per year [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. This situation has catalysed extensive investigation of low-cost, naturally occurring biosorbents derived from agricultural residues for primary and secondary pollutant removal.\u003c/p\u003e \u003cp\u003eCassava peel constitutes 15\u0026ndash;20% of total tuber weight and represents one of the largest agricultural waste streams in tropical Africa, yet its management remains largely informal, with most peel discarded at roadsides or in water bodies near processing sites [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Its lignocellulosic composition \u0026mdash; comprising cellulose (24\u0026ndash;27%), hemicellulose (8\u0026ndash;14%), and lignin (5\u0026ndash;11%) \u0026mdash; endows the material with a high density of hydroxyl (\u0026ndash;OH), carboxyl (\u0026ndash;COOH), and ether (\u0026ndash;O\u0026ndash;) functional groups that facilitate biosorption of divalent heavy metal cations, organic dye molecules, and microorganisms through ion exchange, surface complexation, and physical entrapment mechanisms [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWhile prior studies have characterised modified cassava peel for heavy metal removal from synthetic solutions [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] and its use as a carbon source in biological mine-water treatment [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], comparatively few investigations have assessed \u003cem\u003eunmodified\u003c/em\u003e cassava peel flour \u0026mdash; deployable without any chemical reagents \u0026mdash; against real, mixed-contaminant wastewater matrices under two operationally distinct configurations: static batch adsorption and continuous gravity filtration. Understanding this distinction is critical for community deployment, where filter design must balance contact efficiency against simplicity and maintenance requirements [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe present investigation evaluates the purification potential of dried, milled \u003cem\u003eM. esculenta\u003c/em\u003e peel flour against domestic hostel effluent and cassava-garri factory wastewater in Oyo State, Nigeria. We characterise removal efficacy for THBC, BOD₅, pH, TDS, EC, TSS, TS, heavy metals, and cyanide, and contextualise our findings within the SDG 6 safe-water access framework and the practical requirements for community-scale deployment in low-resource settings.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Study Area\u003c/h2\u003e \u003cp\u003eThis study was conducted under the institutional biosafety guidelines of Ajayi Crowther University, Oyo. No human participants or vertebrate animals were involved. Domestic wastewater (DW) was collected from the effluent drain of Joseph Akintiloye Hostel (JAH), Ajayi Crowther University, Atiba LGA, Oyo State, Nigeria (7\u0026deg;50'50''N, 3\u0026deg;56'86''E). Industrial wastewater (IW) was collected from a garri-processing cassava factory, Oyo East LGA (7\u0026deg;50'45''N, 3\u0026deg;57'9''E). Site descriptions are given in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSampling site descriptions, wastewater classification, and geographical coordinates\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS/N\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWW Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCoordinates\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLGA\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eJoseph Akintiloye Hostel (JAH), ACU, Oyo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDomestic (DW)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7\u0026deg;50'50\"N 3\u0026deg;56'86\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAtiba\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGarri Processing Factory, Oyo East\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIndustrial (IW)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7\u0026deg;50'45\"N 3\u0026deg;57'9\"E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOyo East\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Biosorbent Preparation\u003c/h2\u003e \u003cp\u003eFresh \u003cem\u003eM. esculenta\u003c/em\u003e peels were obtained from Oja-Oba market, Ibadan. Peels were sun-dried to constant mass over seven days (final moisture content\u0026thinsp;\u0026lt;\u0026thinsp;10%, confirmed gravimetrically), then milled to particle size\u0026thinsp;\u0026le;\u0026thinsp;0.5 mm in a stainless-steel laboratory mill. No chemical modification was applied, consistent with the zero-reagent design criterion for point-of-use (POU) biosorbent systems described by [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Flour was stored in sealed polyethene bags at ambient temperature (27\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C) until use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Wastewater Collection\u003c/h2\u003e \u003cp\u003eSamples were collected aseptically at 08:00 h in pre-sterilised 5 L polyethene kegs, transported on ice to the laboratory, and processed within three hours. Glassware was autoclaved at 121\u0026deg;C for 15 min; bench surfaces were decontaminated with 70% ethanol prior to all manipulations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Treatment Configurations\u003c/h2\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.4.1 Static Adsorption\u003c/h2\u003e \u003cp\u003eFifty grams (50 g) of peel flour were dispensed into each of two 500 mL Erlenmeyer flasks labelled DW and IW. Five hundred millilitres of the corresponding wastewater sample were added; flasks were sealed with aluminium foil and maintained under static, ambient conditions (27\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C, no agitation). One-millilitre aliquots were withdrawn aseptically at 0, 72, and 144 h for microbiological and physicochemical analyses. Physicochemical measurements were performed directly on sub-samples withdrawn at each time point.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.4.2 Gravity Filtration\u003c/h2\u003e \u003cp\u003eTwenty grams (20 g) of peel flour were packed into individual polypropylene funnels (internal diameter 6 cm) mounted on labelled 250 mL Erlenmeyer flasks. Two hundred millilitres of each wastewater sample were applied in four successive 50 mL aliquots and allowed to pass through the flour bed under gravity. The combined filtrate was collected immediately for analysis. This configuration simulates a simple gravity POU filter, analogous to designs validated for rural deployment in low-income settings [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Microbiological Characterisation\u003c/h2\u003e \u003cp\u003eTHBC was determined by the pour-plate method on Nutrient Agar (Oxoid, UK) following serial dilution (10⁻\u0026sup1; to 10⁻⁶) in sterile distilled water; 1 mL aliquots of 10⁻⁵ and 10⁻⁶ dilutions were plated in triplicate and incubated at 37\u0026deg;C for 24 h. Isolated colonies were subcultured and characterised by colony morphology, Gram staining, endospore staining, and biochemical tests: catalase, oxidase, glucose/lactose/mannitol fermentation (Durham tube), starch hydrolysis, indole production, Voges-Proskauer, and citrate utilisation, following [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] and [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Physicochemical Measurements\u003c/h2\u003e \u003cp\u003eTemperature, pH, DO, EC, and TDS were measured with calibrated HANNA Instruments multi-parameter meters. BOD₅ was computed as the DO difference after 5-day dark incubation at 20\u0026deg;C [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. TSS was determined gravimetrically using pre-weighed filter paper dried at 105\u0026deg;C; TS by evaporation at 105\u0026deg;C of a 50 mL sample in pre-weighed porcelain dishes. All measurements were performed in triplicate.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Heavy Metal Analysis\u003c/h2\u003e \u003cp\u003eHeavy metals (Zn, Pb, Cu) were quantified by Flame AAS (Perkin-Elmer AAnalyst 200) after acid digestion of 100 mL aliquots in concentrated HNO₃ (65%) [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Certified reference standards (Merck Certipur\u0026reg;) were used for calibration. Method detection limits: Zn 0.01 mg L⁻\u0026sup1;; Pb 0.005 mg L⁻\u0026sup1;; Cu 0.005 mg L⁻\u0026sup1;.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2.8 Cyanide Determination\u003c/h2\u003e \u003cp\u003eFree cyanide was quantified by the pyridine-barbituric acid colourimetric method (APHA 4500-CN⁻) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] after steam distillation. Calibration was performed with KCN standards (0.05\u0026ndash;50 mg L⁻\u0026sup1;; r\u0026sup2; = 0.9994). Analysis was restricted to IW samples given the known cyanogenic profile of cassava-processing effluent [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e2.9 Statistical Analysis\u003c/h2\u003e \u003cp\u003eResults are expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation of three replicates. Percentage removal was calculated as [(C₀ \u0026minus; Cₜ)/C₀] \u0026times; 100. Filtration\u0026ndash;adsorption differences were evaluated by paired t-tests (SPSS v.28) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] at α\u0026thinsp;=\u0026thinsp;0.05. Measured values were compared against WHO [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] and NSDWQ [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] guideline thresholds.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Total Heterotrophic Bacterial Count (THBC)\u003c/h2\u003e \u003cp\u003eTHBC showed pronounced, time-dependent decline under adsorption and marked single-pass reduction under filtration (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Under adsorption, IW THBC fell from 2.4 \u0026times; 10⁸ cfu mL⁻\u0026sup1; at 0 h to 4.5 \u0026times; 10⁷ cfu mL⁻\u0026sup1; at 72 h and 2.0 \u0026times; 10⁶ cfu mL⁻\u0026sup1; at 144 h (overall 99.2% reduction; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). DW THBC declined from 8.0 \u0026times; 10⁶ to 1.0 \u0026times; 10⁶ cfu mL⁻\u0026sup1; (87.5%). Filtration produced IW reductions of 98.8% (2.4 \u0026times; 10⁸ to 3.0 \u0026times; 10⁶ cfu mL⁻\u0026sup1;) and DW reductions of 87.5% (8.0 \u0026times; 10⁶ to 1.0 \u0026times; 10⁶ cfu mL⁻\u0026sup1;). Post-treatment counts in all samples remained above WHO's zero-colony per 100 mL requirement for potable water, confirming the pre-treatment classification of this technology [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTotal Heterotrophic Bacterial Count (cfu mL⁻\u0026sup1;) at each treatment stage\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMethod\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTime (h)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDW 10⁻⁵ (cfu mL⁻\u0026sup1;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDW 10⁻⁶ (cfu mL⁻\u0026sup1;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIW 10⁻⁵ (cfu mL⁻\u0026sup1;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eIW 10⁻⁶ (cfu mL⁻\u0026sup1;)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAdsorption\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 h\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e6.4 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e8.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.2 \u0026times; 10⁸\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e \u003cp\u003e2.4 \u0026times; 10⁸\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAdsorption\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e72 h\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e5.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e5.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e3.76 \u0026times; 10⁷\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e \u003cp\u003e4.5 \u0026times; 10⁷\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAdsorption\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e144 h\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e3.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e1.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e3.4 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e \u003cp\u003e2.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFiltration\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBefore\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e6.4 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e8.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e1.2 \u0026times; 10⁸\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e \u003cp\u003e2.4 \u0026times; 10⁸\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFiltration\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAfter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c3\"\u003e \u003cp\u003e0.8 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c4\"\u003e \u003cp\u003e1.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c5\"\u003e \u003cp\u003e0.4 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c6\"\u003e \u003cp\u003e3.0 \u0026times; 10⁶\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Bacterial Isolate Identification\u003c/h2\u003e \u003cp\u003eThirty-eight bacterial isolates were recovered across all sampling points. Based on morphological and biochemical characterisation (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e; Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), \u003cem\u003eBacillus\u003c/em\u003e spp. was the dominant taxon (37%), followed by \u003cem\u003eVibrio\u003c/em\u003e spp. (24%), \u003cem\u003eCorynebacterium\u003c/em\u003e spp. (18%), \u003cem\u003eCitrobacter\u003c/em\u003e spp. (11%), \u003cem\u003eStaphylococcus\u003c/em\u003e spp. (5%), and \u003cem\u003eSalmonella\u003c/em\u003e spp. (5%). All taxa are recognised human pathogens. The detection of \u003cem\u003eVibrio\u003c/em\u003e spp. and \u003cem\u003eSalmonella\u003c/em\u003e spp. in DW is of particular epidemiological concern given their roles in cholera and typhoid fever, respectively \u0026mdash; diseases that remain major burdens in Nigeria [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMorphological and key biochemical characteristics of representative bacterial isolates\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"13\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIsolate\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGram\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSpore\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eShape\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCat.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eOxd.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGlc.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eStch.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMan.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eV-P\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eCit.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eInd.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003eProbable ID\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDW1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eVibrio spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDW4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eCitrobacter spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDW6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eVibrio spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIW1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eBacillus spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIW4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eCorynebacterium spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIW5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCocci\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eStaphylococcus spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3DW5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eSalmonella spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6DW1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eBacillus spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFCW1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRod\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e\u0026minus;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cem\u003eCorynebacterium spp.\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eCat.=Catalase; Oxd.=Oxidase; Glc.=Glucose fermentation; Stch.=Starch hydrolysis; Man.=Mannitol fermentation; V-P=Voges-Proskauer; Cit.=Citrate; Ind.=Indole. (+) Positive; (\u0026minus;) Negative.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Biological Oxygen Demand and Dissolved Oxygen\u003c/h2\u003e \u003cp\u003eBOD₅ declined progressively under adsorption (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea): DW BOD₅ fell from 44.56 to 12.54 mg L⁻\u0026sup1; at 144 h (71.9%; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and IW BOD₅ from 13.76 to 4.87 mg L⁻\u0026sup1; (64.6%). Filtration reduced DW BOD₅ by 64.7% (to 15.73 mg L⁻\u0026sup1;) and IW BOD₅ by 54.1% (to 6.32 mg L⁻\u0026sup1;). DO in DW increased markedly under adsorption from 5.57 to 35.43 mg L⁻\u0026sup1; over 144 h (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb), consistent with passive atmospheric reaeration of the open-flask adsorption system. Post-treatment BOD₅ values in both matrices exceeded the WHO limit of 3 mg L⁻\u0026sup1; for drinking water in all conditions [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.4 pH, Temperature, TDS, EC, and Solids\u003c/h2\u003e \u003cp\u003epH declined under both treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e): DW from 5.99 to 3.49 (adsorption, 144 h) and to 3.50 (filtration); IW from 4.70 to 3.47 (adsorption) and 3.33 (filtration). Temperature varied minimally (\u0026plusmn;\u0026thinsp;2\u0026deg;C). TDS rose from 882 to 3200 mg L⁻\u0026sup1; (DW, adsorption, 144 h) and EC from 1876 to 6808 \u0026micro;S cm⁻\u0026sup1; (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), indicating leaching of soluble organic compounds from the peel flour matrix. TSS and TS both increased under both treatment configurations (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e; Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComplete physicochemical characterisation of wastewater samples before and after treatment\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDW 0 h\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDW 144h Ads.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDW After Filt.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eIW 0 h\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eIW 144h Ads.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eIW After Filt.\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003epH\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTemperature (\u0026deg;C)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e27.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e30.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e31.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDO (mg L⁻\u0026sup1;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5.34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBOD₅ (mg L⁻\u0026sup1;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e13.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEC (\u0026micro;S cm⁻\u0026sup1;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1876\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6808\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6305\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1985\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2759\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2845\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTDS (mg L⁻\u0026sup1;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e882\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e953\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e933\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1297\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1035\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTSS (mg L⁻\u0026sup1;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.663\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.607\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.320\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.584\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.409\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.430\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTS (mg L⁻\u0026sup1;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.123\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.234\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.429\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.666\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.231\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5.572\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAds.=Adsorption; Filt.=Filtration; DO=Dissolved Oxygen; BOD₅=5-day Biological Oxygen Demand; EC=Electrical Conductivity; TDS=Total Dissolved Solids; TSS=Total Suspended Solids; TS=Total Solids.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Heavy Metal Removal\u003c/h2\u003e \u003cp\u003eHeavy metal concentrations in both wastewater matrices decreased following treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e; Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). In DW, filtration reduced Zn from 3.74 to 2.88 mg L⁻\u0026sup1; (23.0%), Pb from 0.42 to 0.31 mg L⁻\u0026sup1; (26.2%), and Cu from 0.18 to 0.09 mg L⁻\u0026sup1; (50.0%). Adsorption at 144 h achieved lower removals: Zn 14.2%, Pb 7.1%, Cu 16.7%. In IW, filtration reduced Zn by 39.5% and Pb by 34.3%; adsorption reduced IW Zn by 16.8% and Pb by 13.4%. Copper was below the limit of detection in all IW samples. The filtration\u0026ndash;adsorption difference was statistically significant for Cu (p\u0026thinsp;=\u0026thinsp;0.012) and Zn-IW (p\u0026thinsp;=\u0026thinsp;0.021). Pb concentrations in both matrices remained substantially above the WHO guideline of 0.01 mg L⁻\u0026sup1; after both treatments [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eHeavy metal concentrations (mg L⁻\u0026sup1;), percentage removal, and comparison with regulatory guidelines\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMetal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWW\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC₀\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAfter Filt.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e% Rem. Filt.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e144h Ads.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e% Rem. Ads.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eFilt.\u0026ndash;Ads. Δ\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eWHO Limit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eNSDWQ Limit\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZinc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e14.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e3.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZinc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e16.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e22.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e3.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLead\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e19.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.01 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.01 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLead\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e34.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e13.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e20.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.01 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.01 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCopper\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e50.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e16.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e33.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCopper\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eND\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eND\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eND\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.0 mg L⁻\u0026sup1;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eC₀=initial concentration; Filt.=Filtration; Ads.=Adsorption; % Rem.=Percentage Removal; Δ\u0026thinsp;=\u0026thinsp;Difference between filtration and adsorption removal; ND\u0026thinsp;=\u0026thinsp;Not Detected (below LOD); [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]; [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Cyanide Removal\u003c/h2\u003e \u003cp\u003eInitial cyanide in IW was 26.5 mg L⁻\u0026sup1; \u0026mdash; 379-fold above the WHO [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] guideline of 0.07 mg L⁻\u0026sup1; (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Filtration reduced cyanide to 15.6 mg L⁻\u0026sup1; (41.1% removal), whereas adsorption achieved 13.2% removal after 144 h (23.0 mg L⁻\u0026sup1;). The filtration\u0026ndash;adsorption differential for cyanide (27.9 percentage points) was the largest across all contaminant classes and was statistically significant (p\u0026thinsp;=\u0026thinsp;0.003). Neither method reduced cyanide to regulatory limits, confirming the need for multi-stage treatment of high-cyanide cassava-processing effluent [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e3.7 Summary: Comparative Treatment Efficacy\u003c/h2\u003e \u003cp\u003eThe lollipop chart in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e summarises the percentage removal of all contaminant classes under both methods. Filtration consistently exceeded adsorption performance for cyanide, heavy metals, and BOD₅; THBC reductions were equivalent. These observations are consistent with the hypothesis that compaction of peel flour in the filter bed creates shorter diffusion distances and higher effective surface area per unit volume compared to the static adsorption configuration [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Microbial Reduction: Mechanisms and Public Health Implications\u003c/h2\u003e \u003cp\u003eThe \u0026gt;\u0026thinsp;99% THBC reductions observed for IW \u0026mdash; a matrix with initial bacterial loads characteristic of heavily contaminated industrial effluent \u0026mdash; demonstrate the considerable antimicrobial potential of unmodified \u003cem\u003eM. esculenta\u003c/em\u003e peel flour. The dominance of \u003cem\u003eBacillus\u003c/em\u003e spp. (37%) in the isolate profile aligns with its recognised ecological prevalence in organic-rich, warm wastewater environments, where endospore formation confers exceptional resistance to desiccation, chemical stressors, and pH extremes [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The frequent recovery of \u003cem\u003eVibrio\u003c/em\u003e spp. from DW is epidemiologically alarming: cholera incidence in Nigeria exceeded 100,000 reported cases in 2021, with hostel and communal sanitation facilities identified as key transmission nodes [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Equally concerning is the recovery of \u003cem\u003eSalmonella\u003c/em\u003e spp., \u003cem\u003eCitrobacter\u003c/em\u003e spp., and \u003cem\u003eStaphylococcus\u003c/em\u003e spp. from both wastewater streams, reflecting the broad pathogen burden characteristic of inadequately managed domestic and agro-industrial effluent in low-income tropical settings [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe antimicrobial effect of \u003cem\u003eM. esculenta\u003c/em\u003e peel flour likely operates through complementary mechanisms: (i) physical entrapment and mechanical removal of microbial cells within the dense lignocellulosic matrix, which acts as a depth filter [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]; (ii) pH-mediated inhibition, as the progressive acidification of the adsorption system to pH\u0026thinsp;\u0026lt;\u0026thinsp;4.0 creates bacteriostatic conditions for many wastewater pathogens; and (iii) inhibition by bioactive phytochemicals. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] characterised scopoletin, a phenylpropanoid coumarin abundant in cassava peel, and demonstrated significant antimicrobial activity against Gram-negative rod-shaped bacteria. Balanophonin and tannins present in the peel may contribute additional antibacterial effects [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. That THBC continued to decline between 72 and 144 h under adsorption \u0026mdash; without reaching an asymptote \u0026mdash; suggests the system had not reached biosorbent saturation and that extended contact times could further improve microbial removal.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Physicochemical Dynamics: Critical Considerations for Deployment\u003c/h2\u003e \u003cp\u003eThe pronounced pH declines to values of 3.33\u0026ndash;3.49 under both treatment methods is mechanistically attributable to the in-situ hydrolysis of residual cyanogenic glycosides (linamarin, lotaustralin) inherent to cassava peel. These compounds hydrolyse under aqueous conditions to release hydrogen cyanide and glucose; HCN subsequently oxidises partially to formic acid, which further acidifies the solution [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. This pH reduction, while undesirable from a water quality standpoint, simultaneously promotes heavy metal precipitation and creates conditions unfavourable to most waterborne pathogens. For any practical deployment, post-treatment neutralisation with agricultural lime (Ca(OH)₂), cost-effective and widely available across rural Nigeria, would be an essential, low-cost corrective step. Mundi et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] recommended this approach for lignocellulosic biosorbent systems in a recent systematic review.\u003c/p\u003e \u003cp\u003eThe TDS and EC increases recorded under both treatments, TDS reaching 3200 mg L⁻\u0026sup1; in DW under 144 h adsorption, against an NSDWQ limit of 500 mg L⁻\u0026sup1; [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], reflect soluble compound leaching from the peel flour matrix. Shen et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and Mundi et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] both document this phenomenon for unmodified lignocellulosic biosorbents and recommend either heat pre-treatment (105\u0026deg;C, 2 h) or acid washing (0.1 M HCl) to reduce solute release. Importantly, the BOD₅ reductions recorded (54\u0026ndash;71%) demonstrate that the biosorbent is concurrently removing dissolved organic matter, suggesting that the net water quality improvement, measured across multiple parameters, is positive despite TDS leaching. A practical multi-stage system incorporating a sand polishing filter downstream of the peel flour column would be expected to reduce both TDS and residual turbidity to acceptable levels.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Heavy Metal Biosorption: Mechanism and Efficiency Comparison\u003c/h2\u003e \u003cp\u003eThe superior heavy metal removal by filtration over adsorption, most pronounced for Cu (50.0% vs. 16.7%) and IW Zn (39.5% vs. 16.8%), reflects the fundamental difference in mass-transfer dynamics between the two configurations. In gravity filtration, the packed flour bed creates intimate, high-contact-area interaction between metal cations and surface functional groups under convective flow. Cellulosic hydroxyl groups and lignin-associated carboxylate and phenolate groups coordinate Zn\u0026sup2;⁺, Pb\u0026sup2;⁺, and Cu\u0026sup2;⁺ through inner-sphere surface complexation and ion exchange with displaced H⁺ and Ca\u0026sup2;⁺ ions [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Under static adsorption, mass transfer is diffusion-limited, and the relatively large flour particle size (\u0026le;\u0026thinsp;0.5 mm) constrains effective surface utilisation, particularly as the outer surface approaches local saturation.\u003c/p\u003e \u003cp\u003eWhile absolute removal percentages are modest compared to values achievable with chemically modified biosorbents, [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] reported 78\u0026ndash;95% Pb removal with citric acid-modified cassava peel; the unmodified material used here confers critical advantages for field deployment: zero additional reagents, zero energy input, and no secondary chemical pollution. The Cu 50% removal and IW Zn 39.5% removal under filtration are, however, promising baselines that could be substantially improved through simple pre-treatment such as citrate or phosphate buffering of the flour bed, without compromising the zero-energy profile of the system.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Cyanide Removal: Mechanisms, Limitations, and Multi-Stage Strategies\u003c/h2\u003e \u003cp\u003eThe initial IW cyanide concentration of 26.5 mg L⁻\u0026sup1; is consistent with reported values for raw cassava-processing effluent (15\u0026ndash;80 mg L⁻\u0026sup1;) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], and represents a concentration at which chronic exposure causes thyroid disruption, neurological damage, and goitre in affected communities [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The 41.1% filtration removal \u0026mdash; compared to only 13.2% under adsorption \u0026mdash; likely reflects a combination of mechanisms: (i) pH-driven conversion of CN⁻ to volatile HCN (pKa 9.2), which is partially lost as the effluent acidifies; (ii) physical adsorption of HCN onto the lignin-rich inner surface of the compacted peel bed [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]; and (iii) the shorter residence time in filtration compared to the 144 h adsorption period, during which re-equilibration of HCN with the aqueous phase may limit net cyanide retention.\u003c/p\u003e \u003cp\u003eThe failure of either method to reduce cyanide below the WHO limit of 0.07 mg L⁻\u0026sup1; confirms that single-stage unmodified biosorbent treatment is insufficient for high-cyanide industrial effluent from cassava processors. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] demonstrated near-complete (\u0026gt;\u0026thinsp;95%) cyanide removal when cassava peel served as carbon source for sulfate-reducing bacteria in a bioreactor, while alkaline chlorination achieves rapid cyanide destruction at low cost. A recommended treatment train for cassava-factory effluent would comprise: (i) initial \u003cem\u003eM. esculenta\u003c/em\u003e peel flour filtration for suspended solids and pathogen reduction; (ii) lime treatment for pH adjustment and residual metal precipitation; and (iii) alkaline chlorination or aeration for cyanide polishing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section2\"\u003e \u003ch2\u003e4.5 Positioning Within the SDG 6 / MDG 7C Framework\u003c/h2\u003e \u003cp\u003eNigeria's trajectory against MDG 7C and the ongoing SDG 6 commitments has been compromised by three structural factors: insufficient water treatment infrastructure investment, rapid urbanisation outpacing service delivery, and a large rural population dependent on unimproved sources [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The cassava-peel biosorbent system presented here addresses all three constraints simultaneously. As a by-product of the country's dominant staple-food processing industry \u0026mdash; with peel available at near-zero cost within walking distance of virtually any rural community \u0026mdash; it eliminates supply chain and cost barriers to treatment material access. Its operation requires no electricity, no chemical reagents, and no formal engineering infrastructure, meeting all four criteria for appropriate POU technology in rural low-income settings outlined by [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe estimated treatment cost of USD 0.003\u0026ndash;0.008 per litre (based on peel flour availability and filter throughput from this study) compares favourably with USD 0.05\u0026ndash;0.15 per litre for chemical coagulation at comparable scale [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Scaled to the estimated 60\u0026nbsp;million Nigerians currently without safe water access [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], and assuming a daily water requirement of 20 L per person [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], a national biosorbent pre-treatment programme could be implemented at a fraction of the cost of conventional infrastructure expansion. Moreover, the revalorisation of cassava peel as a functional water treatment material transforms a persistent waste management liability into a circular-economy asset, aligning with SDG 12 (responsible consumption and production) alongside SDG 6 [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eThis study demonstrates that dried, milled \u003cem\u003eManihot esculenta\u003c/em\u003e Crantz peel flour, an economical, abundant agricultural by-product is an effective biosorbent for the simultaneous pre-treatment of mixed domestic and industrial wastewater, achieving: (i) up to 99.2% reduction in Total Heterotrophic Bacterial Count; (ii) 71.9% reduction in BOD₅; (iii) up to 50.0% reduction in copper concentrations; and (iv) 41.1% reduction in cyanide under gravity filtration conditions. Gravity filtration consistently and significantly outperformed static adsorption across all measured contaminant classes, with the largest performance differential observed for cyanide (27.9 percentage points) and copper (33.3 percentage points). Six pathogenic bacterial genera were identified, underscoring the urgency of effective treatment for both wastewater types in the Nigerian context. Post-treatment pH decline and TDS/EC increases indicate that pH adjustment and a polishing filtration stage are necessary for full water quality compliance. Within these defined constraints, \u003cem\u003eM. esculenta\u003c/em\u003e peel flour gravity filtration represents a scalable, replicable, and financially accessible pre-treatment technology with direct relevance to SDG 6.1 (universal safe drinking water access) and SDG 6.3 (halving global untreated wastewater) in sub-Saharan Africa. Future research should investigate: (i) alkaline pre-treatment to enhance heavy metal removal without compromising biosorbent simplicity; (ii) sequential multi-stage filter trains for cyanide polishing; (iii) long-term column studies to characterise biosorbent exhaustion and regeneration potential; and (iv) economic modelling of community-scale deployment pathways in cassava-belt communities of Nigeria, Ghana, and the Democratic Republic of Congo.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u0026nbsp;\u003c/strong\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests:\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no competing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eThis research received no specific grant from any public, commercial, or not-for-profit funding agency.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions:\u0026nbsp;\u003c/strong\u003eOAA, TSA and JIO contributed to the study design. OAA and TSA contributed to laboratory execution. All authors contributed to data analysis and manuscript preparation. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e: Not applicable.\u0026nbsp;\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWHO/UNICEF. Progress on Household Drinking Water, Sanitation and Hygiene 2000\u0026ndash;2020: Five Years into the SDGs. Geneva: WHO; 2021.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUnited Nations. The Sustainable Development Goals Report 2020. New York: United Nations. 2020. 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Lagos: Standards Organisation of Nigeria; 2020.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkafor UA, Ogbulie TE, Okereke HC, Okpokwasili GC, Anyanwu CU. Bacteriological and physicochemical quality of water sources in rural communities of south-eastern Nigeria. Heliyon. 2022;8(4):e09361.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAkpor OB, Adelani-Akande TA, Adeoye MD, Akinpelumi OT. Physiochemical and microbiological water quality of river water in Ondo State. Nigeria Sci Afr. 2021;14:e01030.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYuan C, Wang MH, Wang F. Network pharmacology and molecular docking reveal the mechanism of scopoletin against non-small cell lung cancer. Life Sci. 2021;270:119105.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNhamo G, Ndlela B, Nhamo S. Water and sanitation as prerequisites for achieving the SDGs in Southern Africa. Water. 2020;12(8):2128.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUnited Nations. The Human Right to Water and Sanitation: Resolutions and Documents. New York: United Nations. 2020. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.un.org/waterforlifedecade/human_right_to_water.shtml\u003c/span\u003e\u003cspan address=\"https://www.un.org/waterforlifedecade/human_right_to_water.shtml\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-environmental-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [BMC Environmental Science](https://bmcenvsci.biomedcentral.com/)","snPcode":"44329","submissionUrl":"https://submission.nature.com/new-submission/44329/3","title":"BMC Environmental Science","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"cassava peel, biosorbent, wastewater treatment, heavy metals, cyanide, SDG 6, MDG 7C, Nigeria, adsorption, filtration, Manihot esculenta","lastPublishedDoi":"10.21203/rs.3.rs-9130280/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9130280/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eGlobal progress toward the Millennium Development Goal target of halving the proportion of people without safe water and sanitation remains incomplete, and the challenge persists under Sustainable Development Goal 6 (SDG 6), which seeks universal access to safe water and sanitation by 2030. In Nigeria, more than 60\u0026nbsp;million people lack access to safely managed water, while untreated agro-industrial effluents continue to degrade surface and groundwater resources. Cassava (\u003cem\u003eManihot esculenta\u003c/em\u003e Crantz) peel, generated in excess of 12\u0026nbsp;million tonnes annually in Nigeria as a by-product of cassava processing, contains a lignocellulosic matrix rich in functional groups capable of binding microbial contaminants, heavy metals, and cyanogenic compounds.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis study evaluated the purification efficiency of dried \u003cem\u003eM. esculenta\u003c/em\u003e peel flour for treating domestic wastewater (DW) from a university dormitory and industrial wastewater (IW) from a cassava-\u003cem\u003egarri\u003c/em\u003e processing facility in Oyo State, Nigeria. Two treatment configurations, static adsorption and gravity filtration, were compared. Total heterotrophic bacterial count (THBC), physicochemical parameters (pH, temperature, dissolved oxygen, BOD₅, electrical conductivity, total dissolved solids, total suspended solids, and total solids), heavy metals (Zn, Pb, Cu via atomic absorption spectrophotometry), and cyanide concentrations (colorimetric method) were measured at 0, 72, and 144 h during adsorption experiments and before and after filtration.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eTHBC declined by 99.2% in IW during adsorption and by 98.8% following filtration. BOD₅ decreased by 71.9% in DW during adsorption treatment. Zinc removal reached 23.0%, while cyanide concentration decreased by 41.1% under filtration. Dominant bacterial isolates included \u003cem\u003eBacillus\u003c/em\u003e spp. (37%), \u003cem\u003eVibrio\u003c/em\u003e spp. (24%), and \u003cem\u003eCorynebacterium\u003c/em\u003e spp. (18%). Overall, gravity filtration consistently outperformed adsorption across contaminant classes.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThese findings demonstrate that cassava peel flour is an effective, low-cost biosorbent suitable for decentralised wastewater pre-treatment in low-resource communities.\u003c/p\u003e","manuscriptTitle":"Cassava Peel Biosorbent for Sustainable Wastewater Treatment: Implications for Achieving SDG-6 in Low-Resource Communities","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-21 14:12:47","doi":"10.21203/rs.3.rs-9130280/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-05-18T14:21:20+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-02T07:09:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"243836938862266220045859424122109824225","date":"2026-04-30T12:25:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"335207026737237495820423852663193740325","date":"2026-04-29T10:51:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"174135584920564851834105319628402089546","date":"2026-04-29T08:53:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"93834401332672389018629899656986317308","date":"2026-04-14T09:38:23+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-14T08:58:05+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-03-19T22:23:43+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-17T11:40:39+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-17T11:40:25+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Environmental Science","date":"2026-03-15T17:12:25+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-environmental-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [BMC Environmental Science](https://bmcenvsci.biomedcentral.com/)","snPcode":"44329","submissionUrl":"https://submission.nature.com/new-submission/44329/3","title":"BMC Environmental Science","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b392170d-2193-48a3-ac85-4e44abf60f04","owner":[],"postedDate":"April 21st, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-18T14:21:20+00:00","index":36,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-02T07:09:09+00:00","index":35,"fulltext":""},{"type":"reviewerAgreed","content":"243836938862266220045859424122109824225","date":"2026-04-30T12:25:28+00:00","index":34,"fulltext":""},{"type":"reviewerAgreed","content":"335207026737237495820423852663193740325","date":"2026-04-29T10:51:14+00:00","index":33,"fulltext":""},{"type":"reviewerAgreed","content":"174135584920564851834105319628402089546","date":"2026-04-29T08:53:18+00:00","index":32,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-21T14:12:48+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-21 14:12:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9130280","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9130280","identity":"rs-9130280","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}