Removal Of Organic Substances Research Articles

Assembly of core-shell Fe3O4 @CD-MOFs derived hollow magnetic microcubes for efficient extraction of hazardous substances: Plausible mechanisms for selective adsorption

Hazardous heavy metals and organic substances removal is of great significance for ensuring the safety of aquatic-ecosystem, yet the highly effective and selective extraction always remains challenging. To address this problem, magnetic hollow microcubes were fabricated through thermal carbonization of Fe3O4-COOH@ γ-CD-MOFs, and core-shell structured precursors were in-situ greenly constructed on a large scale via microwave-assisted self-assembly strategy. As noted, the development of secondary crystallization was utilized to achieve uniform dispersion of cores within MOFs frameworks and thus improved magnetic and adsorption ability of composites. Acquired magnetic Fe3O4 @HC not only can harvest excellent extraction of heavy metals (Cd, Pb, and Cu of 129.87, 151.05, and 106.98 mg·g−1) but also exhibit highly selective adsorption ability for cationic organics (separation efficiency higher than 95.0 %). Impressively, Fe3O4 @HC achieved outstanding adsorption (60–80 %) of Cd in realistic mussel cooking broth with no obvious loss in amino acid. Characterizations better offer mechanistic insight into the enhanced selectivity of positively charged pollutants can be attributed to synergistic effect of ions exchange and electrostatic interaction of abundant oxygen-containing functional groups. Our study provides a feasible route by rationally developing core-shell structured composites to promote the practical applications of sustainable water treatment and value-added utilization of processing by-products.

Mechanistic insights into different illumination positions control algae production in anaerobic dynamic membrane filtration (AnDM) during decentralized wastewater treatment

Sunlight illumination has the potential to control the stability and sustainability of dynamic membrane (DM) systems. In this study, an up-flow anaerobic sludge blanket (UASB) reactor was combined with DM under different illumination positions (direct, indirect and no illumination) to treat wastewater. Results indicated that the UASB achieved a COD removal up to 87.05 % with an average methane production of 0.28 L/d. Following treatment by the UASB, it was found that under illumination, the removal of organic substances by DM exhibited poor performance due to algal proliferation. However, the DM systems demonstrated efficient removal of ammonia nitrogen, ranging from 96.21 % to 97.67 % after stabilization. Total phosphorus removal was 45.72 %, and membrane flux remained stable when directly illuminated. Conversely, the DM system subjected to indirect illumination showed unstable membrane flux and severe fouling resistance. These findings offer valuable insights into optimizing illumination positions in DM systems under anaerobic conditions.

Synergistic photocatalytic ozonation of eliminating chloramphenicol over a 2D MXene-derived heterojunction

Herein, we demonstrate the first example of applying 2D MXene hetero-interfaced nanocomposites for a photocatalytic ozonation of chloramphenicol (CAP). The hierarchical 2D/2D Bi2MoO6/Ti3C2Tx MXene (BMT) hybrid enables a high CAP removal ratio of 95 % within 60 min that outperforms bare Bi2MoO6. Evidences from theoretical calculations and experimental findings prove that the adsorption capability of O3/O2 onto BMT surfaces is elevated and the electron transfer process is accelerated by virtue of hybridization with Ti3C2Tx, thus facilitating the generation of reactive oxygen species (ROSs) including •OH, 1O2 and •O2−. Such elaborate design provides a novel type of robust and cost-effective material adapted for integrated advanced oxidation processes (AOPs) in highly efficient removal of refractory organic substances in water environments.

Removing refractory organic substances from landfill leachate using a nanofiltration membrane bioreactor: Performance and mechanisms

Membrane bioreactors (MBRs) are typically used to dispose landfill leachate, but they are challenged by the low removal of refractory organic substances. To address this challenge, in this study, we replaced the commonly used microfiltration (MF) membranes in conventional MBRs with nanofiltration (NF) membranes, i.e., MBRNF. We operated a one-step MBRNF for 127 days and benchmarked against a conventional MBRMF in terms of membrane fouling, pollutants removal, and bulk solution properties. The results showed that the NF membrane could effectively reject refractory organic substances, leading to a longer organic retention time (ORT) and a higher concentration of refractory organic substances in the bioreactor. Consequently, the MBRNF outperformed MBRMF by 20 %–30 % in removing of refractory organic substances, mainly by the enhanced biodegradation of refractory organic substances with low molecular weight. Further investigation suggested that the enhanced biodegradation in the MBRNF could be ascribed to 1) more biomass in the bioreactor; 2) higher concentration of refractory organic substances in the bioreactor; and 3) the enrichment of dominant bacteria such as Chloroflexi. These findings highlight the potential of MBRNF in removing refractory organic substances from landfill leachate and other wastewaters with poor biodegradability.

Simultaneous removal of lead, cadmium, and norfloxacin by Calcite/PMS system: Performance and mechanisms

This work investigated the performance and mechanisms of calcite activating peroxymonosulfate (PMS) for the simultaneous elimination of lead (Pb(II)), cadmium (Cd(II)), and norfloxacin (NOR). At an initial pH = 7, 1.0 g/L calcite, and 0.5 mM PMS, the removal of Pb(II), Cd(II), and NOR was 97.5%, 96.0%, and 98.1%, respectively. The results of EPR, quenching, and chemical probe quantification experiments revealed that singlet oxygen (1O2) derived from calcite activating PMS dominated NOR degradation. Meanwhile, surface complexation and carbonate precipitation were identified as the main mechanisms in the removal of Pb(II) and Cd(II) by ATR-FTIR and different ionic strength experiments, respectively. Kinetic analysis and XPS results indicated that the solid phase Pb(IV) generated through surface complexed Pb(II) oxidized by PMS facilitated the NOR degradation. The NOR degradation pathway along with biological toxicity assessment was also presented through HPLC-MS and ECOSAR software. This study provides the prospects of using natural carbonate minerals to activate PMS for treating the combined contamination of antibiotics and heavy metal ions, and also provides a new understanding of the removal of organic substances in the presence of heavy metal ions.

HORIZONTAL FLOW PILOT CONSTRUCTED WETLAND FOR DAIRY WASTEWATER PURIFICATION

Due to the natural energy sources used in constructed wetlands, minimal energy and chemicals are required for wastewater treatment. For the successful wastewater treatment via constructed wetlands, adequate pretreatment and a sufficient amount of oxygen are crucial. Constructed wetlands can be used to treat industrial wastewater, such as wastewater from the dairy industry, with prior degreasing. This study was conducted on a horizontal flow pilot constructed wetland located on a plot of land used by the Biotechnical Faculty in Bihać. The constructed wetland consisted of two fields planted with rushes (Typha latifolia) and reeds (Phragmites australis). The substrate and plants were not changed during the experimental period. We monitored the efficiency of industrial wastewater treatment (wastewater from the dairy industry) by season, varying the flow rate as well as the hydraulic retention time of the water in the device. The quality of the influent and effluent was monitored by determining analytical parameters. The constructed wetland showed the highest efficiency in the summer period, with a hydraulic retention time of 6 days, with removal efficiencies of 98.03% for ammonia, 98.19% for total nitrogen, 95.27% for total phosphorous, 94.50% for COD and 97.73% for BOD5. The organic substance removal efficiency across all four seasons was 94.68%.

Combination of activated carbon/ultrafiltration as pre-treatment for seawater reverse osmosis plants

Seawater Reverse Osmosis (SWRO) is a common technology to treat seawater to comply high freshwater demand. Currently, the main issue of seawater/brackish water as the potential sources for drinking water is vulnerable to organic pollutants. An effective pre-treatment is crucial to maintain the efficiency of SWRO for sustainable operation. Optimization of the process could be performed by a hybrid membrane combination using commercial Activated Carbon (AC) with based material coconut shell/coal and Ultrafiltration membrane (UF). For hybrid process, the activated carbon was continuously dosed into the pilot scale filtration employing PES Hollow Fiber membrane with active area of 4 m² and average pore size of 10 nm that represents a real operation filtration process (i.e., filtration flux, filtration time, backwashing, and cleaning in place), and was performed until 8 filtration cycle sequence. This study investigated membrane performance with combination technique PAC/UF and GAC/UF in Pilot scale experiments within resistance membrane and retention membrane. Combination of Activated Carbon/Ultrafiltration showed synergistic effects in the removal of organic content for COD 40%-96%, UV-VIS 43%-92% and Turbidity 73%-99%. High removal of organics pollutants (COD, UV-VIS and Turbidity) was attributed to small average pore distribution of Activated Carbon (<10 µm) that increase adsorption process. Moreover, hybrid Activated Carbon/UF adsorption kinetics can reduce filtration times to achieved optimal retention. Related to membrane performance, hybrid AC/UF resulted in less permeability declines almost double in first two filtration cycle and slightly less permeability decline until fifth cycle in comparison with single UF process. Better membrane performance can furtherly be explained from less irreversible fouling in case of AC/UF. Combination AC/UF enhanced the control of Irreversible fouling and resulted in better filtration performance as well as higher organic substance removal. Therefore, hybrid AC/UF could be seen as an effective system as pretreatment for SWRO.

Sustainable power production from petrochemical industrial effluent using dual chambered microbial fuel cell

Dual chambered microbial fuel cell (DMFC) is an advanced and effective treatment technology in wastewater treatment. The current work has made an effort to treat petrochemical industrial wastewater (PWW) as a DMFC substrate for power generation and organic substance removal. Investigating the impact of organic load (OL) on organic reduction and electricity generation is the main objective of this study. At the OL of 1.5 g COD/L, the highest total chemical oxygen demand (TCOD) removal efficiency of 88%, soluble oxygen demand (SCOD) removal efficiency of 80% and total suspended solids (TSS) removal efficiency of 71% were seen, respectively. In the same optimum condition of 1.5 g COD/L, the highest current and power density of about 270 mW/m2 and 376 mA/m2 were also observed. According to the results of this study, using high-strength organic wastewater in DMFC can assist in addressing the issue of the petrochemical industries and minimize the energy demand.

Effect of light wavelengths on algal-bacterial symbiotic particles (ABSP): Nitrogen removal, physicochemical properties, community structure

The accumulation of nitrogenous waste, such as ammonia, and its biological nitrification products, namely nitrite and nitrate, poses one of the primary challenges in the water treatment process for Recirculating Aquaculture Systems (RAS). This study proposed the incorporation of light and algal-bacterial symbiotic particles (ABSP)into RAS as a viable solution to address these challenges. The findings indicated that ABSP achieved the RAS water quality standards (ammonia nitrogen <0.5 mg/L, nitrite nitrogen <0.1 mg/L) by the 14th day of operation, while red light achieved and maintained these standards from as early as the 9th day. Further analysis of chemical stoichiometry and functional genes revealed that microalgae (32.7%, 15.6%, 0%) and bacteria (47.7%, 55.8%, 48.4%) were responsible for the assimilation and removal of most organic and nutrient substances under red light, white light, and dark conditions, respectively. Additionally, it was observed that the presence of algae and bacteria in ABSP was significantly influenced by the wavelength of light. Under red light, an optimal distribution of functional species for both microalgae (Characium, Microcoleus, and Uronema) and bacteria (Nakamurella and Micropruina) was achieved, which is crucial for the self-sustaining synergistic reaction and stability of ABSP. This study may offer a promising engineering alternative with enormous potential to achieve energy-efficient and environmentally sustainable RAS water treatment.

Ionic solvent-mediated electrolytic decontamination of pesticide-containing wastewater

Abstract This study investigated the performance of different ionic solvents (NaCl, KNO3, and Na2SO4) in mediating electrolytic decontamination of pesticide-containing wastewaters and established the most suitable ionic solvent that can satisfactorily achieve decontamination of such wastewaters. These were done to find a water-purification technique suitable for the removal of recalcitrant and hazardous trace organic substances from wastewater. Organochlorine pesticide (OCP)-containing wastewaters were constituted according to prescribed modalities. It was observed that complete decontamination of the wastewater was achieved within 2 h of using Na2SO4. The study concluded that the 1.0 M of Na2SO4 solution-mediated electrolytic process was most efficient in decontaminating OCP-containing wastewater.

Floc aging: Crystallization and improving low molecular weight organic removal in re-coagulation.

Iron coagulants have been used extensively in drinking water treatment. This typically produces substantial quantities of insoluble iron hydrolysis products which interact with natural and anthropogenic organic substances during the coagulation process. Previous studies have shown that the removal of low molecular weight (MW) organics is relatively poor by coagulation, which leads to their presence during disinfection, with the formation of halogenated byproducts, and in treated water supplies as potentially biodegradable material. Currently, there is little knowledge about the changes that occur in the nature of coagulant flocs as they age with time and how such changes affect interactions with organic matter, especially low MW organics. To improve this deficiency, this study has investigated the variation of aged flocs obtained from two commonly used iron salts and their impact on representative organic contaminants, natural organic matter (NOM) and tetracycline antibiotic (TC), in a real surface water. It was found that aging resulted in increasing crystallization of the flocs, which can play a beneficial role in activating persulfate oxidant to remove the representative organics. Furthermore, acidification was also found to further improve the removal of low MW natural organics and tetracycline. In addition, the results showed that the low MW fractions of NOM (<1K Dalton) were substantially removed by the aging flocs. These results are in marked contrast to the poor removal of low MW organic substances by conventional coagulation, with or without added oxidants, and show that aged flocs have a high potential of reuse for re-coagulation and activation of oxidants to reduce low MW organics, and enhance drinking water quality.

Efficient removal of organic matters and typical odor substances in rural drinking water using Ozone-BAC-UF combined system to meet new water quality standards in China

China has just implemented new drinking water quality standards, canceling the provisions detailed in the previous standards that allowed relatively lenient water quality standards in rural areas, and unifying the water quality requirements for urban and rural areas. In rural areas of China, lakes are important sources of drinking water, but their water typically contain high concentrations of organic pollutants. In addition, removal odorous substances from such sources is challenging. In response to these issues, an ozone-biological activated carbon-ultrafiltration process is proposed and its efficiency in drinking water treatment is explored. The results indicate that O3-BAC pretreatment significantly improved the efficiency of the membrane process in removing organic and odor substances. At an ozone dosage of 2 mg/L, with granular activated carbon as filler and an EBCT of 25 min, the O3-BAC pretreatment allowed removal rates in the membrane system equal to 71.5% of CODMn, 84.2% of UV254, as well as 92.2% and 92.5% of GSM and 2-MIB, respectively, the latter being typical odor compounds. In addition, the function and diversity of the microbial communities in the reactor were evaluated under different pretreatment conditions at different stages: functionally specific microorganisms were enriched in different systems, and some microorganisms contributing to the removal of organic and odorous substances were identified. The effluent from the combined Ozone-BAC-UF process consistently met the new requirements for drinking water in China, implying that the combined system has significant potential for practical applications for drinking water treatment in rural areas.

Environmental Assessment of Microplastic Pollution Induced by Solid Waste Landfills in the Akmola Region (North Kazakhstan)

This paper presents the outcomes derived from an environmental assessment of microplastic pollution resulting from solid waste landfills in the Akmola Region, situated in North Kazakhstan. This research represents a pioneering investigation conducted on microplastics within this specific region. This study encompasses a comprehensive examination of plastic waste disposal sites across the Akmola region, with a particular emphasis on evaluating the status of the municipal solid waste management system. To characterize the plastic content within the waste present at the landfill sites, quantitative techniques were employed. Through experimental means, the composition and fractionation of plastics within the municipal solid waste (MSW) at the landfills were determined. These data were subjected to a comparative analysis, aligning them with official statistics and previously published scientific data from both Kazakhstan and other regions globally. The methodologies employed focused on the “soft” removal of organic substances through the use of oxidants which do not damage plastics, and were tested using a water-bath therapeutic treatment. Furthermore, an analysis of soil samples taken from the landfills unveiled the ultimate retention of microplastic particles, attributed to leachate and rainwater runoff. Extracts were obtained from the subsoil samples using a density-based separation process, involving a three-step extraction followed by subsequent filtration of the resulting supernatants. In addition, the soil samples underwent examination through dry-phase particle fractional separation. The particles were meticulously enumerated and classified, and their dimensions were measured employing microscopic techniques coupled with photographic documentation. The outcomes stemming from these diverse tests will serve as fundamental input for the forthcoming numerical modeling endeavor, which aims to simulate the behavior of microplastics within both soil and water. This endeavor represents a continuation of the research project, the preliminary findings of which are expounded upon in this paper.

Kinetic coefficients of cell growth and removal of organic substances for modeling Anaerobic-anoxic-aerobic method.

Anaerobic-anoxic-aerobic process is one of the biological removal processes of nutrients in wastewater treatment. Phosphorus removal by biological method is a new and developed technique that is done by changing the design of suspended growth systems. This is a cross-sectional descriptive study, which is a pilot workshop based in the first module, and chemistry, physics and microbiological tests were carried out at the wastewater treatment plant laboratory in one of the cities (Pardis) of Tehran province in 2020-2021 during a period of 12months. Was completed. In this research, a total of 500 samples were taken from raw wastewater, aeration pond, effluent, secondary sedimentation and return activated sludge. In this research, the internal decay coefficient and the growth efficiency coefficient are equal to d-1 0.1264 and 0.6579 gVSS/gCOD, respectively. And the maximum specific rate of consumption of food substance and the semi-saturation constant of food substance respectively were gCOD/gVSS.d 3.3467 gCOD/m 25.305. If the specific rate of consumption of food substance or efficiency factor in our research is 0.27 gCOD/gVSS.d and the semi-constant Ks saturation equal to 27.9 gCOD/m has been obtained, this actually shows that the organic matter (COD) in the waste water of Pardis city had a higher degradability (sbCOD). According to the obtained results, the synthetic coefficients in the Lineweaver-Burk and Hanes models are suitable, but in the Hofstee model, the amount of K and Kd is less than the optimal amount for the proper exploitation of the pilot.

The effect of the combined system of hydrodynamic cavitation, ozone, and hydrogen peroxide on chlorophyll a and organic substances removal in the raw water

Increased levels of nutrients and algae can cause drinking water problems in communities. Harmful algal blooms affect humans, fish, marine mammals, birds, and other animals. In the present study, we investigated the use of a combined system [Hydrodynamic Cavitation, Ozone (O3), and Hydrogen Peroxide (H2O2)] on the removal of Chlorophyll a and Organic substances in the raw water was investigated. The Effect of different operating conditions such as pH, cavitation time, pressure, distance, flow rate, ozone dose, and hydrogen peroxide concentration was studied. Utilizing the Taguchi design method, experiments were planned and optimized. The combined system treatment yielded a maximum reduction in Chlorophyll a and Total Organic Carbon (TOC) at an optimum condition of pH 5, cavitation pressure 5 bar, flow rate of 1 m3/h, a distance of 25 cm from the orifice plate, O3 3 g/h and 2 g/l of H2O2 concentrations. The most efficient factor in the degradation of TOC and Chlorophyll a, was cavitation pressure based on the percentage contributions of each parameter (38.64 percent and 35.05 percent, respectively). H2O2 was found to have the most negligible impact on degradation efficiency (4.24 percent and 4.11 percent, respectively).

Effects of the Addition of Bamboo Charcoal on the Water Purification Ability of Micro-organism-Supported Crystallization Type Phosphorus Removal Materials

In order to prevent water pollution in closed waters such as inner bays and lakes, it is essential to establish a method to remove phosphorus and organic substances which cause water pollution. We have tried to give organic substances removal ability to a crystallization type phosphorus remover composed of gypsum and CaCO3 by supporting useful microorganisms on the surface of the remover. In this study, the effects of loading micro-organisms derived from activated sludge on the water purification ability of the phosphorus remover were investigated. In addition, the effects of adding bamboo charcoal as a carbon source to the phosphorus remover on the adherence of microorganisms and the organic matter removal capacity were examined. The phosphorus removal material was obtained by mixing gypsum, CaCO3 and bamboo charcoal in specified volume proportions. Microorganisms were loaded on the specimens by immersing them in activated sludge for 5 days. The microorganisms supported samples by immersing in activated sludge showed higher organic matter removal capacity than the non-microbial-supported sample. Furthermore, the bamboo charcoal-added samples were able to remove organic matter in a short time than the samples without bamboo charcoal. The phosphorus removal ratio of the sample after immersing in activated sludge was almost the same as that before immersion, but when the amount of bamboo charcoal added was excessive, the phosphorus removal ratio decreased drastically. This decrease in phosphorus removal ratio would be attributed to a decrease in the content of CaCO3, which acts as a crystallization site for calcium phosphate, and to the coating of CaCO3 exposed on the surface of the phosphorus remover by the adherence of a large amount of microorganisms due to the excessive addition of bamboo charcoal.

Effects of the Type of Micro-Organism on the Water Purification Ability of Micro-Organism Supported Crystallization Type Phosphorus Removal Materials

In order to prevent water pollution in closed waters such as inner bays and lakes, it is essential to establish a method to remove phosphorus and organic substances which cause water pollution. We have tried to give organic substances removal ability to a crystallization type phosphorus remover composed of gypsum and CaCO3 by supporting useful microorganisms on the surface of the remover. In this study, the effects of types of microorganisms derived from activated sludge or culture solution on the water purification ability of the phosphorus remover supported with microorganisms were investigated. The porous phosphorus removal material was obtained from solidified gypsum containing NaCl by washing to dissolve the NaCl, silica coating and carbonating. The phosphorus removal material supported with micro-organisms by immersing in activated sludge showed high organic matter removal ability, and there was almost no change in phosphorus removal ability before and after the micro-organisms were supported. In contrast, when microorganisms were supported by immersing materials in culture solution, the phosphorus removal capacity was significantly lower than that before immersing in the culture solution. In addition, the removal capacity of organic substances was lower than that of the materials immersed in activated sludge. The decrease in phosphorus removal ability and low organic matter removal ability of the materials immersed in the culture solution are caused by the detachment of the silica coating layer and CaCO3 on the surface of the phosphorus removal material. Therefore, activated sludge as the type of microorganisms is more effective than culture solution to prepare the water purification material which has both the phosphorus removal and organic substances removal capabilities.

Pilot-scale removal of persistent and mobile organic substances in granular activated carbon filters and experimental predictability at lab-scale

Present knowledge about the fate of persistent and mobile (PM) substances in drinking water treatment is limited. Hence, this study assesses the potential of fixed-bed granular activated carbon (GAC) filters to fill the treatment gap for PM substances and the elimination predictability from lab-scale experiments. Two parallel pilot filters (GAC bed height 2 m, diameter 15 cm) with different GAC were operated for 1.5 years (ca. 47,000 BV throughput) alongside rapid small-scale column tests (RSSCT) designed based on the proportional diffusivity (PD) and the constant diffusivity (CD) approaches. Background dissolved organic matter (DOM) and a set of 17 target substances were investigated, among them 2-acrylamido-2-methylpropane sulfonate (AAMPS), adamantan-1-amine (ATA), melamine (MEL) and trifluoromethanesulfonic acid (TFMSA). Nine substances were predominantly present in the drinking water used as pilot filter influent (frequencies of detection above 80 %, median concentrations 0.003–1.868 μg/L) and their breakthrough behaviors could be observed: TFMSA was not retained at all, four substances including AAMPS and ATA reached complete breakthrough below 20,000 BV, three compounds were partially retained until the end of operation and oxypurinol was retained completely. The comparable PM candidate and DOM removal performances of both GAC aligns with their very similar surface characteristics and elemental compositions. The agreement of results between RSSCT with the pilot-scale filters were substance specific and no superior RSSCT design could be identified. However, CD-RSSCT provide a conservative removal prediction for most studied compounds. MEL adsorption was significantly underestimated by both RSSCT designs. Using the criterion of a carbon usage rate (with respect to 50 % breakthrough) below 25 mgGAC/Lwater for an economic retention by fixed-bed GAC filters, five (out of nine) substances met the requirement.

The degradation of high emulsified oil wastewater in an intermittently-aerated MBBR packed with magnetic polystyrene particles

This work aims to explore the effects of the magnetic polystyrene particles (MPS) on contaminants removal of the high emulsified oil wastewater. 26 days intermittently-aerated progress illustrated that COD removal efficiency and the resistance to the shock loading was promoted in the presence of MPS. Gas chromatography (GC) results also indicated that MPS enhanced the number of organic species reduced. According to the cyclic voltammetry test, conductive MPS appeared special redox performance which was considered could to facilitate the extracellular electron transfer. Furthermore, MPS dosing accelerated the electron-transporting system (ETS) activity by 24.91% compared the control. Based on the superior performance above, the conductivity of MPS is considered to be responsible for the enhanced organic removal efficiency. Moreover, the high-throughput sequencing displayed that electroactive Cloacibacterium and Acinetobacter accounted for a higher proportion in the MPS reactor. Additionally, Porphyrobacter and Dysgonomonas which were capable of degrading organics were also enriched more by MPS. To sum up, MPS is a promising additive to enhance the organic substances removal for the high emulsified oil wastewater.

Impact of Polarization Reversal during Photoelectrocatalytic Treatment of WWTP Effluents

Photoelectrocatalysis (PEC) has been already proposed as a polishing treatment for wastewater treatment plants (WWTPs) effluents. In this work, the impact of polarization reversal during PEC process has been studied and evaluated on the basis of the removal of organic substance and color, biodegradability of the matrix, and inactivation of the catalyst. Effluents were sampled from a full-scale WWTP and alternatively treated by electrochemical oxidation (EC), photolysis (PL), photocatalysis (PC), photoelectrocatalysis, and photoelectrocatalysis with reverse polarization (PECr). The efficiency and the kinetics of the process, in terms of removal of organic substance and color, were not affected by reverse polarization and very similar results were obtained by PEC and PECr. The biodegradability of the effluents strongly increased both by PECr (RSBR: 0.84 ± 0.07), and by PEC and PL (0.89 ± 0.11, and 0.78 ± 0.02, respectively). In the selected polarization reversal mode (100 s at −0.1 V every 500 s at 4 V, cell voltage), a similar photocurrent loss after PEC and PECr was observed, suggesting no effect on the activity of the TiO2 mesh. This study can serve as a base for future research on polarization reversal to optimize operation parameters and exploit the procedure to preventing fouling and inactivation of the catalyst.