Municipal Secondary Effluent Research Articles

Impact of Suspended Solids on the Use of LuminoTox to Detect Toxicity of Micropollutants.

There is an increasing need for tools to monitor toxicity of contaminants of emerging concern (CECs) in wastewater. The purpose of this work was to assess interferences in the presence of total solids (TS) and total suspended solids (TSS) in the LuminoTox at concentrations typical of those found in municipal secondary effluent (SE) and to evaluate a simple sample enrichment method for increased CEC sensitivity. 4 or 10µg/L atrazine in different TS concentrations and in corresponding filtrates (TSS removed) exhibited equivalent toxicities. Because the only difference between these two fractions is theTSS, this result demonstrates that, generally, this fraction does not induce toxicity nor interfere with the bioassay. At constant medium-low TS, the LuminoTox was able to detect the presence of 4µg/L of atrazine but could not distinguish the change in atrazine concentration between 4 and 6µg/L. No inhibition was observed in the presence of a mix of 14 CECs each at 0.23µg/L. However, upon sample enrichment by lyophilization (50×), an inhibition of 81±3% was observed. The enriched SE alone (not spiked with CECs) led to an inhibition of 49±1%, indicating the detection of the CEC contribution to toxicity after sample preconcentration. The LuminoTox is a promising tool for monitoring SE; however, if the intent is to detect CECs, enrichment method optimization is required.

Reduction of Human Norovirus GI, GII, and Surrogates by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent.

The objective of this study was to characterize human norovirus (hNoV) GI and GII reductions during disinfection by peracetic acid (PAA) and monochloramine in secondary wastewater (WW) and phosphate buffer (PB) as assessed by reverse transcription-qPCR (RT-qPCR). Infectivity and RT-qPCR reductions are also presented for surrogate viruses murine norovirus (MNV) and bacteriophage MS2 under identical experimental conditions to aid in interpretation of hNoV molecular data. In WW, RT-qPCR reductions were less than 0.5 log10 for all viruses at concentration-time (CT) values up to 450 mg-min/L except for hNoV GI, where 1 log10 reduction was observed at CT values of less than 50 mg-min/L for monochloramine and 200 mg-min/L for PAA. In PB, hNoV GI and MNV exhibited comparable resistance to PAA and monochloramine with CT values for 2 log10 RT-qPCR reduction between 300 and 360 mg-min/L. Less than 1 log10 reduction was observed for MS2 and hNoV GII in PB at CT values for both disinfectants up to 450 mg-min/L. Our results indicate that hNoVs exhibit genogroup dependent resistance and that disinfection practices targeting hNoV GII will result in equivalent or greater reductions for hNoV GI. These data provide valuable comparisons between hNoV and surrogate molecular signals that can begin the process of informing regulators and engineers on WW treatment plant design and operational practices necessary to inactivate hNoVs.

Removal of Crotamiton from Reverse Osmosis Concentrate by a TiO2/Zeolite Composite Sheet

Reverse osmosis (RO) concentrate from wastewater reuse facilities contains concentrated emerging pollutants, such as pharmaceuticals. In this research, a paper-like composite sheet consisting of titanium dioxide (TiO2) and zeolite was synthesized, and removal of the antipruritic agent crotamiton from RO concentrate was studied using the TiO2/zeolite composite sheet. The RO concentrate was obtained from a pilot-scale municipal secondary effluent reclamation plant. Effective immobilization of the two powders in the sheet made it easy to handle and to separate the photocatalyst and adsorbent from purified water. The TiO2/zeolite composite sheet showed excellent performance for crotamiton adsorption without obvious inhibition by other components in the RO concentrate. With ultraviolet irradiation, crotamiton was simultaneously removed through adsorption and photocatalysis. The photocatalytic decomposition of crotamiton in the RO concentrate was significantly inhibited by the water matrix at high initial crotamiton concentrations, whereas rapid decomposition was achieved at low initial crotamiton concentrations. The major degradation intermediates were also adsorbed by the composite sheet. This result provides a promising method of mitigating secondary pollution caused by the harmful intermediates produced during advanced oxidation processes. The cyclic use of the HSZ-385/P25 composite sheet indicated the feasibility of continuously removing crotamiton from RO concentrate.

Toxicity of Wastewater with Elevated Bromide and Iodide after Chlorination, Chloramination, or Ozonation Disinfection.

Water reuse is receiving unprecedented attention as many areas around the globe attempt to better-manage their fresh water resources. Wastewaters in coastal regions may contain elevated levels of bromide (Br-) and iodide (I-) from seawater intrusion or high mineral content in the source waters. Disinfection of such wastewater is essential to prevent the spread of pathogens; however, little is known about the toxicity of the treated wastewater. In this study, we evaluated the genotoxicity to Chinese hamster ovary (CHO) cells induced by municipal secondary wastewater effluent amended with elevated Br- and I- after disinfection by chlorine, chloramines, or ozone. We calibrated and applied an N-acetylcysteine (NAC) thiol reactivity assay as a surrogate for thiol reactivity with biological proteins (glutathione) of wastewater samples. Chlorination of wastewaters produced CHO cell genotoxicity comparable to chloramination, 3.9 times more genotoxic than the nondisinfected controls. Ozonated wastewater was at least 3 times less genotoxic than the samples treated with chlorine-based disinfectants and was not significantly different compared with the nondisinfected controls. Positive and significant correlations were observed among genotoxicity, cytotoxicity, and NAC thiol reactivity for all disinfected samples. These results indicate that the ozonation of wastewater with high Br- and I- levels may yield organics with lower genotoxicity to CHO cells than chlorine-based disinfection. NAC thiol reactivity, although excluding the possible effect of bromate from ozonation in this work, could be used as a rapid in chemico screen for potential genotoxicity and cytotoxicity in mammalian cells exposed to disinfected wastewaters.

Removal of Nitrogen in Municipal Secondary Effluent by a Vertical Flow Constructed Wetland Associated with Iron-carbon Internal Electrolysis

Aiming at the problem of high concentration of total nitrogen (TN) and low available carbon source for microorganisms in municipal secondary effluent, the vertical flow constructed wetland associated with iron-carbon internal electrolysis (ICIE-VFCW) was applied to investigate the removal efficiencies of pollutants in municipal secondary effluent. Moreover, the mechanism for enhanced nitrogen removal was primarily discussed by the applications of UV visible spectrum (UV-VIS) and gel filtration chromatography (GFC). The results showed that the ICIE-VFCW could improve the COD removal efficiencies and the effluent COD of less than 30 mg·L-1could be stably obtained. The average COD removal efficiencies of the whole year, warm months, and cold months could be increased by 10.16%, 9.81%, 11.22%, respectively, compared to the control group. The effluent TN of the ICIE-VFCW could be maintained below 10 mg·L-1, and the average TN removal efficiencies of the whole year, warm months and cold months could be increased by 13.72%,12.90%,16.17%, respectively. Besides, compared to the influent, the humification, aromaticity and average relative molecular weight (Mr) in the effluent obviously decreased, and the Mr decreased more significantly in the ICIE-VFCW. The ICIE-VFCW could promote the conversion of refractory organics in municipal secondary effluent to the small and readily biodegradable molecules, which could enhance the utilization of organic compounds by microorganisms, thus improving the removal efficiency of nitrogen.

Sensitivity of the LuminoTox tool to monitor contaminants of emerging concern in municipal secondary wastewater effluent

Contaminants of emerging concern (CECs) are generally poorly removed during conventional wastewater treatment. There is a need for rapid, sensitive and inexpensive methods to monitor the quality of treated wastewater effluent. The purpose of this study was to assess the applicability of the LuminoTox as a tool to monitor municipal secondary effluent (SE) and to determine its sensitivity to the presence of CECs. The effect of exposure method on a 14 CECs mix was explored; 20min in the dark or 30min under light were both recommended as they were sensitive to the detection of CECs in wastewater while providing a short run time. Stabilized aqueous photosynthetic systems (SAPS) detected the 14 CECs mix in the wastewater matrices when they were present at a concentration in the 6μg/L to 50μg/L range. Interference on the biosensors were examined in a range of wastewater characteristics commonly observed in SE and, for most cases, biosensors were not inhibited which suggests that, in most cases, wastewater characteristics would not cause toxic interferences. SAPS detected CECs in SE with different modes of action with the degree of sensitivity of individual CECs developed from experimental and literature values as follows: inhibitors of the plastoquinone binding site within photosystem II>direct or indirect inhibitors of photosynthesis acting on binding sites other than that of the QB. SAPS were assessed for their ability to detect residual CECs in SE without sample preparation, however, the effluent examined exhibited minimal inhibition for SAPS II (7±1%) and no inhibition for SAPS I. These results highlight the need for the development of a sample pre-concentration method to increase the biosensor sensitivity towards native CECs. This would allow the LuminoTox to be an effective tool for monitoring wastewater quality with the intent of residual CECs detection.

Comparative mammalian cell cytotoxicity of wastewater with elevated bromide and iodide after chlorination, chloramination, or ozonation

Recycling wastewater is becoming more common as communities around the world try to better control their water resources against an increased frequency of either prolonged droughts or intense flooding. For communities in coastal areas, wastewaters may contain elevated levels of bromide (Br−) and iodide (I−) from seawater intrusion or high mineral content of source waters. Disinfection of such wastewater is mandatory to prevent the spread of pathogens, however little is known about the toxicity of wastewater after disinfection in the presence of Br− and I−. In this study we compared the induction of chronic cytotoxicity in mammalian cells in samples of municipal secondary wastewater effluent amended with elevated levels of Br−/I− after disinfection by chlorine, chloramines or ozone to identify which disinfection process generated wastewater with the lowest level of adverse biological response. Chlorination increased mammalian cell cytotoxicity by 5 times as compared to non-disinfected controls. Chloramination produced disinfected wastewater that expressed 6.3 times more cytotoxicity than the non-disinfected controls and was 1.3 times more cytotoxic than the chlorinated samples. Ozonation produced wastewater with cytotoxicity comparable to the non-disinfected controls and was at least 4 times less cytotoxic than the chlorine disinfected wastewaters. These results indicate that compared to chlorination and chloramination, ozonation of wastewater with high Br−/I− levels yielded the lowest mammalian cell cytotoxicity, suggesting its potential as a more favorable method to disinfect wastewater with minimizing the biological toxicity in mind.

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.

Advanced treatment of municipal secondary effluent by catalytic ozonation using Fe3O4-CeO2/MWCNTs as efficient catalyst.

The advanced treatment of municipal secondary effluent was performed by catalytic ozonation using Fe3O4-CeO2/MWCNTs as catalyst. The experimental results showed that in catalytic ozonation system, the removal efficiency of soluble COD was more than 46% after 30min reaction, and about 36% of effluent organic matters (EfOMs) were mineralized, which was four times higher than that in single ozonation system. Moreover, proteins, humic acids, and UV254 decreased obviously after 30min reaction, but polysaccharides did not significantly decrease. In catalytic ozonation system, the ozone utilization increased, which is favorable for the degradation of EfOM. The organic compounds and alkalinity were the main hydroxyl radical consumers in municipal secondary effluent. The catalytic ozonation process was also effective for the degradation of two target micropollutants (sulfamethazine and carbamazepine). The catalyst could be stable after five-time reuse for catalytic ozonation of effluent.

Microalgae-based advanced municipal wastewater treatment for reuse in water bodies.

Reuse of secondary municipal effluent from wastewater treatment plants in water bodies could effectively alleviate freshwater resource shortage. However, excessive nutrients must be efficiently removed to prevent eutrophication. Compared with other means of advanced wastewater treatment, microalgae-based processes display overwhelming advantages including efficient and simultaneous N and P removal, no requirement of additional chemicals, O2 generation, CO2 mitigation, and potential value-added products from harvested biomass. One particular challenge of microalgae-based advanced municipal wastewater treatment compared to treatment of other types of wastewater is that concentrations of nutrients and N:P ratios in secondary municipal effluent are much lower and imbalanced. Therefore, there should be comprehensive considerations on nutrient removal from this specific type of effluent. Removal of nutrients and organic substances, and other environmental benefits of microalgae-based advanced municipal wastewater treatment systems were summarized. Among the existing studies on microalgal advanced nutrient removal, much information on major parameters is absent, rendering performances between studies not really comparable. Mechanisms of microalgae-based nitrogen and phosphorus removal were respectively analyzed to better understand advanced nutrient removal from municipal secondary effluent. Factors influencing microalgae-based nutrient removal were divided into intrinsic, environmental, and operational categories; several factors were identified in each category, and their influences on microalgal nutrient removal were discussed. A multiplicative kinetic model was integrated to estimate microalgal growth-related nutrient removal based majorly on environmental and intrinsic factors. Limitations and prospects of future full-scale microalgae-based advanced municipal wastewater treatment were also suggested. The manuscript could offer much valuable information for future studies on microalgae-based advanced wastewater treatment and water reuse.

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

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

Assessment of the Viability of the Reuse of Sedibeng District Municipal Secondary Effluent in Southern Gauteng, South Africa

Population growth, urbanization, water resources pollution, environmental awareness, uneven distribution of water resources and water scarcity have necessitated water reuse especially in arid and semi-arid countries. Influent and effluent data of chemical and biological analyses from four wastewater treatment plants (WWTPs) in the Sedibeng district municipality (SDM) were used to assess the viability of water reuse. Available worldwide water reuse criteria of Water Reclamation Plants (WRPs) for different reuse options were used to characterize the SDM’s four WWTPs for potable water, power and steel industrial water reuse. Only WWTP4 does not meet the influent design criteria of the New Goreangab WRP in Windhoek, Namibia of 43 mg/l and the DWAF general limit of discharge of 75 mg/l used by Beaufort West WRP in South Africa for COD. WWTP2 and 4 do not meet the DWAF general limit of 25 mg/l for suspended solids. Some of the water quality parameters of the effluents from these plants were non-compliant to the requirements for reuse in power generation and steel manufacturing. However, the implementation of advance treatment technologies such as membrane or advanced oxidation processes (AOPs) as part of the treatment train in a potential WRP would address the water quality issues. Water reclamation of SDM effluent either through direct (DPR) or indirect potable (IPR) water reuse, power generation and steel manufacturing industry has the potential of reuse in the Southern Gauteng region. The success of the selected option would be depended on cost effectiveness, stakeholder commitment and public acceptance of the reuse strategy.

Comparative Mammalian Cell Cytotoxicity of Wastewaters for Agricultural Reuse after Ozonation.

Reusing wastewater in agriculture is becoming increasingly common, which necessitates disinfection to ensure reuse safety. However, disinfectants can react with wastewater constituents to form disinfection byproducts (DBPs), many of which are toxic and restrict the goal of safe reuse. Our objective was to benchmark the induction of mammalian cell cytotoxicity after ozonation against chlorination for three types of real wastewaters: municipal secondary effluent and two sources of minimally treated swine farm wastewaters. A new method to evaluate samples of suspected high cytotoxicity was devised. For the secondary effluent, ozonation reduced the cytotoxicity by as much as 10 times; chlorination lowered the cytotoxicity only when followed by dechlorination. The swine farm wastewaters were up to 2000 times more cytotoxic than the secondary effluent, and the highest reduction in cytotoxicity was 17 times as achieved by ozonation. These results indicate that secondary effluent is preferred over swine wastewaters for agricultural reuse regardless of the tested disinfectants. Ozonation consistently reduced the cytotoxicity of both the full strength and the organic extracts of all tested wastewaters more than chlorination. The only significant correlation was observed in the secondary wastewater between total haloacetonitriles and cytotoxicity. While the association of reduced toxicity with the modification or reduction of specific compound(s) is unclear, regulated DBPs may not be the primary forcing agents.

Disinfection of municipal secondary effluents with microwave-induced electrodeless ultraviolet irradiation for water reuse

BACKGROUND Disinfection is an essential way to ensure the safety of recycled water. Ultraviolet (UV) is an effective and environmentally friendly technique suitable for the disinfection of recycled water. However, UV disinfection also leads to photoreactivation. This work proposes a combined use of UV irradiation and microwave technique to compensate for the limitations of UV disinfection. RESULTS The process of microwave-induced electrodeless ultraviolet (MW-EUV) irradiation was utilized to disinfect municipal secondary effluents. A homemade columnar electrodeless UV lamp was used as the source of UV irradiation. Good disinfection results the under optimal microwave power at 600 W were obtained. There was no photoreactivation after sufficient irradiation. Cell damage of Escherichia coli by MW-EUV irradiation was investigated by measuring the leakage of K+ and protein from cells and was observed by an atomic force microscope (AFM). CONCLUSION The MW-EUV irradiation is demonstrated to be a faster and more effective disinfection method in this study. The irradiated samples could meet the hygienic standards for the reuse of urban recycling water (Standard Number GB/T 18920–2002) in China. The disinfection mainly depends on UV irradiation. The microwave was the main causes of bacterial breakup and deformation. This irreversible damage offsets the biological self-healing phenomenon in UV disinfection.

Transformation of erythromycin during secondary effluent soil aquifer recharging: Removal contribution and degradation path

Erythromycin (ERY), a widely used antibiotic, has recently been detected in municipal secondary effluents and poses serious threats to human health during wastewater reusing. In this study, the removal, fate, and degradation pathway of ERY in secondary effluent during soil aquifer treatment was evaluated via laboratory-scale SAT tests. Up to a 92.9% reduction of ERY in synthetic secondary effluent was observed in 1.0m depth column system, which decreased to 64.7% when recharged with wastewater treatment plant secondary effluent. XRD-fractionation results demonstrated that the transphilic acid and hydrophobic acid fractions in secondary effluent compete for the adsorption sites of the packed soil and lead to a declined ERY removal. Moreover, aerobic biodegradation was the predominant role for ERY removal, contributing more than 60% reduction of ERY when recharged with synthetic secondary effluent. Destruction of 14-member macrocyclic lactone ring and breakdown of two cyclic sugars (l-cladinose and d-desosamine) were main removal pathways for ERY degradation, and produced six new intermediates.

Ecotoxicity evaluation of a WWTP effluent treated by solar photo-Fenton at neutral pH in a raceway pond reactor.

Some pollutants can be resistant to wastewater treatment, hence becoming a risk to aquatic and terrestrial biota even at the very low concentrations (ng L-1-μg L-1) they are commonly found at. Tertiary treatments are used for micropollutant removal but little is known about the ecotoxicity of the treated effluent. In this study, a municipal secondary effluent was treated by a solar photo-Fenton reactor at initial neutral pH in a raceway pond reactor, and ecotoxicity was evaluated before and after micropollutant removal. Thirty-nine micropollutants were identified in the secondary effluent, mainly pharmaceuticals, with a total concentration of ≈80μgL-1. After treatment, 99% microcontaminant degradation was reached. As for ecotoxicity reduction, the assayed organisms showed the following sensitivity levels: Tetrahymena thermophila > Daphnia magna > Lactuca sativa > Spirodela polyrhiza ≈ Vibrio fischeri. The initial effluent showed an inhibitory effect of 40% for T. thermophila and 20% for D. magna. After 20min of photo-Fenton treatment, no toxic effect was observed for T. thermophila and toxicity dropped to 5% for D. magna. Graphical abstract Ecotoxicity removal by solar photo-Fenton at neutral pH. ᅟ.

Micropollutants removal from retentates generated in ultrafiltration and nanofiltration treatments of municipal secondary effluents by means of coagulation, oxidation, and adsorption processes

One important disadvantage of using ultrafiltration (UF) and nanofiltration (NF) for reclamation of secondary effluents from municipal wastewater treatment plants (WWTPs) is the necessity to dispose of the UF and NF retentates. Different advanced treatments including coagulation (iron and alum), oxidation (chlorine, permanganate and ozone) and powdered activated carbon (PAC) adsorption were compared for their efficiencies in removing 11 selected micropollutants and effluent organic matter (EfOM) from UF and NF retentates generated in the filtration of secondary effluents. Ozone exhibited better micropollutants and UV254 removal efficiencies than chlorine and permanganate. Similar abatement of organics was observed when the same specific oxidant dose was applied to UF and NF retentates. Coagulation preferentially removed high molecular weight compounds, being ineffective for the elimination of most micropollutants. In general terms, iron coagulation was more efficient than alum, since iron achieved higher DOC and UV254 removal at lower molar doses. In addition, PAC was an effective method for removing micropollutants, especially hydrophobic and aromatic compounds. The hybrid coagulation/ozonation process improved micropollutants and EfOM (DOC and UV254) removal. A specific ozone dose of 1mgO3mgDOC−1 was able to almost completely remove selected micropollutants from the UF retentate. The final effluent, which is likely more biodegradable and less toxic, could be recirculated to biological treatment processes in the WWTP, avoiding the continuous discharge of non-biodegradable micropollutants through the WWTP effluents.

Inadequacy of carbamazepine-spiked model wastewaters for testing photocatalysis efficiency

The study was performed in order to clarify whether carbamazepine-spiked solutions used as model wastewaters are suitable for the assessment of carbamazepine removal from real secondary municipal effluents by photocatalytic oxidation in the presence and absence of activated carbon. Therefore, carbamazepine (10mgL−1) was dissolved in deionized water or in secondary municipal effluent. Photocatalytic oxidation of these model wastewaters was carried out with TiO2 “P25” (100mgL−1) and UV-A lamps in the absence and in the presence of 20mgL−1 powdered activated carbon (PAC). Carbamazepine was analyzed photometrically. In deionized water at pH5.5, carbamazepine was nearly completely removed with a UV dose of 6.48kJL−1. A similar efficiency of photocatalytic oxidation of carbamazepine added to secondary effluent was observed when the suspension pH was 2.7, while at pH8 and 10.6, carbamazepine removal from spiked secondary effluent with the same UV dose was only 40 and 60%, respectively. Although PAC addition resulted in an initial adsorptive carbamazepine reduction of 20 to 35% from the model wastewaters, it did not lead to markedly enhanced carbamazepine removal in the subsequent photocatalysis phase. During photocatalytic oxidation of unspiked secondary effluent (initial carbamazepine concentration: 133ngL−1) at pH7.3 with and without PAC, carbamazepine concentrations were analyzed by HPLC/MS/MS. While PAC addition resulted in the adsorption of about 90% of the initial carbamazepine, photocatalysis did not lead to any carbamazepine removal at all. This indicates that the experiments with spiked model wastewaters – even in a secondary effluent matrix – are absolutely inadequate for predicting photocatalytic carbamazepine removal under real conditions.

Removal of organophosphate esters from municipal secondary effluent by ozone and UV/H2O2 treatments

Organophosphate esters (OPEs) have emerged as a new class of contaminants due to their massive use as flame retardants and plasticizers. These contaminants are toxic to aquatic organisms and some of them are not biodegradable in wastewater treatment plants. This study investigated the degradation kinetics of eight typical OPEs during ozone and UV/H2O2 treatments in Milli-Q water, humic acid (HA) solution, and municipal secondary effluent. The studied OPEs included three chlorinated: tris(2-chloroethyl) phosphate (TCEP), tris(chloropropyl) phosphate (TCPP) and tris(dichloropropyl) phosphate (TDCP); two aromatic: triphenyl phosphate (TPhP) and tricresyl phosphate (TCrP); and three aliphatic: tri-n-butyl phosphate (TnBP), tris(2-butoxyethyl) phosphate (TBEP), and tris(2-ethylhexyl) phosphate (TEHP). Results indicate that the degradation of target OPEs conformed to the pseudo-first-order kinetics and UV/H2O2 was more effective than ozone for their elimination by comparing the overall removal efficiencies and energy consumptions. Two aromatic and two aliphatic OPEs (i.e., TPhP, TCrP, TnBP and TBEP) were effectively degraded by ozone and UV/H2O2 in the test water matrices, while all chlorinated and one aliphatic OPEs (i.e., TCEP, TCPP, TDCP and TEHP) were found to be recalcitrant to oxidation. Moreover, the presence of HA significantly enhanced the degradation of reactive OPEs in ozone treatment. (C) 2015 Elsevier B.V. All rights reserved.

Degradation of N,N-diethyl-m-toluamid (DEET) on lead dioxide electrodes in different environmental aqueous matrixes

This study investigates the electrochemical degradation of N,N-diethyl-m-toluamide (DEET) on PbO2 and Bi-PbO2 anodes. The difference in electrode crystalline structure was responsible for the better DEET degradation and TOC removal on PbO2 than on Bi-PbO2. In 1 M Na2SO4, the degradation efficiency and apparent rate constant (kapp) of DEET oxidation on PbO2 increased with the increase in current density or temperature (activation energy = 24.4 kJ mol−1). The kapp values in DEET-spiked environmental matrixes (municipal wastewater treatment plant secondary effluent (MWTPSE), groundwater (GW), and river water (RW)) were the same (6.05 × 10−4 s−1), but significantly smaller than that in 1 M Na2SO4 (2.23 × 10−3 s−1). The TOC removal efficiency was better in MWTPSE than in RW and GW; however, the mineralization current efficiencies in MWTPSE and RW were similar but higher than that in GW. During electrolysis, the aromaticity was lower in GW than in RW.