Removal of Escherichia coli from Domestic Wastewater using Electrocoagulation

The objective of this study was to evaluate the efficiency of electrocoagulation for the removal of Escherichia coli from domestic and urban wastewaters and to determine the effects of the main operational parameters on the process. An electrocoagulation reactor with aluminum and iron electrodes was built for this purpose. A factorial design was applied, where amperage, treatment time, and pH were considered as the factors and E. coli percent removal was the response variable. After 20 min of treatment, >97% removal efficiency was achieved. The highest E. coli removal efficiency achieved was 99.9% at a neutral pH of 7, amperage of 3 A, and treatment time of 60 min. However, removal efficiency of close to 99% was also achieved at natural wastewater pH of 8.5. Statistical analyses showed that the three tested factors significantly affected E. coli percent removal (p 97%. La mayor eficiencia de eliminación de E. coli alcanzada fue del 99.9% a un pH neutro de 7, un amperaje de 3 A y un tiempo de tratamiento de 60 min. Sin embargo, también se logró una eficiencia de remoción cercana al 99% a un pH de agua residual natural de 8.5. Los análisis estadísticos mostraron que los tres factores probados afectaron significativamente la eliminación del porcentaje de E. coli (p <0.05). Estos resultados indican que la electrocoagulación tiene un alto poder de desinfección en un reactor primario para eliminar los contaminantes del agua y, al mismo tiempo, eliminar los microorganismos patógenos en comparación con los procesos de tratamiento biológico. Esto representa un beneficio adicional porque reducirá considerablemente el uso de cloro durante la etapa final de desinfección

Inactivation of microbiota from urban wastewater by single and sequential electrocoagulation and electro-Fenton treatments

This work aims at comparing the ability of two kinds of electrochemical technologies, namely electrocoagulation (EC) and electro-Fenton (EF), to disinfect primary and secondary effluents from municipal wastewater treatment plants. Heterotrophic bacteria, Escherichia coli, enterococci, Clostridium perfringens spores, somatic coliphages and eukaryotes (amoebae, flagellates, ciliates and metazoa) were tested as indicator microorganisms. EC with an Fe/Fe cell at 200 A m-2 and natural pH allowed > 5 log unit removal of E. coli and final concentration below 1 bacteria mL-1 of coliphages and eukaryotes from both effluents in ca. 60 min, whereas heterotrophic bacteria, enterococci and spores were more resistant. A larger removal was obtained for the primary effluent, probably because the flocs remove higher amount of total organic carbon (TOC), entrapping more easily the microbiota. EF with a boron-doped diamond (BDD) anode and an air-diffusion cathode that produces H2O2 on site was first performed at pH 3.0, with large or even total inactivation of microorganisms within 30 min. A more effective microorganism removal was attained as compared to EC thanks to ¿OH formed from Fenton's reaction. A quicker disinfection was observed for the secondary effluent owing to its lower TOC content, allowing the attack of greater quantities of electrogenerated oxidants on microorganisms. Wastewater disinfection by EF was also feasible at natural pH (~7), showing similar abatement of active microorganisms as a result of the synergistic action of generated oxidants like active chlorine and coagulation with iron hydroxides. A sequential EC/EF treatment (30 min each) was more effective for a combined decontamination and disinfection of urban wastewater

Impact of Electrocoagulation Pretreatment on E. Coli Mitigation using Electrooxidation

Small drinking water systems serve approximately 20% of the US population, but they can struggle to comply with the Total Coliform Rule and the Disinfectant and Disinfection Byproduct Rule. Issues with insufficient funds to effectively treat the water and difficulties with the transportation of required chemicals can affect compliance. Electrochemical processes may offer an alternative approach for small water systems as they have demonstrated some advantages over traditional treatments, such as reduced handling and storage of chemicals and cost effectiveness. Sequential electrochemical processes have yet to be tested for the treatment of E. coli in drinking waters. In this study, electrocoagulation (EC) and electrooxidation (EO) were investigated using two model surface waters and two model groundwaters to determine the efficacy of sequential EC-EO for mitigating E. coli. At a current density of 1.67 mA/cm2 for 1 minute, bench-scale EO alone achieved 4-logs mitigation of E. coli in the model shallow aquifer. Increasing the EO current density to 6.67 mA/cm2 for 1 minute provided similar levels of E. coli mitigation in the model deep aquifer (characterized by lower initial chloride concentrations compared to the shallow aquifer). Using a current density of 10 mA/cm2 for 5 minutes EC achieved 1-log or greater E. coli mitigation in all model waters. No additional mitigation beyond EC alone was achieved using sequential EC-EO. Reductions in the initial pH of the surface waters to target higher natural organic matter (NOM) removal did not enhance E. coli treatment with EC-EO compared to EC alone. In fact, an average of 64% of NOM was removed no matter the change in pH, which likely limited E. coli mitigation. Additional reasons for the lack of improvement in E. coli treatment may have included the presence of iron following EC or insufficient EO current density. Decreasing the initial water pH did improve E. coli mitigation using EO when pretreated by EC compared to the baseline water matrix pH. Total EC residual iron concentration also increased, and it correlated slightly with E. coli mitigation. This correlation and oxidation of ferrous iron may indicate that Fenton-like reactions occurred during EO after EC pretreatment

بررسی کارایی فرآیند انعقاد الکتریکی در حذف باکتری­های بیماری­ زا از فاضلاب بیمارستانی پیش از تخلیه به آب‌های پذیرنده

      Backgrounds and Objective: Due to population growth and expansion of agricultural industry in recent years, wastewater treatment is unavoidable. Therefore, using the Electrocoagulation process with aluminum electrodes to eliminate bacteria in hospital wastewater. Materials and Methods: This study is a pilot-scale batch that to verify removal rate of bacteria in hospital wastewater by using direct current electric. In this study, the effects of variables such as time (30, 60, 90 min), voltage (10, 20, 30 v) and type of electrode (Al) on the efficiency of bacterial removal were studied. Results: The results shows that with increasing contact time and voltage, removal efficiency increases. The results indicate that the retention time and voltage changes can have different effects on bacterial removal efficiency. The rising voltage and time are causing increase bacterial removal efficiency due to the rapid production of hydrolysis products. Conclusion: The research results indicate that electric voltage treatment is effective for rapid removal of microorganisms in hospital wastewaters. REFERENCES   سابقه و هدف: با توجه به رشد فزاینده جمعیت و گسترش صنعت کشاورزی درسال­های اخیر، تصفیه فاضلاب­ها کاری اجتناب ناپذیر می­باشد. در این راستا با استفاده از فرآیند انعقاد الکتریکی و الکترودهای آلومینیوم اقدام به حذف باکتری­های موجود در فاضلاب بیمارستانی گردید.روش بررسی: مطالعه حاضر مطالعه مقطعی در مقیاس آزمایشگاهی و در سیستم ناپیوسته می­باشد که برای بررسی درصد حذف توده باکتری‌ها در فاضلاب بیمارستانی به وسیله جریان مستقیم الکتریکی روی فاضلاب بیمارستانی انجام گرفت. در این تحقیق تأثیر متغیرهای ولتاژ (10، 20، 30 ولت)، و زمان (10، 20، 30 دقیقه) و نوع الکترود (آلومینیوم) بر کارایی حذف باکتری‌ها ارزیابی گردید.یافته‌ها: نتايج برآمده از آزمايش­ها نشان داد كه با افزايش زمان تماس و ولتاژ، كارايي حذف به سبب تولید سریع محصولات ناشی از هیدرولیز افزایش می‌یابد. همچنین تغییرات زمان و ولتاژ می‌تواند آثار متفاوتی بر کارایی حذف توده باکتری‌ها داشته باشد.نتيجه گيري: نتایج به­دست­آمده از این مطالعه نشان می‌دهد که انعقاد الکتریکی روش سریع برای حذف باکتری‌ها از فاضلاب بیمارستانی می­باشد

Iron-Enhanced Mitigation of Viruses in Drinking Water

Waterborne viruses are ubiquitous in the environment and present a global threat to public health. Previous research has suggested that iron-based water treatment has promise as a low-cost, non-toxic means of virus mitigation. In particular, zero-valent and ferrous iron have shown evidence of inactivating bacteria and viruses. The purpose of this research was to elucidate the relationship between iron oxidation and virus inactivation and determine if iron-based inactivation can enhance two water treatment processes, electrocoagulation and electrooxidation, for virus mitigation. This research first investigated bacteriophage inactivation due to ferrous oxidation in batch tests using ferrous chloride salt. Ferrous iron oxidation correlated to bacteriophage inactivation, indicating that viruses can be inactivated as well as physically removed by ferrous iron coagulation. Greater inactivation was associated with both a higher ferrous iron dose and a slower rate of iron oxidation. Next, the importance of ferrous oxidation was determined for virus mitigation via iron electrocoagulation. Ferrous-based inactivation was an important fate of viruses in iron electrocoagulation. However, some bacteriophages showed far greater inactivation than human viruses. Physical removal was the dominant fate under most conditions for the three mammalian viruses tested, as well as bacteriophage ΦX174. This result casts doubt on the appropriateness of using common bacteriophages for research into iron-based water treatment technologies. However, most viruses did demonstrate some inactivation at low pH (pH 6).Finally, an electrocoagulation-electrooxidation treatment train was investigated to capitalize on the strengths of iron electrocoagulation. At typical coagulation doses (\u3c30 mg/L Fe), ferrous iron did not enhance electrooxidation with boron-doped diamond electrodes. Nevertheless, the electrocoagulation-electrooxidation treatment train was beneficial in model surface waters, though electrocoagulation alone achieved equal or better mitigation in model groundwaters. The electrocoagulation-electrooxidation system also outperformed conventional treatment (ferric salt coagulant and free chlorine disinfection) in model groundwaters

Field Study of Electrochemical Disinfection of Municipal Wastewater

Research on electrochemical disinfection of municipal wastewater has been conducted at the University of New Orleans using a continuous flow electrochemical reactor connected to a direct current (DC) power supply changing its polarity and varying the electrode distance. Bacterial inactivation and chlorine production were the main parameters that were recorded. After months of research, it was determined that the electrochemical disinfection reactor is efficient and has a great potential for the future. There is no need to use chlorine and it has low operation costs. The following design recommendations for an electrochemical disinfection unit were given: A detention time of 5 +- 0.3 minutes A minimum volumetric current density of 1000 amps/m3 A minimum detention current density of 80 amps.hr/m3 The combination of the three recommended design values yielded excellent disinfection efficiencies and low chlorine production

Disinfection efficiency of secondary effluents with ultraviolet light in a Mediterranean area

This paper deals with the study of physicochemical and microbiological parameters affecting disinfection efficiency of secondary effluents in a municipal wastewater treatment plant, for irrigation purposes. There appears to be an important increase on turbidity values as chlorine values increases, due to the conversion of particulate organic carbon into dissolved organic carbon. The nitrification-denitrificacion processes appeared to be sensitive to changes in pH, with a minimum nitrate value in the wastewater when pH ranged between 7.01-8.00. With a similar behaviour, the phosphate removal was conditioned by pH, showing the highest efficiency in the same pH range. Both anions probed to be strongly correlated. Total coliforms were more UV light resistant than faecal coliforms, after an exposure of 10 min, corresponding to an UV dose of 73 mJ/cm2. The experimental results for both groups of microorganisms followed first order reaction kinetics, with a gradual flattening at higher UV doses. A total elimination of both indicators would be achieved with doses over 95 mJ/cm2. A previous step on the treated wastewater would improve its quality before the disinfection process

Electrolytic purification of water

This thesis develops the concept of an in situ electrolytic processor, a machine with electrochemical functions that purifies aqueous fluids at the point of production, whether from a bore water supply or effluent from a tannery. Where the contaminants in an effluent are useful they are separated in a specialised electrolyser for re-use in the process that produced the original effluent. The value in doing this exceeds the cost of electrolytic processing for tannery effluent. The functions of an electrolytic purifier were resolved into: flotation by bubbles, flocculation by corrosion of aluminium anodes, electrowinning by cathodic plating, disinfection, oxidation-reduction and pH modification. Improved understanding of the control of these functions has led to the ability to design better electrolysers because the functions were combined in a form that was appropriate to the required purification process. A link between extra-faradic corrosion of an aluminium anode and pH modification is postulated. Electrochemical principles were used as the basis for development of real processor models. These models were tested using bore water, cooling tower fluid, virus contaminated water, laundry water, municipal waste water, landfill leachate and pulp mill effluent. The most effective model, designed during the course of the project and described as the Flume, incorporated a novel corroding anode composed of thin pieces of aluminium, water flow in a cathodic flume, and a cheap water-porous membrane to separate the electrolyte into anolyte and catholyte. The novel anode was designed to improve clearance of corrosion products by maintaining a fast flow speed in proximity to the zone of anodic corrosion. The Flume model was used in an extensive test at a tannery. Greater than 90% of chromium in tannery effluent was removed by a combination of electroflocculation and electroflotation, at a lower cost than by treatment using standard chemical flocculent, using a side-stream Flume processor at a tannery. A smaller scale Flume model was used to test mechanisms of treatment in the laboratory using synthetic tannery effluent. When treating alkaline effluent, the separating membrane in the Flume model enabled production of alkali at the cathode and production of acid at the anode. This was used for pH modification of effluent and, where the majority of the flow was anolyte, was able to produce a catholyte of pH greater than 13 from a wide range of inflow pH. The caustic catholyte is a valuable by-product of the electrolytic processing, especially when the upstream processes require net input of alkali (as is the case at a tannery or kraft pulp mill) and more generally because downstream biological treatment processes benefit from receiving neutralised effluent. The degree of pH moderation of the whole outflow compared to the inflow was found to be controllable by adjustment of cell voltage. This effect enables treatment of effluent with variable pH. Optimisation of an electrolyser for energy recovery, by both reduction of electrode over-potentials and electrolyte resistance, was incorporated in the full-scale designs. Based on a feasible cell voltage of 5 V, 20% recovery of the energy input is expected

Benchmarking tertiary water treatments for the removal of micropollutants and pathogens based on operational and sustainability criteria

In a context of increasing water scarcity, it is essential to ensure an integrated watershed management, savings in the consumption of water as a finite resource and improve the performance of wastewater treatment plants to guarantee the quality of treated effluents. Therefore, advanced technologies for tertiary wastewater treatment have been widely studied in recent decades. These treatments have been reviewed over the years mainly providing comparisons from a technical perspective. However, there is a lack of a holistic evaluation considering environmental and economic aspects together with the aforementioned technical aspects. In this review, treatment alternatives for micropollutant and pathogen abatement have been identified based on technologies implemented on a large scale (ozonation, ultraviolet treatment, adsorption on activated carbon or membrane filtration) as well as those treatments in the process of implementation, such as electrochemical, Fenton-based or photocatalytic techniques. Thus, a systematic bibliographic search was performed considering works applying pilot and full-scale equipment, leaving lab-scale results out of the analysis. The description of each process allowed the identification of the technical feasibility, operating costs and associated environmental impacts, providing a comparative assessment that will help decision-making in the development and application of the different technologies. The benchmarking results reveal that the selected treatment should be chosen based on the source and specific pollutants present in the wastewater, as there is no single solution for the treatment of micropollutants and pathogens. In addition, recommendations are presented for the publication of reliable process-related data to facilitate comparison between different technologies and treatment scenarios.This research was supported by HP-NANOBIO (PID2019-111163RB-I00) and SPOTLIGHT (PDC2021-121540-I00) projects, granted by Spanish Ministry of Science and InnovationS

Mitigation of hazards and risks of emerging pollutants through innovative treatment techniques of post methanated distillery effluent - A review

Distillery wastewater has high biological and chemical oxygen demand and requires additional treatment before it can be safely discharged into receiving water. It is usually processed through a biomethanation digester and the end product is the post-methanated distillery effluent (PMDE). Research have shown that PMDE released by molasses-based distilleries is a hazardous effluent that can cause harm to the biota and the environment; it contains elevated amount of total dissolved solids (TDS), total suspended solids (TSS) and excess levels of persistent organic compounds (POPs), heavy metals, phenolic compounds, and salts. The practice of wastewater reuse for irrigation in many water scarce countries necessitates the proper treatment of PMDE before it is discharged into receiving water. Convention methods have been in practice for decades, but innovative technologies are needed to enhance the efficiency of PMDE treatment. Advance physical treatment such as membrane separation technology using graphene, ion-exchange and ultrafiltration membranes; chemical treatment such as advanced oxidation methods, electrocoagulation and photocatalytic technologies; biological treatment such as microbial and enzymatic treatment; and hybrid treatment such as microbial-fuel cell (MFC), genetically modified organisms (GMO) and constructed wetland technologies, are promising new methods to improve the quality of PMDE. This review provides insight into current accomplishments evaluates their suitability and discusses future developments in the detoxification of PMDE. The consolidated knowledge will help to develop a better management for the safe disposal and the reuse of PMDE wastewater