Novel electro-oxidation unite for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: Batch and continuous experiments

Novel electro-oxidation unite for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: Batch and continuous experiments | 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 Article Novel electro-oxidation unite for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: Batch and continuous experiments Mohamed S. Hellal, Bahaa A. Hemdan, Marwa Youssef, Gamila El-TAweel, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1809352/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract This study aimed to evaluate the performance of the Novel electro-oxidation unit for the disinfection of wastewater from technoeconomic point of view. The cell was fabricated based on patent design with a total volume of 3L containing nine electrodes (6graphite and 3stainless steel) with cylindrical shape and connected to DC power supply. Determination of optimum operating parameters were investigated in batch mode on synthetic wastewater through studying effect of contact time, current density(CD), total dissolved solids concentration(TDS) and bacterial density. Also, continuous mode experiment was studied on real wastewater from agricultural drain and secondary wastewater treatment plant. The results of batch mode revealed that the optimum operational conditions that achieved the complete removal E.coli was at contact time of 5 minutes, TDS = 2000 mg/L and CD = 4mA/Cm 2 . Application of these conditions on the continuous mode experiment indicated the complete removal of all bacterial indicators after 5 minutes in the drainage wastewater and after 2 minutes in the secondary treated wastewater. The physico-chemical characterization indicated also, no formation of chlorine by products in the process. The electrical consumption was calculated in the continuous mode and found to be 0.5 kWh/m 3 with operational cost about 0.06 $ /m 3 including cost of adding chemicals to increase the TDS. This proved that this novel electro-oxidation unite is cost effective for disinfection of wastewater and complete removal bacterial pollutants than other conventional treatment methods. electro-oxidation Graphite electrode electro-disinfection E.coli current density wastewater treatment Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Inconsistencies between water availability and demand are increasing worldwide, especially in countries suffering from water scarcity like Egypt. By the year 2050, urban areas in these countries will be susceptible to water scarcity due to an increase of 80% in urban water demand due to rapid population 1 . To close the gap between water demand and supply, the reliance should be on alternative water sources such as reusing treated municipal wastewater. Tertiary or advanced treatment is necessary for urban reuse of municipal wastewater 2 . However, disinfection of this treated wastewater is mandatory to safely reuse as residual microbial pollutants such as Escherichia coli still exist in the treated wastewater. Disinfection is unquestionably crucial in the water treatment process to yield safe water free from these pathogenic microorganisms. Classification of water disinfection methods could be three broad groups; chemical, physical, and physicochemical. Physical disinfection depends mainly on physical processes without any chemical that does not involve chemicals and relies on physical means without adding a chemical that may change water properties 3 . These methods varied between thermal disinfection (heating/boiling), ultra-sonication, membrane filtration, and UV irradiation 4 . However, this disinfection method has several disadvantages, such as the need for a long time, many personnel to monitor flushing times and temperatures of the water tanks, and only effective for a short term 5 . Another type of disinfection is the chemical method that uses chemical compounds to deactivate waterborne pathogens in water and wastewater. The common chemical disinfectants utilized in wastewater are sodium hypochlorite, chlorine dioxide, hydrogen peroxide ozone, (mono) chloramine, and chlorine gas, the most used among them 6 . The side effects of chemical disinfection became harmful to human health and the environment as a result of the formation of toxic organic compounds such as chlorinated by-products (DBPs), besides the high price of chemicals and energy 7 . Physiochemical disinfection includes chemical and physical approaches such as electro-disinfection in which mixed oxidants (disinfection agents) are formed from electrolytic cells 8 . Recently there was a great tendency to use electro-disinfection as an important alternative technic to chemical disinfection for upcoming years 9 . This new technology can achieve an acceptable level of disinfection for treated wastewater with limited chemical additions in a short time. The mechanism of electro-disinfection is based on the destruction of microorganisms by passing an electric current through the water using appropriate electrodes. Pathogenic bacteria are destroyed by various oxidants that are produced during the electrolysis of water 10 . There are two categories of electrochemical disinfection devices; electrolysers, which is based on the direct interaction with contaminated water, and mixed oxidant generators, which use a concentrated brine solution to generate oxidizing species (e.g. free chlorine [Cl 2 ], chlorine dioxide [ClO 2 ], ozone [O 3 ], hydrogen peroxide [H 2 O 2 ], and other short-lived radicals) that can enhance the overall disinfection efficiency 11 , 12 . In free chloride waters, the oxidation of water on the anode surface produces physisorbed hydroxyl radicals M ( • OH). At a limited release rate, • OH reacts non-selectively with waterborne pathogenic agents or with a wide range of recalcitrant organics 9 . When the chloride is present, whether it is naturally present (e.g., toilet, wastewater, seawater) or is added artificially, reactive chlorine species (RCS) such as free chlorine ([Cl 2 ], [HOCl], [ClO − ]) and chlorine radical species ([ • Cl 2 − ], [ • Cl]) are generated and considered as primary disinfectants 11 . In wastewaters, the organic matter could be oxidized in the electrolytic cell through two mechanisms: (i) Direct oxidation via a direct electron transfer to the anode, and (ii) mediated oxidation via the electro-generation of oxidizing species from wastewater itself or supporting electrolyte oxidation at the anode at high intensity 9 . The types of electrochemical cells used in disinfection varied between electro-oxidation, electro-coagulation, and electrolysis. Electro-oxidation is the most functional unit as it is non-consumable, can generate oxidants without chemical addition, and disinfection can occur directly through electron transfer to the anode 13 . The factors affecting the degree of elect-disinfection are cell design, electrode types and shapes, time, electrolyte conductivity, applied current density, and pathogen concentration. The type and composition of the anode is a significant factor that plays an essential role in the efficiency of the electrochemical disinfection process because it affects the generation of oxidants and determines their nature and their oxidation power. Previous studies have used various electrodes such as platinum, titanium, stainless steel, graphite, PbO 2 , boron-doped diamond (BDD), carbon-cloth, graphite and silicone rubber, and so on 12 , 14 . Other operational parameters, such as current intensity, cell voltage, reaction time, pH, and temperature, are also crucial in the optimization of the electrochemical disinfection process. Optimizing these factors is very important in terms of a techno-economic point of view. Consequently, the main aim of this analysis is to implement a revolutionary, affordable electro-oxidation system to evaluate operational parameters for electro-disinfection of municipal wastewater. The extraordinary circumstances are time, current density, NaCl, and bacterial population. The preferred circumstances for the operating system were engaged for the inactivation of bacterial populations in both actual wastewater and synthetic contaminated water. 2. Materials And Method 2.1 Electro-oxidation reactor design and In this study, the experimental setup is given schematically in Fig. 1 Electro-disinfection treatment was done in an electro-oxidation cell in an electrolytic cell designed based on patent No. EGPO 30235 15 is made of a Perspex glass container with a net volume 3L. and fabricated of Perspex glass material container with a net volume 3L. The EC unit has dimensions of 12.5 cm ×12 cm ×20 cm (L× W× H), while the water level was kept below 5 cm resulting an effective volume of 2.25 liter. Nine identical cylindrical shape electrodes were distributed in three horizontal, and two rows have 6 graphite electrodes between; one contains three stainless electrodes with a binary distance between all electrodes of 2 cm. Each electrode has 15 cm height and 1.6 cm diameter and volume of about 12 cm 3 , and the working surface area is 0.054 m 2 . Accordingly, the total volume of the electrodes in the cell is 0.24 liter, which means that the adequate volume of the cell is about 2 liters. The electrodes were connected to the D.C power supply with a variable output voltage range from 0–30 volt and current from 0 to 10 ampere. The treatment runs were performed at constant temperature (25˚C), mixing speed (250 rpm), and with 2 L of synthetic contaminated solution. 2.2 Operating conditions The study is conducted in several experimental runs; each one represents operational parameters such as contact time, conductivity, microorganisms count, and current density. The effect of operational time was investigated by applying current density of 2 mA/cm 2 at TDS 1000 mg/L for 30 min. The current density was investigated for values of 2, 4, 6, and 8 mA / cm 2 at the determined optimum time. Effect of electrolyte concentration was analyzed by preparation of electrolyte solution of sodium chloride (NaCl) with the concentration of 17.5, 35, 52.5, 70, and 87.5 mM to obtain TDS values of 1000, 2000, 3000, 4000, nd 5000 mg/L whiledifferent biomasses and bacterial densities were evaluated at the received optimum time, TDS and current density. In each experiment, treated samples were collected in sterile tubes; bacterial concentration was evaluated for treated and control samples. Before each run, the electrodes were washed to remove any surface attachments and impurities on electrodes with a solution freshly prepared by mixing 100 mL of HCl solution (35%) and 200 mL of chloroform solution. After the electrodes had been washed, they were dried in the oven at 105ºC to remove the residuals on their surfaces of any bacterial contamination. 2.3 Wastewater sources 2.3.1 Simulated wastewater This study used simulated wastewater containing non-pathogenic E. coli as a model microorganism. The bacterial stock culture was obtained by seeding some pure colonies in sterile nutrient broth medium (5 mL) incubated at 37°C for 24 hours. Fresh Hektoen medium (500 mL) was used to inoculate 3% (v/v) of this culture for two incubation times (24 h/each at 37°C). Before any experiment, a certain amount of E. coli culture (100 mL) was centrifuged at 6000 rpm for 10 min. The obtained biomass was washed twice with sterile standard saline solution (9 g/L NaCl). After centrifugation, it was subsequently resuspended in the sterile solution of distilled water and sodium chloride with different concentrations to achieve a final concentration of around 10 6 -10 7 CFU/mL. 2.3.2 Real wastewater After obtaining optimum operating conditions, two real wastewater sources were collected and subjected to an electrooxidation unit. The first source is the agricultural drain in Menufia governorate that receive agricultural drainage water mixed with the sewage water. The other source is the effluent from the secondary treatment wastewater treatment plant at Giza, Egypt. prior chlorine tank. The wastewater was fed continuously using a peristaltic pump at the optimum conditions. 2.4. wastewater analysis For each experimental run, bacterial indicators, pH, and NaCl were analyzed. To evaluate the bacterial concentration in each experiment after the treatment of the water sample (level of removal of E. coli by electrochemical disinfection), influent and effluent samples were collected in sterile tubes. Influent samples were serially diluted in a standard saline solution. Diluted and undiluted samples (1.0 mL) were seeded in triplicate on nutrient agar plates and incubated at 37°C for 24 h. For real wastewater samples, complete analysis was characterized at optimum conditions in terms of pH, (COD), biological oxygen demand (BOD), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH 4 − N ), nitrite ( \({\text{N}\text{O}}_{2}^{-}\) ). nitrate ( \({\text{N}\text{O}}_{3}^{-}\) ), oil and grease total phosphorus and trihalomethanes beside the bacterial indicators heterotrophic bacteria, total coliform, fecal coliform (thermophilic), Streptococcus faecalis , and Pseudomonas aeruginosa. Heterotrophic bacteria were measured in R2A agar medium by counting colonies formed for each plate (colony-forming unit (CFU)). These analyses, unless otherwise specified, were performed according to the Standard Methods for the Examination of Water and Wastewater 16 . 2.5. Calculation of removal efficiency, operating cost, and energy consumption, The percentage removal efficiency r was calculated using Eq. (1): % Removal = \(\frac{Câˆ?-C}{Câˆ?} ?—100\) (1) where C 0 is the initial concentration and C is the final concentration of the pollutant The operating cost is one of the most critical parameters in the EC process because it affects the application of any wastewater treatment method. The operating price includes material (mainly electrodes), electrical energy, labor, maintenance, and other expenses. The latter cost items are mainly independent of the electrode material. Thus, this study calculated the operating cost as electrical energy costs. The energy consumption is consumption quantities per m 3 of wastewater treated. calculation of energy consumption is expressed as in Eq. (2) E C = \(\frac{(V?—I?—t)}{v}\) (2) where E C is energy consumption (kWh/m 3 ), V is voltage (Volt), I is current (Ampere), t is contact time (seconds), and v is the volume of the treated wastewater (m 3 ), respectively. 3. Results And Discussions 3.1 Electro-disinfection of synthetic microbial contaminated water The bacteria E. coli was selected as models of pathogens for the preparation of synthetic wastewater in the disinfection study due to its high environmental and sanitary risks. The electro-disinfection of synthetic water contaminated with the E.coli bacteria was studied in terms of operational characteristics such as the concentration of E.coli as a function of the experimental time period of exposure, current density, TDS, and microbial cell densities. 3.1.1 Effect of electro-disinfection contact times The effect contact time was carried out at the current density of 4 mA/cm 2 and electrolyte concentration of 17.5 mM NaCl (1000 mg/L) with initial E.coli log count of 3.2 CFU/mL. Samples were collected in sterile tubes every min, starting from zero to 15min. The results in Fig. 2 show that a 100% E. coli elimination occurred at the third min of contact time. E.coli count was reduced to 1.2 and 1.9 CFU/mL after 1min and 2min exposure times, indicating that disinfection performance of more than 99.98% required a residence time of 2 min. The obtained time is auspicious, cost-effective and better than other electro-disinfection studies carried out by Herraiz-Carbon´ et al., 17 , who studied disinfection polymicrobial urines from hospital wastewater using electro-oxidation unites. They achieved 4–6 logs of bacterial removal after 180min using electrooxidation reactor with two boron-doped diamond and stainless-steel electrodes at the current density of 50 A/m 2 . Also, the results proved that electro-oxidation is significantly more effective than chemical disinfection using chlorine, where chlorination requires longer exposure (at least 30min) to achieve a bactericidal performance of 99.94% or higher 18 . Time is essential in designing a disinfection technique as it is related to power and chemicals consumption and capital construction 13 . Accordingly, the other operating parameters were studied as a function of time to determine their optimal values. 3.1.2 Effect of Current Density The current density is a significant factor as it determines the cost related to power consumption and also electrode dimensions. The effect of current density as a function of time on the electro-disinfection was carried out at electrolyte concentration of 17.5 mM NaCl (1000 mg/L) and doubled initial E. coli log count (6.6 CFU/mL) with different current densities 2, 4, 6, 8 mA/cm 2 . Figure 3 shows the log reduction of E.coli at different current densities. Application of 2 mA/cm 2 was not very efficient for removal of E.coli , and the maximum log counts reduced was about 3.7 CFU/mL at 6 min. The reduction rate was fixed after this time, which indicated that more current is required for removal of high logs values. Increasing current density by two folds to be 4 mA/cm 2 showed a gradual reduction of E.coli starting with a log reduction of 3.9 CFU/mL at the first min, reaching complete removal at the fourth min. The same behavior was observed at 6 mA/cm 2 as the gradual reduction was observed comparing the third min, at which complete removal achieved. The full reduction of E. coli was performed within the first min at 8 mA/cm 2 , indicating that the contact time could be seconds at that current density. The results are consistent with those of Ghasemian et al., 19 who proved that increasing the current density from 0.2 to 1 mA/cm 2 led to a more than 50% reduction in log10-bacterial concentration after 20 min, and within 5 min for 2 mA/cm 2 , 2 min for 4 mA/cm 2 using electrochemical cell with doped tin-tungsten-oxide electrodes. Increasing the applied current density resulted in enhanced inactivation efficacy of E.coli . The main reason for this phenomenon is that increasing current densities accelerate the movement of the electrons, which increases the generation of more oxidizing species at the anode surface, which attack and destroy bacteria 20 . Furthermore, a tremendous amount of electrical charge will pass through the electrolyte with a more significant current density, potentially resulting in faster disinfection rates 21 . However, from the economic point of view, the high current density could be not cost-effective due to the high consumption rate of electrical power. Accordingly, 4mA/cm 2 was chosen as the optimum current density. 3.1.3 Effect of different electrolyte concentrations Synthetic wastewater was prepared with different electrolyte concentrations to obtain values of about 17.5, 35, 52.5, 70 and 87.5 mM NaCl, with corresponding TDS values from 1000 to 5000 mg/L. The experiment was carried out at a current density 2 mA/cm 2 and time up to 10min. The results in Fig. 4 showed that TDS strongly affects the removal of E.coli with electro-disinfection. The increase of TDS concentration in the electrolyte solution is accompanied by a high reduction of E.coli in a shorter time. The electrolyte concentration of 17.5 mM NaCl (1000 mg/L) is not sufficient for the complete removal of E.coli as the maximum log reduction achieved was about 5.5 CFU/mL after 6 min contact time. The initial log count of E.coli dropped gradually over 4 min in a solution of 35 mM NaCl (2000 mg/L), while 3 min was enough for elimination of E.coli at 52.5 mM NaCl (TDS 3000 mg/L). In contrast, complete disinfection was achieved in a shorter time (2 min) for 70 and 87.5 mM NaCl (4000 and 5000 mg/L) as a whole log decrease (6.5 CFU/mL) was achieved with a current density of 4 mA/cm 2 . The performance of electro-disinfection has worsened at low TDS concentrations, which suggests at the respective current level of 2 mA/cm 2 , TDS concentrations of 2000 and 3000 mg/L were found to be sufficient for effective inactivation of E. coli in this study. The results were directly compared with the previously reported findings by Ghasemian et al. 19 , where the complete disinfection of E. coli in 100 mM NaCl was obtained at 2 min with the current density of 4 mA/cm 2 , respectively. 3.1.4 Effect of cell densities of E.coli From the pervious obtained results above, the best condition for electro-disinfection is TDS concentration of 2000 mg/L( 35 mM NaCl), the current density of 4 mA/cm 2, and the contact time up to 5 min. At these conditions, solutions are different E. coli with three different bacterial densities (3.37 as a low, 6.31 as a moderate, 6.31, and 8.29 as an intense, high CFU/mL) was prepared and subjected to electro-disinfection. The inactivation of E. coli cells is seen in Fig. 5 . In truth, bacterial damage is evident at low cellular density. The results revealed that the low bacterial load (log 3.37 CFU) was destroyed within 3 min of treatment, and E. coli cell survival was substantially and quickly reduced. Log 6.31 CFU of E.coli was effectively inactivated after 4 min. The high bacterial population burden required a longer treatment time (6 min) to inactivate log 8.29 CFU/mL (Fig. 4 ). The findings align with previous research that shows that low densities of E.coli cells might be easily killed in a shorter amount of time following inactivation 22 . EC inactivation, chlorination, ozonation, and the Fenton reaction were all found to be successful in eliminating E. coli with a starting density of 10 8 /mL from wastewater in their investigation. With an elimination rate of 99.4 percent or better, nearly all of the cells in the disinfected samples lost their viability in terms of being physiologically available for incubation 23 . 3.2 Mechanism of E. coli elimination using electro-oxidation The mechanism of Electro disinfection using the electro-oxidation unit mainly depends on the generation of strong oxidants such as oxygen, ozone, or hypochlorite in the anode during water electrolysis. These chemical oxidants are produced when plunging electrodes apply electric current to aqueous microbe solutions. When the solution contains salts such as chloride salts, electrolysis has a range of oxidants, including hydrogen peroxide and ozone when oxygen is available, as well as free chlorine and chlorine dioxide when chloride ions are present 24 . However, the type of oxidant depends on the applied current, electrolyte solution, and anode electrode type 25 . For example, Anodes used for the process of electro-disinfection by hypochlorite ions should have low overpotential toward chlorine gas evolution, such as platinum electrodes. However, pure Pt anodes are not used in industrial applications because of their high costs, and the alternatives for Cl 2 gas evolution are PbO 2 electrodes 26 . Electro-disinfection by oxygen gas resulting from the anodic generation of oxygen, which shows some germicidal activity, is used mainly for removing microorganisms from water in small applications where the generation of chlorine species is undesirable. The most used electrodes for oxygen evolution are stainless steel and graphite electrodes. For our study, the removal mechanism is probably the destruction of E.coli due to the production of oxidants derivatives of oxygen caused by the applied electric field, which causes irreversible permeabilization of cell membranes 27 . The type of electrodes used in this study are graphite at the anode and stainless steel at the cathode; with short contact time, it was not possible to generate choline compounds for disinfection. This was confirmed with gas chromatographic analysis of the solution after disinfection with electro-oxidation at optimum conditions for detecting any chlorinated by-products (DBPs) as a result of generation of chlorin compounds (Fig. 6 ) and free chlorin determination in the solution. The results showed no detection of any halogenated or chlorinated compound in the solution. Accordingly, the mechanism of inactivation of E. coli in this study is the electro-disinfection by oxygen gas. 3.3 Application of elect-disinfection on real wastewater under continuous operation The results obtained in the previous section indicated that electro-disinfection could be applied at detention time up to 5 min in the highest bacterial concentration and current density of 4 mA/cm 2 . At this optimum condition, wastewater from secondary wastewater treatment plant and agricultural drainage was subjected to electro-disinfection continuously to simulate a full-scale electro-oxidation treatment cell. The treated wastewater was collected every min to investigate the best time for disinfection for each type of wastewater. 3.3.1 Application of drainage wastewater The raw drainage wastewater was subjected to disinfection by applying current density of 4 mA/cm 2 , TDS of 987 mg/L, and a hydraulic retention time of 5 min. At the start of the experiment, samples were collected from the effluent at zero time and every min till 5 min, representing the actual retention time. The results depicted in Fig. 7 indicated that the bacterial densities of total heterotrophic bacteria, coliform group (TC, FC, and E. coli ), and some pathogenic species, including P.aeruginosa, B.subtilis, Vibrio spp., and S.typhie was, initially enumerated in all samples before and after disinfecting with ED within varying exposure time. The average log counts was 6.2, 6.6, 4.6, 3.6, 3.2, 2.3, 3.13, 3.17, 2.6, and 2.2 CFU/mL, respectively for HPC at 37 o C, HPC at 22 o C, TC, FC, E.coli, P.aeruginosa, B.subtilis, Vibrio spp., and S. typhie . The results showed that E. coli and pathogenic bacteria were completely eradicated after 3 min exposure time. This result is in agreement with the obtained results from batch experiments on the synthetic wastewater under the same conditions. As the TDS concentration is about 1000 mg/L, the whole electro-disinfection time was about 5 min, with slight residuals of total bacterial counts still existing. In addition, the high bacterial load in the wastewater affected the time required for the disinfection. Likewise, the sample was collected during continuous experiments and subjected to the physico-chemical characterization, as depicted in Table 1 . The results showed slight removal of chemical pollutants, which is expected due to the short treatment time. Similarly, there was no detection of chlorinated organic compounds such as THMs, indicating no formation of chlorin derivatives as a result of electrolysis. From the outcomes mentioned above, it could be concluded that the utilization of lower current density may avoid higher power consumption for the disinfection process. The complete inactivation of E. coli was attained with 5min contact time, 4 mA/cm 2 of current density, and 1000 mg/L of TDS concentration. These optimized conditions would be involved in the disinfection strategy in wastewater treatment steps. Table 1 Physico-chemical characterization of agricultural drainage water before and after electro-disinfection. Parameters Units Result Before After Flow rate mL/min 360 HRT min 5 Operation time min 30 mins pH -- 7.14 7.35 Total dissolved solids mg/L 987 1071 Total suspended solids mg/L 15 10.5 Chemical oxygen demand mgO 2 /L 36 25 Biochemical oxygen demand mgO 2 /L 12 9 Ammonia mg/L 3 ND Total sulfides mg/L 2 ND Oil and grease mg/L 8 2 Tri-halomethane µg/L N.D 3.3.1 Application of secondary treated municipal wastewater Due to the excessive microbial burdens inherent in wastewater effluents, disinfection operations for effluents have become necessary to improve wastewater treatment facilities' performance and eradicate dangerous bacteria 28 . Within wastewater, a vast range of pathogenic organisms survive, but if not effectively managed, they can cause a significant threat to public health 29 . As during ultimate effluent release, wastewater effluents may transport harmful microbes into watersheds. Some dangerous diseases such as cholera, typhoid, and hepatitis A may occur due to polluted rivers. Polluted rivers might damage sea life, notably seafood, cockles, and shrimp. Those who consume this poisoned seafood risk getting extremely unhealthy 30 . Therefore, the secondary treated wastewater was subjected to continuous electro-disinfection as done for drainage wastewater. The experiment was carried out at a current density of 4 mA/cm2, the TDS was found to be 1987 mg/L, and the hydraulic retention time was adjusted to 3 min. The samples were collected every minute, starting from zero to 5 min, to investigate the time of electro disinfection. The results depicted in Table (2) and Fig. 8 . showed complete removal of all bacterial indicators after the first min. Monitoring the bacterial densities of HPC at 37 o C, HPC at 22 o C, TC, FC, E.coli , P.aeruginosa, B.subtilis, Vibrio spp., and S. typhie showed that a comprehensive decline in the number of bacteria occurred after 2 min of exposure time. Also, secondary treated although containing significant amount of COD value is present, mor than 50% removal of this organic matter was removed as result of electro-oxidation. investigated of halogenated organic compounds indicated no formation of these compound during the disinfection process. Electrochemical disinfection, analogous to standard chemical disinfection strategies, would indeed happen subsequent to clarification system and filtration processes in water purification 31 . Hence, the wastewater sample after secondary treatment was selected to be disinfected with ED. It is well-known that the microbial population densities in secondary treated wastewater are lower than in untreated or raw wastewater, as the treatment process could efficiently reduce the microbial load during the operational process. Up to 99% of fecal indicator bacteria (FIB) can be dismissed using primary and secondary treatment processes 32 . According to the FIB levels in the influent, this level of reduction may not be adequate to fulfill the standard of the specifications for using handled domestic wastewater for agriculture and irrigations uses and enabling leisure activities in receiving water bodies 33 . Table (2): Physico-chemical characterization of secondary wastewater before and after electro-disinfection. Parameters Units Result Before After Flow rate mL/min 600 HRT min 3 Operation time min 30 min pH -- 7.1 7.54 Total dissolved solids mg/L 1997 2080 Total suspended solids mg/L 15 10.5 Chemical oxygen demand mgO 2 /L 52 23 Biochemical oxygen demand mgO 2 /L 21 11 Ammonia mg/L 3.2 ND Total sulfides mg/L 2 ND Oil and grease mg/L 9 2.5 Tri-halomethane µg/L N.D 3.4 Techno-economic evaluation Electro-disinfection in this study involved creating a direct current (DC) by graphite anode and stainless steel cathode that pass through the water and prohibit the growth of microbes. The results obtained showed some technical benefits, including ease of use and installation, simple equipment, and high-performance treatment effectiveness 34 . requirement less energy, making it affordable and ecologically friendly technology, and it might be operated using fuel batteries or solar system 9 . As a result, the inactivation effectiveness of E. coli was studied using a variety of process factors, including the. The optimized settings were utilized to disinfect real wastewater samples. The optimum operating conditions for this study are pH 7–8, TDS > 2000, Current density 4 mA/cm 2, and operation time 3–5 min. At these optimum conditions, real wastewater samples were adjusted to continuous flow in the reactor through feeding with peristaltic pump to simulate the actual application of such treatment technology. After the continuous experimental study on the different operating parameters, the operational cost was calculated based on the operation time and electrical consumption. Data depicted in Table 3 displayed the complete elimination of the initial log count (3.2 CFU/mL) of E.coli in real drainage wastewater after 3 min of operation. Further, the results revealed this study's cost estimation and power consumption. Based on the commercial prices in Egypt, the cost of electricity for commercial use is L.E 1.6 /kWh (about 0.09 $ / kWh). The cost of sodium chloride added to the solution to increase the TDS to 2000 mg/L was calculated based on the amount required was 1.2 kg/m 3, and the cost of commercial salt is 0.25 L.E/kg. Accordingly the cost of added sodium chloride salt is 0.3L.E/m 3 (0.15 $ /m 3 ) the operation cost at 4 mA/cm 2 ranged from 0.57 L.E/ m 3 (0.03 $ /m 3 ) to 1.7 L.E/m 3 (0. 89 $ /m 3 ). The operating cost at the optimum conditions (TDS 2000, 4mA/cm 2 and 3 min) were calculated as 1.13 L.E/ m 3 (0.06 $ /m 3 ). This cost is meager compared to conventional disinfection methods that could achieve the same efficiency. Table (3): Electrical consumption and cost estimation at optimum operating conditions. Time (min) Current density Log removal of E.coli Electrical consumption(kWh/m 3 ) Total running cost ( $ /m 3 ) 0 4 mA/cm 2 0 0.0 0.0 1 0.8 0.2 0.030 2 1.4 0.3 0.045 3 3.2 0.5 0.060 4 3.2 0.7 0.074 5 3.2 0.9 0.089 From these calculations, Electro-disinfection is a promising solution for application in wastewater treatment plants because of its modular design, high efficiency, and ease of automation and transportation. This study looked at three different treatment scenarios: water treatment, centralized wastewater treatment, and distributed wastewater treatment 35 . 4. Conclusion In this study, electro-disinfection of the bacterial indicator is dependent on current density, time, and TDS concentration. E.coli was found to completely remove after 5 mins time TDS 1000 mg/L and 4 mA/cm 2 current density at initial E.coli log count of 6.6 CFU/ml. The increase in current density and Current and TDS concentration decreased the time required for disinfection. However, from the economic point of view, this might increase operating costs due to high power consumption and chemical added to increase the TDS. The electro-oxidation unit configuration with the order of the electrodes had a determining impact on the reactor performance; the cathode–anode configuration and types also directed the electro disinfection type to oxygen gas disinfection. The added chloride concentrations did not significantly affect free chlorine production in the reactor. Cost analysis for disinfection of secondary wastewater treatment effluent indicated that graphite and stainless steel electrodes in an electro-disinfection unit are more appropriate due to low power consumption (0.5 kWh/m 3 ) and low operating cost (0.06 $ /m 3 ) compared to conventional methods. Declarations Competing interests: The authors have no competing interests Data availability : The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. References Abou-Taleb, E. M. et al. Sustainable solutions for urban wastewater management and remediation. Egypt. J. Chem. 63 , 405–415 (2020). Bracher, G. H., Carissimi, E., Wolff, D. B., Glusczak, A. G. & Graepin, C. Performance of an electrocoagulation-flotation system in the treatment of domestic wastewater for urban reuse. Environ. Sci. Pollut. Res. (2022) doi: 10.1007/s11356-022-20630-2 . Vasilyak, L. M. Physical Methods of Disinfection (A Review). Plasma Physics Reports vol. 47 318–327 (2021). Burch, J. D. & Thomas, K. E. Water disinfection for developing countries and potential for solar thermal pasteurization. Sol. Energy 64 , 87–97 (1998). Blanc, D. S., Carrara, P., Zanetti, G. & Francioli, P. Water disinfection with ozone, copper and silver ions, and temperature increase to control Legionella: Seven years of experience in a university teaching hospital. J. Hosp. Infect. 60 , 69–72 (2005). Malato, S., Fernández-Ibáñez, P., Maldonado, M. I., Blanco, J. & Gernjak, W. Decontamination and disinfection of water by solar photocatalysis: Recent overview and trends. Catalysis Today vol. 147 1–59 (2009). HAWRYLIK, E. Methods Used in Disinfections of Wastewater and Sewage Sludge – Short Review. Archit. Civ. Eng. Environ. 13 , 57–63 (2020). Huang, X. Microbial Pathogen Detection and Removal in Water Reuse Practices. ProQuest Dissertations and Theses (2015). Martínez-Huitle, C. A. & Brillas, E. A critical review over the electrochemical disinfection of bacteria in synthetic and real wastewaters using a boron-doped diamond anode. Curr. Opin. Solid State Mater. Sci. 25 , 100926 (2021). Raut, A. S. et al. Reduction in energy for electrochemical disinfection of E. coli in urine simulant. J. Appl. Electrochem. 49 , 443–453 (2019). Huang, X. et al. Electrochemical disinfection of toilet wastewater using wastewater electrolysis cell. Water Res. 92 , 164–172 (2016). Rahmani, A. R., Nematollahi, D., Poormohammadi, A., Azarian, G. & Zamani, F. Electrodisinfection of bacteria-laden in surface water using modified Ti electrode by antimony-and nickel-doped tin oxide composite. Chemosphere 263 , (2021). Abou-Taleb, E. M., Hellal, M. S. & Kamal, K. H. Electro‐oxidation of phenol in petroleum wastewater using a novel pilot‐scale electrochemical cell with graphite and stainless‐steel electrodes. Water Environ. J. 35 , 259–268 (2021). da Silva, A. J. C., dos Santos, E. V., de Oliveira Morais, C. C., Martínez-Huitle, C. A. & Castro, S. S. L. Electrochemical treatment of fresh, brine and saline produced water generated by petrochemical industry using Ti/IrO2-Ta2O5 and BDD in flow reactor. Chem. Eng. J. 233 , 47–55 (2013). Abou-Taleb, E.., Hellal, M. ., Abdel-Salam, O. E. & Abdel Maksod, A. Innovative model for the application of electrochemical oxidation of high organic load wastewater treatment. (2021) doi: https://search.egpo.gov.eg/?radio-34=patent-utility-model#/search/result/patent-utility-model?q=FP%3A30235 . APHA. Standard Methods for the Examination of Water and Wastewater . American Water Works Association/American Public Works Association/Water Environment Federation (2017). Herraiz-Carboné, M. et al. Disinfection of polymicrobial urines by electrochemical oxidation: Removal of antibiotic-resistant bacteria and genes. J. Hazard. Mater. 426 , (2022). A. Hemdan, B., Azab El-Liethy, M. & El-Taweel, G. E. The destruction of Escherichia coli adhered to pipe surfaces in a model drinking water distribution system via various antibiofilm agents. Water Environ. Res. 92 , 2155–2167 (2020). Ghasemian, S., Asadishad, B., Omanovic, S. & Tufenkji, N. Electrochemical disinfection of bacteria-laden water using antimony-doped tin-tungsten-oxide electrodes. Water Res. 126 , 299–307 (2017). Schmalz, V., Dittmar, T., Haaken, D. & Worch, E. Electrochemical disinfection of biologically treated wastewater from small treatment systems by using boron-doped diamond (BDD) electrodes - Contribution for direct reuse of domestic wastewater. Water Res. 43 , 5260–5266 (2009). Lakshmi, E., Priya, M. & Achari, V. S. An overview on the treatment of ballast water in ships. Ocean Coast. Manag. 199 , 105296 (2021). Trigueiro, L. F. et al. Inactivation, lysis and degradation by-products of Saccharomyces cerevisiae by electrooxidation using DSA. Environ. Sci. Pollut. Res. 24 , 6096–6105 (2017). Collivignarelli, M. C., Abbà, A., Benigna, I., Sorlini, S. & Torretta, V. Overview of the main disinfection processes for wastewater and drinking water treatment plants. Sustain. 10 , 1–21 (2018). Kourdali, S., Badis, A., Boucherit, A., Boudjema, K. & Saiba, A. Electrochemical disinfection of bacterial contamination: Effectiveness and modeling study of E. coli inactivation by electro-Fenton, electro-peroxi-coagulation and electrocoagulation. J. Environ. Manage. 226 , 106–119 (2018). Sillanpää, M. & Shestakova, M. Electrochemical Water Treatment Methods. in Electrochemical Water Treatment Methods 47–130 (Elsevier, 2017). doi: 10.1016/B978-0-12-811462-9.00002-5 . Kraft, A. Electrochemical Water Disinfection: A Short Review ELECTRODES USING PLATINUM GROUP METAL OXIDES. Platin. Met. Rev. 52 , 177–185 (2008). López-Gálvez, F. et al. Electrochemical disinfection: An efficient treatment to inactivate Escherichia coli O157:H7 in process wash water containing organic matter. Food Microbiol. 30 , 146–156 (2012). Gheethi, A. A. Al, Efaq, R. M. M. A. N. & Adib, I. N. M. R. Reduction of bacteria in storage system of sewage effluents. Sustain. Water Resour. Manag. 3 , 193–203 (2017). Ibrahim, E. M. M. E. M., El-Liethy, M. A., Abia, A. L. K., Hemdan, B. A. & Shaheen, M. N. Survival of E. coli O157:H7, Salmonella Typhimurium, HAdV2 and MNV-1 in river water under dark conditions and varying storage temperatures. Sci. Total Environ. 648 , 1297–1304 (2019). Mohamed, R. M. S. R. et al. Bioaugmentation process of secondary ef fl uents for reduction of pathogens, heavy metals and antibiotics. 780–795 (2016) doi: 10.2166/wh.2016.046 . Sowah, R., Zhang, H., Radcliffe, D., Bauske, E. & Habteselassie, M. Y. Evaluating the influence of septic systems and watershed characteristics on stream faecal pollution in suburban watersheds in Georgia, USA. J. Appl. Microbiol. 117 , 1500–1512 (2014). Fouad, H. A., Hefny, R. M., Kamel, A. M. B. M. M., El-Liethy, M. A. & Hemdan, B. A. Bioaugmentation and Advanced Oxidation Process for Organic and Inorganic Pollutants Removal and Pathogenic Bacteria Inactivat El-Rahawy Drain, Egypt. Egypt. J. Chem. 63 , 4075–4082 (2020). Nasr, F. A., El-Shafai, S. A., Abdelfadil, A. S., Ibrahim, H. S. & Hemdan, B. A. Potential use of treated domestic sewage for cultivation of biofuel crops in Egypt. Int. J. Environ. Sci. Technol. (2018) doi: 10.1007/s13762-018-2101-4 . Sayinli, B., Dong, Y., Park, Y., Bhatnagar, A. & Sillanpää, M. Recent progress and challenges facing ballast water treatment - A review. Chemosphere 291 , 132776 (2022). Yang, Y. Recent advances in the electrochemical oxidation water treatment: Spotlight on byproduct control. Front. Environ. Sci. Eng. 14 , (2020). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major revision 24 Aug, 2022 Reviews received at journal 26 Jul, 2022 Reviewers agreed at journal 14 Jul, 2022 Reviewers agreed at journal 06 Jul, 2022 Reviewers invited by journal 05 Jul, 2022 Editor assigned by journal 05 Jul, 2022 Editor invited by journal 05 Jul, 2022 Submission checks completed at journal 05 Jul, 2022 First submitted to journal 29 Jun, 2022 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Hellal","email":"","orcid":"","institution":"National Research Centre","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mohamed","middleName":"S.","lastName":"Hellal","suffix":""},{"id":118681748,"identity":"34b89621-7c0d-4850-aeea-674baea68870","order_by":1,"name":"Bahaa A. Hemdan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACAwYeKIu9gYGZRC08B0jWIpFApBZz9rMHP/xguJPPP/ON4eeCChsG/vbuBLxaLHvykiV7GJ5ZzridYyw940wag8SZsxvwO+xAjoEED8NhAwPpHANp3rbDDAYSuQS0nH9j/PMPSIvkGePfxGm5kWMmDbZFgseMOFssZ7wxs5YBapE4k1ZmzXMmjYegX8z5c4xvvgFq4W8/vPk2T4WNHH97L34tYMD4D0RyGIBIHvxKUQH7A1JUj4JRMApGwQgCAGRQQWFRpJnRAAAAAElFTkSuQmCC","orcid":"","institution":"National Research Centre","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Bahaa","middleName":"A.","lastName":"Hemdan","suffix":""},{"id":118681749,"identity":"a464634d-2511-49ac-8b7b-a9b5154c08e1","order_by":2,"name":"Marwa Youssef","email":"","orcid":"","institution":"National Research Centre","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Marwa","middleName":"","lastName":"Youssef","suffix":""},{"id":118681750,"identity":"31f9a63d-06df-4c1b-9c3e-8da738bd158b","order_by":3,"name":"Gamila El-TAweel","email":"","orcid":"","institution":"National Research Centre","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Gamila","middleName":"","lastName":"El-TAweel","suffix":""},{"id":118681751,"identity":"d468fb3d-124c-41ee-8862-8d9522c3a568","order_by":4,"name":"Enas M. Abou Taleb","email":"","orcid":"","institution":"National Research Centre","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Enas","middleName":"M. Abou","lastName":"Taleb","suffix":""}],"badges":[],"createdAt":"2022-06-29 22:29:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1809352/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1809352/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":23823348,"identity":"ae3b7569-25af-4a86-8f5b-5fd27c15dbf2","added_by":"auto","created_at":"2022-07-13 16:40:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":69734,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eElectrooxidation treatment cell\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/7528762b2be9f0f5b13076c7.png"},{"id":23823347,"identity":"242056c0-6450-4c47-96ef-2e07b2c9959c","added_by":"auto","created_at":"2022-07-13 16:40:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":53594,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of treated time (1-15 min) on \u003cem\u003eE.coli\u003c/em\u003e during electrochemical inactivation treatment. Experimental data are shown as mean ± standard deviation (n = 3).\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/764684dbc490bf0c86593aad.png"},{"id":23823994,"identity":"11f9245f-aa59-41f6-b090-42476401b0a8","added_by":"auto","created_at":"2022-07-13 16:50:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":69293,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of different current densities (2-8 mAm/cm\u003csup\u003e2\u003c/sup\u003e) on \u003cem\u003eE.coli\u003c/em\u003e bacterial inactivation during electrochemical inactivation treatment of solutions containing initial concentration of ∼10\u003csup\u003e6\u003c/sup\u003e\u0026nbsp;CFU/mL \u003cem\u003eE.\u0026nbsp;coli\u003c/em\u003e. Experimental data are shown as mean value\u0026nbsp;± standard deviation (n=3).\u003c/p\u003e","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/6d14403ffb057e14ef3b2c42.png"},{"id":23823350,"identity":"38888d49-434f-480a-9d1b-c9784e3397ab","added_by":"auto","created_at":"2022-07-13 16:40:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":107904,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of different concentrations of electrolyte concentration\u0026nbsp;(17.5 -87.5 mM NaCl) on \u003cem\u003eE.coli\u003c/em\u003e during electrochemical inactivation treatment Experimental data are shown as mean ± standard deviation (n = 3).\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/6bd9532e57b5c6731ea343c9.png"},{"id":23823354,"identity":"df47841f-40fb-4b9e-aee2-96cf739e5418","added_by":"auto","created_at":"2022-07-13 16:40:44","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":142823,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of various bacterial populations on \u003cem\u003eE.coli\u003c/em\u003e during electrochemical inactivation treatment. Experimental data are shown as mean ± standard deviation (n = 3).\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/d23c225cb91e45315c14c27b.png"},{"id":23823799,"identity":"d91b0c01-e10f-4ecf-b860-bce65dc30caf","added_by":"auto","created_at":"2022-07-13 16:45:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":65403,"visible":true,"origin":"","legend":"\u003cp\u003eGas chromatography scan of chlorinated compounds for the solution after disinfection\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/ec2511c258e66a1d526c1412.png"},{"id":23823352,"identity":"dc8543c5-82b4-46c4-87d7-432e713e9dd9","added_by":"auto","created_at":"2022-07-13 16:40:43","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":101140,"visible":true,"origin":"","legend":"\u003cp\u003eEfficacy of electrochemical disinfection, as a function of time, of some waterborne pathogens for drainage wastewater under stable conditions.\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/cae2c895caf383af5a18d031.png"},{"id":23823353,"identity":"25b5fcfb-7f60-47e7-9dd3-7f4368cfb9b4","added_by":"auto","created_at":"2022-07-13 16:40:43","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":56930,"visible":true,"origin":"","legend":"\u003cp\u003eEfficacy of electrochemical disinfection, as a function of time, of some waterborne pathogens for drainage wastewater under stable conditions. \u003c/p\u003e\u003cp\u003e\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/41c5b839a497094792563ba6.png"},{"id":23823995,"identity":"58226334-d006-42c7-a9d8-57484d6a11c0","added_by":"auto","created_at":"2022-07-13 16:50:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":999741,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1809352/v1/b5ae69b5-f1a0-4ffa-a494-33fe3a7a2a79.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Novel electro-oxidation unite for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: Batch and continuous experiments","fulltext":[{"header":"1. Introduction","content":" \u003cp\u003eInconsistencies between water availability and demand are increasing worldwide, especially in countries suffering from water scarcity like Egypt. By the year 2050, urban areas in these countries will be susceptible to water scarcity due to an increase of 80% in urban water demand due to rapid population \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. To close the gap between water demand and supply, the reliance should be on alternative water sources such as reusing treated municipal wastewater. Tertiary or advanced treatment is necessary for urban reuse of municipal wastewater\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. However, disinfection of this treated wastewater is mandatory to safely reuse as residual microbial pollutants such as \u003cem\u003eEscherichia coli\u003c/em\u003e still exist in the treated wastewater. Disinfection is unquestionably crucial in the water treatment process to yield safe water free from these pathogenic microorganisms. Classification of water disinfection methods could be three broad groups; chemical, physical, and physicochemical. Physical disinfection depends mainly on physical processes without any chemical that does not involve chemicals and relies on physical means without adding a chemical that may change water properties \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. These methods varied between thermal disinfection (heating/boiling), ultra-sonication, membrane filtration, and UV irradiation \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. However, this disinfection method has several disadvantages, such as the need for a long time, many personnel to monitor flushing times and temperatures of the water tanks, and only effective for a short term \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Another type of disinfection is the chemical method that uses chemical compounds to deactivate waterborne pathogens in water and wastewater. The common chemical disinfectants utilized in wastewater are sodium hypochlorite, chlorine dioxide, hydrogen peroxide ozone, (mono) chloramine, and chlorine gas, the most used among them \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. The side effects of chemical disinfection became harmful to human health and the environment as a result of the formation of toxic organic compounds such as chlorinated by-products (DBPs), besides the high price of chemicals and energy\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Physiochemical disinfection includes chemical and physical approaches such as electro-disinfection in which mixed oxidants (disinfection agents) are formed from electrolytic cells\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Recently there was a great tendency to use electro-disinfection as an important alternative technic to chemical disinfection for upcoming years \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. This new technology can achieve an acceptable level of disinfection for treated wastewater with limited chemical additions in a short time. The mechanism of electro-disinfection is based on the destruction of microorganisms by passing an electric current through the water using appropriate electrodes. Pathogenic bacteria are destroyed by various oxidants that are produced during the electrolysis of water\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. There are two categories of electrochemical disinfection devices; electrolysers, which is based on the direct interaction with contaminated water, and mixed oxidant generators, which use a concentrated brine solution to generate oxidizing species (e.g. free chlorine [Cl\u003csub\u003e2\u003c/sub\u003e], chlorine dioxide [ClO\u003csub\u003e2\u003c/sub\u003e], ozone [O\u003csub\u003e3\u003c/sub\u003e], hydrogen peroxide [H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e], and other short-lived radicals) that can enhance the overall disinfection efficiency\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. In free chloride waters, the oxidation of water on the anode surface produces physisorbed hydroxyl radicals M (\u003csup\u003e\u0026bull;\u003c/sup\u003eOH). At a limited release rate, \u003csup\u003e\u0026bull;\u003c/sup\u003eOH reacts non-selectively with waterborne pathogenic agents or with a wide range of recalcitrant organics \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. When the chloride is present, whether it is naturally present (e.g., toilet, wastewater, seawater) or is added artificially, reactive chlorine species (RCS) such as free chlorine ([Cl\u003csub\u003e2\u003c/sub\u003e], [HOCl], [ClO\u003csup\u003e\u0026minus;\u003c/sup\u003e]) and chlorine radical species ([\u003csup\u003e\u0026bull;\u003c/sup\u003eCl\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e], [\u003csup\u003e\u0026bull;\u003c/sup\u003eCl]) are generated and considered as primary disinfectants \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. In wastewaters, the organic matter could be oxidized in the electrolytic cell through two mechanisms: (i) Direct oxidation via a direct electron transfer to the anode, and (ii) mediated oxidation via the electro-generation of oxidizing species from wastewater itself or supporting electrolyte oxidation at the anode at high intensity\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe types of electrochemical cells used in disinfection varied between electro-oxidation, electro-coagulation, and electrolysis. Electro-oxidation is the most functional unit as it is non-consumable, can generate oxidants without chemical addition, and disinfection can occur directly through electron transfer to the anode\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. The factors affecting the degree of elect-disinfection are cell design, electrode types and shapes, time, electrolyte conductivity, applied current density, and pathogen concentration. The type and composition of the anode is a significant factor that plays an essential role in the efficiency of the electrochemical disinfection process because it affects the generation of oxidants and determines their nature and their oxidation power. Previous studies have used various electrodes such as platinum, titanium, stainless steel, graphite, PbO\u003csub\u003e2\u003c/sub\u003e, boron-doped diamond (BDD), carbon-cloth, graphite and silicone rubber, and so on\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Other operational parameters, such as current intensity, cell voltage, reaction time, pH, and temperature, are also crucial in the optimization of the electrochemical disinfection process. Optimizing these factors is very important in terms of a techno-economic point of view. Consequently, the main aim of this analysis is to implement a revolutionary, affordable electro-oxidation system to evaluate operational parameters for electro-disinfection of municipal wastewater. The extraordinary circumstances are time, current density, NaCl, and bacterial population. The preferred circumstances for the operating system were engaged for the inactivation of bacterial populations in both actual wastewater and synthetic contaminated water.\u003c/p\u003e"},{"header":"2. Materials And Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Electro-oxidation reactor design and\u003c/h2\u003e \u003cp\u003eIn this study, the experimental setup is given schematically in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e Electro-disinfection treatment was done in an electro-oxidation cell in an electrolytic cell designed based on patent No. EGPO 30235 \u003csup\u003e15\u003c/sup\u003e is made of a Perspex glass container with a net volume 3L. and fabricated of Perspex glass material container with a net volume 3L. The EC unit has dimensions of 12.5 cm \u0026times;12 cm \u0026times;20 cm (L\u0026times; W\u0026times; H), while the water level was kept below 5 cm resulting an effective volume of 2.25 liter. Nine identical cylindrical shape electrodes were distributed in three horizontal, and two rows have 6 graphite electrodes between; one contains three stainless electrodes with a binary distance between all electrodes of 2 cm. Each electrode has 15 cm height and 1.6 cm diameter and volume of about 12 cm\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003c/sup\u003e and the working surface area is 0.054 m\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Accordingly, the total volume of the electrodes in the cell is 0.24 liter, which means that the adequate volume of the cell is about 2 liters. The electrodes were connected to the D.C power supply with a variable output voltage range from 0\u0026ndash;30 volt and current from 0 to 10 ampere. The treatment runs were performed at constant temperature (25˚C), mixing speed (250 rpm), and with 2 L of synthetic contaminated solution.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Operating conditions\u003c/h2\u003e \u003cp\u003eThe study is conducted in several experimental runs; each one represents operational parameters such as contact time, conductivity, microorganisms count, and current density. The effect of operational time was investigated by applying current density of 2 mA/cm\u003csup\u003e2\u003c/sup\u003e at TDS 1000 mg/L for 30 min. The current density was investigated for values of 2, 4, 6, and 8 mA / cm\u003csup\u003e2\u003c/sup\u003e at the determined optimum time. Effect of electrolyte concentration was analyzed by preparation of electrolyte solution of sodium chloride (NaCl) with the concentration of 17.5, 35, 52.5, 70, and 87.5 mM to obtain TDS values of 1000, 2000, 3000, 4000, nd 5000 mg/L whiledifferent biomasses and bacterial densities were evaluated at the received optimum time, TDS and current density. In each experiment, treated samples were collected in sterile tubes; bacterial concentration was evaluated for treated and control samples. Before each run, the electrodes were washed to remove any surface attachments and impurities on electrodes with a solution freshly prepared by mixing 100 mL of HCl solution (35%) and 200 mL of chloroform solution. After the electrodes had been washed, they were dried in the oven at 105\u0026ordm;C to remove the residuals on their surfaces of any bacterial contamination.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Wastewater sources\u003c/h2\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.3.1 Simulated wastewater\u003c/h2\u003e \u003cp\u003eThis study used simulated wastewater containing non-pathogenic E. coli as a model microorganism. The bacterial stock culture was obtained by seeding some pure colonies in sterile nutrient broth medium (5 mL) incubated at 37\u0026deg;C for 24 hours. Fresh Hektoen medium (500 mL) was used to inoculate 3% (v/v) of this culture for two incubation times (24 h/each at 37\u0026deg;C). Before any experiment, a certain amount of \u003cem\u003eE. coli\u003c/em\u003e culture (100 mL) was centrifuged at 6000 rpm for 10 min. The obtained biomass was washed twice with sterile standard saline solution (9 g/L NaCl). After centrifugation, it was subsequently resuspended in the sterile solution of distilled water and sodium chloride with different concentrations to achieve a final concentration of around 10\u003csup\u003e6\u003c/sup\u003e -10\u003csup\u003e7\u003c/sup\u003e CFU/mL.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.3.2 Real wastewater\u003c/h2\u003e \u003cp\u003eAfter obtaining optimum operating conditions, two real wastewater sources were collected and subjected to an electrooxidation unit. The first source is the agricultural drain in Menufia governorate that receive agricultural drainage water mixed with the sewage water. The other source is the effluent from the secondary treatment wastewater treatment plant at Giza, Egypt. prior chlorine tank. The wastewater was fed continuously using a peristaltic pump at the optimum conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.4. wastewater analysis\u003c/h2\u003e \u003cp\u003eFor each experimental run, bacterial indicators, pH, and NaCl were analyzed. To evaluate the bacterial concentration in each experiment after the treatment of the water sample (level of removal of \u003cem\u003eE. coli\u003c/em\u003e by electrochemical disinfection), influent and effluent samples were collected in sterile tubes. Influent samples were serially diluted in a standard saline solution. Diluted and undiluted samples (1.0 mL) were seeded in triplicate on nutrient agar plates and incubated at 37\u0026deg;C for 24 h.\u003c/p\u003e \u003cp\u003eFor real wastewater samples, complete analysis was characterized at optimum conditions in terms of pH, (COD), biological oxygen demand (BOD), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH\u003csub\u003e4\u0026thinsp;\u0026minus;\u0026thinsp;N\u003c/sub\u003e), nitrite (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{N}\\text{O}}_{2}^{-}\\)\u003c/span\u003e\u003c/span\u003e). nitrate (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\text{N}\\text{O}}_{3}^{-}\\)\u003c/span\u003e\u003c/span\u003e), oil and grease total phosphorus and trihalomethanes beside the bacterial indicators heterotrophic bacteria, total coliform, fecal coliform (thermophilic), \u003cem\u003eStreptococcus faecalis\u003c/em\u003e, and \u003cem\u003ePseudomonas aeruginosa.\u003c/em\u003e Heterotrophic bacteria were measured in R2A agar medium by counting colonies formed for each plate (colony-forming unit (CFU)). These analyses, unless otherwise specified, were performed according to the Standard Methods for the Examination of Water and Wastewater\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Calculation of removal efficiency, operating cost, and energy consumption,\u003c/h2\u003e \u003cp\u003eThe percentage removal efficiency r was calculated using Eq.\u0026nbsp;(1):\u003c/p\u003e \u003cp\u003e% Removal =\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{C\u0026acirc;\u0026circ;?-C}{C\u0026acirc;\u0026circ;?} ?\u0026mdash;100\\)\u003c/span\u003e\u003c/span\u003e (1)\u003c/p\u003e \u003cp\u003ewhere C\u003csub\u003e0\u003c/sub\u003e is the initial concentration and C is the final concentration of the pollutant\u003c/p\u003e \u003cp\u003eThe operating cost is one of the most critical parameters in the EC process because it affects the application of any wastewater treatment method. The operating price includes material (mainly electrodes), electrical energy, labor, maintenance, and other expenses. The latter cost items are mainly independent of the electrode material. Thus, this study calculated the operating cost as electrical energy costs. The energy consumption is consumption quantities per m\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e of wastewater treated. calculation of energy consumption is expressed as in Eq.\u0026nbsp;(2)\u003c/p\u003e \u003cp\u003eE\u003csub\u003e\u003cem\u003eC\u003c/em\u003e\u003c/sub\u003e =\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{(V?\u0026mdash;I?\u0026mdash;t)}{v}\\)\u003c/span\u003e\u003c/span\u003e (2)\u003c/p\u003e \u003cp\u003ewhere E\u003csub\u003e\u003cem\u003eC\u003c/em\u003e\u003c/sub\u003e is energy consumption (kWh/m\u003csup\u003e3\u003c/sup\u003e), V is voltage (Volt), I is current (Ampere), t is contact time (seconds), and v is the volume of the treated wastewater (m\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e), respectively.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results And Discussions","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Electro-disinfection of synthetic microbial contaminated water\u003c/h2\u003e \u003cp\u003eThe bacteria \u003cem\u003eE. coli\u003c/em\u003e was selected as models of pathogens for the preparation of synthetic wastewater in the disinfection study due to its high environmental and sanitary risks. The electro-disinfection of synthetic water contaminated with the \u003cem\u003eE.coli\u003c/em\u003e bacteria was studied in terms of operational characteristics such as the concentration of \u003cem\u003eE.coli\u003c/em\u003e as a function of the experimental time period of exposure, current density, TDS, and microbial cell densities.\u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e3.1.1 Effect of electro-disinfection contact times\u003c/h2\u003e \u003cp\u003eThe effect contact time was carried out at the current density of 4 mA/cm\u003csup\u003e2\u003c/sup\u003e and electrolyte concentration of 17.5 mM NaCl (1000 mg/L) with initial \u003cem\u003eE.coli\u003c/em\u003e log count of 3.2 CFU/mL. Samples were collected in sterile tubes every min, starting from zero to 15min. The results in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e show that a 100% \u003cem\u003eE. coli\u003c/em\u003e elimination occurred at the third min of contact time. \u003cem\u003eE.coli\u003c/em\u003e count was reduced to 1.2 and 1.9 CFU/mL after 1min and 2min exposure times, indicating that disinfection performance of more than 99.98% required a residence time of 2 min. The obtained time is auspicious, cost-effective and better than other electro-disinfection studies carried out by Herraiz-Carbon\u0026acute; et al.,\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, who studied disinfection polymicrobial urines from hospital wastewater using electro-oxidation unites. They achieved 4\u0026ndash;6 logs of bacterial removal after 180min using electrooxidation reactor with two boron-doped diamond and stainless-steel electrodes at the current density of 50 A/m\u003csup\u003e2\u003c/sup\u003e. Also, the results proved that electro-oxidation is significantly more effective than chemical disinfection using chlorine, where chlorination requires longer exposure (at least 30min) to achieve a bactericidal performance of 99.94% or higher \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Time is essential in designing a disinfection technique as it is related to power and chemicals consumption and capital construction\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Accordingly, the other operating parameters were studied as a function of time to determine their optimal values.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e3.1.2 Effect of Current Density\u003c/h2\u003e \u003cp\u003eThe current density is a significant factor as it determines the cost related to power consumption and also electrode dimensions. The effect of current density as a function of time on the electro-disinfection was carried out at electrolyte concentration of 17.5 mM NaCl (1000 mg/L) and doubled initial \u003cem\u003eE. coli\u003c/em\u003e log count (6.6 CFU/mL) with different current densities 2, 4, 6, 8 mA/cm\u003csup\u003e2\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the log reduction of \u003cem\u003eE.coli\u003c/em\u003e at different current densities. Application of 2 mA/cm\u003csup\u003e2\u003c/sup\u003e was not very efficient for removal of \u003cem\u003eE.coli\u003c/em\u003e, and the maximum log counts reduced was about 3.7 CFU/mL at 6 min. The reduction rate was fixed after this time, which indicated that more current is required for removal of high logs values. Increasing current density by two folds to be 4 mA/cm\u003csup\u003e2\u003c/sup\u003e showed a gradual reduction of \u003cem\u003eE.coli\u003c/em\u003e starting with a log reduction of 3.9 CFU/mL at the first min, reaching complete removal at the fourth min. The same behavior was observed at 6 mA/cm\u003csup\u003e2\u003c/sup\u003e as the gradual reduction was observed comparing the third min, at which complete removal achieved. The full reduction of \u003cem\u003eE. coli\u003c/em\u003e was performed within the first min at 8 mA/cm\u003csup\u003e2\u003c/sup\u003e, indicating that the contact time could be seconds at that current density. The results are consistent with those of Ghasemian et al.,\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e who proved that increasing the current density from 0.2 to 1 mA/cm\u003csup\u003e2\u003c/sup\u003e led to a more than 50% reduction in log10-bacterial concentration after 20 min, and within 5 min for 2 mA/cm\u003csup\u003e2\u003c/sup\u003e, 2 min for 4 mA/cm\u003csup\u003e2\u003c/sup\u003e using electrochemical cell with doped tin-tungsten-oxide electrodes. Increasing the applied current density resulted in enhanced inactivation efficacy of \u003cem\u003eE.coli\u003c/em\u003e. The main reason for this phenomenon is that increasing current densities accelerate the movement of the electrons, which increases the generation of more oxidizing species at the anode surface, which attack and destroy bacteria \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFurthermore, a tremendous amount of electrical charge will pass through the electrolyte with a more significant current density, potentially resulting in faster disinfection rates \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. However, from the economic point of view, the high current density could be not cost-effective due to the high consumption rate of electrical power. Accordingly, 4mA/cm\u003csup\u003e2\u003c/sup\u003e was chosen as the optimum current density.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.1.3 Effect of different electrolyte concentrations\u003c/h2\u003e \u003cp\u003eSynthetic wastewater was prepared with different electrolyte concentrations to obtain values of about 17.5, 35, 52.5, 70 and 87.5 mM NaCl, with corresponding TDS values from 1000 to 5000 mg/L. The experiment was carried out at a current density 2 mA/cm\u003csup\u003e2\u003c/sup\u003e and time up to 10min. The results in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e showed that TDS strongly affects the removal of \u003cem\u003eE.coli\u003c/em\u003e with electro-disinfection. The increase of TDS concentration in the electrolyte solution is accompanied by a high reduction of \u003cem\u003eE.coli\u003c/em\u003e in a shorter time. The electrolyte concentration of 17.5 mM NaCl (1000 mg/L) is not sufficient for the complete removal of \u003cem\u003eE.coli\u003c/em\u003e as the maximum log reduction achieved was about 5.5 CFU/mL after 6 min contact time. The initial log count of \u003cem\u003eE.coli\u003c/em\u003e dropped gradually over 4 min in a solution of 35 mM NaCl (2000 mg/L), while 3 min was enough for elimination of E.coli at 52.5 mM NaCl (TDS 3000 mg/L).\u003c/p\u003e \u003cp\u003eIn contrast, complete disinfection was achieved in a shorter time (2 min) for 70 and 87.5 mM NaCl (4000 and 5000 mg/L) as a whole log decrease (6.5 CFU/mL) was achieved with a current density of 4 mA/cm\u003csup\u003e2\u003c/sup\u003e. The performance of electro-disinfection has worsened at low TDS concentrations, which suggests at the respective current level of 2 mA/cm\u003csup\u003e2\u003c/sup\u003e, TDS concentrations of 2000 and 3000 mg/L were found to be sufficient for effective inactivation of \u003cem\u003eE. coli\u003c/em\u003e in this study. The results were directly compared with the previously reported findings by Ghasemian et al. \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e, where the complete disinfection of \u003cem\u003eE. coli\u003c/em\u003e in 100 mM NaCl was obtained at 2 min with the current density of 4 mA/cm\u003csup\u003e2\u003c/sup\u003e, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.1.4 Effect of cell densities of \u003cem\u003eE.coli\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eFrom the pervious obtained results above, the best condition for electro-disinfection is TDS concentration of 2000 mg/L( 35 mM NaCl), the current density of 4 mA/cm\u003csup\u003e2,\u003c/sup\u003e and the contact time up to 5 min. At these conditions, solutions are different \u003cem\u003eE. coli\u003c/em\u003e with three different bacterial densities (3.37 as a low, 6.31 as a moderate, 6.31, and 8.29 as an intense, high CFU/mL) was prepared and subjected to electro-disinfection. The inactivation of E. coli cells is seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. In truth, bacterial damage is evident at low cellular density. The results revealed that the low bacterial load (log 3.37 CFU) was destroyed within 3 min of treatment, and \u003cem\u003eE. coli\u003c/em\u003e cell survival was substantially and quickly reduced. Log 6.31 CFU of \u003cem\u003eE.coli\u003c/em\u003e was effectively inactivated after 4 min. The high bacterial population burden required a longer treatment time (6 min) to inactivate log 8.29 CFU/mL (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The findings align with previous research that shows that low densities of \u003cem\u003eE.coli\u003c/em\u003e cells might be easily killed in a shorter amount of time following inactivation \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. EC inactivation, chlorination, ozonation, and the Fenton reaction were all found to be successful in eliminating \u003cem\u003eE. coli\u003c/em\u003e with a starting density of 10\u003csup\u003e8\u003c/sup\u003e/mL from wastewater in their investigation. With an elimination rate of 99.4 percent or better, nearly all of the cells in the disinfected samples lost their viability in terms of being physiologically available for incubation \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Mechanism of \u003cem\u003eE. coli\u003c/em\u003e elimination using electro-oxidation\u003c/h2\u003e \u003cp\u003eThe mechanism of Electro disinfection using the electro-oxidation unit mainly depends on the generation of strong oxidants such as oxygen, ozone, or hypochlorite in the anode during water electrolysis. These chemical oxidants are produced when plunging electrodes apply electric current to aqueous microbe solutions. When the solution contains salts such as chloride salts, electrolysis has a range of oxidants, including hydrogen peroxide and ozone when oxygen is available, as well as free chlorine and chlorine dioxide when chloride ions are present \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. However, the type of oxidant depends on the applied current, electrolyte solution, and anode electrode type\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. For example, Anodes used for the process of electro-disinfection by hypochlorite ions should have low overpotential toward chlorine gas evolution, such as platinum electrodes. However, pure Pt anodes are not used in industrial applications because of their high costs, and the alternatives for Cl\u003csub\u003e2\u003c/sub\u003e gas evolution are PbO\u003csub\u003e2\u003c/sub\u003e electrodes\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. Electro-disinfection by oxygen gas resulting from the anodic generation of oxygen, which shows some germicidal activity, is used mainly for removing microorganisms from water in small applications where the generation of chlorine species is undesirable. The most used electrodes for oxygen evolution are stainless steel and graphite electrodes.\u003c/p\u003e \u003cp\u003eFor our study, the removal mechanism is probably the destruction of \u003cem\u003eE.coli\u003c/em\u003e due to the production of oxidants derivatives of oxygen caused by the applied electric field, which causes irreversible permeabilization of cell membranes\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. The type of electrodes used in this study are graphite at the anode and stainless steel at the cathode; with short contact time, it was not possible to generate choline compounds for disinfection. This was confirmed with gas chromatographic analysis of the solution after disinfection with electro-oxidation at optimum conditions for detecting any chlorinated by-products (DBPs) as a result of generation of chlorin compounds (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) and free chlorin determination in the solution. The results showed no detection of any halogenated or chlorinated compound in the solution. Accordingly, the mechanism of inactivation of E. coli in this study is the electro-disinfection by oxygen gas.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Application of elect-disinfection on real wastewater under continuous operation\u003c/h2\u003e \u003cp\u003eThe results obtained in the previous section indicated that electro-disinfection could be applied at detention time up to 5 min in the highest bacterial concentration and current density of 4 mA/cm\u003csup\u003e2\u003c/sup\u003e. At this optimum condition, wastewater from secondary wastewater treatment plant and agricultural drainage was subjected to electro-disinfection continuously to simulate a full-scale electro-oxidation treatment cell. The treated wastewater was collected every min to investigate the best time for disinfection for each type of wastewater.\u003c/p\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Application of drainage wastewater\u003c/h2\u003e \u003cp\u003eThe raw drainage wastewater was subjected to disinfection by applying current density of 4 mA/cm\u003csup\u003e2\u003c/sup\u003e, TDS of 987 mg/L, and a hydraulic retention time of 5 min. At the start of the experiment, samples were collected from the effluent at zero time and every min till 5 min, representing the actual retention time. The results depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e indicated that the bacterial densities of total heterotrophic bacteria, coliform group (TC, FC, and \u003cem\u003eE. coli\u003c/em\u003e), and some pathogenic species, including \u003cem\u003eP.aeruginosa, B.subtilis, Vibrio\u003c/em\u003e spp., and \u003cem\u003eS.typhie\u003c/em\u003e was, initially enumerated in all samples before and after disinfecting with ED within varying exposure time. The average log counts was 6.2, 6.6, 4.6, 3.6, 3.2, 2.3, 3.13, 3.17, 2.6, and 2.2 CFU/mL, respectively for HPC at 37\u003csup\u003eo\u003c/sup\u003eC, HPC at 22\u003csup\u003eo\u003c/sup\u003eC, TC, FC, \u003cem\u003eE.coli, P.aeruginosa, B.subtilis, Vibrio\u003c/em\u003e spp., and \u003cem\u003eS. typhie\u003c/em\u003e. The results showed that \u003cem\u003eE. coli\u003c/em\u003e and pathogenic bacteria were completely eradicated after 3 min exposure time. This result is in agreement with the obtained results from batch experiments on the synthetic wastewater under the same conditions. As the TDS concentration is about 1000 mg/L, the whole electro-disinfection time was about 5 min, with slight residuals of total bacterial counts still existing. In addition, the high bacterial load in the wastewater affected the time required for the disinfection. Likewise, the sample was collected during continuous experiments and subjected to the physico-chemical characterization, as depicted in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The results showed slight removal of chemical pollutants, which is expected due to the short treatment time. Similarly, there was no detection of chlorinated organic compounds such as THMs, indicating no formation of chlorin derivatives as a result of electrolysis.\u003c/p\u003e \u003cp\u003eFrom the outcomes mentioned above, it could be concluded that the utilization of lower current density may avoid higher power consumption for the disinfection process. The complete inactivation of \u003cem\u003eE. coli\u003c/em\u003e was attained with 5min contact time, 4 mA/cm\u003csup\u003e2\u003c/sup\u003e of current density, and 1000 mg/L of TDS concentration. These optimized conditions would be involved in the disinfection strategy in wastewater treatment steps.\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\u003ePhysico-chemical characterization of agricultural drainage water before and after electro-disinfection.\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\" 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=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eResult\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eBefore\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eAfter\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlow rate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emL/min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e360\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOperation time\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e30 mins\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e--\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.35\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal dissolved solids\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\u003e987\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1071\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal suspended solids\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\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChemical oxygen demand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emgO\u003csub\u003e2\u003c/sub\u003e/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiochemical oxygen demand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emgO\u003csub\u003e2\u003c/sub\u003e/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAmmonia\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\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eND\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal sulfides\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\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eND\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOil and grease\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\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTri-halomethane\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026micro;g/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN.D\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\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Application of secondary treated municipal wastewater\u003c/h2\u003e \u003cp\u003eDue to the excessive microbial burdens inherent in wastewater effluents, disinfection operations for effluents have become necessary to improve wastewater treatment facilities' performance and eradicate dangerous bacteria \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Within wastewater, a vast range of pathogenic organisms survive, but if not effectively managed, they can cause a significant threat to public health\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. As during ultimate effluent release, wastewater effluents may transport harmful microbes into watersheds. Some dangerous diseases such as cholera, typhoid, and hepatitis A may occur due to polluted rivers. Polluted rivers might damage sea life, notably seafood, cockles, and shrimp. Those who consume this poisoned seafood risk getting extremely unhealthy \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Therefore, the secondary treated wastewater was subjected to continuous electro-disinfection as done for drainage wastewater. The experiment was carried out at a current density of 4 mA/cm2, the TDS was found to be 1987 mg/L, and the hydraulic retention time was adjusted to 3 min. The samples were collected every minute, starting from zero to 5 min, to investigate the time of electro disinfection. The results depicted in Table\u0026nbsp;(2) and Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. showed complete removal of all bacterial indicators after the first min. Monitoring the bacterial densities of HPC at 37\u003csup\u003eo\u003c/sup\u003eC, HPC at 22\u003csup\u003eo\u003c/sup\u003eC, TC, FC, \u003cem\u003eE.coli\u003c/em\u003e, \u003cem\u003eP.aeruginosa, B.subtilis, Vibrio\u003c/em\u003e spp., and \u003cem\u003eS. typhie\u003c/em\u003e showed that a comprehensive decline in the number of bacteria occurred after 2 min of exposure time. Also, secondary treated although containing significant amount of COD value is present, mor than 50% removal of this organic matter was removed as result of electro-oxidation. investigated of halogenated organic compounds indicated no formation of these compound during the disinfection process.\u003c/p\u003e \u003cp\u003eElectrochemical disinfection, analogous to standard chemical disinfection strategies, would indeed happen subsequent to clarification system and filtration processes in water purification \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Hence, the wastewater sample after secondary treatment was selected to be disinfected with ED. It is well-known that the microbial population densities in secondary treated wastewater are lower than in untreated or raw wastewater, as the treatment process could efficiently reduce the microbial load during the operational process. Up to 99% of fecal indicator bacteria (FIB) can be dismissed using primary and secondary treatment processes \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. According to the FIB levels in the influent, this level of reduction may not be adequate to fulfill the standard of the specifications for using handled domestic wastewater for agriculture and irrigations uses and enabling leisure activities in receiving water bodies \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTable\u0026nbsp;(2): Physico-chemical characterization of secondary wastewater before and after electro-disinfection.\u003c/b\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\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\" 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=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eResult\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eBefore\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eAfter\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlow rate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emL/min\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOperation time\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e30 min\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e--\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal dissolved solids\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\u003e1997\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2080\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal suspended solids\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\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChemical oxygen demand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emgO\u003csub\u003e2\u003c/sub\u003e/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiochemical oxygen demand\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emgO\u003csub\u003e2\u003c/sub\u003e/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAmmonia\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\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eND\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal sulfides\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\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eND\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOil and grease\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\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTri-halomethane\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026micro;g/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN.D\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\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Techno-economic evaluation\u003c/h2\u003e \u003cp\u003eElectro-disinfection in this study involved creating a direct current (DC) by graphite anode and stainless steel cathode that pass through the water and prohibit the growth of microbes. The results obtained showed some technical benefits, including ease of use and installation, simple equipment, and high-performance treatment effectiveness \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. requirement less energy, making it affordable and ecologically friendly technology, and it might be operated using fuel batteries or solar system \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. As a result, the inactivation effectiveness of \u003cem\u003eE. coli\u003c/em\u003e was studied using a variety of process factors, including the. The optimized settings were utilized to disinfect real wastewater samples.\u003c/p\u003e \u003cp\u003e The optimum operating conditions for this study are pH 7\u0026ndash;8, TDS\u0026thinsp;\u0026gt;\u0026thinsp;2000, Current density 4 mA/cm\u003csup\u003e2,\u003c/sup\u003e and operation time 3\u0026ndash;5 min. At these optimum conditions, real wastewater samples were adjusted to continuous flow in the reactor through feeding with peristaltic pump to simulate the actual application of such treatment technology. After the continuous experimental study on the different operating parameters, the operational cost was calculated based on the operation time and electrical consumption. Data depicted in Table\u0026nbsp;3 displayed the complete elimination of the initial log count (3.2 CFU/mL) of \u003cem\u003eE.coli\u003c/em\u003e in real drainage wastewater after 3 min of operation. Further, the results revealed this study's cost estimation and power consumption. Based on the commercial prices in Egypt, the cost of electricity for commercial use is L.E 1.6 /kWh (about 0.09 \u003cspan\u003e$\u003c/span\u003e/ kWh). The cost of sodium chloride added to the solution to increase the TDS to 2000 mg/L was calculated based on the amount required was 1.2 kg/m\u003csup\u003e3,\u003c/sup\u003e and the cost of commercial salt is 0.25 L.E/kg. Accordingly the cost of added sodium chloride salt is 0.3L.E/m\u003csup\u003e3\u003c/sup\u003e (0.15\u003cspan\u003e$\u003c/span\u003e/m\u003csup\u003e3\u003c/sup\u003e) the operation cost at 4 mA/cm\u003csup\u003e2\u003c/sup\u003e ranged from 0.57 L.E/ m\u003csup\u003e3\u003c/sup\u003e (0.03 \u003cspan\u003e$\u003c/span\u003e/m\u003csup\u003e3\u003c/sup\u003e) to 1.7 L.E/m\u003csup\u003e3\u003c/sup\u003e (0. 89 \u003cspan\u003e$\u003c/span\u003e/m\u003csup\u003e3\u003c/sup\u003e). The operating cost at the optimum conditions (TDS 2000, 4mA/cm\u003csup\u003e2\u003c/sup\u003e and 3 min) were calculated as 1.13 L.E/ m\u003csup\u003e3\u003c/sup\u003e (0.06 \u003cspan\u003e$\u003c/span\u003e/m\u003csup\u003e3\u003c/sup\u003e). This cost is meager compared to conventional disinfection methods that could achieve the same efficiency.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTable\u0026nbsp;(3): Electrical consumption and cost estimation at optimum operating conditions.\u003c/b\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTime (min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCurrent density\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLog removal of \u003cem\u003eE.coli\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eElectrical consumption(kWh/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTotal running cost (\u003cspan\u003e$\u003c/span\u003e/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e4 mA/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.030\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.045\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.060\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.074\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.089\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\u003eFrom these calculations, Electro-disinfection is a promising solution for application in wastewater treatment plants because of its modular design, high efficiency, and ease of automation and transportation. This study looked at three different treatment scenarios: water treatment, centralized wastewater treatment, and distributed wastewater treatment \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this study, electro-disinfection of the bacterial indicator is dependent on current density, time, and TDS concentration. \u003cem\u003eE.coli\u003c/em\u003e was found to completely remove after 5 mins time TDS 1000 mg/L and 4 mA/cm\u003csup\u003e2\u003c/sup\u003e current density at initial E.coli log count of 6.6 CFU/ml. The increase in current density and Current and TDS concentration decreased the time required for disinfection. However, from the economic point of view, this might increase operating costs due to high power consumption and chemical added to increase the TDS. The electro-oxidation unit configuration with the order of the electrodes had a determining impact on the reactor performance; the cathode\u0026ndash;anode configuration and types also directed the electro disinfection type to oxygen gas disinfection. The added chloride concentrations did not significantly affect free chlorine production in the reactor. Cost analysis for disinfection of secondary wastewater treatment effluent indicated that graphite and stainless steel electrodes in an electro-disinfection unit are more appropriate due to low power consumption (0.5 kWh/m\u003csup\u003e3\u003c/sup\u003e ) and low operating cost (0.06 \u003cspan\u003e$\u003c/span\u003e/m\u003csup\u003e3\u003c/sup\u003e ) compared to conventional methods.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e The authors have no competing interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e: The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. \u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbou-Taleb, E. M. \u003cem\u003eet al.\u003c/em\u003e Sustainable solutions for urban wastewater management and remediation. Egypt. J. Chem. \u003cb\u003e63\u003c/b\u003e, 405\u0026ndash;415 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBracher, G. H., Carissimi, E., Wolff, D. B., Glusczak, A. G. \u0026amp; Graepin, C. Performance of an electrocoagulation-flotation system in the treatment of domestic wastewater for urban reuse. Environ. Sci. Pollut. Res. (2022) doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s11356-022-20630-2\u003c/span\u003e\u003cspan address=\"10.1007/s11356-022-20630-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVasilyak, L. M. Physical Methods of Disinfection (A Review). Plasma Physics Reports vol.\u0026nbsp;47 318\u0026ndash;327 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurch, J. D. \u0026amp; Thomas, K. E. Water disinfection for developing countries and potential for solar thermal pasteurization. Sol. Energy \u003cb\u003e64\u003c/b\u003e, 87\u0026ndash;97 (1998).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBlanc, D. S., Carrara, P., Zanetti, G. \u0026amp; Francioli, P. Water disinfection with ozone, copper and silver ions, and temperature increase to control Legionella: Seven years of experience in a university teaching hospital. J. Hosp. Infect. \u003cb\u003e60\u003c/b\u003e, 69\u0026ndash;72 (2005).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMalato, S., Fern\u0026aacute;ndez-Ib\u0026aacute;\u0026ntilde;ez, P., Maldonado, M. I., Blanco, J. \u0026amp; Gernjak, W. Decontamination and disinfection of water by solar photocatalysis: Recent overview and trends. Catalysis Today vol.\u0026nbsp;147 1\u0026ndash;59 (2009).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHAWRYLIK, E. Methods Used in Disinfections of Wastewater and Sewage Sludge \u0026ndash; Short Review. Archit. Civ. Eng. Environ. \u003cb\u003e13\u003c/b\u003e, 57\u0026ndash;63 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang, X. Microbial Pathogen Detection and Removal in Water Reuse Practices. \u003cem\u003eProQuest Dissertations and Theses\u003c/em\u003e (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMart\u0026iacute;nez-Huitle, C. A. \u0026amp; Brillas, E. A critical review over the electrochemical disinfection of bacteria in synthetic and real wastewaters using a boron-doped diamond anode. Curr. Opin. Solid State Mater. Sci. \u003cb\u003e25\u003c/b\u003e, 100926 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRaut, A. S. \u003cem\u003eet al.\u003c/em\u003e Reduction in energy for electrochemical disinfection of E. coli in urine simulant. J. Appl. Electrochem. \u003cb\u003e49\u003c/b\u003e, 443\u0026ndash;453 (2019).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang, X. \u003cem\u003eet al.\u003c/em\u003e Electrochemical disinfection of toilet wastewater using wastewater electrolysis cell. Water Res. \u003cb\u003e92\u003c/b\u003e, 164\u0026ndash;172 (2016).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRahmani, A. R., Nematollahi, D., Poormohammadi, A., Azarian, G. \u0026amp; Zamani, F. Electrodisinfection of bacteria-laden in surface water using modified Ti electrode by antimony-and nickel-doped tin oxide composite. Chemosphere \u003cb\u003e263\u003c/b\u003e, (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbou-Taleb, E. M., Hellal, M. S. \u0026amp; Kamal, K. H. Electro‐oxidation of phenol in petroleum wastewater using a novel pilot‐scale electrochemical cell with graphite and stainless‐steel electrodes. Water Environ. J. \u003cb\u003e35\u003c/b\u003e, 259\u0026ndash;268 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eda Silva, A. J. C., dos Santos, E. V., de Oliveira Morais, C. C., Mart\u0026iacute;nez-Huitle, C. A. \u0026amp; Castro, S. S. L. Electrochemical treatment of fresh, brine and saline produced water generated by petrochemical industry using Ti/IrO2-Ta2O5 and BDD in flow reactor. Chem. Eng. J. \u003cb\u003e233\u003c/b\u003e, 47\u0026ndash;55 (2013).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbou-Taleb, E.., Hellal, M. ., Abdel-Salam, O. E. \u0026amp; Abdel Maksod, A. Innovative model for the application of electrochemical oxidation of high organic load wastewater treatment. (2021) doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://search.egpo.gov.eg/?radio-34=patent-utility-model#/search/result/patent-utility-model?q=FP%3A30235\u003c/span\u003e\u003cspan address=\"https://search.egpo.gov.eg/?radio-34=patent-utility-model#/search/result/patent-utility-model?q=FP%3A30235\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAPHA. \u003cem\u003eStandard Methods for the Examination of Water and Wastewater\u003c/em\u003e. American Water Works Association/American Public Works Association/Water Environment Federation (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerraiz-Carbon\u0026eacute;, M. \u003cem\u003eet al.\u003c/em\u003e Disinfection of polymicrobial urines by electrochemical oxidation: Removal of antibiotic-resistant bacteria and genes. J. Hazard. Mater. \u003cb\u003e426\u003c/b\u003e, (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. Hemdan, B., Azab El-Liethy, M. \u0026amp; El-Taweel, G. E. The destruction of Escherichia coli adhered to pipe surfaces in a model drinking water distribution system via various antibiofilm agents. Water Environ. Res. \u003cb\u003e92\u003c/b\u003e, 2155\u0026ndash;2167 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhasemian, S., Asadishad, B., Omanovic, S. \u0026amp; Tufenkji, N. Electrochemical disinfection of bacteria-laden water using antimony-doped tin-tungsten-oxide electrodes. Water Res. \u003cb\u003e126\u003c/b\u003e, 299\u0026ndash;307 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchmalz, V., Dittmar, T., Haaken, D. \u0026amp; Worch, E. Electrochemical disinfection of biologically treated wastewater from small treatment systems by using boron-doped diamond (BDD) electrodes - Contribution for direct reuse of domestic wastewater. Water Res. \u003cb\u003e43\u003c/b\u003e, 5260\u0026ndash;5266 (2009).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLakshmi, E., Priya, M. \u0026amp; Achari, V. S. An overview on the treatment of ballast water in ships. Ocean Coast. Manag. \u003cb\u003e199\u003c/b\u003e, 105296 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTrigueiro, L. F. \u003cem\u003eet al.\u003c/em\u003e Inactivation, lysis and degradation by-products of Saccharomyces cerevisiae by electrooxidation using DSA. Environ. Sci. Pollut. Res. \u003cb\u003e24\u003c/b\u003e, 6096\u0026ndash;6105 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCollivignarelli, M. C., Abb\u0026agrave;, A., Benigna, I., Sorlini, S. \u0026amp; Torretta, V. Overview of the main disinfection processes for wastewater and drinking water treatment plants. Sustain. \u003cb\u003e10\u003c/b\u003e, 1\u0026ndash;21 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKourdali, S., Badis, A., Boucherit, A., Boudjema, K. \u0026amp; Saiba, A. Electrochemical disinfection of bacterial contamination: Effectiveness and modeling study of E. coli inactivation by electro-Fenton, electro-peroxi-coagulation and electrocoagulation. J. Environ. Manage. \u003cb\u003e226\u003c/b\u003e, 106\u0026ndash;119 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSillanp\u0026auml;\u0026auml;, M. \u0026amp; Shestakova, M. Electrochemical Water Treatment Methods. in \u003cem\u003eElectrochemical Water Treatment Methods\u003c/em\u003e 47\u0026ndash;130 (Elsevier, 2017). doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/B978-0-12-811462-9.00002-5\u003c/span\u003e\u003cspan address=\"10.1016/B978-0-12-811462-9.00002-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKraft, A. Electrochemical Water Disinfection: A Short Review ELECTRODES USING PLATINUM GROUP METAL OXIDES. Platin. Met. Rev. \u003cb\u003e52\u003c/b\u003e, 177\u0026ndash;185 (2008).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eL\u0026oacute;pez-G\u0026aacute;lvez, F. \u003cem\u003eet al.\u003c/em\u003e Electrochemical disinfection: An efficient treatment to inactivate Escherichia coli O157:H7 in process wash water containing organic matter. Food Microbiol. \u003cb\u003e30\u003c/b\u003e, 146\u0026ndash;156 (2012).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGheethi, A. A. Al, Efaq, R. M. M. A. N. \u0026amp; Adib, I. N. M. R. Reduction of bacteria in storage system of sewage effluents. Sustain. Water Resour. Manag. \u003cb\u003e3\u003c/b\u003e, 193\u0026ndash;203 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIbrahim, E. M. M. E. M., El-Liethy, M. A., Abia, A. L. K., Hemdan, B. A. \u0026amp; Shaheen, M. N. Survival of E. coli O157:H7, Salmonella Typhimurium, HAdV2 and MNV-1 in river water under dark conditions and varying storage temperatures. Sci. Total Environ. \u003cb\u003e648\u003c/b\u003e, 1297\u0026ndash;1304 (2019).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMohamed, R. M. S. R. \u003cem\u003eet al.\u003c/em\u003e Bioaugmentation process of secondary ef fl uents for reduction of pathogens, heavy metals and antibiotics. 780\u0026ndash;795 (2016) doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.2166/wh.2016.046\u003c/span\u003e\u003cspan address=\"10.2166/wh.2016.046\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSowah, R., Zhang, H., Radcliffe, D., Bauske, E. \u0026amp; Habteselassie, M. Y. Evaluating the influence of septic systems and watershed characteristics on stream faecal pollution in suburban watersheds in Georgia, USA. J. Appl. Microbiol. \u003cb\u003e117\u003c/b\u003e, 1500\u0026ndash;1512 (2014).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFouad, H. A., Hefny, R. M., Kamel, A. M. B. M. M., El-Liethy, M. A. \u0026amp; Hemdan, B. A. Bioaugmentation and Advanced Oxidation Process for Organic and Inorganic Pollutants Removal and Pathogenic Bacteria Inactivat El-Rahawy Drain, Egypt. Egypt. J. Chem. \u003cb\u003e63\u003c/b\u003e, 4075\u0026ndash;4082 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNasr, F. A., El-Shafai, S. A., Abdelfadil, A. S., Ibrahim, H. S. \u0026amp; Hemdan, B. A. Potential use of treated domestic sewage for cultivation of biofuel crops in Egypt. Int. J. Environ. Sci. Technol. (2018) doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s13762-018-2101-4\u003c/span\u003e\u003cspan address=\"10.1007/s13762-018-2101-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSayinli, B., Dong, Y., Park, Y., Bhatnagar, A. \u0026amp; Sillanp\u0026auml;\u0026auml;, M. Recent progress and challenges facing ballast water treatment - A review. Chemosphere \u003cb\u003e291\u003c/b\u003e, 132776 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang, Y. Recent advances in the electrochemical oxidation water treatment: Spotlight on byproduct control. Front. Environ. Sci. Eng. \u003cb\u003e14\u003c/b\u003e, (2020).\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":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"electro-oxidation, Graphite electrode, electro-disinfection, E.coli, current density, wastewater treatment ","lastPublishedDoi":"10.21203/rs.3.rs-1809352/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1809352/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study aimed to evaluate the performance of the Novel electro-oxidation unit for the disinfection of wastewater from technoeconomic point of view. The cell was fabricated based on patent design with a total volume of 3L containing nine electrodes (6graphite and 3stainless steel) with cylindrical shape and connected to DC power supply. Determination of optimum operating parameters were investigated in batch mode on synthetic wastewater through studying effect of contact time, current density(CD), total dissolved solids concentration(TDS) and bacterial density. Also, continuous mode experiment was studied on real wastewater from agricultural drain and secondary wastewater treatment plant. The results of batch mode revealed that the optimum operational conditions that achieved the complete removal E.coli was at contact time of 5 minutes, TDS\u0026thinsp;=\u0026thinsp;2000 mg/L and CD\u0026thinsp;=\u0026thinsp;4mA/Cm\u003csup\u003e2\u003c/sup\u003e. Application of these conditions on the continuous mode experiment indicated the complete removal of all bacterial indicators after 5 minutes in the drainage wastewater and after 2 minutes in the secondary treated wastewater. The physico-chemical characterization indicated also, no formation of chlorine by products in the process. The electrical consumption was calculated in the continuous mode and found to be 0.5 kWh/m\u003csup\u003e3\u003c/sup\u003e with operational cost about 0.06 \u003cspan\u003e$\u003c/span\u003e/m\u003csup\u003e3\u003c/sup\u003e including cost of adding chemicals to increase the TDS. This proved that this novel electro-oxidation unite is cost effective for disinfection of wastewater and complete removal bacterial pollutants than other conventional treatment methods.\u003c/p\u003e","manuscriptTitle":"Novel electro-oxidation unite for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: Batch and continuous experiments","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-07-13 16:40:40","doi":"10.21203/rs.3.rs-1809352/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2022-08-24T06:18:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2022-07-26T10:52:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"92bb1944-ba23-4ced-a1ab-cb6f6aea338f","date":"2022-07-14T13:35:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"7847a5da-9266-43b3-98d8-1bb4e1e7b370","date":"2022-07-06T05:44:20+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-07-06T01:33:52+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-07-06T01:29:06+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2022-07-05T10:58:31+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2022-07-05T10:55:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2022-06-29T22:23:51+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"497dd28c-3877-456f-a369-8d2e426277f4","owner":[],"postedDate":"July 13th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2022-09-13T11:14:14+00:00","versionOfRecord":[],"versionCreatedAt":"2022-07-13 16:40:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1809352","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1809352","identity":"rs-1809352","version":["v1"]},"buildId":"-HB7Z8yhvgn0wM9Nzuekk","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}