Disinfection Of Municipal Wastewater Research Articles

UV LED Wastewater Disinfection: The Future is Upon Us

The world's first full-scale, 280 nm UV LED reactor for wastewater disinfection was tested at flows of 545 and 817 m3 day−1. The system achieved a >3 average log reduction of total coliform at 545 m3 day−1 and the 817 m3 day−1 flow rate achieved over a >2.5 average log reduction for all operational conditions. The delivered fluence of the full-scale system ranged from 28-148 mJ cm−2 and aligns with a UV auditing study that was conducted prior to the installation of the wastewater reactor. These results benchmark the performance that can be achieved by UV LED disinfection and further connect bench-scale disinfection results with full-scale performance. The approach established in this manuscript provides a novel tool for utilities when considering emerging UV disinfection technologies. In summary, this study establishes that UV LEDs are an effective wastewater disinfectant at-scale and are comparable to conventional low-pressure UV systems. This is the first instance where the efficacy of UV LEDs for municipal wastewater disinfection has been demonstrated using a large-scale installation at a functioning wastewater facility.

Photoelectrocatalytic treatment of municipal wastewater with emerging concern pollutants using modified multi-layer catalytic anode

Municipal wastewater contains emergent chemical and biological pollutants that are resistant to conventional wastewater treatments. Therefore, the focus of the current study was to address the challenge of removing emergent chemical and biological pollutants present in municipal wastewater. To achieve this, a photo electro-catalytic (PEC) treatment approach was employed, focusing on the removal of both micro and biological pollutants that are of emergent concern, as well as the reduction of Chemical Oxidation Demand (COD) and Total Organic Carbon (TOC). The treatment involved the use of a modified multi-layer catalytic anode photo-electroactive anode as an effective anode for PEC treatment of municipal wastewater. In the continuous mode of operation, %COD removal was optimized for the treatment of municipal wastewater under Ultra-Violet C (UVc), 280 nm, and Visible (Vis) radiation, 400 nm. Therefore, a comparative study was performed to investigate the effect of Vis radiation on %COD removal, micropollutants removal, and disinfection of municipal wastewater. Micropollutants present in municipal wastewater were effectively oxidized/degraded with the highest reduction rate between 100% and 80% under the influence of UVc and Vis radiation respectively by the PEC treatment process. Disinfection of various microorganisms present in the wastewater with the effect of UVc and Vis assisted PEC treatment was also monitored. Overall, 75–80% of the disinfection of municipal wastewater was contributed by the modified multi-layer catalytic anode. The UVc in the PEC system, contributes approximately 20–25% to the overall disinfection of municipal wastewater.

Quantitative Evaluation of Municipal Wastewater Disinfection by 280 nm UVC LED

UV-LED irradiation has attracted attention in water and wastewater disinfection applications. However, no studies have quantitatively investigated the impact of light intensity on the UV dosage for the same magnitude of disinfection. This study presents a powerful 280 nm UV-LED photoreactor with adjustable light intensity to disinfect municipal wastewater contaminated with E. coli, SARS-CoV-2 genetic materials and others. The disinfection performance of the 280 nm LED was also compared with 405 nm visible light LEDs, in terms of inactivating E. coli and total coliforms, as well as reducing cATP activities. The results showed that the UV dose needed per log reduction of E. coli and total coliforms, as well as cATP, could be decreased by increasing the light intensity within the investigated range (0–9640 µW/cm2). Higher energy consumption is needed for microbial disinfection using the 405 nm LED when compared to 280 nm LED. The signal of SARS-CoV-2 genetic material in wastewater and the SARS-CoV-2 spike protein in pure water decreased upon 280 nm UV irradiation.

Investigating the effectiveness of bifacial mixed metal MOF electrodes for the photoelectro-catalytic treatment of municipal wastewater

The effectiveness of bifacial mixed metal-metal organic framework (MOF) anodes for municipal wastewater's photoelectro-catalytic (PEC) treatment has been rarely explored. Herein, pollutants removal efficiency from the municipal wastewater and the effect of operational parameters is verified under a visible range of light in a PEC system using TiO2–Bi(mixed metal)-MOF and TiO2–Sb(mixed metal)-MOF anodes, respectively. The comparable efficiency of pollutant removal from municipal wastewater in the PEC system with TiO2–Bi(mixed metal)-MOF anodes is high. At optimum operation parameters, TiO2–Bi(mixed metal)-MOF anodes in the PEC system play a positive role in the removal of micropollutants and the disinfection of municipal wastewater. This study reveals that PEC treatment of municipal wastewater contributes (35% of relative luminescence inhibition) to toxic biproducts.

Application of iron-activated persulfate for municipal wastewater disinfection

To address the increasing contamination of aquatic environments and incidence of waterborne diseases, advanced oxidation processes with activated persulfate have emerged as tools to inactivate wastewater microorganisms and contaminants. In this work, the disinfection of a secondary effluent from a wastewater treatment plant by iron-based persulfate activation was studied. Experiments in a batch stirred tank reactor were carried out to evaluate the performance along reaction time and the effect of operational parameters in the oxidative process efficiency (oxidant and iron concentration, pH and temperature). After 60 min of reaction, persulfate and iron concentrations of 3 mM and 0.75 mM, respectively, combined with a neutral initial pH (7.5) and a temperature of 40 °C, allowed to reach values below the detection limit (<10 CFU/100 mL) of enterococci and enterobacteria with and without ciprofloxacin resistance, as well as a 91% inactivation of total heterotrophic organisms and a 70% removal of total organic carbon. Regrowth of microorganisms was evaluated 72 h after treatment and it was only noticed a slight increase in total heterotrophs. Evaluation of physico-chemical characteristics of the treated water showed that it meets the requirements imposed by European and Portuguese legislation for its reuse in irrigation and most urban utilities.

Testing the feasibility of geothermal heat sinks with concentrated solar power for effective municipal wastewater disinfection: A pilot study

Efficient disinfection is of prime importance for safe drinking. Despite Kolkata’s significant progress in the socio-economic fronts, the conservative and disjointed approaches used in dealing with the city’s sanitation and wastewater treatment problems have collectively made it one of the hotspots of water-borne diseases, resulting in thousands of deaths per year. Additionally, the high operating cost of the conventional wastewater treatment plants based in Kolkata poses a major concern. This study has therefore, for the very first time integrated geothermal heat sinks with concentrated solar power for wastewater treatment, replacing the need for mechanical heat exchangers and excess cooling water requirement. It is estimated that nearly 67% of the total operating cost of the treatment process associated with disinfection would be reduced, along with zero electricity consumption for cooling the high temperature treated effluent. The study reports that with addition of catalyst, namely TiO2, the disinfection could be further enhanced by removing almost 99.999% of the microbial population. Applications of geothermal heat sinks are available in other domains such as building heating or cooling, refrigerated storages and many others, but, literature specific to its use in wastewater treatment is missing till date.

Performic Acid Disinfection of Municipal Secondary Effluent Wastewater: Inactivation of Murine Norovirus, Fecal Coliforms, and Enterococci.

Performic acid (PFA) is an emerging disinfectant to inactivate bacterial and viral microorganisms in wastewater. In this study, the inactivation kinetics of murine norovirus (MNV) by PFA, in phosphate buffer and municipal secondary effluent wastewater, are reported for the first time. PFA decay followed first-order kinetics and the inactivation of MNV was governed by the exposure of microorganisms to PFA, i.e., the integral of the PFA concentration over time (integral CT or ICT). The extension of the Chick-Watson model, in the ICT domain, described well the reduction of MNV by PFA, with determined ICT-based inactivation rate constants, kd, of 1.024 ± 0.038 L/(mg·min) and 0.482 ± 0.022 L/(mg·min) in phosphate buffer and wastewater, respectively, at pH 7.2. Furthermore, the simultaneous PFA inactivation of MNV and fecal indicators indigenously present in wastewater such as fecal coliforms and enterococci showed that 1-log reduction could be achieved with ICT of 2, 1.5, and 3.5 mg·min/L, respectively. When compared with the most commonly used peracid disinfectant of municipal wastewater, peracetic acid (PAA), the ICT requirements determined using the fitted ICT-based kinetic models were ∼20 times higher for PAA than PFA, indicating a much stronger inactivation power of the PFA molecule.

Wastewater disinfection: long-term laboratory and full-scale studies on performic acid in comparison with peracetic acid and chlorine

Chemical disinfection of municipal wastewater to preserve the microbiological quality of discharges has traditionally relied on chlorine, and more recently on peracetic acid (PAA). A more recent option is performic acid (PFA). This work uses laboratory and full-scale studies over a span of 15 years and five wastewater treatment plants (WWTPs) in Italy, to compare the efficacy of these three disinfectants and identify the differences among peracids in a context where both can be an alternative to chlorine. The investigations focused on treatment effectiveness and bacterial inactivation kinetics using E. coli and the more resistant enterococci, as well as on PFA and PAA decomposition as the residuals may affect the downstream microenvironment. Furthermore, the potential for the two peracids to oxidize organic substances and create troublesome byproducts was also studied. Chlorine, applied as hypochlorite (“HYP”) and here essentially functioning as chloramines, was used as a baseline comparison for the two peracids. Appropriate statistical tests were applied to the data from different WWTPs to account for potential interferences and compounding effects of the different matrices. Average doses of 0.8, 2.9 and 1.4 mg/L and contact times of 18, 21 and 31 min, respectively for PFA, chlorine and PAA guaranteed with a high level of assurance the 5000 CFU/100 mL E. coli limit; the order of effectiveness was PFA > HYP > PAA, refined as PFA > HYP ≈ PAA against E. coli and PFA ≈ HYP > PAA with enterococci. Similar bacterial reductions for the peracids were found at higher disinfectant doses used for the kinetic tests. PFA decayed more quickly than PAA. The first-order decay constants were 0.031 and 0.007 min−1, respectively, suggesting that disinfection residuals when PFA is used may be less of a concern than with PAA. This faster decomposition did not affect the PFA oxidation power on estrone, which was as weak as that of PAA.

Effectiveness of Solar Driven Anodic Oxidation and Uv Methods for Disinfection of Municipal Wastewater in India

This paper presents the performance of the two disinfection methods experimented at a pilot scale level as part of an integrated treatment system involving Anaerobic Digestion (UASB Process) followed by the Constructed Wetlands (CW) for municipal wastewater treatment under Indian conditions. The disinfection methods were installed in parallel at a pilot scale levels involving solar driven Anodic Oxidation (AO) and Ultra-violet (UV). The systems were implemented within the Indo-Euro Research Project “SWINGS” at three places in India namely, Aligarh, Kalyani and Amarkantak, with aim to develop / deploy sustainable wastewater management. This study mainly focused on three microbial groups, total coliforms (TC), fecal coliforms (FC) and E-coli. Both the systems, AO and UV were operated at a very less energy demand. This was in the range 0.25 to 0.30 kWh/m3. The energy requirements was met with the help of roof top solar panels. The raw municipal wastewater contained TC, FC and E. coli in the range of 105 to 107 CFU/100ml. It was found that about 3-log unit indicator organisms were removed in the UASB &amp; CWs. The effluent of CWs were equally fed to the two parallel disinfection systems, AO and UV. Results indicate that UV has shown better performance. The final effluent of AO contains average (TC 42.0±39.2, FC 16.1±13.2, E-coli 5.6±6.3) CFU/100 ml whereas UV effluent was TC 6.6±4.1, FC 1.2±1.0, E-coli 0.1 ±0.3 CFU/100 ml. The study concludes that solar driven disinfection systems like AO and UV are very effective for small flow rates and offers a promising way to energy scarce regions or in remote areas.

Catalytic ozonation by metal ions for municipal wastewater disinfection and simulataneous micropollutants removal

Several works in literature demonstrated that catalytic ozonation using metal ions promotes the decomposition of ozone and generation of hydroxyl radicals (HO•). The purpose of this study was to assess the effects of different metal ions (Fe2+, Co2+ and Al3+) in disinfection of urban wastewater through E.coli and Pseudomonas spp inactivation along with cellular adenosine triphosphate (ATP) depletion. Simultaneously, the effect of catalytic ozonation of secondary effluent on the selected micropollutants removal with different ozone kinetics (acetamiprid, dichlorvos and atrazine) was evaluated in semi-continuous operation. Results demonstrated that E.coli and Pseudomonas spp inactivation increased almost 20% with 1 mg L−1 Fe2+, Co2+, Al3+ and 40% with 10 mg L−1 Fe2+ compared with single ozonation. Fe2+ was the most effective metal ion on inhibiting regrowth after the treatments. The cellular ATP followed the same trend as the indicators microorganisms inactivation, with significant reduction of ATP over the treatment to single ozonation comparison. The ROH,O3 was applied for the treatments to quantify and compare the micropollutants removal by the radical pathway. The improvement of metal ions on ROH,O3 values occurred significantly for both stages of ozonation (before and after initial ozone demand) for all tested metals. Thus, metal ions addition to ozonation process provided an increase in simultaneous disinfection and pesticides removal as well as in the inhibition of bacterial reactivation, which resulted in savings between 30–50% of ozone dose needs compared with the same attainment in single ozonation.

UV and solar photocatalytic disinfection of municipal wastewater: inactivation, reactivation and regrowth of bacterial pathogens

Pollution of water sources by pathogens is a major concern worldwide. This study investigated critical disinfection aspects such as bacterial regrowth or decay and evaluation of metal-ion leaching during photocatalytic disinfection. The inactivation of waterborne bacterial pathogens (Escherichia coli, Salmonella species, Shigella species and Vibrio cholerae) using ultraviolet and solar photocatalysis was evaluated. Bare and metal-ion (silver, copper and iron)-doped titanium dioxide photocatalysts were used to explore comparative performance. The influence of photocatalyst concentration (0.1–1.0 g/L), source of radiation (ultraviolet or solar light) and water type (synthetic and municipal wastewater) was examined. The disinfection data were fitted to the pseudo-first-order model. The disinfection efficiency was higher in saline deionized water (99.9998–100%) that was spiked with the target pathogens (106 colony forming units/mL), compared to actual wastewater samples. Within 180 min of treatment under solar irradiation, disinfection efficacy of 86.8–100% was achieved, while 99.4–100% disinfection efficacy was attained under ultraviolet irradiation within 60 min. A significant difference (p < 0.05) between ultraviolet and solar photocatalysis was observed, and silver-doped titanium dioxide displayed the best performance under all conditions tested. Nevertheless, after a contact time of 180 min, there was no bacterial regrowth observed even for the solar photocatalysis processes; in fact, bacterial decay occurred. The elution of doping metals into the treated wastewater was insignificant. Therefore, the metal-ion-doped photocatalysts were effective under solar radiation, thus overcoming the limitation of bare titanium dioxide which is only effective under ultraviolet light and preventing bacterial regrowth.

Evaluation of synergy and bacterial regrowth in photocatalytic ozonation disinfection of municipal wastewater

The use of solar and ultraviolet titanium dioxide photocatalytic ozonation processes to inactivate waterborne pathogens (Escherichia coli, Salmonella species, Shigella species and Vibrio cholerae) in synthetic water and secondary municipal wastewater effluent is presented. The performance indicators were bacterial inactivation efficiency, post-disinfection regrowth and synergy effects (collaboration) between ozonation and photocatalysis (photocatalytic ozonation). Photocatalytic ozonation effectively inactivated the target bacteria and positive synergistic interactions were observed, leading to synergy indices (SI) of up to 1.86 indicating a performance much higher than that of ozonation and photocatalysis individually (SI≤1, no synergy; SI>1 shows synergy between the two processes). Furthermore, there was a substantial reduction in contact time required for complete bacterial inactivation by 50–75% compared to the individual unit processes of ozonation and photocatalysis. Moreover, no post-treatment bacterial regrowth after 24 and 48h in the dark was observed. Therefore, the combined processes overcame the limitations of the individual unit processes in terms of the suppression of bacterial reactivation and regrowth owing to the fact that bacterial cells were irreparably damaged. The treated wastewater satisfied the bacteriological requirements in treated wastewater for South Africa.

Comparative Inactivation of Murine Norovirus and MS2 Bacteriophage by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent.

Chlorination has long been used for disinfection of municipal wastewater (MWW) effluent while the use peracetic acid (PAA) has been proposed more recently in the United States. Previous work has demonstrated the bactericidal effectiveness of PAA and monochloramine in wastewater, but limited information is available for viruses, especially ones of mammalian origin (e.g., norovirus). Therefore, a comparative assessment was performed of the virucidal efficacy of PAA and monochloramine against murine norovirus (MNV) and MS2 bacteriophage in secondary effluent MWW and phosphate buffer (PB). A suite of inactivation kinetic models was fit to the viral inactivation data. Predicted concentration-time (CT) values for 1-log10 MS2 reduction by PAA and monochloramine in MWW were 1254 and 1228 mg-min/L, respectively. The 1-, 2-, and 3-log10 model predicted CT values for MNV viral reduction in MWW were 32, 47, and 69 mg-min/L for PAA and 6, 13, and 28 mg-min/L for monochloramine, respectively. Wastewater treatment plant disinfection practices informed by MS2 inactivation data will likely be protective for public health but may overestimate CT values for reduction of MNV. Additionally, equivalent CT values in PB resulted in greater viral reduction which indicate that viral inactivation data in laboratory grade water may not be generalizable to MWW applications.

Photocatalytical Deactivation of Pathogens for Municipal Wastewater Reusing

Photocatalysis is one of environment-friendly and efficient methods for municipal wastewater disinfection. In this research, two pathogens, Staphylococcus aureus and fecal coliform, were chosen to investigate the disinfection effects of several TiO2 photocatalysts on sewage plant secondary treatment effluent, compared with UV disinfection. The results show that TiO2 species and concentrations, light intensity, light time, and pH all have significant influences on the pathogen deactivation. It was found that the optimum operation parameters were as follows: the P25 commercial TiO2 powder at the concentration of 0.5 g/L, the light intensity of 40 W, and the radiation duration of 20 min. The photocatalyst performed better at either acid or alkaline condition than neutral. The TiO2 photocatalytic deactivation to S. aureus was more effective than the UV.

State of the Industry Update on the Use of Peracetic Acid for Municipal Wastewater Disinfection

State of the Industry Update on the Use of Peracetic Acid for Municipal Wastewater Disinfection

Disinfection of municipal wastewater by TiO2 photocatalysis with UV-A, visible and solar irradiation and BDD electrolysis

The efficiency of TiO2 photocatalysis induced by ultraviolet and visible irradiation and salt-free&#x0D; electrolysis over boron-doped diamond electrodes to inactivate total (TC) and fecal (FC)&#x0D; coliforms in secondary treated municipal wastewater was evaluated. Photocatalytic&#x0D; experiments were conducted with two types of titania (Degussa P25 and sulfur-doped&#x0D; catalyst) at loadings in the range 0.1-0.5 g l-1 and three types of irradiation, i.e. artificial UV-A,&#x0D; artificial visible and solar. Electrolysis was conducted in a flow-through cell at anodic current&#x0D; densities of 14.3 and 28.6 mA cm-2 without the addition of auxiliary chemicals. Inactivation&#x0D; followed a first-order kinetic expression with regard to bacteria population and the rate was&#x0D; dependent of the experimental conditions in question. In general, electrochemical disinfection&#x0D; was up to about two orders of magnitude faster than photocatalysis; for instance, TC&#x0D; population decreased to less than 5% of the initial population after 9 and 4 min at 14.3 mA&#x0D; cm-2 and 28.6 mA cm-2 respectively. Similar efficiencies with TiO2 photocatalysis would&#x0D; require at least 30 min of contact time. Interestingly, energy consumption for the&#x0D; electrochemical process was computed to about 0.5 kWh per m3 of treated effluent, well&#x0D; below the respective value for photocatalysis.&#x0D;

Solar photocatalytic oxidation and disinfection of municipal wastewater using advanced oxidation processes based on pH, catalyst dose, and oxidant

There are great interests in photocatalytic oxidation of contaminants using advanced oxidation processes (AOP) based on photocatalytic oxidation in recent years. The main aim of the paper is to develop a method which takes care of energy and water conservation together. The study was performed on photocatalytic disinfection of total coliform (TC) bacteria as water microbial pollution and reducing the chemical oxygen demand (COD) as organic pollution index using catalytic and oxidant in present of sun light. The municipal wastewater was monitored for TC and in then was irradiated with solar light, solar light/TiO2, and solar light/TiO2/H2O2. Various parameters such as contact time, pH, and different concentration of TiO2 and H2O2 were studied for their effect on reaction process. The result showed that in presence of solar light, catalyst, and oxidant, very effective disinfection and reduction of TC and COD took place. 95.2% and 97% of TC and COD were reduced by irradiation for 240-300 min. Based on the results of various AOP combinations, Solar photolytic, solar/TiO2, Solar/TiO2/H2O2, the rate of COD, and TC removal was in the order of TiO2/H2O2 &amp;gt; TiO2 &amp;gt; Solar photolytic. It can be suggested as an effective treatment method for wastewater containing microbial and organic contamination.

Disinfection of Municipal Wastewater Using ZnO Nanofluids

Due to the rapid elevation of health standards and the limit water resources, disinfection has become a challenging aspect for wastewater treatment. This work uses ZnO nanofluids as disinfection for municipal wastewater treatment. The effects of concentration, the presence of light, treatment time and induction of ultrasound are examined. The results reveal that ZnO nanofluids show the potential to be disinfection. With higher concentration of ZnO, the presence of light, longer treatment time and the induction of ultrasound, ZnO nanofluids showed better disinfection efficiency against wastewater.

Disinfection of Wastewater by Infiltration-Percolation Coupled to UV Irradiation in an Arid Tunisian Area

This paper aimed to the study of microbiological quality of wastewater effluents issued from a sand filter system used as a secondary treatment; this sand filter was coupled to UV irradiation system as a tertiary treatment to assume their possible application as alternatives to chemical disinfection of municipal wastewater before agronomic utilization. For that reason, an infiltration basin of 100 m² of area equipped with two wells of sampling, in the center and in the periphery, has been constructed on the irrigated perimeter of Dissa in Gabes (south east of Tunisia). A comparative study was undertaken concerning the quality of effluents obtained from the sand filter as secondary effluent and from the UV irradiation disinfection system as a tertiary municipal wastewater treatment. Both the combined systems gave effluent of excellent microbiological quality (almost total absence of E. coli, faecal coliforms and P. aeruginosa). However, if the microbiological quality of effluent remained constant in the case of a sand filter system which depends only on the quality of the influent, while with the UV-disinfection process, microbiological quality of tertiary effluent was shown to depend on the quality of secondary effluent. The monitoring of the UV irradiation device using a UV dose of around 96 mW.s.cm-2 and corresponding to an exposure time of 16 sec, for the secondary effluent at the outlet of Sand Filter, showed that the average bacterial inactivation rate was around 3 U-Log for E. coli, faecal coliforms and P. aeruginosa, respectively. Therefore, the average concentration remaining in the effluent at the output of the UV reactor, was less than a 100 cfu/ 100 ml for E. coli and faecal coliforms, and less than a 100 bacteria/ 100 ml for P. aeruginosa. These values coincided with the range recommended by several standardized international guidelines.

Ozone and UV254 Radiation for Municipal Wastewater Disinfection

Bench-scale experiments were conducted with municipal wastewater effluent samples to examine the feasibility of combined application of ozone and ultraviolet (UV) radiation for disinfection. Effluent samples displayed rapid initial ozone demand, which promotes ozone transfer but diminishes disinfection efficacy. Ozone doses up to 10 mg/L yielded only trace quantities of residual ozone; despite the fact that initial ozone demand was never exceeded, quantifiable (though variable) inactivation of E. coli was observed, along with modest improvements of UV transmittance. Results from collimated beam experiments demonstrated that compliance with effluent discharge permit limitations could be achieved consistently with a UV254 dose of 12.4 mJ/cm2 at a pre-ozonation dose of 2 to 3 mg/L. In the absence of pre-ozonation, consistent compliance was observed at a UV dose of 16.5 mJ/cm2. No evidence of synergism between ozone and UV254 radiation was found in the measured inactivation responses of E. coli.