Advanced Oxidation Processes For Treatment Research Articles

Improved mixing of hydrogen peroxide injection in advanced oxidation process treatment using computational fluid dynamics

Improved mixing of hydrogen peroxide injection in advanced oxidation process treatment using computational fluid dynamics

Synergistic effect of biological and advanced oxidation process treatment in the biodegradation of Remazol yellow RR dye

The current study investigated the efficiency of synergistic biological and Advanced Oxidation Process (AOPs) treatment (B-AOPs) using Aeromonas hydrophila SK16 and AOPs-H2O2 in the removal of Remazol Yellow RR dye. Singly, A. hydrophila and AOPs showed 90 and 63.07% decolourization of Remazol Yellow RR dye (100 mg L−1) at pH 6 and ambient temperature within 9 h respectively. However, the synergistic B-AOPs treatments showed maximum decolorization of Remazol Yellow RR dye within 4 h. Furthermore, the synergistic treatment significantly reduced BOD and COD of the textile wastewater by 84.88 and 82.76% respectively. Increased levels in laccase, tyrosinase, veratryl alcohol oxidase, lignin peroxidase and azo reductase activities further affirmed the role played by enzymes during degradation of the dye. UV–Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and gas chromatography–mass spectroscopy (GC–MS) confirmed the biotransformation of dye. A metabolic pathway was proposed based on enzyme activities and metabolites obtained after GC–MS analysis. Therefore, this study affirmed the efficiency of combined biological and AOPs in the treatment of dyes and textile wastewaters in comparison with other methods.

N-Nitrosodimethylamine Formation during UV/Hydrogen Peroxide and UV/Chlorine Advanced Oxidation Process Treatment Following Reverse Osmosis for Potable Reuse.

Chloramines applied to control microfiltration and reverse osmosis (RO) membrane biofouling in potable reuse trains form the potent carcinogen, N-nitrosodimethylamine (NDMA). In addition to degrading other contaminants, UV-based advanced oxidation processes (AOPs) strive to degrade NDMA by direct photolysis. The UV/chlorine AOP is gaining attention because of its potential to degrade other contaminants at lower UV fluence than the UV/hydrogen peroxide AOP, although previous pilot studies have observed that the UV/chlorine AOP was less effective for NDMA control. Using dimethylamine (DMA) as a model precursor and secondary municipal wastewater effluent, this study evaluated NDMA formation during the AOP treatment via two pathways. First, NDMA formation by UV treatment of monochloramine (NH2Cl) and chlorinated DMA (Cl-DMA) passing through RO membranes was maximized at 350 mJ/cm2 UV fluence, declining at higher fluence, where NDMA photolysis outweighed NDMA formation. Second, this study demonstrated that chlorine addition to the chloramine-containing RO permeate during the UV/chlorine AOP treatment initiated rapid NDMA formation by dark breakpoint reactions associated with reactive intermediates from the hydrolysis of dichloramine. At pH 5.7, this formation was maximized at a chlorine/ammonia molar ratio of 3 (out of 0-10), conditions typical for UV/chlorine AOPs. At 700 mJ/cm2 UV fluence, which is applicable to current practice, NDMA photolysis degraded a portion of the NDMA formed by breakpoint reactions. Lowering UV fluence to ∼350 mJ/cm2 when switching to the UV/chlorine AOP exacerbates effluent NDMA concentrations because of concurrent NDMA formation via the UV/NH2Cl/Cl-DMA and breakpoint chlorination pathways. Fluence >700 mJ/cm2 or chlorine doses greater than the 3:1 chlorine/ammonia molar ratios under consideration for the UV/HOCl AOP treatment are needed to achieve NDMA control.

Eco-Friendly Cotton/Linen Fabric Treatment Using Aqueous Ozone and Ultraviolet Photolysis

Chemicals for the scouring and bleaching of fabrics have a high environmental load. In addition, in recent years, the high consumption of these products has become a problem in the manufacture of natural fabric products. Therefore, environmentally friendly, low-waste processes for fabric treatment are required. In this paper, we discuss the bleaching of fabrics using advanced oxidation processes (AOP). These processes use electrochemically generated aqueous ozone and ultraviolet (UV) irradiation to achieve bleaching. However, colour reversion often occurs. In this study, we suppressed unwanted colour reversion by treatment with rongalite. After treatment, changes in fabric colour were determined by measuring the colour difference and reflectance spectra. The best bleaching effect was obtained when ozone and UV irradiation treatments were combined, achieving results similar to those of a conventional bleaching method after 60 min of UV irradiation. In addition, the AOP treatment resulted in the simultaneous scouring of the fabric, as shown by the increased hydrophilicity of the fabric after AOP treatment. Thus, this AOP process represents a new fabric bleaching process that has an extremely low environmental impact.

Evaluation of toxicity and mutagenicity of a synthetic effluent containing azo dye after Advanced Oxidation Process treatment

Approximately 20% industrial water pollution comes from textile dyeing process, with Azo dyes being a major problem in this scenario and requiring new forms of efficient treatment. Effluent treatments using the Advanced Oxidation Processes (AOP) are justified by the potential of application in the dyed effluent treatments once they can change the Azo dye chemical structure. Thus, this study aimed to evaluate the toxicity and mutagenic capacity of a synthetic effluent containing Amido Black 10B (AB10B) azo dye before treatment with AOP, named Gross Synthetic Effluent (GSE), and after the AOP, named Treated Synthetic Effluent (TSE). Daphnia magna and Allium cepa tests were used to evaluate acute toxicity effects and chromosomal mutagenesis, respectively. The Salmonella/microsome assay was performed to evaluate gene mutations. In silico assays were also performed aiming to identify the mutagenic and carcinogenic potential of the degradation byproducts of AB10B. There was 100% immobility to D. magna after 24 h and 48 h of treatments with TSE, showing EC50 values around 5%, whereas GSE did not show acute toxicity. However, GSE induced chromosomal mutations in A. cepa test. Both GSE and TSE were not able to induce gene mutations in S. typhimurium strains. These effects can be associated with two byproducts generated with the cleavage of the azo bonds of AB10B, 4-nitroaniline and -2-7-triamino-8-hydroxy-3-6-naphthalinedisulfate (TAHNDS). In conclusion, AOP is an efficient method to reduce the mutagenicity of synthetic effluent containing AB10B and additional methods should be applied aiming to reduce the toxicity.

Comparison of O3-BAC, UV/H2O2-BAC, and O3/H2O2-BAC treatments for limiting the formation of disinfection byproducts during drinking water treatment in India

Natural organic matter (NOM) acts as a precursor to toxic disinfection byproducts (DBPs). Recently it has been established that a mixture of natural and effluent derived organic matter (NefOM) leads to very high concentration of DBPs. Both conventional and non-conventional/advanced ways of drinking water treatment do not remove NefOM sufficiently. Advanced oxidation processes (AOPs) have been shown to oxidize dissolved organic carbon (DOC) effectively but entail high energy inputs. Therefore, combining AOP as a pre-oxidation step with an economical system like biological activated carbon (BAC) filtration is a more economical solution. In this study, BAC was developed from virgin granular activated carbon (GAC) with river Yamuna water, which has the highest levels of DOC in the world, as influent water. Two columns were used, with one of them as a control. For the development of BAC from GAC, Empty bed contact time (EBCT) of 12 min was found to be effective. Steady-state was achieved after 90 days of continuous operation of the columns. After the steady-state was achieved, EBCT of 16 min was found to be optimum for the diffusion of organic molecules inside the biofilm and mineralization by the attached biomass on the surface of BAC.The percentage DO consumption and, DOC/UV254 reduction was found to be constant from t = 90 to t = 120 days, after which the column was assumed to be acting as a BAC column. To optimize the AOP dose for AOP-BAC experiments, biodegradable DOC (BDOC) was measured after various doses of individual AOP treatments. The maximum increase in biodegradability was observed in case of O3/H2O2 with BDOC of 3.43 mg/L at an ozone dose of 5.44 mg/L and 0.5 mM H2O2. All three AOP treated water were passed through BAC columns and change in BDOC, DOC, hydrophobic fraction of DOC and UV254 were observed. The maximum DOC, hydrophobic fraction of DOC and UV254 reduction was observed with O3/H2O2-BAC, as expected from BDOC results. The primary reason is enhanced biodegradability after optimum O3/H2O2 treatment and thus better utilization of simpler organic molecules by microbes in the BAC column. Maximum trihalomethane formation potential (THMFP) reduction was also observed in the case of O3/H2O2-BAC treatment.

Reductive Electrochemical Activation of Hydrogen Peroxide as an Advanced Oxidation Process for Treatment of Reverse Osmosis Permeate during Potable Reuse

The UV/hydrogen peroxide (H2O2) advanced oxidation process (AOP) frequently employed to generate hydroxyl radical (•OH) to treat reverse osmosis permeate (ROP) in potable reuse treatment trains is inefficient, using only 10% of the H2O2. This study evaluated ·OH generation by electron transfer from a low-cost stainless steel cathode. In deionized water, the electrochemical system achieved 0.5 log removal of 1,4-dioxane, a benchmark for AOP validation for potable reuse, within 4 min using only 1.25 mg/L H2O2. Hydrogen peroxide and 1,4-dioxane degradations were maximized near -0.18 and + 0.02 V versus standard hydrogen electrode, respectively. Degradations of positively and negatively charged compounds were comparable to neutral 1,4-dioxane, indicating that degradation occurs by ·OH generation from neutral H2O2 and that electrostatic repulsion of contaminants from the electrode is not problematic. For ROP without chloramines, 0.5 log 1,4-dioxane removal was achieved in 6.7 min with 7 mM salts for ionic strength and 2.5 mg/L H2O2. For ROP with 1.4 mg/L as Cl2 chloramines, 0.5 log 1,4-dioxane removal was achieved in 13.2 min with 7 mM salts and 4.5 mg/L total H2O2 dosed in three separate injections in 5 min intervals. Initial estimates based on lab-scale electrochemical AOP treatment indicated that, except for the cost of salts, the electrochemical AOP featured lower reagent costs than the UV/H2O2 AOP but higher electricity costs that could be reduced by optimization of the electrochemical design.

Inactivation of Salmonella and Listeria monocytogenes on dried fruit, pistachio nuts, cornflakes and chocolate crumb using a peracetic acid-ethanol based sanitizer or Advanced Oxidation Process

Two decontamination methods were evaluated for inactivating a cocktail of Salmonella or Listeria monocytogenes inoculated onto model low moisture foods (LMFs; dried strawberry, dried apple, raisins, chocolate crumb, cornflakes, shell-on or deshelled pistachio nuts). One treatment was based on a peracetic acid-ethanol (PAA-ethanol) sanitizer combination with the other being an Advanced Oxidation Process (AOP) that simultaneously applied UV-C (254 nm), ozone and hydrogen peroxide. The low moisture food was spray inoculated then dried prior to treatment. With Salmonella it was found that a pre-incubation step in 1% w/v glycerol-tryptic soy broth for 1 h prior to plating, significantly increased recovery of the pathogen compared to TSB alone. However, no increased recovery of L. monocytogenes was observed using the TSB-glycerol pre-incubation step. No Salmonella was detected on cornflakes, chocolate crumb and strawberry using 1.25 parts per thousand (‰) PAA-ethanol. The inactivation of Salmonella on deshelled pistachio was significantly higher using 2.5‰ PAA-ethanol sanitizer compared to the AOP treatments tested. Only negligible reductions of Salmonella (<1 log cfu) were obtained with shell-on pistachio treated with PAA-ethanol sanitizer or AOP. Salmonella could be reduced on dried apple slices by >4 log CFU when 5.0‰ PAA-ethanol was applied. L. monocytogenes was more sensitive to PAA-ethanol compared to Salmonella and could be eliminated on all the LMFs apart from shell-on pistachio. An AOP treatment applied 10% v/v hydrogen peroxide, ozone and 54 mJ/cm2 UV-C could significantly reduce Salmonella on dried apple slices compared to when the individual elements (hydrogen peroxide, ozone or UV-C) were applied. Salmonella was also eliminated by AOP on the other LMFs (apart from shell-on pistachio) although the same level of inactivation was achieved by spraying with 10% v/v hydrogen peroxide alone. L. monocytogenes was sensitive to hydrogen peroxide and AOP being eliminated from all the LMFs. Although this may suggest that hydrogen peroxide spray was equivalent to AOP treatment it was noted that no residual H2O2 or changes in visual appearance was evident on samples treated with the latter process. The study has demonstrated that the two decontamination methods assessed can be applied to reduce Salmonella and L. monocytogenes on LMFs although efficacy is dependent on the pathogen and product type.

Organic phosphorus removal using an integrated advanced oxidation-ultrafiltration process

Non-reactive phosphorus (nRP) contains condensed phosphates and organic phosphorus (OP) species that are recalcitrant in secondary wastewater treatment and tend to remain in final effluents. To meet ultra-low effluent P discharge limits, persistent nRP must be removed. The objective of this study was to evaluate the use of an advanced oxidation process (AOP) which couples TiO2/UV photolysis with ultrafiltration to oxidize and remove nRP species. Initial tests utilized OP model compounds, adenosine triphosphate (ATP) and aminoethylphosphonate (AEP), in a binary mixture to evaluate AOP treatment and to elucidate possible mechanisms of phosphorus removal. The results were consistent with a model of preferential ATP binding to the TiO2 surface compared to AEP. On UV light exposure, AEP was removed from solution due to the photooxidation of ATP freeing up binding sites for AEP adsorption and subsequent oxidation. Orthophosphate released during AOP treatment was retained on the TiO2 solids. The AOP was applied to three municipal wastewaters and one automotive industry effluent for P removal. In all cases, phosphorus removal was found to occur through filtration, surface complexation and UV oxidation. Total phosphorus removal efficiencies between 90 and 97% were observed for the municipal wastewater effluents and 44% removal was observed in the industrial effluent after treatment using AOP.

Comparison of the Fe2+/H2O2 and Fe2+/PMS systems in simulated sludge: Removal of PAHs, migration of elements and formation of chlorination by-products

In this study, polycyclic aromatic hydrocarbons (PAHs) at practical concentrations in the simulated sludge treated by the Fe2+/H2O2 and Fe2+/peroxymonosulfate (PMS) systems were evaluated in terms of the PAHs (phenanthrene, anthracene, fluoranthene) removal, element migration, Cl− effect, and chlorination by-product formation. The results indicated that according to the removal rate of PAHs, the optimal dosage of the Fe2+/PMS system (∑PAHs removal rate was 64.66 ± 2.82 %) was 1/30 of that for the Fe2+/H2O2 system (∑PAHs removal rate was 78.63 ± 0.38 %). The elemental contents in the simulated sludge were mainly affected by the extent of advanced oxidation and the amount of generated iron flocs. By studying the PAHs removal, free chlorine formation, total organochlorine content, and PAHs products in Fe2+/H2O2/Cl- and Fe2+/PMS/Cl- systems, it was found that chlorine radicals (·Cl) had high reactivity with phenanthrene and fluoranthene, whereas dichloride anion radicals (Cl2·-) exhibited the opposite behavior. Furthermore, PAHs were oxidized by ·Cl and hydroxyl radical in the Fe2+/H2O2/Cl- system, whereas PAHs and their products were chlorinated by free chlorine and ·Cl in the Fe2+/PMS/Cl- system to six chlorinated by-products such as Cl-PAHs (9-Cl-phenanthrene, 2-Cl-anthracene, 9,10-Cl2-anthracene, 3-Cl-fluoranthene). These results provide some useful suggestions for the safe advanced oxidation process treatment of textile dyeing sludge.

Adsorbable organic halogens formed during treatment of Cl−-containing wastewater by sulfate and hydroxyl radical-based advanced oxidation processes

The formation of adsorbable organic halogens (AOX) in two typical advanced oxidation processes (AOPs), OH-based (UV/H2O2) and SO4−-based (UV/potassium persulfate (PDS)) processes, was investigated during the treatment of Cl−-containing wastewater. Compared with the original AOX concentration (0.08 mg/L), a significant increase in the AOX concentration was observed in both AOPs under the condition that TOC concentration was minimized. Higher concentration of AOX was formed in the UV/PDS process than that in the UV/H2O2 process under all experimental conditions, although the former showed a better performance on TOC removal. An increase of effluent AOX concentration from 0.4 mg/L to 1.1 mg/L in the UV/H2O2 process and from 1.9 mg/L to 3.4 mg/L in the UV/PDS process was observed, respectively, when the Cl− concentration increased from 1800 mg/L to 10000 mg/L. This enhancement of high Cl−concentration on the AOX formation was attributed to the reactive halogen species generated in the AOP treatment. The term AOXMFP was created to determine the AOX formation potential of wastewater and AOPs system. The results showed that organic matters with a molecular weight (MW) between 1 k ∼ 100 k Da tend to form AOX more easily than those with a MW lower than 1 k Da and higher than 100 k Da. In addition, eight and fourteen kinds of formed organic halogens were identified in UV/H2O2 and UV/PDS treated wastewater, respectively. Five kinds of them have been proved to be toxic, which partially contributed to the increase of acute toxicity of effluent. The results of this work provides a new perspective to evaluate, in terms of eco-safety and efficiency, the application of AOPs to wastewater containing high concentration of Cl−.

Treatment of Diethyl Phthalate Leached from Plastic Products in Municipal Solid Waste Using an Ozone-Based Advanced Oxidation Process.

Plastic products in municipal solid waste result in the extraction of phthalates in leachate that also contains large amounts of organic matter, such as humic substances, ammonia, metals, chlorinated organics, phenolic compounds, and pesticide residues. Phthalate esters are endocrine disruptors, categorized as a priority pollutant by the US Environmental Protection Agency (USEPA). Biological processes are inefficient at degrading phthalates due to their stability and toxic characteristics. In this study, the peroxone (ozone/hydrogen peroxide) process (O3/H2O2), an O3-based advanced oxidation process (AOP), was demonstrated for the removal of diethyl phthalate (DEP) in synthetic leachate simulating solid-waste leachate from an open dump. The impact of the O3 dose during DEP degradation; the formation of ozonation intermediate by-products; and the effects of H2O2 dose, pH, and ultraviolet absorbance at 254 nm (UVC) were determined during ozonation. Removal of 99.9% of an initial 20 mg/L DEP was obtained via 120 min of ozonation (transferred O3 dose = 4971 mg/L) with 40 mg/L H2O2 in a semi-batch O3 system. Degradation mechanisms of DEP along with its intermediate products were also determined for the AOP treatment. Indirect OH radical exposure was determined by using a radical probe compound (pCBA) in the O3 treatment.

Sanitization of Chicken Frames by a Combination of Hydrogen Peroxide and UV Light To Reduce Contamination of Derived Edible Products

Chicken carcass frames are used to obtain mechanically separated chicken (MSC) for use in other further processed food products. Previous foodborne disease outbreaks involving Salmonella-contaminated MSC have demonstrated the potential for the human pathogen to be transmitted to consumers via MSC. The current study evaluated the efficacy of multiple treatments applied to the surfaces of chicken carcass frames to reduce microbial loads on noninoculated frames and frames inoculated with a cocktail of Salmonella enterica serovar Enteritidis and Salmonella enterica serovar Typhimurium. Inoculated or noninoculated frames were left untreated (control) or were subjected to treatment using a prototype sanitization apparatus. Treatments consisted of (i) a sterile water rinse, (ii) a water rinse followed by 5 s of UV-C light application, or (iii) an advanced oxidation process (AOP) combining 5 or 7% (v/v) hydrogen peroxide (H2O2) with UV-C light. Treatment with 7% H2O2 and UV-C light reduced numbers of aerobic bacteria by up to 1.5 log CFU per frame (P < 0.05); reductions in aerobic bacteria subjected to other treatments did not statistically differ from one another (initial mean load on nontreated frames: 3.6 ± 0.1 log CFU per frame). Salmonella numbers (mean load on inoculated, nontreated control was 5.6 ± 0.2 log CFU per frame) were maximally reduced by AOP application in comparison with other treatments. No difference in Salmonella reductions obtained by 5% H2O2 (1.1 log CFU per frame) was detected compared with that obtained following 7% H2O2 use (1.0 log CFU per frame). The AOP treatment for sanitization of chicken carcass frames reduces microbial contamination on chicken carcass frames that are subsequently used for manufacture of MSC.

Degradation of chlorpyrifos and inactivation of Escherichia coli O157:H7 and Aspergillus niger on apples using an advanced oxidation process

Chlorpyrifos is a widely used insecticide in apple production but there are concerns that residues ingested by consumers can lead to chronic neurological conditions. In the following, a method based on Advanced Oxidation Process (AOP) was validated for the degradation of chlorpyrifos on apples and inactivating Escherichia coli O157:H7, along with Aspergillus niger spores. AOP is a process that generates free-radicals from the UV-C (at 254 nm) mediated degradation of hydrogen peroxide thereby leading to highly oxidative species. By using Response Surface Methodology (RSM) it was found that the degradation of chlorpyrifos was primarily dependent on UV-C dose and synergistically enhanced by applying the hydrogen peroxide at temperatures up to 66 °C. However, the degradation of chlorpyrifos was independent on the hydrogen peroxide concentration up to 6% v/v. Maximal degradation of chlorpyrifos on apples was achieved through an AOP treatment applying 68.4 kJ/m2 UV dose and 1.22% v/v H2O2 at 66 °C that resulted in 118 μg degradation (representing 59% of the original level) of the pesticide with <20 ppb accumulation of the degradative photoproduct, CPY-O. The same treatment supported a >6.6 log CFU reduction in E. coli O157:H7 and >4.7 log CFU reduction of A. niger spores. Applying UV alone in the case of E. coli O157:H7 or hydrogen peroxide alone against A. niger spores supported a lower level of lethality compared to AOP. In conclusion, the study has demonstrated that an AOP based process can support the degradation of chlorpyrifos and address microbiological hazards associated with apples.

Comparison of toxicity induced by EDTA-Cu after UV/H2O2 and UV/persulfate treatment: Species-specific and technology-dependent toxicity

Advanced oxidation processes (AOPs) can degrade heavy metal complexes in wastewater to improve the removal efficiency of metals. However, the influences of AOP treatments on toxicity induced by metal complexes are not well understood. This study compared the toxicity induced by EDTA-copper (Cu) after UV/persulfate (PS) and UV/H2O2 treatments on luminescent bacteria and human HepG2 cells. The results showed that EDTA-Cu complexes decreased Cu toxicity in luminescent bacteria but increased the cytotoxicity in HepG2 cells, indicating species-specific toxicity. The UV/PS and UV/H2O2 treatments under most pH values and [oxidant]/[EDTA-Cu] conditions decreased the toxicity of EDTA-Cu in HepG2 cells but increased the toxicity in luminescent bacteria. When the ratio of [oxidant] to [EDTA-Cu] was 10, low toxicity in treated solutions was observed in both UV treatment processes. The alkaline precipitation treatment had a significant influence on toxicity reduction after UV/PS treatment; however, it had minimal influence on the UV/H2O2 treatment system. The Cu and total organic carbon (TOC) removal efficiency cannot completely explain the results of toxicity assays. EDTA-Cu intermediates might play important roles in changing the toxicity of EDTA-Cu after both UV treatments. This study provides insights into evaluating the treatment efficiency of UV/PS and UV/H2O2 on EDTA-Cu decomplexation.

Endogenous respiration process analysis between aMBR and UV/O3-aMBR for polluted surface water treatment

Abstract The microbial endogenous respiration process is very important in biological water treatment processes. This study analyzed and compared the endogenous respiration process in an attached growth membrane bioreactor (aMBR) system and a UV/O3 integrated aMBR system (UV/O3-aMBR) in treating polluted surface water with CODMn around 10 mg/L. The endogenous respiration activity of heterotrophic microbes and autotrophic nitrifiers activity in both systems was analyzed and compared. Results show that heterotrophic bacteria and autotrophic nitrifiers enter endogenous respiration at 6 h aeration in an aMBR and 0 h in a UV/O3-aMBR system. Biomass amount on PVA-gel in aMBR was higher than in UV/O3-aMBR in terms of specific respiration rates SOURt, SOURH, and SOURA. Substrate remained on PVA-gel in the aMBR system, but no substrate remained on PVA-gel in the UV/O3-aMBR system. Higher species of microbes, including recoverable and irrecoverable components, existed in the aMBR system as compared to the UV/O3-aMBR system. The UV/O3-aMBR system could make full use of the advanced oxidation process (AOP) and biological process, leading to a higher treatment performance, and has the potential to mitigate total energy demand. Thus, the UV/O3-aMBR system can be used as a new technology for treating polluted surface water with the co-contribution of biological process and AOP treatment.

Functional categories of microbial toxicity resulting from three advanced oxidation process treatments during management and disposal of contaminated water

Large volumes of contaminated water are produced via intentional and unintentional incidents, including terrorist attacks, natural disasters and accidental spills. Contaminated waters could contain harmful chemicals, which present management and disposal challenges. This study investigates three Advanced Oxidation Processes (AOPs) - UV/H2O2, O3/H2O2, and electrochemical oxidation using a boron-doped diamond (BDD) anode - to treat eleven contaminants including herbicides, pesticides, pharmaceuticals, and flame retardant compounds. To address treatment and toxicity concerns, this study focuses on the resulting microbial toxicity via Microtox® toxicity and Nitrification Inhibition tests. The results suggest four functional Microtox® toxicity categories upon AOP treatment, which are useful for streamlining AOP selection for specific applications. Except for one compound, the O3/H2O2 and UV/H2O2 AOPs achieved, within experimental error, 100% parent compound degradation during 2 h of treatment for all contaminants, as well as Microtox® toxicities that declined below 10% by the end of the treatment. In addition, anodic oxidation with a BDD electrode exhibited slower degradation and some increases in Microtox® toxicity. Only one compound exhibited above 50% Nitrification Inhibition, indicating the robustness of activated sludge to many contaminated and AOP-treated waters. These results indicate that AOP pre-treatment can be a viable strategy to facilitate drain disposal of contaminated waters, but that eco-toxicity may remain a concern.

Pilot-scale evaluation of oxidant speciation, 1,4-dioxane degradation and disinfection byproduct formation during UV/hydrogen peroxide, UV/free chlorine and UV/chloramines advanced oxidation process treatment for potable reuse

Advanced oxidation using UV/free chlorine and UV/chloramines are being considered as alternatives to UV/H2O2 for treatment of reverse osmosis (RO) permeate in treatment trains for the potable reuse of municipal wastewater. This pilot-scale comparison of the three advanced oxidation processes (AOPs) evaluated three factors important for selecting among these alternatives. First, the study characterized the speciation of oxidants serving as the source of radicals within the AOPs to facilitate process modeling. Kinetic modeling that included consideration of the chloramines occurring in RO permeate accurately predicted oxidant speciation. Modeling of the UV/free chlorine AOP indicated that free chlorine is scavenged by reactions with ammonia and monochloramine in RO permeate, such that oxidant speciation can shift in favor of dichloramine over the short (∼30 s) timescale of AOP treatment. Second, the order of efficacy for degrading the target contaminant, 1,4-dioxane, in terms of minimizing UV fluence was UV/free chlorine > UV/H2O2 ≫ UV/chloramines. However, estimates indicated that the UV/chloramines and UV/H2O2 AOPs could be similar on a cost-effectiveness basis due to savings in reagent costs by the UV/chloramines AOP, provided the RO permeate featured >3 mg/L as Cl2 chloramines. Third, the study evaluated whether the use of chlorine-based oxidants within the UV/free chlorine and UV/chloramines AOPs enhanced disinfection byproduct (DBP) formation. Even after AOP treatment and chloramination, total halogenated DBP formation remained low at <15 μg/L for all three AOPs. DBP formation was similar between the AOPs, except that the UV/free chlorine AOP promoted haloacetaldehyde formation, while the UV/H2O2 and UV/chloramines AOPs followed by chloramination increased chloropicrin formation. However, total DBP formation on a toxic potency-weighted basis was similar among the AOPs, since haloacetonitriles and haloacetamides were the dominant contributors and did not differ significantly among the AOPs.

Advanced oxidation processes for treatment of leachate from hazardous waste landfill: A critical review

Abstract Leachate produced from hazardous waste landfills (HWLs) is toxic and contain high concentration of refractory organics, ammoniacal-nitrogen, heavy metals, inorganic salts and organo-chloro compounds. Various Advanced Oxidation Processes (AOPs) have been developed in last few decades for efficiently treating the landfill leachate and many are still under development. Researchers have reviewed the performance of conventional AOPs for treating leachate produced from municipal solid waste landfills (MSWLs) but as this leachate is entirely different in characteristics from HWL leachate, these studies are not very useful when it comes to management of HWL leachate; also, specific studies focused on HWL leachate are rarely available. Present study critically reviews various AOPs involving ozone, UV radiation, hydrogen peroxide, electrocoagulation and electrochemical oxidation for their mechanism, treatment efficacy, advantages and limitations with a focus on HWL leachate. A brief review of emerging AOPs like wet air oxidation, hydrodynamic cavitation and ultrasound assisted AOPs is also discussed. This study also aims to identify the AOP which is user friendly, capable to treat the HWL leachate efficiently, discourage the use of chemicals and can be operated at ambient temperature and pressure. After thorough review of different AOPs, Electrocoagulation appears to be a very promising and effective AOP involving in-situ generation of coagulants and converting the organic pollutants in simpler and noble compounds like carbon dioxide and water. Electrocoagulation can be considered as one of the greener and cleaner technology for treatment of HWL leachate, which on optimization can result in a reduction of COD up to 60% along with considerable decrease in metal content in range of 70%–90% and has further potential of improvement and research.

Efficient abatement of an iodinated X-ray contrast media iohexol by Co(II) or Cu(II) activated sulfite autoxidation process.

Efficient abatement of an iodinated X-ray contrast media iohexol by an emerging sulfite autoxidation advanced oxidation process is demonstrated, which is based on transition metal ion-catalyzed autoxidation of sulfite to form active oxidizing species. The efficacy of the combination of sulfite and transition metal ions (Ag(I), Mn(II), Co(II), Fe(II), Cu(II), Fe(III), or Ce(III)) was tested for iohexol abatement. Co(II) and Cu(II) are proven to show more pronounced catalytic activity than other metals at pH8.0. According to the quenching studies, sulfate radical (SO4•-) is identified to be the primary species for oxidation of iohexol. Increasing dosages of metal ion or sulfite and higher pH values are favorable for iohexol abatement. Inhibition of iohexol abatement is observed in the absence of dissolved oxygen, which is vital for the production of SO5•- and subsequent formation of SO4•-. Overall, activation of sulfite to produce reactive radicals with extremely low Co(II) or Cu(II) concentrations (in the range of μgL-1) in circumneutral conditions is confirmed, which offers a potential SO4•--based advanced oxidation process in treatment of aquatic organic contaminants.