Advanced Oxidation Processes For Treatment Research Articles

Toxicological Comparison of Water, Wastewaters, and Processed Wastewaters.

Drinking water utilities will increasingly rely on alternative water sources in the future, including wastewater reuse. Safety must be assured in the application of advanced oxidation processes (AOPs) and supporting treatments for wastewater effluent reuse. This study developed toxicological profiles for source and tap waters, wastewaters, and treated effluents by different processes from four military installation locations. The objective of this study was to evaluate the toxicity of extracted organics from diverse source waters and after reuse treatments. The toxicity analyses included thiol reactivity, mammalian cell cytotoxicity, and genotoxicity. Differences in toxicity between source or tap waters and effluents from wastewater treatment processes supported AOP treatment to reduce risks of potable reuse. An anoxic and aerobic activated sludge process followed by sand filtration controlled toxicity to levels similar to a municipal drinking water. An anaerobic membrane bioreactor process exceeded the toxicity levels of a typical drinking water. Two AOP processes (ultraviolet (UV) + reverse osmosis (RO) + chlorination (NaOCl) or RO + UV-H2O2 + NaOCl) significantly reduced toxicity. The integration of the wastewater systems with ultrafiltration, AOP, and RO was effective to reduce the toxicity to levels comparable to, or better than, tap water samples.

Inactivation of Salmonella, Listeria monocytogenes, Aspergillus and Penicillium on lemons using advanced oxidation process optimized through response surface methodology

An advanced Oxidation process (AOP) based on using hydrogen peroxide, ozone and ultraviolet light (UV-C) was developed for inactivating mould spores (Penicillium expansum and Aspergillus niger) and bacterial pathogens (Salmonella Typhimurium and Listeria monocytogenes) inoculated onto lemons. Response Surface Methodology (RSM) with the central rotatable composite design was applied to study the combined effects of the percent of H2O2 (1–6% v/v), UV-C intensity (0.6–3.6 mW/cm2) and treatment time (20–60 s) as independent variables. The dependent variables were the colour change of lemons induced by AOP and log count reductions (LCR) of A. niger spores. Hydrogen peroxide concentration was the key parameter for both antimicrobial efficacy and discoloration of lemons. The optimal conditions for the AOP treatment were 1.88% v/v H2O2, 3.26 mW/cm2, UV-C intensity and 65.2 mJ/cm2 UV-C dose. From an initial loading between 7.23 and 7.62 log CFU/lemon of test microbes, the optimized treatment resulted in a LCR of 1.54 log CFU/lemon for Aspergillus spores and >5 log CFU/lemon for Salmonella and Listeria without changing the sensory characteristics of lemons. Over 30% of citrus fruit is lost to post-harvest spoilage and consequently, decontamination methods are required to reduce the carriage of moulds such as Aspergillus, in addition to inactivating potential human pathogens (e.g. Salmonella and L. monocytogenes). Currently, there is a reliance on post-harvest washing to remove contamination although has low efficacy and potentially can spread contamination between batches. Advanced Oxidation Process (AOP) is an alternative decontamination method that generates antimicrobial free radicals from the UV-C degradation of hydrogen peroxide and ozone. Although antimicrobial, the free radicals also discolor lemons and hence a balance needs to be made between decontamination efficacy and fruit quality. In this study, RSM was applied to identify the optimum treatment that was subsequently verified. Although the current study was limited to lemons, the same approach could be applied to other fresh produce when designing AOP-based treatments.

Predicting the Contribution of Chloramines to Contaminant Decay during Ultraviolet/Hydrogen Peroxide Advanced Oxidation Process Treatment for Potable Reuse

Chloramines applied to control membrane biofouling in potable reuse trains pass through reverse osmosis membranes, such that downstream ultraviolet (UV)/H2O2 advanced oxidation processes (AOPs) are de facto UV/H2O2-chloramine AOPs. Current models for UV/chloramine AOPs, which use inaccurate chloramine quantum yields and ignore the fate of •NH2, are unable to simultaneously predict the loss of chloramines and contaminants, such as 1,4-dioxane. This study determined quantum yields for NH2Cl (0.35) and NHCl2 (0.75). Incorporating these quantum yields and the formation from •NH2 of the radical scavengers, •NO and NO2-, was important for simultaneously modeling the loss of chloramines, H2O2, and 1,4-dioxane in the UV/H2O2-chloramine AOP. Although the level of radical production was higher for the UV/H2O2-chloramine AOP than for the UV/H2O2 AOP, the UV/H2O2 AOP was at least 2-fold more efficient with respect to 1,4-dioxane degradation, because chloramines efficiently scavenged radicals. At low chloramine concentrations, the UV/chloramine AOP efficiency increased with an increase in chloramine concentration, as the level of radical production increased relative to that of radical scavenging by the dissolved organic carbon in RO permeate. However, the efficiency leveled out at higher chloramine concentrations as radical scavenging by chloramines offset the increased level of radical production. The level of 1,4-dioxane degradation was ∼30-50% lower for the UV/chloramine AOP than for the UV/H2O2-chloramine AOP when the concentration of residual chloramines in RO permeate was ∼50 μM (3.3 mg/L as Cl2). Initial cost estimates indicate that the UV/chloramine AOP using the residual chloramines in RO permeate could be a cost-effective alternative to the current UV/H2O2-chloramine AOP in some cases, because the savings in reagent costs offset the ∼30-50% reduction in 1,4-dioxane degradation efficiency.

Pilot-scale comparison of microfiltration/reverse osmosis and ozone/biological activated carbon with UV/hydrogen peroxide or UV/free chlorine AOP treatment for controlling disinfection byproducts during wastewater reuse

Ozone and biological activated carbon (O3/BAC) is being considered as an alternative advanced treatment process to microfiltration and reverse osmosis (MF/RO) for the potable reuse of municipal wastewater. Similarly, the UV/free chlorine (UV/HOCl) advanced oxidation process (AOP) is being considered as an alternative to the UV/hydrogen peroxide (UV/H2O2) AOP. This study compared the performance of these alternative treatment processes for controlling N-nitrosamines and chloramine-reactive N-nitrosamine and halogenated disinfection byproduct (DBP) precursors during parallel, pilot-scale treatment of tertiary municipal wastewater effluent. O3/BAC outperformed MF/RO for controlling N-nitrosodimethylamine (NDMA), while MF/RO was more effective for controlling N-nitrosomorpholine (NMOR) and chloramine-reactive NDMA precursors. The UV/H2O2 and UV/HOCl AOPs were equally effective for controlling N-nitrosamines in O3/BAC effluent, but UV/HOCl was less effective for controlling NDMA in MF/RO effluent, likely due to the promotion of dichloramine under these conditions. MF/RO was more effective than O3/BAC for controlling chloramine-reactive halogenated DBP precursors on both a mass and toxicity-weighted basis. UV/H2O2 AOP treatment was more effective at controlling the toxicity-weighted chloramine-reactive DBP precursors for most halogenated DBP classes by preferentially degrading the more toxic brominated species. However, the total toxicity-weighted DBP precursor concentrations were similar for treatment by either AOP because UV/H2O2 AOP treatment promoted the formation of iodoacetic acid, which exhibits a very high toxic potency. The combined O3/BAC/MF/RO train was the most effective for controlling N-nitrosamines and the total toxicity-weighted DBP precursor concentrations with or without treatment by either AOP.

Degradation of the pharmaceuticals nimesulide and ibuprofen using photo-Fenton process: toxicity studies, kinetic modeling and use of artificial neural networks

The growth of pollution in aquatic environments increases every day, causing compounds like pharmaceuticas to be detected in surface waters. Thus, tecniques such as advanced oxidation processes (AOP) have been used to degrade this compounds. In this work, the efficiency of AOP in the degradation of nimesulide and ibuprofen pharmaceuticals was evaluated through chromatographic analysis as well as organic matter through the levels of chemical oxygen demand (COD) and total organic carbon (TOC). It was verified that the photo-Fenton process presented the bests results, degrading 89.70% of nimesulide and 93.35% of ibuprofen. This same process managed to reduce COD by 91.60% and mineralize 90.04% of the TOC. The kinetic study showed a good linear fit (R2=0.993) for the clustered kinetic model, as well as a good fit to the mathematical model of artificial neural networks (ANNs), with a value of R2=1.000 for the MLP4-4-1 BFGS 4567 model. Finally, the toxicity of the solution after treatment was verified against the seeds of Lactuta sativa, Cichorium endívia, Ocimum basilicum and American Hard grain. It was found that the seeds that received the solution before treatment had a lower germination amount than the ones where the post AOP treatment solution was added. Then, the root growth was evaluated, in which a relative toxic effect was observed.

Advanced oxidation processes for treatment of 17β-Estradiol and its metabolites in aquaculture wastewater

Recirculating aquaculture systems (RAS) allow food fish to be grown in a contained system with minimal water use (up to 99% recirculation) and a small land footprint. Currently, the use of natural estrogen (17β-estradiol; E2) as a feed additive is being studied to increase growth and feminization in American eels (Anguilla rostrata) being grown in a RAS. This study aimed to degrade concentrations of E2 and its metabolites, estrone (E1) and estriol (E3), in aquaculture effluent to below detectable levels to ensure the safe discharge of waste streams. Advanced oxidation processes (AOPs) have been previously used to degrade trace organic contaminants to great effect. This study tested two AOPs (UV and UV/H2O2) for the removal of E2 and its metabolites at low concentrations. Estrogen levels were analyzed using liquid chromatography-tandem mass spectrometry (LC–MS/MS). Increasing UV dose increased the degradation of estrogens and their removal was improved in aquaculture wastewater versus in pure water. The addition of H2O2 did not consistently improve the efficacy of the UV treatments. The results of this study indicate that these processes may be of future commercial use to remove estrogenic compounds from aquaculture wastewater.

Inuence of major anions on the 185 nm advanced oxidation process - Sulphate, bicarbonate, and chloride

The 185 nm wavelength radiation generated by the conventional low pressure mercury lamp forms the basis of an advanced oxidation process (AOP) that does not require chemical addition. The photolysis of water by 185 nm photons generates the hydroxyl radical (OH) used to degrade trace organic contaminants. While AOPs in general suffer decreased efficiency in direct proportion to the concentrations of dissolved organic matter (DOM) and alkalinity (HCO3−/CO32−), acting as OH scavengers, such solutes impose an additional parasitic effect on the 185 nm AOP as absorbers of photons. Furthermore, the major inorganic anions sulphate (▪) and chloride (Cl−) also absorb at 185 nm to generate the highly reactive sulphate (▪) and chlorine (Cl) radicals. Like OH, ▪ and Cl. are also scavenged by DOM and HCO3−/CO32−. Using carbamazepine as a radical probe, and t-butanol or Suwannee River isolate as model DOM, the relative reactivity of these radicals with both DOM and HCO3− was found consistent with the order ▪. Experimental evidence suggests some interconversion between these radicals. The 185 nm AOP treatment efficiency thus depends strongly on the anionic composition of the water matrix, as well as on the relative reactivities of the target contaminant, DOM, and HCO3− with the three radicals OH, Cl., and ▪. Changes in any of these parameters may result in substantial differences in treatment efficiency.

Degradation of ethyl paraben in aqueous medium using advanced oxidation processes: Efficiency evaluation of UV-C supported oxidants

Abstract UV-C-mediated advanced oxidation processes (AOPs) for the enhanced degradation of ethyl paraben (EP) in the presence of oxidants such as persulfate (PS), hydrogen peroxide (H2O2) and peroxymonosulfate (PMS) were systematically investigated. The AOP treatments showed 98.1%, 97.0% and 81.3% degradation of EP with rates of 0.0373, 0.0339, and 0.0202 min−1 within 90 min for UV/PS, UV/H2O2 and UV/PMS, respectively. Degradation rates of EP increased with higher initial dosages of oxidant(s), while the opposite trend was observed in the case of increasing initial EP concentration. Maximum EP removal was achieved at pH 6.5 for UV/PS and UV/PMS and at pH 3 for UV/H2O2. Humic acid significantly retarded the degradation of EP. Chloride (Cl−) and carbonate (CO32−) suppressed reaction rates using UV/PS and UV/H2O2 systems, whereas they elevated the degradation rates with UV/PMS treatment. Degradation of EP in each of the UV-C based AOPs followed pseudo-first-order kinetics. The use of ethanol and t-butyl alcohol as scavengers revealed that HO and radicals were the major reactive radicals in UV/H2O2, UV/PS, and UV/PMS treatments. The efficiency (according to electrical energy per order and total cost per cubic meter) of the systems followed the order UV/PS > UV/H2O2 > UV/PMS. Thus, UV/PS process was more efficient and economical for EP degradation than the other processes examined in this study.

Influence of chloride on the 185 nm advanced oxidation process

The use of 185 nm radiation from a conventional low pressure mercury lamp generates the hydroxyl radical (OH) from the photolysis of water and offers an advanced oxidation process (AOP) for water treatment that does not require chemical addition. However, the influence of the water matrix on the process differs substantially from that of other ultraviolet and ozone based processes. In particular chloride (Cl−), and not water, absorbs the majority of 185 nm photons when [Cl−]>20mgL−1 and generates the chlorine atom radical (Cl) as a reactive species. Evidence suggests that when Cl− is present, Cl and OH both contribute to contaminant degradation to varying extents. Using nonselective (carbamazepine) and selective (nitrobenzene) radical probes, as well as nonselective (t-butanol), and selective (acetone and acetate) radical scavengers, the influence of Cl−, and therefore 185 nm AOP treatment efficiency, is observed to strongly depend on four independent second-order radical rate constants. Furthermore, ionic strength effects support the assumption that Cl is in equilibrium with the relatively nonreactive dichlorine radical anion (▪).

Gene expression in Pseudomonas aeruginosa exposed to hydroxyl-radicals

Recent studies have shown the efficiency of hydroxyl radicals generated via ultraviolet (UV)-based advanced oxidation processes (AOPs) combined with hydrogen peroxide (UV/H2O2) as a treatment process in water. The effects of AOP treatments on bacterial gene expression was examined using Pseudomonas aeruginosa strain PAO1 as a model-organism bacterium. Many bacterial genes are not expressed all the time, but their expression is regulated. The regulation is at the beginning of the gene, in a genetic region called “promoter” and affects the level of transcription (synthesis of messenger RNA) and translation (synthesis of protein). The level of expression of the regulated genes can change as a function of environmental conditions, and they can be expressed more (induced, upregulated) or less (downregulated). Exposure of strain PAO1 to UV/H2O2 treatment resulted in a major change in gene expression, including elevated expression of several genes. One interesting gene is PA3237, which was significantly upregulated under UV/H2O2 as compared to UV or H2O2 treatments alone. The induction of this gene is probably due to formation of radicals, as it is abolished in the presence of the radical scavenger tert-butanol (TBA) and is seen even when the bacteria are added after the treatment (post-treatment exposure). Upregulation of the PA3237 promoter could also be detected using a reporter gene, suggesting the use of such genetic constructs to develop biosensors for monitoring AOPs in water-treatment plants. Currently biosensors for AOPs do not exist, consequently impairing the ability to monitor these processes on-line according to radical exposure in natural waters.

Techno-economical assessment of coupling Fenton/biological processes for the treatment of a pharmaceutical wastewater

A wastewater coming from a pharmaceutical plant of chemical organic synthesis with a TOC of ca 1.4 g/L and low biodegradability has been treated by coupling of advanced Fenton oxidation process and subsequent biological treatment. The influence of the reaction temperature, the hydrogen peroxide concentration and the iron/copper loadings as catalysts in the Fenton process were studied. A moderate oxidant concentration (7.5 mgH2O2/mgTOC) and a temperature of 70 °C enhanced the biodegradability of the wastewater with a TOC reduction of ca. 35%. A subsequent biological treatment operating with HRT and SRT of 2 days and 20 days, respectively, allowed increasing the TOC removal above 90%. The oxidant concentration and the reaction temperature of Fenton process as pre-treatment to increase biodegradability were significantly lower than the values of the Fenton process currently implemented in the pharmaceutical plant to achieve an almost complete mineralization of the organic matter (21.4 mgH2O2/mgTOC and 120 °C, respectively). The techno-economical evaluation of the coupling Fenton/biological system compared to the Fenton process as unique treatment, showed that the lower oxidant uptake of the Fenton process for the coupling system is economically more profitable than using an excess of oxidant and a higher reaction temperature for the intensive Fenton process.

Comparing the UV/Monochloramine and UV/Free Chlorine Advanced Oxidation Processes (AOPs) to the UV/Hydrogen Peroxide AOP Under Scenarios Relevant to Potable Reuse.

Utilities incorporating the potable reuse of municipal wastewater are interested in converting from the UV/H2O2 to the UV/free chlorine advanced oxidation process (AOP). The AOP treatment of reverse osmosis (RO) permeate often includes the de facto UV/chloramine AOP because chloramines applied upstream permeate RO membranes. Models are needed that accurately predict oxidant photolysis and subsequent radical reactions. By combining radical scavengers and kinetic modeling, we have derived quantum yields for radical generation by the UV photolysis of HOCl, OCl-, and NH2Cl of 0.62, 0.55, and 0.20, respectively, far below previous estimates that incorporated subsequent free chlorine or chloramine scavenging by the •Cl and •OH daughter radicals. The observed quantum yield for free chlorine loss actually decreased with increasing free chlorine concentration, suggesting scavenging of radicals participating in free chlorine chain decomposition and even free chlorine reformation. Consideration of reactions of •ClO and its daughter products (e.g., ClO2-), not included in previous models, were critical for modeling free chlorine loss. Radical reactions (indirect photolysis) accounted for ∼50% of chloramine decay and ∼80% of free chlorine loss or reformation. The performance of the UV/chloramine AOP was comparable to the UV/H2O2 AOP for degradation of 1,4-dioxane, benzoate and carbamazepine across pH 5.5-8.3. The UV/free chlorine AOP was more efficient at pH 5.5, but only by 30% for 1,4-dioxane. At pH 7.0-8.3, the UV/free chlorine AOP was less efficient. •Cl converts to •OH. The modeled •Cl:•OH ratio was ∼20% for the UV/free chlorine AOP and ∼35% for the UV/chloramine AOP such that •OH was generally more important for contaminant degradation.

Treatability Studies of Hospital Wastewaters with AOPs by Taguchi’s Experimental Design

In this study, it was studied various advanced oxidation treatment processes; Fenton, UV/H2O2, UV/O3/H2O2 for treatability of hospital wastewaters containing antibiotics (cephalosporines). Taguchi’s L25 orthogonal array design was applied to design of advanced oxidation processes, for simplification of the analysis and calculations. 95,7%, 90,65%, 91,8% COD and 55,86%, 60,83%, 70,8% TOC removal efficiencies were obtained under the best operation conditions for UV/H2O2, UV/O3/H2O2 and Fenton processes, respectively. According to the ANOVA results, pH was of great importance in COD removal for Fenton. For the UV/H2O2 processes, H2O2 has significance in COD and TOC removals. As for the O3/UV/H2O2 processes, O3/UV reaction time was found as an important parameter effecting the removal rates. Also, cephalosporine antibiotic active compounds (cefradine and cefaclor) were degraded completely within minutes for all of the processes. Taguchi’s Method was found useful for the environmental applications and simplifications of advanced oxidation processes for treatment of hospital wastewaters and calculations.

Advanced Oxidation Process sanitization of hatching eggs reduces Salmonella in broiler chicks

The microbial quality of eggs entering the hatchery is an important critical control point for biosecurity, pathogen reduction, and food safety programs in poultry production. Developing interventions to reduce Salmonella contamination of eggs is important to improving the microbial food safety of poultry and poultry products. The hydrogen peroxide (H2O2) and ultraviolet light (UV) Advanced Oxidation Process (AOP) has been previously demonstrated to be effective in reducing Salmonella on the surface of experimentally contaminated eggs. The objective of this study was to evaluate the effect of treating eggs with an egg-sanitizing apparatus using the H2O2/UV AOP on Salmonella contamination during incubation, hatching, and in broiler chicks during grow-out. Experimentally contaminated eggs were treated using the automated H2O2/UV AOP egg sanitizer and incubated for 21 d. AOP sanitization reduced Salmonella up to 7 log10 cfu egg-1 (P < 0.05) from the surface of experimentally contaminated eggs and reduced the number of Salmonella positive eggs by up to 75% (P < 0.05) when treated 1 h post-inoculation. AOP treatment also reduced the number of Salmonella-positive eggs during incubation. Additionally, Salmonella was recovered from more chicks hatched from untreated eggs than from eggs treated using the H2O2/UV AOP egg sanitizer (P < 0.05) through 14 d posthatch. These data suggest reduction of Salmonella contamination on the surface of eggs using the H2O2/UV AOP egg sanitizer prior to incubation may reduce the gastrointestinal colonization of chicks by Salmonella.

Sulfate Radical Technologies as Tertiary Treatment for the Removal of Emerging Contaminants from Wastewater

Water scarcity and water pollution is a worldwide problem and has driven research into eco-friendly and low-energy cost efficient remediation. The reuse of wastewater for non-potable purpose after proper treatment is the only sustainable solution to the problem. Advanced oxidation processes (AOP) based on the in-situ generation of hydroxyl radicals have been intensively investigated for this purpose as a treatment step to achieve wastewater reuse. The main degradation mechanism of AOPs is based on the reaction of hydroxyl radicals with dissolved organic matter. However, hydroxyl radicals follow unselective multi-step pathways, limiting their efficiency in complex environmental matrices. To overcome such limitations, AOP treatment, based on generation of sulfate radicals, has been developed and widely investigated. This current mini-review will cover the most recent developments regarding emerging contaminant removal, i.e., organic micropollutants, using sulfate radicals generated by active persulfate or peroxymonosulfate, with a focus on an application to wastewater effluents for possible wastewater reuse.

Temperature dependence of hydroxyl radical reactions with chloramine species in aqueous solution

The absolute temperature-dependent kinetics for the reaction between hydroxyl radicals and the chloramine water disinfectant species monochloramine (NH2Cl), as well as dichloramine (NHCl2) and trichloramine (NCl3), have been determined using electron pulse radiolysis and transient absorption spectroscopy. These radical reaction rate constants were fast, with values of 6.06 × 108, 2.57 × 108, and 1.67 × 108 M−1 s−1 at 25 °C for NH2Cl, NHCl2, and NCl3, respectively. The corresponding temperature dependence of these reaction rate constants, measured over the range 10–40 °C, is well-described by the transformed Arrhenius equations:ln k (OH & NH2Cl) = (23.68 ± 0.23) – {(8570 ± 580)/(8.314*T/K)}ln k (OH & NHCl2) = (21.96 ± 0.56) – {(6110 ± 400)/(8.314*T/K)}ln k (OH & NCl3) = (21.26 ± 0.29) – {(5770 ± 720)/(8.314*T/K)}giving activation energies of 8.57 ± 0.58, 6.11 ± 0.40, and 5.77 ± 0.72 kJ mol−1 for these three chloramines, respectively. These data will aid water utilities in predicting hydroxyl radical partitioning and chemical contaminant removal efficiencies under real-world advanced oxidation process treatment conditions.

Impact of O3 or O3/H2O2 treatment via a membrane contacting system on the composition and characteristics of the natural organic matter of surface waters.

The present study aims to evaluate changes in the structure-composition of natural organic matter (NOM) that occur after the application of bubbleless ozonation or peroxone treatment of surface waters. The oxidation experiments (using 0.5-2mgO3/mgDOC, or 2:1 O3:H2O2 molar ratio) were performed in a continuous mode, using a tubular ceramic membrane contactor. Fluorescence spectroscopy (emission-excitation matrix) and liquid chromatography-organic carbon detection (LC-OCD) were mainly used for the detailed DOC characterization. In brief, the application of single ozonation resulted to high reduction of humic-like peak fluorescence intensities (50-85%) and also to the formation of two new peaks in the region of protein-like components. The co-addition of H2O2 did not present the anticipated increase in the reduction of fluorescence intensity; however, it resulted to the further oxidation of protein-like fluorophores. LC-OCD measurements confirmed the decrease of average molecular weight of NOM during ozone treatment, due to the gradual degradation of biopolymers (14-23%) and humic substances (11-17%) towards building blocks and low molecular weight (LMW) neutrals. Advanced oxidation process (AOP) treatment by the mixture O3/H2O2 resulted in the simultaneous decrease of building blocks and LMW neutral concentrations. Conventional batch ozonation and AOP experiments were conducted using ozone-saturated solutions to investigate the effect of different contacting patterns. The results revealed that the different reaction pathways followed during bubbleless and conventional batch experiments may also influence the formation of NOM oxidation intermediates.

UV/H2O2 advanced oxidation for abatement of organophosphorous pesticides and the effects on various toxicity screening assays

Advanced oxidation processes (AOPs) are utilized due to their ability to treat emerging contaminants with the fast reacting and non-selective hydroxyl radical (OH). Organophosphorous insecticides are common drinking water contaminants, with 12 different compounds of this class being found on the US EPA’s most recent Candidate Contaminant List (CCL4). The use of the AOP UV/H2O2 for the treatment of organophosphorous insecticides was explored in this study, by coupling biological and analytical tools to follow the abatement of the target compounds. Four insecticides were explored for advanced oxidation treatment: acephate, dicrotophos, fenamiphos, and methamidophos. All four compounds were fast reacting with OH, all reacting with second order rate constants ≥5.5 × 109 M−1s−1. Three major endpoints of toxicity were studied: estrogenicity, genotoxicity (mutagenicity) and neurotoxicity. None of the target compounds showed any estrogenic activity, while all compounds showed an active genotoxic (mutagenic) response (AMES II assay) and most compounds had some level of neurotoxic activity. AOP treatment did not induce any estrogenic activity, and reduced the compounds’ neurotoxicity and genotoxicity in all but one case. Methamidophos degradation by UV/H2O2 resulted in an increase in genotoxicity, likely due to the formation of toxic transformation products. The increase in toxicity gradually decreased with time, possibly due to hydrolysis of the transformation products formed. This study provides insights into parent compound abatement and the changes in toxicity due to transformation products.

Advanced oxidation process and biological treatments for table olive processing wastewaters: constraints and a novel approach to integrated recycling process: a review.

Table olive processing wastewaters constitute a dangerous environmental problem in the Mediterranean countries because of their large volumes, high organic matter and salt concentration. The quantity and the characteristics of wastewaters produced, and thus, their environmental impact, varied depending on the season, varieties, soil and process employed. Several chemicals, biological and combined technologies have proven effective at bringing down organic pollution and toxicity of these effluents. Advanced oxidation processes have recognized as highly efficient treatments for the degradation of organic matter. Nonetheless, complete mineralization is generally expensive without salt removal. Biological processes are the most environmentally compatible and least-expensive treatment methods, but these operations do not always provide satisfactory results. This article surveys the current available technologies and suggests an effective, cheaper alternative for the recycling and the valorization of green table olives wastewaters.

Coupled Inverse Fluidized Bed Bioreactor with Advanced Oxidation Processes for Treatment of Vinasse

Vinasse is the wastewater generated from ethanol distillation; it is characterized by high levels of organic and inorganic matter, high exit temperature, dissolved salts and low pH. In this work the treatment of undiluted vinasse was achieved using sequentially-coupled biological and advanced oxidation processes. The initial characterization of vinasse showed a high Chemical Oxygen Demand (COD, 32 kg m -3 ), high Total Organic Carbon (TOC, 24.5 kg m -3 ) and low pH (2.5). The first stage of the biological treatment of the vinasse was carried out in an inverse fluidized bed bioreactor with a microbial consortium using polypropylene as support material. The fluidized bed bioreactor was kept at a constant temperature (37 ± 1oC) and pH (6.0 ± 0.5) for 90 days. After the biological process, the vinasse was continuously fed to the photoreactor using a peristaltic pump 2.8 × 10 -3 kg of FeSO 4 •7H 2 O were added to the vinasse and allowed to dissolve in the dark for five minutes; after this time, 15.3 m 3 of hydrogen peroxide (H 2 O 2 ) (30% w/w) were added, and subsequently, the UV radiation was allowed to reach the photoreactor to treat the effluent for 3600 s at pH = 3. Results showed that the maximum organic matter removed using the biological process, measured as COD, was 80% after 90 days. Additionally, 88% of COD removal was achieved using the photo-assisted Fenton oxidation. The overall COD removal after the sequentially-coupled processes reached a value as low as 0.194 kg m -3 , achieving over 99% of COD removal as well as complete TOC removal.