Cyanobacteria-Based Bioremediation and Biomass Recovery from Agro-Industrial Wastewater

Cyanobacteria-Based Bioremediation and Biomass Recovery from Agro-Industrial Wastewater | 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 Cyanobacteria-Based Bioremediation and Biomass Recovery from Agro-Industrial Wastewater Sachini P. Ariyachandra, Ahmed Ahsan, Tharangika K. Bowange, Eranga M. Wimalasiri, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7369414/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 17 You are reading this latest preprint version Abstract Cyanobacteria offer a sustainable and cost-effective approach to wastewater bioremediation due to their adaptability and nutrient removal efficiency. This study assessed the performance of Synechocystis sp., Synechococcus sp., and Oscillatoria sp. in treating agro-industrial wastewater, while evaluating the potential of such wastewater as a growth medium for large-scale cyanobacterial biomass production. Two wastewater sources, agricultural runoff water (AROW) and poultry meat processing effluent, were tested at 25% and 50% dilutions under controlled laboratory conditions for 14 days. Growth (OD₆₈₀) and changes in physicochemical parameters (pH, EC, TDS, DO, BOD, COD, NO₃⁻, PO₄³⁻) were monitored. All strains achieved biomass yields comparable to the synthetic BG-11 medium, with Synechocystis sp. showing the highest growth in 25% AROW. Significant pollutant reductions (70–90%, p < 0.05) were recorded across treatments; notably, Synechocystis sp. and Oscillatoria sp. removed up to 95% and 98% of NO₃⁻ and PO₄³⁻, respectively, in 25% wastewater. This is the first report demonstrating that diluted AROW can outperform synthetic media for certain cyanobacterial strains, combining effective nutrient removal with low-cost biomass production potential. These findings highlight the dual utility of agro-industrial wastewater as both a treatment target and a cultivation resource, with implications for scalable, resource-efficient bioprocesses. Agro-industrial wastewater Biological treatment Mass culturing Nitrate removal Phosphate removal Wastewater treatment Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Agricultural freshwater use accounts for more than 70% of global freshwater consumption (Iqbal et al., 2021 ). The agriculture sector is not only the greatest consumer of water but is also the biggest generator of wastewater in global scale (Mateo-Sagasta et al., 2017 ). Agricultural wastewater is being discharged from both point and non-point sources. Poultry farms, piggeries, livestock operations, livestock manure are prominent examples of point sources. Non-point sources tend to involve surface runoff and fertilizer runoff resulting from agricultural irrigation and rainfall (Garg et al., 2021 ). Agricultural wastewater exhibits significant contamination due to the presence of chemicals and organic waste originating from fertilizers, pesticides, crop residues and animal faeces (Moss, 2008 ). Utilizing huge quantities of water and agrochemicals for crop cultivation results in transportation of agrochemicals by surface runoff and leaching into the soil (Peña et al., 2020 ). Therefore, prior to being released back into the environment, wastewater must be treated (Alsukaibi, 2022 ). Biological wastewater treatment method is one of the extensively and typically used treatment methods which can be also referred as a process of biodegradation (Roy and Saha., 2021). Cyanobacteria are one of the biological ways of sustainable wastewater treatment due to characteristics such as low energy requirements, eco friendliness, beneficial biomass production, contribution to sludge reduction, effectiveness in heavy metal elimination and exceptional efficacy of treatment (Sismin-Aydin and Simsik., 2022). Moreover, wastewater offers ideal alternatives for low cost, nutrient rich media for industrial scale cultivation of cyanobacteria (Rueda et al., 2020 ). Nostoc , Anabaena , Oscillatoria , Nodularia , and Cyanothece are commonly used cyanobacterial genera that exhibit significant potential of biosorption, biodegradation, and dye decolorization in different industrial effluents (Dubey et al., 2021; Mona et al., 2019 ). According to Cepoi et al., 2016 and Atoku et al., 2021 , the levels of phosphate, ammonium, nitrate, and nitrite ions in wastewater had largely reduced up to acceptable levels within 10 to 15 days of cyanobacteria inoculation. According to studies in the past, different types of wastewaters including sewage wastewater, tannery industry effluent, dairy wastewater, shrimp farm wastewater, fish pond discharge etc have been treated with cyanobacteria as a wastewater treatment (Ahmad, 2022 ). Furthermore, Vijayarasa et al. ( 2021 ) proved the potential of poultry wastewater as a nutrient rich low-cost growth medium for Spirulina platensis , while dairy industry wastewaters were able to provide nutrient rich cost-effective growth media for Arthrospira platensis ( Álvarez et al., 2021). Consequently, greater advantages will come from biological wastewater treatment since it will lessen environmental contamination caused by wastewater discharge and offer inexpensive substrate for cyanobacteria development (Vijayarasa et al., 2021 ). Despite the fact that numerous cyanobacterial strains have the potential to remove pollutants from different types of wastewaters, only a select few appear to be utilized more frequently in agro industry-based wastewater treatment (Plöhn et al., 2021 ). Therefore, discovering the bioremediation potential of various cyanobacterial species is one first step in achieving the aim of sustainable wastewater treatment. The objective of this study was to investigate the potential of improving the physiochemical characteristics of agro-industry-derived wastewater by using selected cyanobacterial species. Moreover, study focused on identifying a growth media that is both cost-effective and conducive to the optimal growth of cyanobacterial species, facilitating efficient wastewater treatment processes. 2. Materials and Methods 2.1 Selection of cyanobacteria strains and collection of wastewater samples 2.1.1 Selection of cyanobacteria strains Cyanobacteria strains of Oscillatoria sp, Synechocystis sp, and Synechococcus sp, Leptolyngbya sp, Pseudanabaena sp, Nostoc elgonese , and Spirulina subsalsa isolated from different aquatic ecosystems in Sri Lanka were selected for the treatment of agro-industry based wastewater. Initially, in order to determine the acclimatization of isolated cyanobacteria strains in wastewater, preliminary test was conducted and the strains of Oscillatoria sp., Synechocystis sp., and Synechococcus sp. acclimatized well with agro industry-based wastewater. Then those three cyanobacterial strains were selected for treatment of agro industry-based wastewater (Table 1 ). Table 1 Selected three cyanobacteria strains for the purpose of wastewater treatment (Hossain et al., 2021 ). Cyanobacterial Strain Isolated Ecosystem GenBank Accession No Oscillatoria sp. Fresh water ecosystem in dry zone, Denagama, Sri Lanka KX962098 Synechocystis sp. Fresh water ecosystem in wet zone, Gregory Lake, Sri Lanka KX962082 Synechococcus sp. Fresh water ecosystem in dry zone, Warapitiya, Sri Lanka KX962092 Isolated strains were cultured in sterile 250 mL Erlenmeyer flasks containing blue-green eleven growth medium (BG 11). Then mother cultures were incubated under the fluorescent light of 2,000 lux light intensity with constant illumination at room temperature 25 ± 2°C (Hossain et al., 2017 ), ensuring adequate aeration reaching the bottom of the flask. 2.1.2 Collection of agro-industry wastewater Agro-industry wastewater was collected from three different sites of Sri Lanka. Altogether two types of wastewater samples namely; poultry meat processing wastewater and agricultural runoff water (AROW) were collected. AROW samples were collected from the discharge canals of the irrigation area of vegetable production fields of upcountry areas of Sri Lanka representing Unanthenna, Hanguranketha district, Sri Lanka (WWH: Wastewater representing location Hanguranketha) and Kandaboda, Nuwara Eliya district, Sri Lanka (WWN: Wastewater representing location Nuwara Eliya). Poultry meat processing effluents were collected from the CRYSBRO poultry meat processing factory (WWC: Wastewater representing location CRYSBRO) located in Ethgala, Gampola, Kandy district of Sri Lanka (Fig. 1 ). Since, water quality parameters of agricultural runoff water can be varied (Linquist et al., 2014 ), AROW was collected from several locations, in order to get an idea about the general composition of AROW. Wastewater samples were collected in high-density polyethylene bottles (HDPE) with appropriate labels from each location for further treatment and physiochemical analysis. Before use, the bottles were soaked in acid overnight, completely rinsed in deionized water, and then dried at 50°C in an oven for three hours. At the sampling site, each bottle was rinsed twice with the respective wastewater before final sample collection. Wastewater samples which were collected for laboratory analysis were filtered through syringe filters (0.45 µm) and acidified by adding several drops of conc. H 2 SO 4 (pH < 2) except the samples collected for Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) analysis. The samples were transported in an ice box and stored at 2°C under normal refrigerated conditions until analysis. 2.1.3 Analysis of physicochemical composition of raw wastewater Physicochemical parameters of raw wastewater including, pH, temperature (T), Electrical Conductivity (EC), Dissolved Oxygen (DO), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Available Phosphorus (PO 4 3− ) and Nitrate (NO 3 − ) were measured in order to determine polluted level of wastewater. All parameters were determined using standard methods described by APHA (1926), originally developed for surface water quality monitoring. 2.2 Experimental design of the study To evaluate the growth potential of pre-selected cyanobacterial strains, a 14-day preliminary trial was conducted using agro-industrial wastewater media at varying concentrations (25%, 50%, 75%, and 100%), diluted with distilled water. Growth was observed only in the 25% and 50% wastewater media. Therefore, the main experiment was conducted using 250 mL Erlenmeyer flasks containing 125 mL of either 25% or 50% wastewater medium, prepared in duplicate. BG11 medium was used as the control. 2.3 Inoculation of cyanobacterial strains The pre-selected strains representing two unicellular cyanobacteria; Synechocystis sp. and Synechococcus sp. and filamentous Oscillatoria sp. were inoculated into two concentrations of wastewater media (25% and 50%) and control medium (BG 11) in duplicates (Table 2 ). Table 2 Types of wastewater, treatments and wastewater dilutions Type of Wastewater Treatment Volume of wastewater (ml) Volume of distilled water (ml) Agricultural Runoff Water (WWH and WWN) Control 31.25 ml (BG 11 25%) 93.75 ml 75% T1 31.25 ml (25%) 93.75 ml 75% Control 62.5 ml (BG 11 50%) 62.5 ml (50%) T2 62.5 ml (50%) 62.5 ml (50%) Poultry Meat Processing Wastewater (WWC) Control 31.25 ml (BG 11 25%) 93.75 ml 75% T1 31.25 ml (25%) 93.75 ml 75% Control 62.5 ml (BG 11 50%) 62.5 ml (50%) T2 62.5 ml (50%) 62.5 ml (50%) Two millilitres of the homogenous cyanobacterial suspension were transferred from initial mother cultures into each flask containing the respective medium. Then cultures were incubated for 14 days under the fluorescent light of 2,000 lux light intensity with constant illumination at room temperature of 25 ± 2°C (Hossain et al., 2017 ), ensuring adequate aeration reaching the bottom of the flask. 2.4 Analysis of physicochemical composition of treated wastewater In order to determine the bioremediation potential of each selected cyanobacterial strain, physicochemical parameters of wastewater including, pH, temperature (T), Electrical Conductivity (EC), Dissolved Oxygen (DO), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Available Phosphorus (PO 4 3− ) and Nitrate (NO 3 − ) were measured after the treatment (Day 7 and Day 14). All parameters were determined following the standard procedures adapted from APHA (1926), originally developed for surface water quality monitoring. 2.5 Analysis of the growth rate of cyanobacteria in different wastewater treatments The growth of the selected cyanobacterial species in each wastewater treatment was determined based on the optical density (OD) measurements obtained at 680 nm for 15 days using SPECORD® PLUS Double Beam UV/Vis Spectrophotometer (Jia et al., 2015 ; Nogueira et al., 2018 ). 2.6 Statistical Analysis For data analysis and presentation, GraphPad Prism version 9 software was used. Analysis of Variance (ANOVA) was used to obtain inter experimental significant difference and Tukey's test at a significance level of 0.05 (α = 0.05) was used in order to assess the significance of differences between pairs of group means. 3. Results 3.1 Physio-chemical composition of raw wastewater The initial physio-chemical characteristics present in the agricultural wastewater are shown in Table 3 . It was observed that the wastewater quality exceeded the maximum permissible limits outlined in the National Environmental (Protection and Quality) Regulations of Sri Lanka (CEA, 2022) and the WHO drinking water standards (WHO, 2011). All types of wastewaters collected indicated higher ranges of chemical oxygen demand (COD) values, exceeding 250 mg/L compared to allowable limits of general standards (Table 3 ). Electrical conductivity (EC) and total dissolved solids (TDS) resulted, exceeding values compared with maximum allowable limits of EC: 400 µS/cm, and TDS: 500 ppm. Furthermore, the nitrate (NO 3 − ) content of agricultural runoff water and poultry meat processing water exceeded allowable limits of 5 mg/L. Agricultural runoff water (WWN) recorded the highest nitrate content of 100 mg/L which was 20 times higher than the allowable limit (5 mg/L), among all types of collected wastewaters. Respectively agricultural runoff water (WWH) recorded the nitrate content of 75 mg/L which was 15 times higher than the allowable limit. Agricultural runoff wastewater (AROW) recorded available phosphorous (PO 4 3− ) levels, exceeding the allowable limit of standard which was 5 mg/L (Table 3 ). Nevertheless, available phosphorous (PO 4 3− ) value recorded for AROW was less than the value recorded for poultry meat processing wastewater (58.4 mg/L). Table 3 Physio-chemical analysis of agro-industry based wastewater Parameters Units Type of wastewater Max Limit References Agricultural runoff water (WWH) Agricultural runoff water (WWN) Poultry meat processing effluents (WWC) pH pH units 6.8 ± 0.08 6.7 ± 0.08 6.45 ± 0.08 6.0– 8.5 (CEA, 2022) Conductivity µS/cm 856.4 ± 1.21 689.2 ± 1.2 2418.7 ± 1.2 400 (WHO, 2011) Temperature °C 24.1 ± 0.12 25.5 ± 0.61 25.3 ± 0.12 30 (WHO, 2011) Total dissolved solids (TDS) ppm 610.8 ± 0.16 670.2 ± 0.09 733 ± 0.10 500 (WHO, 2011) Dissolved Oxygen (DO) mg/L 0.14 ± 0.14 0.17 ± 0.17 0.16 ± 0.16 N/A - Biological Oxygen Demand (BOD 5 ) mg/L 28.6 ± 1.03 25.6 ± 1.03 40.2 ± 1.03 30 (CEA, 2022) Chemical Oxygen demand (COD) mg/L 576 ± 0.06 576 ± 0.06 2304 ± 0.02 250 (CEA, 2022) Nitrate nitrogen (NO 3 − ) mg/L 75 ± 0.26 100 ± 0.26 25 ± 0.19 5 (WHO, 2011) Available phosphorous (PO 4 3− ) mg/L 3.8 ± 0.07 13.9 ± 0.19 58.4 ± 1.7 5 (CEA, 2022) Ammonia-Nitrogen (NH 3 -N) mg/L 9 ± 0.19 161 ± 0.34 43 ± 1.32 50 (CEA, 2022) Total Organic Carbon (TOC) mg/L 0.12 ± 0.08 2.1 ± 0.06 0.29 ± 0.12 N/A - *Mean values are indicated as values ± SD 3.2 Growth rate of cyanobacteria According to the findings, all three strains including, Oscillatoria sp, Synechocystis sp, Synechococcus sp. were capable of growing in all types of agro-industry based wastewater in two different concentrations of 25% (v/v) and 50% (v/v). Optical Density value (at 680 nm); the growth indicator of cyanobacteria (Jia et al., 2015 ; Nogueira et al., 2018 ), has increased by the end of 14 days of the inoculation, in all types of wastewaters containing media. According to the ANOVA analysis, a significant difference ( p < 0.0001) of OD value was observed among the three cyanobacterial strains which were grown in agro-industry based wastewater media (Fig. 2 ). The highest growth rate, in terms of OD 680nm value, was shown by Synechocystis sp. in all types of 25% (v/v) agro industry wastewater containing media. Moreover, Synechocystis sp. showed the maximum growth at end of 14 days of inoculation in 25% (v/v) agricultural runoff water (AROW) compared to poultry meat processing wastewater and control treatment (BG 11). Reaching to day 14, Synechocystis sp. was recorded with the maximum OD 680nm value of 1.05805 which exceeded the OD 680nm value (0.86645) of control treatment (BG 11) in 25% agricultural runoff medium (Fig. 4 ). Similarly, Oscillatoria sp. achieved the maximum growth in 25% AROW at the end of 14-day experimental period, exceeding the growth in control (BG 11). Even though Synechococcus sp. achieved considerable OD 680nm values in wastewater medium at the end of 14 days of the experimental period, values achieved were lower than the OD values achieved in control medium (BG 11) (Fig. 3 ). 3.3 Changes of physicochemical parameters The contents of initial total dissolved solids (TDS) in all types of wastewaters were recorded above 500 mg/L, where it exceeded the general standards of effluent discharge (CEA, 2022). According to results, TDS of all wastewater media inoculated with the three strains were reduced up to very low levels. In both 25% and 50% wastewater media dilutions and in control media (BG 11), three strains were able to remove 99% of dissolved solid, resembling the remarkable ability of cyanobacteria to utilize various nutrients in wastewater. Nevertheless, a significant change of dissolved oxygen (DO) was not observed in any type of wastewater media treated with three strains of cyanobacteria. Results of the present study showed substantial decrease in COD values in all types of wastewaters containing media by all three strains after 14-day treatment (Fig. 4 ). Yet, the efficiency of COD removal of all three strains in 50% wastewater media was lower than in 25% wastewater media. When considering the 25% wastewater media, the highest COD removal efficiency of 97% was achieved by Oscillatoria sp. in poultry meat processing wastewater, followed by Synechocystis sp. with the COD removal efficiency of 90% in 25% poultry meat processing wastewater medium. Initial COD value (2304.02 mg/L) in poultry meat processing wastewater was reduced up to 219.52 mg/L by Synechocystis sp. within 14 days. Considering changes of COD levels by Synechococcus sp. in AROW and poultry meat processing wastewater (Fig. 4 ), the highest COD removal efficiency of 89% was achieved in 25% poultry meat processing wastewater. Considering the activity of all three strains in 25% AROW, Oscillatoria sp. achieved the highest removal of COD (94%), followed by Synechocystis sp. (89%). Synechococcus sp. removed only 73% of COD from AROW (Fig. 4 ). Moreover, all three strains were able to reduce the COD level of AROW less than 250 mg/L (allowable limit) at the end of the experimental period. During the experimental duration, nitrate (NO 3 − ) concentration was decreased in all treated wastewater types. Considering the activity of nitrate (NO 3 − ) removal, ANOVA analysis revealed significant differences among the three strains in both poultry meat processing wastewater and AROW at p < 0.05. During the experimental period, nitrate removal efficiency had been increased from day 0 to day 14. Moreover, out of all three studied strains, the highest nitrate removal efficiency of 95.4% was shown by Synechocystis sp. in 25% AROW containing media (Fig. 5 ). There was a significant difference between the nitrate removal efficiency of day-14 and day-7 in all Synechocystis sp.- treated wastewaters (Fig. 5 ). Oscillatoria sp. recorded the maximum nitrate removal efficiency of 95.2%, almost similar to the removal efficiency of Synechocystis sp. (95.4%) in 25% AROW containing media (Fig. 5 ). The maximum nitrate removal efficiency of Synechococcus sp. was 92% in both 25% and 50% AROW containing media at the end of 14-day treatment. Synechocystis sp. showed a significant difference in nitrate removal, between the control media and AROW, in both 25% and 50% concentrated media. Synechocystis sp. showed 84% of gross nitrate removal efficiency in 25% poultry meat processing wastewater medium. Synechocystis sp. showed an overall gross nitrate removal up to 90% and 73% in 25% and 50% wastewater containing media respectively, at end of 14-day experimental period. In the current study, Oscillatoria sp. removed more than 60% of nitrate in all types of wastewater media. Oscillatoria sp. removed 85% and 64% of nitrate from 25% and 50% poultry meat processing wastewater containing media respectively (Fig. 5 ). Also, Oscillatoria sp. removed 95% of nitrate from the AROW with the initial nitrate concentration of 100 mg/L. Similarly, 92% of nitrate was removed by Oscillatoria sp. from the AROW media with the initial nitrate concentration of 75 mg/L. Therefore, Oscillatoria sp. showed gross nitrate removal efficacy of 91% and 80% in 25% and 50% wastewater containing media respectively. According to the results of the current study, all three strains were able to remove more than 60% of nitrate in both 25% and 50% agro industry wastewater media in an efficacious manner within 14 days of treatment. Furthermore, all three strains were able to achieve nearly total depletion of nitrate (> 80%) in all 25% wastewater media. Similar to the nitrate removal, PO 4 3− concentrations had also been reduced up to certain levels in all treated wastewater media after 14 days of the experimental period. Initially, the raw poultry meat processing water was recorded with the highest available phosphorous (PO 4 3− ) level (58.4 mg/L) (Table 3 ). Therefore, the highest PO 4 3− utilization was recorded in poultry wastewater compared to other AROW media. When considering the PO 4 3− reducing activity of three strains, a significant reduction difference was observed between Synechococcus sp. and Oscillatoria sp. after 7 days of treatment in 50% poultry meat processing wastewater (Fig. 6 ). Nevertheless, significant reduction difference between Oscillatoria sp. vs Synechococcus sp. and Oscillatoria sp. vs Synechocystis sp. was not observed in 50% poultry meat processing wastewater at the end of 14 days period ( p > 0.05). Moreover, a significant difference between 7 days of treatment and 14 days of treatment was observed in all three strains in 25% and 50% poultry meat processing wastewater. Synechococcus sp. removed initial PO 4 3− up to 89% at the end of 7 days, while removal percentage increased up to 93% at the end of 14 days in 50% poultry meat processing wastewater. This PO 4 3− removal percentage was higher than the PO 4 3− removal in control media by Synechococcus sp. A removal efficiency of 81% was observed in 25% Synechococcus sp. treated poultry wastewater containing medium (Fig. 6 ). Referring to the PO 4 3− removal in 25% AROW media, 93% of removal efficacy was observed in AROW wastewaters (both WWH and WWN) by Synechococcus sp. at the end of 14 days (Fig. 6 ). Considering the PO 4 3− removal by Synechocystis sp. in 50% and 25% wastewater containing media, the highest removal efficiency was observed in 25% control medium (BG 11) and 25% poultry wastewater containing medium. The highest PO 4 3− removal percentage of 98.7% was shown by Synechocystis sp. in 25% control media (BG 11) (Fig. 6 ). Considering the PO 4 3− removal efficiency of Synechocystis sp. in AROW, the lowest removal efficiency of 38% was observed in 50% AROW wastewater medium (WWH) (Fig. 6 ). Similar to Synechocystis sp., 98.4% of removal efficiency was resulted by Oscillatoria sp. in 25% poultry meat processing wastewater containing medium (Fig. 6 ). Moreover, Oscillatoria sp. resulted in 88% PO 4 3− removal efficiency in 50% poultry meat processing wastewater containing medium. A significant difference (at p < 0.05) in PO 4 3− removal efficiency was observed in both 50% AROW and poultry wastewater media treated with Oscillatoria sp. (Fig. 6 ). Considering the PO 4 3− removal of Oscillatoria sp. in AROW, 92% removal and 48% removal were observed in AROW 25% and 50% media respectively. 4. Discussion The physio-chemical parameters of collected agro industry-based wastewater exceeded the maximum permissible limits of general standards and criteria for the discharge of industrial effluents into inland surface waters by the National Environmental (Protection and Quality) Regulations, Sri Lanka (CEA, 2022) and World Health Organization (WHO)’s drinking water standards (WHO, 2011). According to Widdison et al. ( 2008 ), growing dependence on the use of nitrogenous fertilizers and overuse of chemical fertilizers and manure has been resulted in overabundance of nitrate in agricultural runoff water. The same scenario can be observed in agricultural fields in Sri Lanka with a higher concentration of nitrates in runoff water. Moreover, the highest available phosphorous (PO 4 3− ) in wastewater (58.4 mg/L) was recorded in poultry meat processing water. According to Sun et al. ( 2021 ), high amount of phosphorous contained in slaughter house wastewater, is the principal industrial contaminant that causes eutrophication. Higher COD values are an indication of higher degree of organic matter contamination (Li and Liu, 2019 ) in collected agro-industry based wastewater. COD values in collected wastewater (> 250 mg/L) indicate how serious the resulted pollution of organic matter could be if the wastewater is released untreated. Therefore, the collected wastewater was identified as harmful and impactful and the proper treatment of the wastewater before releasing them to the environment was identified as an essential necessity. The growth of the three selected cyanobacteria strains in wastewater media represented the stages of a typical growth curve of bacteria. Initially, a slow growth rate was observed between day 0 to day 4, which can be referred as the lag phase of the algal culture. In lag phase, cyanobacterial population gets adapted to existing wastewater media (Vijayarasa et al., 2021 ). An exponential growth pattern could be observed between day 4 to day 10 in majority of cultures, which can be referred as the exponential growth phase in cyanobacterial growth curve (Zhang, 2019 ). According to Vijayarasa et al. ( 2021 ), this exponential growth phase starts with the adaptation to the environment of growth media. Therefore, within average 4 days, the majority of strains have been adapted to wastewater media and started getting available nutrients from the wastewater media for their growth and development. From day 10 to 14, the population growth rate was reduced in most of the cultures, reaching to the stationary phase with the maximum OD value. In stationary phase, the maximum OD value was achieved at which the number of growing cells was close to the number of the dying cells (Nogueira et al., 2018 ). Therefore, all strains showed a typical algae growth curve, up to stationary phase, in majority of cultures with different types of agro-industry based wastewater with different concentrations. As the highest growth rate of selected cyanobacteria, in terms of OD680nm value, was shown in 25% (v/v) agro industry wastewater containing media, compared to 50% (v/v), current study demonstrates the suitability of wastewater with 25% concentration as a growth medium for cyanobacteria. According to Vijayarasa et al. ( 2021 ), Spirulina sp. showed the same steady increasing trend of OD values in 25% wastewater containing media. Moreover, Nostoc sp. showed significant stimulation of growth rate in low concentrations of wastewater, specifically in 25% sewage water. Low concentrations of sewage water (25%) decreased the time required for cyanobacterial cultures to reach their exponential and stationary phases, as well as to increase the number of cells produced. In the same manner, the occurrence of heterocysts and the degree of nitrogenase activity were enhanced in cyanobacteria cultivated under low sewage concentrations (25%)(El-Enany and Issa, 2000 ). Furthermore, Ouhsassi et al. ( 2020 ) proved the ability of Pseudanabaena galeata in promising wastewater treatment, if 25% dilution was applied. According to Bolatkhan et al. ( 2020 ), optimal ratio of wastewater media for cyanobacterial biodiesel production was 25% wastewater dilution. Along with all these studies, the current study further proves the potential of using 25% (v/v) wastewater as an effective low-cost cyanobacteria growth medium for large scale biomass production for industrial purposes. As results of the study demonstrated, Synechocystis sp. showed the highest growth rate compared to other two strains in all types of wastewater media. Moreover, Synechocystis sp. promoted better growth in AROW compared to poultry meat processing wastewater. Since the cyanobacteria biomass resulted during wastewater treatment has the ability to produce a range of valuable products, including biofertilizers, biodiesel and bioplastics, it has gained traction in industrial settings (Zuorra et al., 2020; Castellanos-Estupiñan et al., 2022 ). Therefore, Synechocystis sp. inoculated in 25% AROW media could be identified as an ideal candidate for industrial scale biomass production. Cyanobacteria grow by using organic carbon as well as the inorganic nutrients, nitrate and phosphate (Ouhsassi et al., 2020 ; Singh et al., 2019 ). Organic carbon is measured in terms of BOD and COD (Sarfraz et al., 2023 ). According to the study of Vijaya et al. (2011), Nostoc muscorum cultivation using 75% and 100% kitchen wastewater decreased BOD by 71% and 68% respectively. Study of Gorain et al. ( 2019 )revealed that Anabaena variabilis and Anabaena sphaerica could reduce BOD by 83% and 86% respectively in agricultural runoff water (AROW) supplemented media. Similarly, 76% of BOD reduction was observed in Desmodesmus subspicatus treated sewage wastewater (Sarfraz et al., 2023 ). 85% of decrease in BOD was observed in cassava wastewater remediated by Cholrella vulgaris which reduced BOD from 398 mg/L to 6 mg/L gradually at the end of the 16th day of treatment (Kundu et al., 2019 ). The results of the current study for BOD reduction were comparable with previous studies, with an effective and optimum reduction of BOD up to 80% by selected strains. According to the study of Trentin et al. ( 2019 ), the average COD removal efficacy of Synechocystis sp. was 67%. The results of the current study for COD removal efficacy were more promising. Synechocystis sp. was able to remove COD in wastewater up to 90% and the removal efficiency of Oscillatoria sp. was 97% in poultry meat processing wastewater. Within 14 days of treatment, COD value of AROW had been reduced up to 62.72 mg/L with the treatment of Synechocystis sp. Therefore, Synechococcus sp., Synechocystis sp. and Oscillatoria sp. could be identified and suggested as more promising cyanobacteria for biological treatment, in order to maintain proper organic carbon level (COD and BOD) in wastewater. As cyanobacteria primarily need light, inorganic carbon, and fixed nitrogen for metabolism, their nitrate utilization efficiency is relatively high (Hu and Vermass, 2000). Referring to the highest removal efficiencies of Synechocystis sp. (95.4%), Oscillatoria sp. (95.2%) and Synechococcus sp. (92%) observed, the current study further highlights higher potential of the selected cyanobacterial strains to deplete excess nitrate (NO 3 − ). This scenario could relatively link with the growth of the three strains in different media of wastewater. The high fraction of nitrate removed by these microalgae could be linked to its utilization as nutrient for growth (Kshirsagar, 2013 ). Along with the maximum growth of Synechocystis sp. within 14 days in 25% AROW media (OD 680nm value: 1.153), its nitrate removal efficiency (95.4%) had also become maximum. According to Rasheedy et al. ( 2017 ), Oscillatoria sp. showed 100% removal efficiency of nitrate in municipal wastewater. Atoku et al. ( 2021 ), revealed that Oscillatoria limosa removed 98–99% of nitrate after 45 days of treatment, where Oscillatoria sp. in the current study achieved the removal efficiency of 80–90% within 14 days of treatment. Previously, nitrate reduction rate of Synechocystis sp. was reported as 82% whereas the Synechocystis sp. in the current study was reported with 90% of nitrate removal efficiency. The nitrate removal rates of other species such as Chlorella vulgaris and Gloeocapsa gelatinosa were 84% and 60% respectively (Dominic et al., 2009 ). Spirulina platensis reported 77% of nitrate removal in dairy wastewater (Le and Le, 2014 ). Desmodesmus subspicatus removed nitrate up to 91% in sewage wastewater within 5 days of treatment (Sarfraz et al., 2023 ). According to Castellanos-Estupiñan et al. ( 2022 ), after 20 days of culture in the agricultural runoff, the NO 3 − concentration could be reduced up to 88% by Scenedesmus sp., while Chlorella sp. and Hapalosyphon sp. removed up to 85% of the total NO 3 − present in the wastewater. In the current study, all three species of Synechococcus sp., Oscillatoria sp. and Synechocystis sp. were able to remove more than 80% of nitrate at least in one type of agro industry wastewater. Therefore, the results of the current study for nitrate removal were comparable with many of the previously reported values for different cyanobacterial strains, and these three strains can be identified and suggested as efficient nitrate removers in wastewater. Moreover, Synechocystis sp. + 25% (v/v) agricultural wastewater dilution could be identified as the best species and the wastewater combination for the maximum nitrate removal. The best dilution of wastewater identified during this study was comparable with the study of Ouhsassi et al. ( 2020 ), which identified 25% of dairy wastewater combined with Pseudanabaena sp. as the best total nitrate removal treatment. Nutrients such as N and P are required for several metabolic activities that are essential for the proper cellular activity of microalgae including cyanobacteria (Matamoros and Rodriguez, 2016 ). Algae are renowned for their ability to remove higher phosphorus concentrations from liquid media through many methods, one of which is the chemical precipitation of P (De-Bashan and Bashan, 2004 ). This procedure, however, necessitates a change in the pH of the culture medium (Larsdotter et al., 2010). According to the obtained OD 680nm values in the current study, the highest growth rate was observed in Synechocystis sp. and similarly reported the highest PO 4 3− removal efficiency of 98%. Therefore, higher growth rate could correspond with the highest phosphorus removal efficiency. Similarly, 96% removal of phosphorus in wastewater treated with Synechocystis sp. was previously reported by Trentin et al. ( 2019 ) Trentin et al. ( 2019 ). According to Castellanos-Estupiñan et al., ( 2022 ) Castellanos-Estupiñan et al., ( 2022 ), Scenedesmus sp. could remove PO 4 3− up to 82%, followed by Chlorella sp. and Hapalosyphon sp. with 91% and 70% removal rate respectively, in treated agricultural runoff water. Moreover, Oscillatoria sp. was reported with the phosphorus removal efficiency of 85% in municipal wastewater Madkour et al. (2017) Madkour et al. 2017). The current study reports more than 80% removal efficiency of excess PO 4 3− from wastewater and these strains were able to bring back PO 4 3− levels in wastewater to the acceptable limit of 5 mg/L [24]. Phosphorus removal efficiency also shows a clear correlation with pH up to approximately pH 10 (Larsdotter et al., 2010). During the current study, the treatments with significant PO 4 3− removal, had maintained a pH around 8–10 at the end of 14 days. Therefore, aforementioned correlation with pH is further proven by the current study. According to Larsdotter et al. (2010), high pH also indicates high algal production, hence high phosphorus assimilation. This scenario completely agrees with the results of PO 4 3− removal efficiencies of the current study. 5. Conclusion This study demonstrated that Oscillatoria sp., Synechocystis sp., and Synechococcus sp. can successfully grow in multiple types and dilutions of agro-industrial wastewater, achieving biomass yields comparable to synthetic BG-11 medium. Among the sources tested, agricultural runoff water (AROW) diluted to 25% proved to be the most effective growth medium, supporting optimal biomass production for all three strains without the need for additional nutrient supplementation. Beyond growth performance, the strains achieved substantial bioremediation efficiency, reducing NO₃⁻, PO₄³⁻, COD, and BOD concentrations by 70–98%, with Synechocystis sp. and Oscillatoria sp. recording the highest nutrient removal rates. These findings provide the first evidence that diluted AROW can outperform conventional synthetic media for specific cyanobacterial strains, enabling simultaneous wastewater treatment and biomass generation in a cost-effective manner. Given that the untreated wastewater’s physicochemical parameters significantly exceeded permissible discharge limits, this approach offers a sustainable pathway to meet environmental standards while producing valuable biomass. Future work should focus on scaling up to pilot or industrial levels, assessing long-term strain stability, and optimizing harvesting techniques to facilitate commercial application. Declarations Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Ethics and consent to participate declarations This study did not involve any human participants or animals; therefore, ethics approval and consent to participate were not required. Clinical Trial Registration Not Applicable Data Availability Statement Data sharing not applicable to this article as no datasets were generated or analysed during the current study Code availability Not Applicable Consent to publish declaration Not Applicable Authors’ Approval Statement All authors have read and approved the final version of the manuscript and agree with its submission to Discover Applied Sciences. CRediT authorship contribution statement Sachini P. 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Horizontal lines with \u003cem\u003ep\u003c/em\u003e values indicate statistical significance at \u0026nbsp;\u0026nbsp;\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.0001 and \u003cem\u003ep\u003c/em\u003e \u0026lt;0.05; vertical bars indicate the standard error of the mean.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7369414/v1/4d361fdba58889dc2c641857.jpeg"},{"id":91630656,"identity":"f77e6dcb-cb37-4a52-a399-dae4779047df","added_by":"auto","created_at":"2025-09-18 12:59:00","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":217530,"visible":true,"origin":"","legend":"\u003cp\u003eGrowth curves of (a) \u003cem\u003eSynechocystis\u003c/em\u003e sp. (b) \u003cem\u003eSynechococcus\u003c/em\u003e sp. (c) \u003cem\u003eOscillatoria \u003c/em\u003esp. in 25% (v/v) wastewater media in terms of optical density (OD\u003csub\u003e680nm\u003c/sub\u003e). WWN \u0026amp; WWH: Agricultural runoff water representing two locations, WWC: Poultry meat processing wastewater. Vertical bars indicate the standard error of the mean.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7369414/v1/f8ca23cf163b7003811ae622.png"},{"id":91631011,"identity":"68ef9d23-c16d-47d5-ac28-9da44c6033d2","added_by":"auto","created_at":"2025-09-18 13:07:00","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":23497,"visible":true,"origin":"","legend":"\u003cp\u003eRemoval % of Chemical Oxygen Demand (COD) in 25% wastewater treated with the three strains; \u003cem\u003eSynechococcus\u003c/em\u003esp., \u003cem\u003eSynechocystis\u003c/em\u003e sp., and \u003cem\u003eOscillatoria\u003c/em\u003e sp. at the end of 14 days of inoculation. WWN \u0026amp; WWH: Agricultural runoff water representing locations; WWC: Poultry meat processing wastewater. Horizontal lines with \u003cem\u003ep \u003c/em\u003evalues indicate statistical significance between removal % of COD each strain at \u0026nbsp;\u0026nbsp;\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.0001, \u003cem\u003ep\u003c/em\u003e\u0026lt;0.05. Vertical bars indicate the standard error of the mean.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7369414/v1/5af96a7f6add5022e86e05c1.jpeg"},{"id":91630667,"identity":"5bc106ad-a535-457d-90d8-6a0c1ca6ecb3","added_by":"auto","created_at":"2025-09-18 12:59:00","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":265040,"visible":true,"origin":"","legend":"\u003cp\u003eRemoval % of Nitrate Nitrogen (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e) by (a) \u003cem\u003eSynechocystis\u003c/em\u003e sp. (b) \u003cem\u003eSynechococcus\u003c/em\u003e sp. and (c) \u003cem\u003eOscillatoria\u003c/em\u003e sp. in 25% wastewater media. WWN \u0026amp; WWH: Agricultural runoff water representing locations; WWC: Poultry meat processing wastewater. Horizontal lines with \u003cem\u003ep\u003c/em\u003e values indicate statistical significance between nitrate removal % in each wastewater media and control at \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.0001, \u003cem\u003ep\u003c/em\u003e \u0026lt;0.05. Vertical bars indicate the standard error of the mean.\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7369414/v1/6800ad5a02de3645bcf9238d.jpeg"},{"id":91630661,"identity":"1beaceac-56ef-49ac-9b77-e086a0bf67c1","added_by":"auto","created_at":"2025-09-18 12:59:00","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":241440,"visible":true,"origin":"","legend":"\u003cp\u003eRemoval % of Available Phosphorous (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3-\u003c/sup\u003e) by (a) \u003cem\u003eSynechocystis\u003c/em\u003e sp. (b) \u003cem\u003eSynechococcus\u003c/em\u003e sp. and (c) \u003cem\u003eOscillatoria\u003c/em\u003e sp. in 25% wastewater media. WWN \u0026amp; WWH: Agricultural runoff water representing locations; WWC: Poultry meat processing wastewater Horizontal lines with \u003cem\u003ep\u003c/em\u003e values indicate statistical significance between phosphorous removal % in each wastewater media and control at \u0026nbsp; \u003cem\u003ep \u003c/em\u003e\u0026lt; 0.0001, \u003cem\u003ep\u003c/em\u003e \u0026lt;0.05. Vertical bars indicate the standard error of the mean.\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7369414/v1/f63a67bbb2af6883ac86a899.jpeg"},{"id":91632512,"identity":"b54121b0-0f0e-4312-9ac7-d607b3d41088","added_by":"auto","created_at":"2025-09-18 13:23:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2144986,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7369414/v1/2fa5fdcc-4d79-468d-aac0-4cbff7522ff1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Cyanobacteria-Based Bioremediation and Biomass Recovery from Agro-Industrial Wastewater","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAgricultural freshwater use accounts for more than 70% of global freshwater consumption (Iqbal et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The agriculture sector is not only the greatest consumer of water but is also the biggest generator of wastewater in global scale (Mateo-Sagasta et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Agricultural wastewater is being discharged from both point and non-point sources. Poultry farms, piggeries, livestock operations, livestock manure are prominent examples of point sources. Non-point sources tend to involve surface runoff and fertilizer runoff resulting from agricultural irrigation and rainfall (Garg et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Agricultural wastewater exhibits significant contamination due to the presence of chemicals and organic waste originating from fertilizers, pesticides, crop residues and animal faeces (Moss, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Utilizing huge quantities of water and agrochemicals for crop cultivation results in transportation of agrochemicals by surface runoff and leaching into the soil (Pe\u0026ntilde;a et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Therefore, prior to being released back into the environment, wastewater must be treated (Alsukaibi, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eBiological wastewater treatment method is one of the extensively and typically used treatment methods which can be also referred as a process of biodegradation (Roy and Saha., 2021). Cyanobacteria are one of the biological ways of sustainable wastewater treatment due to characteristics such as low energy requirements, eco friendliness, beneficial biomass production, contribution to sludge reduction, effectiveness in heavy metal elimination and exceptional efficacy of treatment (Sismin-Aydin and Simsik., 2022). Moreover, wastewater offers ideal alternatives for low cost, nutrient rich media for industrial scale cultivation of cyanobacteria (Rueda et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). \u003cem\u003eNostoc\u003c/em\u003e, \u003cem\u003eAnabaena\u003c/em\u003e, \u003cem\u003eOscillatoria\u003c/em\u003e, \u003cem\u003eNodularia\u003c/em\u003e, and \u003cem\u003eCyanothece\u003c/em\u003e are commonly used cyanobacterial genera that exhibit significant potential of biosorption, biodegradation, and dye decolorization in different industrial effluents (Dubey et al., 2021; Mona et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). According to Cepoi et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e and Atoku et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, the levels of phosphate, ammonium, nitrate, and nitrite ions in wastewater had largely reduced up to acceptable levels within 10 to 15 days of cyanobacteria inoculation. According to studies in the past, different types of wastewaters including sewage wastewater, tannery industry effluent, dairy wastewater, shrimp farm wastewater, fish pond discharge etc have been treated with cyanobacteria as a wastewater treatment (Ahmad, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Furthermore, Vijayarasa et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) proved the potential of poultry wastewater as a nutrient rich low-cost growth medium for \u003cem\u003eSpirulina platensis\u003c/em\u003e, while dairy industry wastewaters were able to provide nutrient rich cost-effective growth media for \u003cem\u003eArthrospira platensis (\u003c/em\u003e\u0026Aacute;lvarez et al., 2021). Consequently, greater advantages will come from biological wastewater treatment since it will lessen environmental contamination caused by wastewater discharge and offer inexpensive substrate for cyanobacteria development (Vijayarasa et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Despite the fact that numerous cyanobacterial strains have the potential to remove pollutants from different types of wastewaters, only a select few appear to be utilized more frequently in agro industry-based wastewater treatment (Pl\u0026ouml;hn et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Therefore, discovering the bioremediation potential of various cyanobacterial species is one first step in achieving the aim of sustainable wastewater treatment.\u003c/p\u003e\u003cp\u003eThe objective of this study was to investigate the potential of improving the physiochemical characteristics of agro-industry-derived wastewater by using selected cyanobacterial species. Moreover, study focused on identifying a growth media that is both cost-effective and conducive to the optimal growth of cyanobacterial species, facilitating efficient wastewater treatment processes.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Selection of cyanobacteria strains and collection of wastewater samples\u003c/h2\u003e\u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\u003ch2\u003e2.1.1 Selection of cyanobacteria strains\u003c/h2\u003e\u003cp\u003eCyanobacteria strains of \u003cem\u003eOscillatoria\u003c/em\u003e sp, \u003cem\u003eSynechocystis\u003c/em\u003e sp, and \u003cem\u003eSynechococcus\u003c/em\u003e sp, \u003cem\u003eLeptolyngbya\u003c/em\u003e sp, \u003cem\u003ePseudanabaena\u003c/em\u003e sp, \u003cem\u003eNostoc elgonese\u003c/em\u003e, and \u003cem\u003eSpirulina subsalsa\u003c/em\u003e isolated from different aquatic ecosystems in Sri Lanka were selected for the treatment of agro-industry based wastewater. Initially, in order to determine the acclimatization of isolated cyanobacteria strains in wastewater, preliminary test was conducted and the strains of \u003cem\u003eOscillatoria\u003c/em\u003e sp., \u003cem\u003eSynechocystis\u003c/em\u003e sp., and \u003cem\u003eSynechococcus\u003c/em\u003e sp. acclimatized well with agro industry-based wastewater. Then those three cyanobacterial strains were selected for treatment of agro industry-based wastewater (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\u003eSelected three cyanobacteria strains for the purpose of wastewater treatment (Hossain et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCyanobacterial Strain\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eIsolated Ecosystem\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGenBank Accession No\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\u003eOscillatoria\u003c/b\u003e \u003cb\u003esp.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFresh water ecosystem in dry zone, Denagama, Sri Lanka\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eKX962098\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSynechocystis\u003c/b\u003e \u003cb\u003esp.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFresh water ecosystem in wet zone, Gregory Lake, Sri Lanka\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eKX962082\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSynechococcus\u003c/b\u003e \u003cb\u003esp.\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFresh water ecosystem in dry zone, Warapitiya, Sri Lanka\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eKX962092\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\u003eIsolated strains were cultured in sterile 250 mL Erlenmeyer flasks containing blue-green eleven growth medium (BG 11). Then mother cultures were incubated under the fluorescent light of 2,000 lux light intensity with constant illumination at room temperature 25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C (Hossain et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), ensuring adequate aeration reaching the bottom of the flask.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.1.2 Collection of agro-industry wastewater\u003c/h2\u003e\u003cp\u003eAgro-industry wastewater was collected from three different sites of Sri Lanka. Altogether two types of wastewater samples namely; poultry meat processing wastewater and agricultural runoff water (AROW) were collected. AROW samples were collected from the discharge canals of the irrigation area of vegetable production fields of upcountry areas of Sri Lanka representing Unanthenna, Hanguranketha district, Sri Lanka (WWH: Wastewater representing location Hanguranketha) and Kandaboda, Nuwara Eliya district, Sri Lanka (WWN: Wastewater representing location Nuwara Eliya). Poultry meat processing effluents were collected from the CRYSBRO poultry meat processing factory (WWC: Wastewater representing location CRYSBRO) located in Ethgala, Gampola, Kandy district of Sri Lanka (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Since, water quality parameters of agricultural runoff water can be varied (Linquist et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), AROW was collected from several locations, in order to get an idea about the general composition of AROW.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eWastewater samples were collected in high-density polyethylene bottles (HDPE) with appropriate labels from each location for further treatment and physiochemical analysis. Before use, the bottles were soaked in acid overnight, completely rinsed in deionized water, and then dried at 50\u0026deg;C in an oven for three hours. At the sampling site, each bottle was rinsed twice with the respective wastewater before final sample collection. Wastewater samples which were collected for laboratory analysis were filtered through syringe filters (0.45 \u0026micro;m) and acidified by adding several drops of conc. H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (pH\u0026thinsp;\u0026lt;\u0026thinsp;2) except the samples collected for Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) analysis. The samples were transported in an ice box and stored at 2\u0026deg;C under normal refrigerated conditions until analysis.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.1.3 Analysis of physicochemical composition of raw wastewater\u003c/h2\u003e\u003cp\u003ePhysicochemical parameters of raw wastewater including, pH, temperature (T), Electrical Conductivity (EC), Dissolved Oxygen (DO), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Available Phosphorus (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) and Nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) were measured in order to determine polluted level of wastewater. All parameters were determined using standard methods described by APHA (1926), originally developed for surface water quality monitoring.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Experimental design of the study\u003c/h2\u003e\u003cp\u003eTo evaluate the growth potential of pre-selected cyanobacterial strains, a 14-day preliminary trial was conducted using agro-industrial wastewater media at varying concentrations (25%, 50%, 75%, and 100%), diluted with distilled water. Growth was observed only in the 25% and 50% wastewater media. Therefore, the main experiment was conducted using 250 mL Erlenmeyer flasks containing 125 mL of either 25% or 50% wastewater medium, prepared in duplicate. BG11 medium was used as the control.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Inoculation of cyanobacterial strains\u003c/h2\u003e\u003cp\u003eThe pre-selected strains representing two unicellular cyanobacteria; \u003cem\u003eSynechocystis\u003c/em\u003e sp. and \u003cem\u003eSynechococcus\u003c/em\u003e sp. and filamentous \u003cem\u003eOscillatoria\u003c/em\u003e sp. were inoculated into two concentrations of wastewater media (25% and 50%) and control medium (BG 11) in duplicates (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\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\u003eTypes of wastewater, treatments and wastewater dilutions\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eType of Wastewater\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTreatment\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eVolume of wastewater (ml)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eVolume of distilled water (ml)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e\u003cb\u003eAgricultural Runoff\u0026nbsp;Water\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e(WWH and WWN)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31.25 ml (BG 11 25%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e93.75 ml 75%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eT1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31.25 ml (25%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e93.75 ml 75%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e62.5 ml (BG 11 50%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e62.5 ml (50%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eT2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e62.5 ml (50%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e62.5 ml (50%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e\u003cb\u003ePoultry Meat Processing Wastewater\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e(WWC)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31.25 ml (BG 11 25%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e93.75 ml 75%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eT1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31.25 ml (25%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e93.75 ml 75%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e62.5 ml (BG 11 50%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e62.5 ml (50%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eT2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e62.5 ml (50%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e62.5 ml (50%)\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\u003eTwo millilitres of the homogenous cyanobacterial suspension were transferred from initial mother cultures into each flask containing the respective medium. Then cultures were incubated for 14 days under the fluorescent light of 2,000 lux light intensity with constant illumination at room temperature of 25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C (Hossain et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), ensuring adequate aeration reaching the bottom of the flask.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Analysis of physicochemical composition of treated wastewater\u003c/h2\u003e\u003cp\u003eIn order to determine the bioremediation potential of each selected cyanobacterial strain, physicochemical parameters of wastewater including, pH, temperature (T), Electrical Conductivity (EC), Dissolved Oxygen (DO), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Available Phosphorus (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) and Nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) were measured after the treatment (Day 7 and Day 14). All parameters were determined following the standard procedures adapted from APHA (1926), originally developed for surface water quality monitoring.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Analysis of the growth rate of cyanobacteria in different wastewater treatments\u003c/h2\u003e\u003cp\u003eThe growth of the selected cyanobacterial species in each wastewater treatment was determined based on the optical density (OD) measurements obtained at 680 nm for 15 days using SPECORD\u0026reg; PLUS Double Beam UV/Vis Spectrophotometer (Jia et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Nogueira et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Statistical Analysis\u003c/h2\u003e\u003cp\u003eFor data analysis and presentation, GraphPad Prism version 9 software was used. Analysis of Variance (ANOVA) was used to obtain inter experimental significant difference and Tukey's test at a significance level of 0.05 (α\u0026thinsp;=\u0026thinsp;0.05) was used in order to assess the significance of differences between pairs of group means.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Physio-chemical composition of raw wastewater\u003c/h2\u003e\u003cp\u003eThe initial physio-chemical characteristics present in the agricultural wastewater are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. It was observed that the wastewater quality exceeded the maximum permissible limits outlined in the \u003cem\u003eNational Environmental (Protection and Quality) Regulations\u003c/em\u003e of Sri Lanka (CEA, 2022) and the WHO drinking water standards (WHO, 2011). All types of wastewaters collected indicated higher ranges of chemical oxygen demand (COD) values, exceeding 250 mg/L compared to allowable limits of general standards (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Electrical conductivity (EC) and total dissolved solids (TDS) resulted, exceeding values compared with maximum allowable limits of EC: 400 \u0026micro;S/cm, and TDS: 500 ppm. Furthermore, the nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) content of agricultural runoff water and poultry meat processing water exceeded allowable limits of 5 mg/L. Agricultural runoff water (WWN) recorded the highest nitrate content of 100 mg/L which was 20 times higher than the allowable limit (5 mg/L), among all types of collected wastewaters. Respectively agricultural runoff water (WWH) recorded the nitrate content of 75 mg/L which was 15 times higher than the allowable limit. Agricultural runoff wastewater (AROW) recorded available phosphorous (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) levels, exceeding the allowable limit of standard which was 5 mg/L (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Nevertheless, available phosphorous (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) value recorded for AROW was less than the value recorded for poultry meat processing wastewater (58.4 mg/L).\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\u003ePhysio-chemical analysis of agro-industry based wastewater\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=\"char\" char=\"\u0026plusmn;\" 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\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eParameters\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eUnits\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e\u003cp\u003eType of wastewater\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eMax Limit\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eReferences\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAgricultural runoff water (WWH)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAgricultural runoff water (WWN)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePoultry meat processing effluents (WWC)\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\u003epH units\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e6.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.45\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e6.0\u0026ndash; 8.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(CEA, 2022)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eConductivity\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026micro;S/cm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e856.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e689.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2418.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e400\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(WHO, 2011)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTemperature\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026deg;C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e25.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e25.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(WHO, 2011)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTotal dissolved solids (TDS)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eppm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e610.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e670.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e733\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(WHO, 2011)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eDissolved Oxygen (DO)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e0.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eBiological Oxygen Demand (BOD\u003c/b\u003e\u003csub\u003e\u003cb\u003e5\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e28.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e25.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e40.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(CEA, 2022)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eChemical Oxygen demand (COD)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e576\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e576\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2304\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(CEA, 2022)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eNitrate nitrogen (NO\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e100\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(WHO, 2011)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAvailable phosphorous (PO\u003c/b\u003e\u003csub\u003e\u003cb\u003e4\u003c/b\u003e\u003c/sub\u003e\u003csup\u003e\u003cb\u003e3\u0026minus;\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e13.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e58.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(CEA, 2022)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAmmonia-Nitrogen (NH\u003c/b\u003e\u003csub\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e-N)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e161\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e43\u0026thinsp;\u0026plusmn;\u0026thinsp;1.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(CEA, 2022)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTotal Organic Carbon (TOC)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emg/L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e2.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eN/A\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e*Mean values are indicated as values\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Growth rate of cyanobacteria\u003c/h2\u003e\u003cp\u003eAccording to the findings, all three strains including, \u003cem\u003eOscillatoria\u003c/em\u003e sp, \u003cem\u003eSynechocystis\u003c/em\u003e sp, \u003cem\u003eSynechococcus\u003c/em\u003e sp. were capable of growing in all types of agro-industry based wastewater in two different concentrations of 25% (v/v) and 50% (v/v).\u003c/p\u003e\u003cp\u003eOptical Density value (at 680 nm); the growth indicator of cyanobacteria (Jia et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Nogueira et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), has increased by the end of 14 days of the inoculation, in all types of wastewaters containing media. According to the ANOVA analysis, a significant difference (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) of OD value was observed among the three cyanobacterial strains which were grown in agro-industry based wastewater media (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe highest growth rate, in terms of OD\u003csub\u003e680nm\u003c/sub\u003e value, was shown by \u003cem\u003eSynechocystis\u003c/em\u003e sp. in all types of 25% (v/v) agro industry wastewater containing media. Moreover, \u003cem\u003eSynechocystis\u003c/em\u003e sp. showed the maximum growth at end of 14 days of inoculation in 25% (v/v) agricultural runoff water (AROW) compared to poultry meat processing wastewater and control treatment (BG 11). Reaching to day 14, \u003cem\u003eSynechocystis\u003c/em\u003e sp. was recorded with the maximum OD\u003csub\u003e680nm\u003c/sub\u003e value of 1.05805 which exceeded the OD\u003csub\u003e680nm\u003c/sub\u003e value (0.86645) of control treatment (BG 11) in 25% agricultural runoff medium (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Similarly, \u003cem\u003eOscillatoria\u003c/em\u003e sp. achieved the maximum growth in 25% AROW at the end of 14-day experimental period, exceeding the growth in control (BG 11). Even though \u003cem\u003eSynechococcus\u003c/em\u003e sp. achieved considerable OD\u003csub\u003e680nm\u003c/sub\u003e values in wastewater medium at the end of 14 days of the experimental period, values achieved were lower than the OD values achieved in control medium (BG 11) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Changes of physicochemical parameters\u003c/h2\u003e\u003cp\u003eThe contents of initial total dissolved solids (TDS) in all types of wastewaters were recorded above 500 mg/L, where it exceeded the general standards of effluent discharge (CEA, 2022). According to results, TDS of all wastewater media inoculated with the three strains were reduced up to very low levels. In both 25% and 50% wastewater media dilutions and in control media (BG 11), three strains were able to remove 99% of dissolved solid, resembling the remarkable ability of cyanobacteria to utilize various nutrients in wastewater. Nevertheless, a significant change of dissolved oxygen (DO) was not observed in any type of wastewater media treated with three strains of cyanobacteria.\u003c/p\u003e\u003cp\u003eResults of the present study showed substantial decrease in COD values in all types of wastewaters containing media by all three strains after 14-day treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Yet, the efficiency of COD removal of all three strains in 50% wastewater media was lower than in 25% wastewater media. When considering the 25% wastewater media, the highest COD removal efficiency of 97% was achieved by \u003cem\u003eOscillatoria\u003c/em\u003e sp. in poultry meat processing wastewater, followed by \u003cem\u003eSynechocystis\u003c/em\u003e sp. with the COD removal efficiency of 90% in 25% poultry meat processing wastewater medium. Initial COD value (2304.02 mg/L) in poultry meat processing wastewater was reduced up to 219.52 mg/L by \u003cem\u003eSynechocystis\u003c/em\u003e sp. within 14 days. Considering changes of COD levels by \u003cem\u003eSynechococcus\u003c/em\u003e sp. in AROW and poultry meat processing wastewater (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), the highest COD removal efficiency of 89% was achieved in 25% poultry meat processing wastewater.\u003c/p\u003e\u003cp\u003eConsidering the activity of all three strains in 25% AROW, \u003cem\u003eOscillatoria\u003c/em\u003e sp. achieved the highest removal of COD (94%), followed by \u003cem\u003eSynechocystis\u003c/em\u003e sp. (89%). \u003cem\u003eSynechococcus\u003c/em\u003e sp. removed only 73% of COD from AROW (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Moreover, all three strains were able to reduce the COD level of AROW less than 250 mg/L (allowable limit) at the end of the experimental period.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDuring the experimental duration, nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) concentration was decreased in all treated wastewater types. Considering the activity of nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) removal, ANOVA analysis revealed significant differences among the three strains in both poultry meat processing wastewater and AROW at \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05. During the experimental period, nitrate removal efficiency had been increased from day 0 to day 14. Moreover, out of all three studied strains, the highest nitrate removal efficiency of 95.4% was shown by \u003cem\u003eSynechocystis\u003c/em\u003e sp. in 25% AROW containing media (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). There was a significant difference between the nitrate removal efficiency of day-14 and day-7 in all \u003cem\u003eSynechocystis\u003c/em\u003e sp.- treated wastewaters (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). \u003cem\u003eOscillatoria\u003c/em\u003e sp. recorded the maximum nitrate removal efficiency of 95.2%, almost similar to the removal efficiency of \u003cem\u003eSynechocystis\u003c/em\u003e sp. (95.4%) in 25% AROW containing media (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The maximum nitrate removal efficiency of \u003cem\u003eSynechococcus\u003c/em\u003e sp. was 92% in both 25% and 50% AROW containing media at the end of 14-day treatment.\u003c/p\u003e\u003cp\u003e\u003cem\u003eSynechocystis\u003c/em\u003e sp. showed a significant difference in nitrate removal, between the control media and AROW, in both 25% and 50% concentrated media. \u003cem\u003eSynechocystis\u003c/em\u003e sp. showed 84% of gross nitrate removal efficiency in 25% poultry meat processing wastewater medium. \u003cem\u003eSynechocystis\u003c/em\u003e sp. showed an overall gross nitrate removal up to 90% and 73% in 25% and 50% wastewater containing media respectively, at end of 14-day experimental period. In the current study, \u003cem\u003eOscillatoria\u003c/em\u003e sp. removed more than 60% of nitrate in all types of wastewater media. \u003cem\u003eOscillatoria\u003c/em\u003e sp. removed 85% and 64% of nitrate from 25% and 50% poultry meat processing wastewater containing media respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Also, \u003cem\u003eOscillatoria\u003c/em\u003e sp. removed 95% of nitrate from the AROW with the initial nitrate concentration of 100 mg/L. Similarly, 92% of nitrate was removed by \u003cem\u003eOscillatoria\u003c/em\u003e sp. from the AROW media with the initial nitrate concentration of 75 mg/L. Therefore, \u003cem\u003eOscillatoria\u003c/em\u003e sp. showed gross nitrate removal efficacy of 91% and 80% in 25% and 50% wastewater containing media respectively. According to the results of the current study, all three strains were able to remove more than 60% of nitrate in both 25% and 50% agro industry wastewater media in an efficacious manner within 14 days of treatment. Furthermore, all three strains were able to achieve nearly total depletion of nitrate (\u0026gt;\u0026thinsp;80%) in all 25% wastewater media.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eSimilar to the nitrate removal, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e concentrations had also been reduced up to certain levels in all treated wastewater media after 14 days of the experimental period. Initially, the raw poultry meat processing water was recorded with the highest available phosphorous (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) level (58.4 mg/L) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Therefore, the highest PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e utilization was recorded in poultry wastewater compared to other AROW media. When considering the PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e reducing activity of three strains, a significant reduction difference was observed between \u003cem\u003eSynechococcus\u003c/em\u003e sp. and \u003cem\u003eOscillatoria\u003c/em\u003e sp. after 7 days of treatment in 50% poultry meat processing wastewater (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Nevertheless, significant reduction difference between \u003cem\u003eOscillatoria\u003c/em\u003e sp. vs \u003cem\u003eSynechococcus\u003c/em\u003e sp. and \u003cem\u003eOscillatoria\u003c/em\u003e sp. vs \u003cem\u003eSynechocystis\u003c/em\u003e sp. was not observed in 50% poultry meat processing wastewater at the end of 14 days period (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Moreover, a significant difference between 7 days of treatment and 14 days of treatment was observed in all three strains in 25% and 50% poultry meat processing wastewater.\u003c/p\u003e\u003cp\u003e\u003cem\u003eSynechococcus\u003c/em\u003e sp. removed initial PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e up to 89% at the end of 7 days, while removal percentage increased up to 93% at the end of 14 days in 50% poultry meat processing wastewater. This PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal percentage was higher than the PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal in control media by \u003cem\u003eSynechococcus\u003c/em\u003e sp. A removal efficiency of 81% was observed in 25% \u003cem\u003eSynechococcus\u003c/em\u003e sp. treated poultry wastewater containing medium (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Referring to the PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal in 25% AROW media, 93% of removal efficacy was observed in AROW wastewaters (both WWH and WWN) by \u003cem\u003eSynechococcus\u003c/em\u003e sp. at the end of 14 days (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Considering the PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal by \u003cem\u003eSynechocystis\u003c/em\u003e sp. in 50% and 25% wastewater containing media, the highest removal efficiency was observed in 25% control medium (BG 11) and 25% poultry wastewater containing medium. The highest PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal percentage of 98.7% was shown by \u003cem\u003eSynechocystis\u003c/em\u003e sp. in 25% control media (BG 11) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Considering the PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal efficiency of \u003cem\u003eSynechocystis\u003c/em\u003e sp. in AROW, the lowest removal efficiency of 38% was observed in 50% AROW wastewater medium (WWH) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Similar to \u003cem\u003eSynechocystis\u003c/em\u003e sp., 98.4% of removal efficiency was resulted by \u003cem\u003eOscillatoria\u003c/em\u003e sp. in 25% poultry meat processing wastewater containing medium (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Moreover, \u003cem\u003eOscillatoria\u003c/em\u003e sp. resulted in 88% PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal efficiency in 50% poultry meat processing wastewater containing medium. A significant difference (at \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) in PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal efficiency was observed in both 50% AROW and poultry wastewater media treated with \u003cem\u003eOscillatoria\u003c/em\u003e sp. (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Considering the PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal of \u003cem\u003eOscillatoria\u003c/em\u003e sp. in AROW, 92% removal and 48% removal were observed in AROW 25% and 50% media respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe physio-chemical parameters of collected agro industry-based wastewater exceeded the maximum permissible limits of general standards and criteria for the discharge of industrial effluents into inland surface waters by the National Environmental (Protection and Quality) Regulations, Sri Lanka (CEA, 2022) and World Health Organization (WHO)\u0026rsquo;s drinking water standards (WHO, 2011). According to Widdison et al. (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), growing dependence on the use of nitrogenous fertilizers and overuse of chemical fertilizers and manure has been resulted in overabundance of nitrate in agricultural runoff water. The same scenario can be observed in agricultural fields in Sri Lanka with a higher concentration of nitrates in runoff water. Moreover, the highest available phosphorous (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) in wastewater (58.4 mg/L) was recorded in poultry meat processing water. According to Sun et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), high amount of phosphorous contained in slaughter house wastewater, is the principal industrial contaminant that causes eutrophication. Higher COD values are an indication of higher degree of organic matter contamination (Li and Liu, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) in collected agro-industry based wastewater. COD values in collected wastewater (\u0026gt;\u0026thinsp;250 mg/L) indicate how serious the resulted pollution of organic matter could be if the wastewater is released untreated. Therefore, the collected wastewater was identified as harmful and impactful and the proper treatment of the wastewater before releasing them to the environment was identified as an essential necessity.\u003c/p\u003e\u003cp\u003eThe growth of the three selected cyanobacteria strains in wastewater media represented the stages of a typical growth curve of bacteria. Initially, a slow growth rate was observed between day 0 to day 4, which can be referred as the lag phase of the algal culture. In lag phase, cyanobacterial population gets adapted to existing wastewater media (Vijayarasa et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). An exponential growth pattern could be observed between day 4 to day 10 in majority of cultures, which can be referred as the exponential growth phase in cyanobacterial growth curve (Zhang, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). According to Vijayarasa et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), this exponential growth phase starts with the adaptation to the environment of growth media. Therefore, within average 4 days, the majority of strains have been adapted to wastewater media and started getting available nutrients from the wastewater media for their growth and development. From day 10 to 14, the population growth rate was reduced in most of the cultures, reaching to the stationary phase with the maximum OD value. In stationary phase, the maximum OD value was achieved at which the number of growing cells was close to the number of the dying cells (Nogueira et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Therefore, all strains showed a typical algae growth curve, up to stationary phase, in majority of cultures with different types of agro-industry based wastewater with different concentrations. As the highest growth rate of selected cyanobacteria, in terms of OD680nm value, was shown in 25% (v/v) agro industry wastewater containing media, compared to 50% (v/v), current study demonstrates the suitability of wastewater with 25% concentration as a growth medium for cyanobacteria. According to Vijayarasa et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), \u003cem\u003eSpirulina\u003c/em\u003e sp. showed the same steady increasing trend of OD values in 25% wastewater containing media. Moreover, \u003cem\u003eNostoc\u003c/em\u003e sp. showed significant stimulation of growth rate in low concentrations of wastewater, specifically in 25% sewage water. Low concentrations of sewage water (25%) decreased the time required for cyanobacterial cultures to reach their exponential and stationary phases, as well as to increase the number of cells produced. In the same manner, the occurrence of heterocysts and the degree of nitrogenase activity were enhanced in cyanobacteria cultivated under low sewage concentrations (25%)(El-Enany and Issa, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). Furthermore, Ouhsassi et al. (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) proved the ability of \u003cem\u003ePseudanabaena galeata\u003c/em\u003e in promising wastewater treatment, if 25% dilution was applied. According to Bolatkhan et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), optimal ratio of wastewater media for cyanobacterial biodiesel production was 25% wastewater dilution. Along with all these studies, the current study further proves the potential of using 25% (v/v) wastewater as an effective low-cost cyanobacteria growth medium for large scale biomass production for industrial purposes. As results of the study demonstrated, \u003cem\u003eSynechocystis\u003c/em\u003e sp. showed the highest growth rate compared to other two strains in all types of wastewater media. Moreover, \u003cem\u003eSynechocystis\u003c/em\u003e sp. promoted better growth in AROW compared to poultry meat processing wastewater. Since the cyanobacteria biomass resulted during wastewater treatment has the ability to produce a range of valuable products, including biofertilizers, biodiesel and bioplastics, it has gained traction in industrial settings (Zuorra et al., 2020; Castellanos-Estupi\u0026ntilde;an et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Therefore, \u003cem\u003eSynechocystis\u003c/em\u003e sp. inoculated in 25% AROW media could be identified as an ideal candidate for industrial scale biomass production.\u003c/p\u003e\u003cp\u003eCyanobacteria grow by using organic carbon as well as the inorganic nutrients, nitrate and phosphate (Ouhsassi et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Singh et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Organic carbon is measured in terms of BOD and COD (Sarfraz et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). According to the study of Vijaya et al. (2011), \u003cem\u003eNostoc muscorum\u003c/em\u003e cultivation using 75% and 100% kitchen wastewater decreased BOD by 71% and 68% respectively. Study of Gorain et al. (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2019\u003c/span\u003e)revealed that \u003cem\u003eAnabaena variabilis\u003c/em\u003e and \u003cem\u003eAnabaena sphaerica\u003c/em\u003e could reduce BOD by 83% and 86% respectively in agricultural runoff water (AROW) supplemented media. Similarly, 76% of BOD reduction was observed in \u003cem\u003eDesmodesmus subspicatus\u003c/em\u003e treated sewage wastewater (Sarfraz et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). 85% of decrease in BOD was observed in cassava wastewater remediated by \u003cem\u003eCholrella vulgaris\u003c/em\u003e which reduced BOD from 398 mg/L to 6 mg/L gradually at the end of the 16th day of treatment (Kundu et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The results of the current study for BOD reduction were comparable with previous studies, with an effective and optimum reduction of BOD up to 80% by selected strains. According to the study of Trentin et al. (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), the average COD removal efficacy of \u003cem\u003eSynechocystis\u003c/em\u003e sp. was 67%. The results of the current study for COD removal efficacy were more promising. \u003cem\u003eSynechocystis\u003c/em\u003e sp. was able to remove COD in wastewater up to 90% and the removal efficiency of \u003cem\u003eOscillatoria\u003c/em\u003e sp. was 97% in poultry meat processing wastewater. Within 14 days of treatment, COD value of AROW had been reduced up to 62.72 mg/L with the treatment of \u003cem\u003eSynechocystis\u003c/em\u003e sp. Therefore, \u003cem\u003eSynechococcus\u003c/em\u003e sp., \u003cem\u003eSynechocystis\u003c/em\u003e sp. and \u003cem\u003eOscillatoria\u003c/em\u003e sp. could be identified and suggested as more promising cyanobacteria for biological treatment, in order to maintain proper organic carbon level (COD and BOD) in wastewater.\u003c/p\u003e\u003cp\u003eAs cyanobacteria primarily need light, inorganic carbon, and fixed nitrogen for metabolism, their nitrate utilization efficiency is relatively high (Hu and Vermass, 2000). Referring to the highest removal efficiencies of \u003cem\u003eSynechocystis\u003c/em\u003e sp. (95.4%), \u003cem\u003eOscillatoria\u003c/em\u003e sp. (95.2%) and \u003cem\u003eSynechococcus\u003c/em\u003e sp. (92%) observed, the current study further highlights higher potential of the selected cyanobacterial strains to deplete excess nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e). This scenario could relatively link with the growth of the three strains in different media of wastewater. The high fraction of nitrate removed by these microalgae could be linked to its utilization as nutrient for growth (Kshirsagar, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Along with the maximum growth of \u003cem\u003eSynechocystis\u003c/em\u003e sp. within 14 days in 25% AROW media (OD\u003csub\u003e680nm\u003c/sub\u003e value: 1.153), its nitrate removal efficiency (95.4%) had also become maximum. According to Rasheedy et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), \u003cem\u003eOscillatoria\u003c/em\u003e sp. showed 100% removal efficiency of nitrate in municipal wastewater. Atoku et al. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), revealed that \u003cem\u003eOscillatoria limosa\u003c/em\u003e removed 98\u0026ndash;99% of nitrate after 45 days of treatment, where \u003cem\u003eOscillatoria\u003c/em\u003e sp. in the current study achieved the removal efficiency of 80\u0026ndash;90% within 14 days of treatment. Previously, nitrate reduction rate of \u003cem\u003eSynechocystis\u003c/em\u003e sp. was reported as 82% whereas the \u003cem\u003eSynechocystis\u003c/em\u003e sp. in the current study was reported with 90% of nitrate removal efficiency. The nitrate removal rates of other species such as \u003cem\u003eChlorella vulgaris\u003c/em\u003e and \u003cem\u003eGloeocapsa gelatinosa\u003c/em\u003e were 84% and 60% respectively (Dominic et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). \u003cem\u003eSpirulina platensis\u003c/em\u003e reported 77% of nitrate removal in dairy wastewater (Le and Le, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). \u003cem\u003eDesmodesmus subspicatus\u003c/em\u003e removed nitrate up to 91% in sewage wastewater within 5 days of treatment (Sarfraz et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). According to Castellanos-Estupi\u0026ntilde;an et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), after 20 days of culture in the agricultural runoff, the NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u003cem\u003e\u0026minus;\u003c/em\u003e\u003c/sup\u003e concentration could be reduced up to 88% by \u003cem\u003eScenedesmus\u003c/em\u003e sp., while \u003cem\u003eChlorella\u003c/em\u003e sp. and \u003cem\u003eHapalosyphon\u003c/em\u003e sp. removed up to 85% of the total NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e present in the wastewater. In the current study, all three species of \u003cem\u003eSynechococcus\u003c/em\u003e sp., \u003cem\u003eOscillatoria\u003c/em\u003e sp. and \u003cem\u003eSynechocystis\u003c/em\u003e sp. were able to remove more than 80% of nitrate at least in one type of agro industry wastewater. Therefore, the results of the current study for nitrate removal were comparable with many of the previously reported values for different cyanobacterial strains, and these three strains can be identified and suggested as efficient nitrate removers in wastewater. Moreover, \u003cem\u003eSynechocystis\u003c/em\u003e sp. + 25% (v/v) agricultural wastewater dilution could be identified as the best species and the wastewater combination for the maximum nitrate removal. The best dilution of wastewater identified during this study was comparable with the study of Ouhsassi et al. (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), which identified 25% of dairy wastewater combined with \u003cem\u003ePseudanabaena\u003c/em\u003e sp. as the best total nitrate removal treatment.\u003c/p\u003e\u003cp\u003eNutrients such as N and P are required for several metabolic activities that are essential for the proper cellular activity of microalgae including cyanobacteria (Matamoros and Rodriguez, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Algae are renowned for their ability to remove higher phosphorus concentrations from liquid media through many methods, one of which is the chemical precipitation of P (De-Bashan and Bashan, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). This procedure, however, necessitates a change in the pH of the culture medium (Larsdotter et al., 2010). According to the obtained OD\u003csub\u003e680nm\u003c/sub\u003e values in the current study, the highest growth rate was observed in \u003cem\u003eSynechocystis\u003c/em\u003e sp. and similarly reported the highest PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal efficiency of 98%. Therefore, higher growth rate could correspond with the highest phosphorus removal efficiency. Similarly, 96% removal of phosphorus in wastewater treated with \u003cem\u003eSynechocystis\u003c/em\u003e sp. was previously reported by Trentin et al. (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) Trentin et al. (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). According to Castellanos-Estupi\u0026ntilde;an et al., (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) Castellanos-Estupi\u0026ntilde;an et al., (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), \u003cem\u003eScenedesmus\u003c/em\u003e sp. could remove PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e up to 82%, followed by \u003cem\u003eChlorella\u003c/em\u003e sp. and \u003cem\u003eHapalosyphon\u003c/em\u003e sp. with 91% and 70% removal rate respectively, in treated agricultural runoff water. Moreover, \u003cem\u003eOscillatoria\u003c/em\u003e sp. was reported with the phosphorus removal efficiency of 85% in municipal wastewater Madkour et al. (2017) Madkour et al. 2017). The current study reports more than 80% removal efficiency of excess PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e from wastewater and these strains were able to bring back PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e levels in wastewater to the acceptable limit of 5 mg/L [24]. Phosphorus removal efficiency also shows a clear correlation with pH up to approximately pH 10 (Larsdotter et al., 2010). During the current study, the treatments with significant PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal, had maintained a pH around 8\u0026ndash;10 at the end of 14 days. Therefore, aforementioned correlation with pH is further proven by the current study. According to Larsdotter et al. (2010), high pH also indicates high algal production, hence high phosphorus assimilation. This scenario completely agrees with the results of PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e removal efficiencies of the current study.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study demonstrated that \u003cem\u003eOscillatoria\u003c/em\u003e sp., \u003cem\u003eSynechocystis\u003c/em\u003e sp., and \u003cem\u003eSynechococcus\u003c/em\u003e sp. can successfully grow in multiple types and dilutions of agro-industrial wastewater, achieving biomass yields comparable to synthetic BG-11 medium. Among the sources tested, agricultural runoff water (AROW) diluted to 25% proved to be the most effective growth medium, supporting optimal biomass production for all three strains without the need for additional nutrient supplementation. Beyond growth performance, the strains achieved substantial bioremediation efficiency, reducing NO₃⁻, PO₄\u0026sup3;⁻, COD, and BOD concentrations by 70\u0026ndash;98%, with \u003cem\u003eSynechocystis\u003c/em\u003e sp. and \u003cem\u003eOscillatoria\u003c/em\u003e sp. recording the highest nutrient removal rates. These findings provide the first evidence that diluted AROW can outperform conventional synthetic media for specific cyanobacterial strains, enabling simultaneous wastewater treatment and biomass generation in a cost-effective manner. Given that the untreated wastewater\u0026rsquo;s physicochemical parameters significantly exceeded permissible discharge limits, this approach offers a sustainable pathway to meet environmental standards while producing valuable biomass. Future work should focus on scaling up to pilot or industrial levels, assessing long-term strain stability, and optimizing harvesting techniques to facilitate commercial application.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003cbr\u003e\u003c/strong\u003e\u003cem\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/em\u003e\u003cbr\u003e\u0026nbsp;\u003cbr\u003e\u003cstrong\u003eCompeting interests\u003cbr\u003e\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics and consent to participate declarations\u003cbr\u003e\u003c/strong\u003eThis study did not involve any human participants or animals; therefore, ethics approval and consent to participate were not required.\u003cbr\u003e\u0026nbsp;\u003cbr\u003e\u003cstrong\u003eClinical Trial Registration\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not Applicable\u003cbr\u003e\u0026nbsp;\u003cbr\u003e \u003cstrong\u003eData Availability Statement\u003cbr\u003e\u003c/strong\u003eData sharing not applicable to this article as no datasets were generated or analysed during the current study\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode availability\u003cbr\u003e\u003c/strong\u003eNot Applicable\u003cbr\u003e\u0026nbsp;\u003cbr\u003e\u003cstrong\u003eConsent to publish declaration\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not Applicable\u003cbr\u003e\u003cstrong\u003e\u003cbr\u003eAuthors\u0026rsquo; Approval Statement\u003cbr\u003e\u0026nbsp;\u003c/strong\u003eAll authors have read and approved the final version of the manuscript and agree with its submission to Discover Applied Sciences.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003cbr\u003e\u003c/strong\u003e\u003cstrong\u003eSachini P. Ariyachandra\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eInvestigation, Methodology, Formal analysis, Validation, Writing - Original Draft. \u003cstrong\u003eAhmed Ahsan:\u0026nbsp;\u003c/strong\u003eWriting - Review \u0026amp; Editing.\u003cstrong\u003e\u0026nbsp;T.K. Bowange:\u0026nbsp;\u003c/strong\u003eSupervision, Writing - Review \u0026amp; Editing. \u003cstrong\u003eR.R. Ratnayake\u0026nbsp;\u003c/strong\u003e\u0026amp;\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eEranga M. Wimalasiri\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e Conceptualization, Supervision, Methodology, Writing - Review \u0026amp; Editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAhmad IZ. The usage of Cyanobacteria in wastewater treatment: prospects and limitations. 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Catalysts 2021, 11, 22.\u003c/em\u003e \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/catal11010022\u003c/span\u003e\u003cspan address=\"10.3390/catal11010022\" targettype=\"DOI\" 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":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Agro-industrial wastewater, Biological treatment, Mass culturing, Nitrate removal, Phosphate removal, Wastewater treatment","lastPublishedDoi":"10.21203/rs.3.rs-7369414/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7369414/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCyanobacteria offer a sustainable and cost-effective approach to wastewater bioremediation due to their adaptability and nutrient removal efficiency. This study assessed the performance of \u003cem\u003eSynechocystis\u003c/em\u003e sp., \u003cem\u003eSynechococcus\u003c/em\u003e sp., and \u003cem\u003eOscillatoria\u003c/em\u003e sp. in treating agro-industrial wastewater, while evaluating the potential of such wastewater as a growth medium for large-scale cyanobacterial biomass production. Two wastewater sources, agricultural runoff water (AROW) and poultry meat processing effluent, were tested at 25% and 50% dilutions under controlled laboratory conditions for 14 days. Growth (OD₆₈₀) and changes in physicochemical parameters (pH, EC, TDS, DO, BOD, COD, NO₃⁻, PO₄\u0026sup3;⁻) were monitored. All strains achieved biomass yields comparable to the synthetic BG-11 medium, with \u003cem\u003eSynechocystis\u003c/em\u003e sp. showing the highest growth in 25% AROW. Significant pollutant reductions (70\u0026ndash;90%, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) were recorded across treatments; notably, \u003cem\u003eSynechocystis\u003c/em\u003e sp. and \u003cem\u003eOscillatoria\u003c/em\u003e sp. removed up to 95% and 98% of NO₃⁻ and PO₄\u0026sup3;⁻, respectively, in 25% wastewater. This is the first report demonstrating that diluted AROW can outperform synthetic media for certain cyanobacterial strains, combining effective nutrient removal with low-cost biomass production potential. These findings highlight the dual utility of agro-industrial wastewater as both a treatment target and a cultivation resource, with implications for scalable, resource-efficient bioprocesses.\u003c/p\u003e","manuscriptTitle":"Cyanobacteria-Based Bioremediation and Biomass Recovery from Agro-Industrial Wastewater","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-18 12:58:55","doi":"10.21203/rs.3.rs-7369414/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-29T17:48:07+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-23T13:11:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-22T12:26:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"219264386401627363632565588852359553361","date":"2025-10-17T01:08:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"280235377450529534143128407665879785553","date":"2025-10-16T22:17:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"252542141900175889970042355457684087675","date":"2025-10-14T11:39:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"133020097733181236778085887958833486952","date":"2025-10-09T13:08:59+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-02T09:56:28+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-25T06:37:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"252542141900175889970042355457684087675","date":"2025-09-15T11:17:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"227364732856963697220660457379081265017","date":"2025-09-13T09:10:39+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"112420479938870833142582789352742187286","date":"2025-09-13T08:44:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-11T08:39:26+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-11T07:50:05+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-10T11:52:19+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-08T04:54:25+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Applied Sciences","date":"2025-09-08T04:36:53+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"af41e160-a17a-4fa7-bd75-a6ec6db13789","owner":[],"postedDate":"September 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-19T18:39:07+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-18 12:58:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7369414","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7369414","identity":"rs-7369414","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}