Sulfate radical-based oxidation of an alcohol ethoxylate (Brij30®) by the PS/UV-C process.

In this study, sulfate radical-based oxidation of an alcohol ethoxylate (AE) was explored by the persulfate (PS)/UV-C process. Poly(oxyethylene)(4)laurylether, commercially known as Brij30®, was used as a model AE. PS/UV-C oxidation of aqueous Brij30® (8-20 mg/L) was performed at initial PS concentrations varying between 0.50 and 6.50 mM and at initial pH values of 3.0 and 6.0. Results indicated that an increase in both initial PS and Brij30® concentrations did not have a significant effect on Brij30® removal efficiency and that Brij30® abatements of more than 90% could be achieved after 60 min of treatment time. Total organic carbon (TOC) removals were significantly improved with increasing initial PS concentrations for both initial pH values. On the other hand, an increase in initial Brij30® concentration had a negative effect on mineralization. By employing the competitive kinetic method, the second-order reaction rate coefficient of Brij30® with the sulfate radical (SO4 •-) was determined as 1.62 × 109 ± 3.5 × 107 M-1s-1. The second-order reaction rate constant of TOC, originating from Brij30® and reaction intermediates, was found to be 9.09 × 105 ± 2.91 × 105 M-1s-1 and 1.13 × 106 ± 0.46 × 106 M-1s-1 for pH values of 6.0 and 3.0, respectively. Toxicity of PS/UV-C treated aqueous Brij30® solutions towards Vibrio fischeri was also investigated to determine the possible toxic behavior of oxidation products.

Performance of ozone and peroxone on the removal of endocrine disrupting chemicals (EDCs) coupled with cost analysis.

Micropollutants such as endocrine disruptors are one of the most important groups of chemicals polluting water resources. Conventional treatment systems may not be effective for the removal of endocrine disrupting chemicals (EDCs), and the fate of these chemicals should be carefully monitored in the effluent of wastewater treatment plants (WWTPs). Additional treatment methods such as advanced oxidation processes can be used for the removal of endocrine disruptors. This study presents the existence of endocrine disruptors in 4 different effluents: (i) municipal WWTP effluent, (ii) textile industry WWTP effluent, (iii) organized industrial zone (OIZ) WWTP effluent and (iv) pharmaceutical industry discharge and also presents their removal efficiencies by ozonation and peroxone oxidation. A broad spectrum of removal efficiencies was observed for the EDCs present in the samples since the oxidation efficiency of wastewaters containing EDCs mainly depends on the wastewater matrix and on the type of the EDCs. Ozonation was found to be a lower-cost option than peroxone oxidation at the investigated conditions.

Zero-valent aluminum-mediated degradation of Bisphenol A in the presence of common oxidants.

The use of a commercial, nano-scale zero-valent aluminum (ZVA) powder was explored for the treatment of aqueous Bisphenol A (BPA). The study focused on the (i) activation of hydrogen peroxide (HP) and persulfate (PS) oxidants with ZVA to accelerate BPA degradation, (ii) comparison of the treatment performance in pure and real surface water (SW) samples, (iii) effects on toxicity and (iv) reuse potential of ZVA nanoparticles after ZVA/HP and ZVA/PS treatments. In pure water, ZVA coupled with HP or PS provided an effective means of BPA treatment particularly when PS was employed as the oxidant. On the other hand, in BPA-spiked SW, the ZVA/HP treatment combination outperformed ZVA/PS oxidation in terms of BPA removal, whereas ZVA/PS oxidation was superior in terms of organic carbon removal. According to the bioassays conducted in pure and real SW samples with the marine photobacteria Vibrio fischeri and the freshwater microalgae Pseudokirchneriella subcapitata, the toxicity response of BPA and its oxidation products was sensitive to the test organism and water matrix. The inhibitory effect of the reaction solution increased at the early stages of ZVA/PS treatment. The reuse potential of the ZVA/HP treatment system was higher than that of the ZVA/PS treatment system.

Enhanced degradation of micropollutants by zero-valent aluminum activated persulfate: assessment of toxicity and genotoxic activity.

Advanced oxidation of the aqueous Triton™ X-45 (TX-45), iopamidol (IOPA), ciprofloxacin (CIP) and bisphenol A (BPA) solutions via activation of persulfate (PS) with zero-valent aluminum (ZVA) was investigated. The study aimed at assessing the effectiveness of the PS/ZVA process in terms of target micropollutants (MPs) and toxicity abatements in raw surface water (RSW) and distilled water (DW). TX-45, CIP and BPA were completely degraded after 90-minute, 120-minute and 40-minute treatment, respectively, with PS/ZVA in DW, whereas 95% IOPA removal was achieved after 120-minute (MPs = 2 mg/L; ZVA = 1 g/L; PS = 0.25 mM for CIP and BPA; PS = 0.50 mM for TX-45 and IOPA; pH = 3). TX-45 (59%), IOPA (29%), CIP (73%) and BPA (46%) removal efficiencies decreased after 120-minute PS/ZVA treatment in RSW. In DW, Vibrio fischeri toxicities of original (untreated) MPs were found as: CIP (51%) > BPA (40%) > TX-45 (15%) > IOPA (1%), and as BPA (100%) > CIP (66%) > IOPA (62%) > TX-45 (35%) in RSW. Acute toxicities of MPs and their degradation products fluctuated during PS/ZVA treatment both in DW and RSW samples and resulted in different relative inhibition values after 120-minute. The original and PS/ZVA-treated TX-45, IOPA and BPA in DW exhibited neither cytotoxic nor genotoxic effects, whereas CIP oxidation ended up in degradation products with genotoxic effects.

Degradation and toxicity assessment of the nonionic surfactant Triton™ X-45 by the peroxymonosulfate/UV-C process.

The degradation and mineralization of the nonionic surfactant octylphenol ethoxylate (OPEO), commercially known as Triton™ X-45, by the peroxymonosulfate (PMS)/UV-C process were investigated. Three different toxicity tests (Daphnia magna, Vibrio fischeri and Pseudokirchneriella subcapitata) as well as the Yeast Estrogen Screen (YES) bioassay were undertaken to evaluate the potential toxic and estrogenic effects of OPEO and its oxidation products. OPEO removal was very fast and complete after 7 min via PMS/UV-C treatment under the investigated reaction conditions (OPEO = 20 mg L(-1) (47 µM); TOC = 12 mg L(-1); PMS = 2.5 mM; initial reaction pH = 6.5; applied UV-C dose = 21 Wh L(-1)). TOC removal also proceeded rapidly; a gradual decrease was observed resulting in an overall TOC removal of 84%. The toxic responses of PMS/UV-C treated OPEO solutions varied according to the test organism used in the bioassay. Daphnia magna was found to be most sensitive to aqueous OPEO, whereas Pseudokirchneriella subcapitata appeared to be the least sensitive one. Daphnia magna and Vibrio fischeri tests revealed that the inhibitory effect of OPEO decreased significantly during the course of treatment. On the other hand, PMS/UV-C oxidation products exhibited a high toxic effect towards Pseudokirchneriella subcapitata (around 60%). YES test results underlined the need for improving the PMS/UV-C treatment performance to remove the estrogenic activity of OPEO and its oxidation products.

Treatment of aqueous bisphenol A using nano-sized zero-valent iron in the presence of hydrogen peroxide and persulfate oxidants.

Bisphenol A (BPA) is an industrial pollutant considered as one of the major endocrine-disrupting chemicals found in natural waters. In the present study, the use of a commercial, air-stable, zero-valent iron (ZVI) powder, consisting of Fe0 surface stabilized nanoparticles was examined for the treatment of 20 mg/L, aqueous BPA solutions. The influence of pH (3, 5, 7), addition of hydrogen peroxide (HP) and persulfate (PS) oxidants (0.0, 1.25 and 2.5 mM) as well as temperature (25 and 50 °C) was studied for BPA treatment with 1 g/L ZVI. ZVI coupled with HP or PS provided an effective treatment system, which was based on rapid ZVI-mediated decomposition of the above-mentioned oxidants, resulting in complete BPA as well as significant total organic carbon (TOC) (88%) removals, in particular when PS was employed as the oxidant. Increasing the PS concentration and reaction temperature dramatically enhanced PS decomposition and BPA removal rates, whereas HP was not very effective in TOC removals and at elevated temperatures. According to the bioassays conducted with Vibrio fischeri and Pseudokirchneriella subcapitata, the acute toxicity of aqueous BPA fluctuated at first but decreased appreciably at the end of ZVI/PS treatment.

A statistical experimental design approach for mineralization and detoxification of diethyl phthalate by H2O2/UV-C process.

In the present study, a three-factor central composite design (CCD) was implemented to evaluate the major factors (treatment time, initial H2O2 dose and initial diethyl phthalate (DEP) concentration) influencing the H2O2/UV-C treatment of aqueous DEP solution. Significant regression models for total organic carbon (TOC) removal and residual H2O2 concentration were derived using analysis of variance (ANOVA), which were found to be adequate to perform the process variables optimization. According to the applied ANOVA, treatment time (positive effect) and initial H2O2 dose (negative effect after an optimum value) were found to be significant on the H2O2/UV-C process performance. TOC removal efficiencies were enhanced with increasing initial H2O2 dose up to an optimum value, and further increases in H2O2 dose resulted in a decrease in TOC removals due to the hydroxyl radical scavenging effect. When initial H2O2 dose increased from 10 to 30 mM, the TOC removal efficiency improved from 41 to 100% for DEPo of 100 mg/L for treatment time of 50 min. Further increase in initial H2O2 dose to 50 mM decreased the TOC removal efficiency down to 38%. The results of toxicity assessments with Vibrio fischeri on aqueous DEP solutions subjected to H2O2/UV-C treatment revealed complete detoxification at the optimum conditions.

Organic matter and heavy metal removals from complexed metal plating effluent by the combined electrocoagulation/Fenton process.

In the present study, the treatment of metal plating wastewater containing complexed metals originating from the nickel and zinc plating process by electrocoagulation (EC) using stainless steel electrodes was explored. In order to improve the organic matter removal efficiency, the effect of H(2)O(2) addition to the electrocoagulation (the combined EC/Fenton process) application was investigated. For this purpose, a wide range of H(2)O(2) concentrations varying between 15 and 230 mM was tested. All EC and EC/Fenton processes were performed at an initial pH of 2.6 and at an optimized current density of 22 mA/cm(2). Although up to 30 mM H(2)O(2) addition improved the EC process performance in terms of organic matter abatement, the highest COD and TOC removal efficiencies were obtained for the combined EC/Fenton process in the presence of 20 mM H(2)O(2). Nickel and zinc were completely removed for all runs tested in the present study after pH adjustments. At the optimized operation conditions, the combined EC/Fenton process proved to be an alternative treatment method for the improvement of organic matter reduction as well as complexed metal removal from metal plating industry wastewater.

Is the naphthalene sulfonate H-acid biodegradable in mixed microbial cultures under aerobic conditions?

Synthetically prepared wastewater originating from the H-acid (4-Amino-5-hydroxy-2,7-naphthalene disulfonic acid) manufacturing process was subjected to respirometric analysis for evaluating the level of achievable biodegradation in the presence of this commercially important azo dye precursor. For this purpose, H-acid was mixed with synthetic substrate having the same characteristics as sewage at a concentration and composition being typical for H-acid manufacturing wastewater. Experimental results indicated that H-acid was not biodegradable under activated sludge treatment conditions even after prolonged acclimation periods. The results were also confirmed by model evaluation of oxygen uptake rate profiles. H-acid also did not inhibit the biodegradation of synthetic sewage but accumulated as soluble inert COD in the treated wastewater.

Effect of Fenton's oxidation on the particle size distribution of organic carbon in olive mill wastewater.

The study evaluated the effect of Fenton's oxidation on the particle size distribution (PSD) of significant parameters reflecting the organic carbon content of olive oil mill wastewater (OMW). The organic carbon content of the studied OMW was characterized by a COD level of around 40,000 mg/L, with 13,500 mg/L of TOC and 1670 mg/L of total phenols. The corresponding antioxidant activity (AOA) was determined as 33,400mg/L. PSD of the selected organic carbon parameters was investigated using a sequential filtration/ultrafiltration procedure. COD fractionation based on PSD revealed two major components, a soluble fraction below 2 nm and a particulate fraction above 1600 nm representing 49% and 20% of the total COD, respectively. The remaining COD was distributed in the colloidal and supracolloidal zones. The PSD of TOC, total phenols and AOA exhibited similar profiles with peaks at the two ends of the studied size range. Overall COD removals achieved via Fenton's oxidation both at pH=3.0 and pH=4.6 (the original pH of the OMW) remained in the range of 40-50%. As anticipated, the effect of Fenton's treatment was more pronounced in the soluble size range. Fenton's oxidation at pH=3.0 resulted in 46% and 63% removals for total phenols and AOA, respectively. The results obtained indicated that Fenton's process could only be useful as an alternative preliminary treatment option of the required full treatment scheme that could involve a sequence of filtration, oxidation and/or biological treatment steps.