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Color and organic matter removal from dyehouse effluent remains a challenging issue for the environmentalist and textile dyer. Until now, various treatment processes have been proposed with limited success. In this study, the textile dye and model industrial pollutant Reactive Black 5 (RB5; 20 mg/L) could be rapidly degraded by persulfate (PS)-enhanced photocatalytic treatment using a novel, home-made lanthanum iron oxide (LF; 0.5 g/L). LF-mediated heterogeneous photocatalysis was effective when the solution pH was kept below 4. The photocatalytic degradation of RB5 solution was enhanced in the presence of 0.6 and 1.2 mM PS. The dissolved organic carbon (DOC) content of the aqueous, hydrolyzed RB5 solution (initial DOC = 5.15 mg/L) was effectively reduced by LF/UV-A (LF = 0.5 g/L; 52–54% DOC removal after 150–180 min) and LF/PS/UV-A (LF = 0.5 g/L; 60–66% DOC removal after 120 min) treatments. LF photocatalyst could be reused in four consecutive cycles for complete color and partial DOC removals without significant deterioration of the treatment performance with the LF/PS/UV-A/pH 3 process. Instrumental analyses of LF’s surface morphology/chemical composition and structural features via EDAX/SEM/Raman/FTIR/UV-vis/fluorescence spectroscopy indicated that LF remained practically intact throughout photocatalytic treatment, though slight changes/decreases in particle size/partial surface deformation and agglomeration coverage were observed, particularly during LF/PS/UV-A treatment. The presence of RB5 and its degradation products on the LF surface revealed that surface adsorption played a major role in LF-mediated photocatalysis. The Fe-content did not deviate appreciably from its original value after photocatalytic treatment.

Zero-valent iron (ZVI)- and zero-valent aluminium (ZVA)-activated persulfate (PS) oxidation procedure was applied to remove the industrial pollutants 3,5-dichlorophenol (3,5-DCP; 12.27 µM) and 2,4-dichloroaniline (2,4-DCA; 12.34 µM) from aqueous solutions. The effects of PS concentration and pH were investigated to optimize heterogeneous treatment systems. Negligible removals were obtained for both pollutants by individual applications of nanoparticles (1 g/L) and PS (1.00 mM). PS activation with ZVI resulted in 59% (1.00 mM PS; 1 g/L ZVI; pH 5.0; 120 min) and 100% (0.75 mM PS; 1 g/L ZVI; pH 5.0; 80 min) 3,5-DCP and 2,4-DCA removals, respectively. The ZVA/PS treatment system gave rise to only 31% 3,5-DCP (1.00 mM PS; 1 g/L ZVA; pH 3.0; 120 min) and 47% 2,4-DCA (0.25 mM PS; 1 g/L ZVA; pH 3.0; 120 min) removals. The pH decreases from 5.0 to 3.0 and from 3.0 to 1.5 enhanced contaminant removals for ZVI/PS and ZVA/PS treatments, respectively. Pollutant removal rates were in correlation with the consumption rates of the oxidants. Metal ion (Al, Fe) release increased in the presence of PS and with decreasing pH.

Antibiotic resistance is frequently being observed in treated urban effluents as an alarming wastewater treatment issue and health risk. The potential of UV-A-assisted iron-based and UV-C-driven advanced oxidation processes to inactivate the ABR E. coli J53 strain bacteria and its aphA (kanamycin resistance gene) and tetA (tetracycline resistance gene) located on the plasmid RP4 was investigated in real tertiary treated urban wastewater. Besides inactivation performance, dissolved organic carbon (DOC) removals were also followed to evaluate the mineralization degree that could be achieved by the proposed photochemical/photocatalytic treatment systems. For UV-A-assisted Fenton/Fenton-like processes, antibiotic resistance and DOC removals (≈20 %) were rather limited. UV-C activation of the oxidants hydrogen peroxide (HP), persulfate (PS) and peroxymonosulfate (PMS) were the key photochemical advanced oxidation processes for efficient inactivation of multi-resistant E. coli bacteria (>6.5-log reduction) and gene copies (>3.0-log reduction) as well. Besides, 31 %, 40 % and 59 % DOC removals were achieved at a UV dose of 0.45 W/m2 for 2.0 mM HP-, PMS- and PS/UV-C treatments, respectively.

Aims: The study aimed at assessing the effectiveness of the PS/UV-C, PS/ZVA and PS/ZVA/UV-C processes in terms of ciprofloxacin, a fluoroquinolone type commercially important antibiotic, and toxicity abatements in raw surface water (RSW) and distilled water (DW). Background: The occurrence of ciprofloxacin (CIP), the most widely prescribed second-generation fluoroquinolone antibiotic, even at trace level (ng/L) gives rise to antibiotic resistant bacteria and resistance genes, which can further impair the selection of genetic variants of microorganisms and impose adverse effect on human health. Objective: The degradation and detoxification of ciprofloxacin with UV-C (PS/UV-C) and ZVA (PS/ZVA) activated PS oxidation systems were investigated in distilled water (DW) and raw (untreated) surface water (RSW) samples. Moreover, CIP degradation with the PS/ZVA/UV-C heterogeneous photochemical treatment combination was also studied. Methods: The process performances of the investigated treatment systems were evaluated in terms of CIP abatement and PS consumption rates as well as dissolved organic carbon (DOC) removal efficiencies. The influence of common inorganic ions and natural organic matter (NOM) on CIP degradation was evaluated. Radical quenching experiments were conducted using probe compounds in order to elucidate the dominant reaction mechanism. In addition, acute toxicity of the original CIP and its degradation products were questioned by employing Vibrio fischeri (V. fischeri), the marine photobacterium, under optimized treatment conditions. Results: CIP was completely degraded in distilled water (DW) and raw (untreated) surface water (RSW) samples after 15 min of treatment with the PS/UV-C process (PS=0.25mM; pH=3; UVC= 2.7W/m2). PS/UV-C experiments conducted with RSW at its natural pH (=8.5) resulted in 98% CIP and practically no DOC removal whereas 56% DOC was removed at pH 3 after 120 min. Radical quenching studies revealed that sulfate radicals prevailed over hydroxyl radicals. CIP degradation was significantly inhibited by the presence of humic acid due to the effect of UV absorption and free radical quenching. Acute toxicity tests with V. fischeri exhibited fluctuating trends throughout the investigated processes and did not change appreciably after 120 min of oxidation. Conclusion: The results of this study demonstrated that PS/UV-C is superior to the PS/ZVA and PS/ZVA/UV-C treatment systems for both DW and RSW samples in terms of CIP removal rates. No additional positive effect was evident for simultaneous catalytic and photochemical PS activation (PS/ZVA/UV-C treatment system). It could be also demonstrated that the selected oxidation processes conducted in pure water might give an idea about the advanced treatment systems but realistic conditions with actual water/wastewater matrices still need to be further investigated to verify their feasibility and ecotoxicological safety.

International audience; Alkylphenols and alkylphenol polyethoxylates are emerging hazardous contaminants due in particular to their endocrine-disrupting properties. These compounds originate from consumer products such as paints and latex paints, adhesives, inks, formulation of pesticides, paper industry, textile and leather industry, petroleum recovery chemicals, metal working fluids, personal care products, washing agents, cleaners, and detergents. Since classical wastewater treatments have not been designed to remove alkylphenols, these compounds end up polluting ecosystems. Here we review three advanced methods to remove alkylphenols and derivatives. First, innovative polymers, such as cyclodextrin polymers and molecularly imprinted polymers, allow to remove alkylphenols from effluents by adsorption. Second, biotechnologies such as microalgae, biodeg-radation in constructed wetlands and sequential anaerobic-aerobic digestion treatments. Third, advanced oxidation processes to degrade recalcitrant alkylphenols, e.g., ozone-carbon coupling, electrochemical degradation, photocatalysis, zero-valent iron-activated persulfate coupling, and catalytic ozonation.

Bu deneysel çalışmada bir zeytinyağı karasuyu örneği (KOİ: 155000 mg/L; TOK: 40000; Toplam fenol (T-Fenol): 4100 mg/L) kimyasal arıtma yöntemlerinden çöktürme, koagülasyon, elektrokoagülasyon ve Fenton prosesi ile arıtmaya tabi tutulduktan sonra içeriğinde meydana gelen değişim, dane boyut dağılımı (DBD) analizi uygulanarak incelenmiştir. Bu kapsamda ham ve arıtılmış karasu örnekleri filtrasyon/ultrafiltrasyon temelli fiziksel ayırma prosedürü kullanılarak 1600, 450, 220, 13, 8, 5, 3, 2 ve 1 nm gözenek boyutlu filtrelerden geçirilmiştir. DBD analizlerinden elde edilen sonuçlara göre ham karasu örneğinde KOİ, TOK, BOİ5 ve renk (absorbans) parametrelerini oluşturan bileşenlerin daha çok partiküler boyut aralığında (>1600 nm; toplam KOİ’nin %54’ü, TOK’un %43’ü, BOİ5’in %43’ü ve rengin %57’si), T-Fenol parametresini oluşturan bileşenlerin ise kolloidal boyut aralığında (2 nm-1600 nm; %54) dağıldığı gözlenmiştir. Çalışılan arıtma proseslerinden en yüksek giderim, faz transferi ile giderim mekanizmasına dayanan koagülasyon ve çöktürme proseslerinden elde edilmiş (%55-60 KOİ, %45-48 TOK ve %32 T-Fenol), öte yandan Fenton prosesinin karasuyun organik madde giderimi için yeterli olmadığı tespit edilmiştir. Arıtma prosesleri sonrasında gerçekleşen giderimlerin KOİ-TOK parametreleri için büyük oranda partiküler boyut aralığında, T-Fenol için partiküler ve kolloidal aralıklarda dağıldığı bulunmuştur.

In this study, the effect of home-made, reduced graphene oxide (rGO) nanoparticles on persulfate (PS)/UV-C oxidation of bisphenol A (BPA; 8.8 μM), an endocrine disruptor and model micropollutant, in real tertiary treated urban wastewater (TWW) was examined. Experimental results revealed that the presence of rGO induced a significant improvement in the degradation of BPA by the PS/UV-C treatment system. Fast and complete BPA removal accompanied with 44% dissolved organic carbon (DOC) abatement was achieved within 30 min at reaction conditions of 0.01 g/L rGO, 0.125 mM PS, at the natural pH of the TWW (pH = 7.5). This high performance on BPA degradation at the natural pH TWW could be attributable to the synergistic effect between the rGO nanoparticles and the PS/UV-C photochemical oxidation causing additional activation of PS and adsorption of BPA, DOC and degradation products onto the rGO surface. Radical quenching studies revealed that sulfate radicals prevailed over hydroxyl radicals. The Vibrio fischeri bioluminescence inhibition assay indicated that no toxic degradation products were formed during rGO/PS/UV-C treatment. By liquid chromatography time of flight mass spectrometry (LC-TOF-MS) analysis the formation of thirteen degradation products during PS/UV-C and rGO/PS/UV-C treatment of BPA was confirmed. This study underlined that the combined rGO/PS/UV-C treatment process could offer a sustainable, ecotoxicologically safe and kinetically attractive solution for the effective elimination of micropollutants from waters and wastewaters.

Treatment of aqueous iopamidol (IOPA, 2 mg/L), an iodinated organic X-ray contrast chemical and micropollutant, with nano-sized zero-valent iron (ZVI) and aluminum (ZVA)-activated hydrogen peroxide (HP) and persulfate (PS) oxidation processes was investigated. Changes in acute toxicity, anaerobic digestion, biogas yield and microbial community were further examined to question the ecotoxicological safety and bioamenability of the proposed treatment systems. For this purpose, two different bioassays were conducted with V. fischeri and P. subcapitata. The cumulative biogas production was monitored in batch anaerobic digestion tests. The microbial community was identified by Illumina MiSeq next generation sequencing (NGS) technology and abundant bacteria and archaea were analysed in the biomass samples taken from anaerobic reactors. The application of activated HP (1.00 mM) and PS (0.50 mM) treatments under acidic conditions (pH 3) resulted in complete IOPA removal. The original IOPA sample caused 5% and 74% inhibitions to V. fischeri and P. subcapitata, respectively. The relative inhibition towards P. subcapitata increased from 74% to 97% and 93% after 5 min HP/ZVI and 120 min PS/ZVA treatments, respectively. No meaningful changes in terms of digestion performance and cumulative biogas production in the presence of untreated and HP/ZVI- or PS/ZVA-treated IOPA samples were evidenced. Moreover, all biomass samples were populated by a bacterial consortium related to different members of Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Hydrogenotrophic (Methanospirillum, Methanobacterium) and acetoclastic (Methanosaeta, Methanosarcina) methanogens were the prevalent members of archaea at genus level. An increase in relative abundance was only identified in Methanobacterium under the phylum namely Euryarchaeota.

International audience; Since the 2000s, among organic contaminants, alkylphenols and alkylphenol polyethoxylates have been listed as hazardous substances by several national, European and international agencies because they are considered endocrine disruptors. Among the molecules classified as priority substances in terms for monitoring and action, nonylphenols and octylphenols and their polyethoxylated derivatives receive particular attention, especially in developing countries. Effluents from treatments plants are considered to be the largest source of alkylphenols in the environment. Although legislation concerning their use has become increasingly strict, these substances are still found in the environment, especially in water resources. The existing water and wastewater treatment plants have not been designated for these emerging contaminants. Conventional treatments such as biodegradation, sand filtration, carbon adsorption and/or chemical oxidation in place are not effective in their elimination removal. No appropriate methods have been developed to deal them at the urban or industrial scale. Thus, alkylphenols have become a relevant research topic for scientists interested in water engineering issues related to their treatment. However, the challenge is not simple, as it is difficult to remove trace contaminants from complex mixtures of substances in a way that is chemically effective, technologically simple, economically viable, and environmentally friendly.The main objective of this chapter is to summarize recent trends in proposed advanced treatment methods for the removal of alkylphenols and alkylphenol polyethoxylates from wastewater. After general and brief considerations on these emergingcontaminants, this chapter focuses on adsorption-oriented processes, biotechnological methods, and advanced oxidation processes. Among the advanced methods described and discussed are removal of alkylphenols and alkylphenol polyethoxylates by adsorption onto cyclodextrin polymers, clays or molecularly imprinted polymer, biodegradation using microalgae or constructed wetlands or by sequential anaerobic-aerobic digestion processes, treatments based on ozone-carbon coupling, electrochemical degradation, photocatalysis, zero-valent iron-activated persulfate coupling and catalytic ozonation. Among these technologies, advanced oxidation processes, in association with biodegradation and/or adsorption, seem to be the technique of the future, although their costs still prevent their widespread use.

The application of layered double hydroxide (LDH) nanomaterials as catalysts has attracted great interest due to their unique structural features. It also triggered the need to study their fate and behavior in the aquatic environment. In the present study, Zn-Fe nanolayered double hydroxides (Zn-Fe LDHs) were synthesized using a co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption analyses. The toxicity of the home-made Zn-Fe LDHs catalyst was examined by employing a variety of aquatic organisms from different trophic levels, namely the marine photobacterium Vibrio fischeri, the freshwater microalga Pseudokirchneriella subcapitata, the freshwater crustacean Daphnia magna, and the duckweed Spirodela polyrhiza. From the experimental results, it was evident that the acute toxicity of the catalyst depended on the exposure time and type of selected test organism. Zn-Fe LDHs toxicity was also affected by its physical state in suspension, chemical composition, as well as interaction with the bioassay test medium.

Since it is difficult to analyze the components of organic matter in complex effluent matrices individually, the use of more collective, but at the same time, specific wastewater characterization methods would be more appropriate to evaluate changes in effluent characteristics during wastewater treatment. For this purpose, size distribution and structural (resin) fractionation tools have recently been proposed to categorize wastewater. There are several case studies available in the scientific literature being devoted to the application of these fractionation methods. This paper aimed to review the most relevant studies dealing with the evaluation of changes in wastewater characteristics using size distribution and structural (resin) fractionation tools. According to these studies, sequential filtration-ultrafiltration procedures, as well as XAD resins, are frequently employed for size and structural fractionations, respectively. This review focuses on the most relevant publications including biological treatment processes, as well as chemical treatment methods such as coagulation-flocculation, electrocoagulation, the Fenton's reagent and ozonation. This study aims at providing an insight into the possible treatment mechanisms and details the understanding what structural features of wastewater components enabled or prevented efficient treatment (removal) or targeted pollutants.

Herein, the main aim is to study the influence of the materials' structural properties on their ecotoxicological properties. The acute toxicity of the bulk (molybdenum disulfide) MoS

The degradation of 2.6 μM (2 mg/L) iopamidol (IOPA), a commercially important nonionic, iodinated X-ray contrast chemical and model micropollutant, by UV-A and UV-C photo-assisted persulfate (PS) oxidation in real, tertiary treated municipal wastewater (Organic carbon = 12.4 mg/L; Alkalinity = 130 mg CaCO3/L; pH = 7.0) was investigated. Preliminary baseline experiments conducted in pure (distilled) water indicated that IOPA could be rapidly and completely removed even by UV-C treatment alone. In the presence of UV-A light, 100% IOPA removal could still be achieved in pure water by PS/UV-A treatment which was studied at varying conditions (0.10–1.00 mM; pH3-11). However, in real wastewater, addition of at least 0.10 mM and 1.00 mM PS was required to achieve high (>90%) IOPA removals by the PS/UV-C and PS/UV-A treatment systems, respectively. PS consumption rates increased under UV-C radiation compared with UV-A radiation and in real wastewater compared to pure water. Organic carbon removals were appreciable for PS/UV-C (48%) and UV-C (40%) treatments in real wastewater. Toxicity assays carried out with the marine photobacteria Vibrio fischeri revealed that the toxicity response did not change significantly after photochemical treatment. According to the bioassay conducted with the freshwater microalga Pseudokirchneriella subcapitata, the toxicity increased after 155 min UV-C photolysis.

Nanoscale zero-valent aluminum (nZVAl)-activated hydrogen peroxide (HP), persulfate (PS) and peroxymonosulfate (PMS) oxidation of Triton™ X-45 (TX-45), an octylphenol polyethoxylate, was investigated. Treatment performances were evaluated in distilled water (DW), raw surface water (SW), tap water (TW) and effluent from a domestic wastewater treatment plant (WW). Two different acute toxicity tests using Vibrio fischeri and Pseudokirchneriella subcapitata as well as the UMU-Chromo genotoxity test were undertaken to evaluate the ecotoxicological effects of TX-45 and its oxidation products. Poor TX-45 removals in the absence of nZVAl (mere HP, PS and PMS treatments) and oxidants (nZVAl/O2/H+ treatment) were obtained (5%-38%). Activation of HP, PS and PMS with nZVAl substantially enhanced TX-45 degradation. Complete TX-45 degradation occurred in DW with the nZVAl/PS and nZVAl/PMS treatment combinations after 90 min and 60 min, respectively, whereas only 76% TX-45 removal was obtained with nZVAl/HP after 120 min (TX–45 = 2 mg/L; nZVAl = 1 g/L; HP-PMS = 0.25 mM; PS = 0.5 mM; pH = 3). In DW, the decreasing order of TX-45 removal efficiencies was obtained as follows; nZVAl/PMS≈nZVAl/PS > nZVAl/HP and as nZVAl/PMS > nZVAl/HP > nZVAl/PS in SW and WW. The nZVAl/PS-treated TX-45 samples did not exhibit toxic effects on V. fischeri; the relative inhibition increased from 15% to 26% in DW and decreased to practically non-toxic levels (< 8%) in SW after 120 min treatment. During the early stages of nZVAl/PS treatment, P. subcapitata toxicity of TX-45 increased from 35% to 44% and from 39% to 52% in DW and SW samples, respectively. After 120 min treatment, it dropped back to 40% and 25% in DW and SW samples, respectively. The original and nZVAl/PS-treated TX-45 neither exhibited cytotoxic nor genotoxic effects.

Recently, the European Food Safety Authority (EFSA) has banned the use of iprodione (IPR), a common hydantoin fungicide and nematicide that was frequently used for the protective treatment of crops and vegetables. In the present study, the treatment of 2 mg/L (6.06 μM) aqueous IPR solution through ultraviolet-C (UV-C)-activated persulfate (PS) advanced oxidation process (UV-C/PS) was investigated. Baseline experiments conducted in distilled water (DW) indicated that complete IPR removal was achieved in 20 min with UV-C/PS treatment at an initial PS concentration of 0.03 mM at pH = 6.2. IPR degradation was accompanied with rapid dechlorination (followed as Cl− release) and PS consumption. UV-C/PS treatment was also effective in IPR mineralization; 78% dissolved organic carbon (DOC) was removed after 120-min UV-C/PS treatment (PS = 0.30 mM) compared with UV-C at 0.5 W/L photolysis where no DOC removal occurred. LC analysis confirmed the formation of dichloroaniline, hydroquinone, and acetic and formic acids as the major aromatic and aliphatic degradation products of IPR during UV-C/PS treatment whereas only dichloroaniline was observed for UV-C photolysis under the same reaction conditions. IPR was also subjected to UV-C/PS treatment in simulated tertiary treated urban wastewater (SWW) to examine its oxidation performance and ecotoxicological behavior in a more complex aquatic environment. In SWW, IPR and DOC removal rates were inhibited and PS consumption rates decreased. The originally low acute toxicity (9% relative inhibition towards the photobacterium Vibrio fischeri) decreased to practically non-detectable levels (4%) during UV-C/PS treatment of IPR in SWW.

Herein, the main aim is to study the influence of the materials' structural properties on their ecotoxicological properties. The acute toxicity of the bulk (molybdenum disulfide) MoS2 and 2D nanosheet MoS2 was investigated using organisms of four different taxonomic groups. Ultrasound-assisted liquid-phase exfoliation method was used for preparing 2D nanosheets from bulk MoS2. Bulk and nanosheet MoS2 were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analyses. The acute toxicity of the bulk and nanosheet MoS2 catalysts was evaluated with four different bioassays using the test organisms Vibrio fischeri (a marine photobacterium), Pseudokirchnerialla subcapitata (a freshwater microalga), Daphnia magna (a freshwater crustacean) and the freshwater duckweed Spirodela polyrhiza. The toxic effect of the materials depended on their structural/size features and the type/sensitivity of the test organism. Generally speaking, bulk MoS2 was more toxic than its nanosheet form. The freshwater crustacean Daphnia magna appeared to be the most suitable, easy-to-handle, and at the same time sensitive test organism for bulk and nanosheet MoS2 among the tested organisms.

In the present study, novel metal-free activation of persulfate (PS) and peroxymonosulfate with reduced graphene oxide (rGO) was investigated to degrade Bisphenol A (BPA), one of the most important endocrine disrupting compounds, from different aqueous matrices, namely distilled water (DW) and municipal wastewater treatment plant effluent (TWW). The home-made rGO was characterize and the effect of oxidant (PS and PMS) and catalyst (rGO) concentrations on BPA degradation rates in DW and TWW samples was examined. Complete BPA degradation occurred in DW and TWW with the PS/rGO treatment system after 10 min and 30 min, respectively, whereas 94% (DW) and 83% (TWW) BPA removals were obtained with PMS/rGO for the same treatment period (BPA = 2 mg/L; rGO = 0.02 g/L; PS = 0.25 mM; PMS = 0.5 mM). The radical quenching experiments demonstrated that the SO4- predominated in the activation of PS and PMS with rGO for BPA removal, however, HO contributed to the catalytic oxidation process but to a lower extend. The reusability test results, where the catalyst was deactivated seriously just after second cycle, highlighted the need for further studies to enhance the stability of rGO. This study represented an environmentally benign and efficient oxidative treatment of BPA along with insights into the rGO activated PS or PMS processes.

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.

The main purpose of this study was to identify the inert fractions in olive mill wastewater (OMW) before and after chemical treatment by employing size distribution and structural resin fractionation procedures. Thermal acid cracking was selected as the chemical treatment process due to its superior performance in terms of organic matter removal from the OMW sample. Size fractionation of OMW before and after thermal acid cracking treatment was carried out using different molecular weight cut-off membranes ranging from >1600 nm to

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.

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.

Increasing attention has been paid to the presence of micropollutants in water and wastewater due to their widespread application and incomplete removal during conventional treatment. Micropollutants may induce harmful impacts on human health as well as aquatic and terrestrial ecosystems at concentrations in the μg/L-ng/L range due to their persistence, bioaccumulation potential and toxicity. Until now, different strategies have been developed to alleviate the problem of micropollutants in the environment. Meanwhile, several types of Advanced Oxidation Processes (AOPs) have also been developed and applied for the effective, destructive treatment of problematic pollutants. AOPs involve the intermediacy of reactive oxygen species such as hydroxyl (HO·) and sulfate (SO 4 · ) radicals. More recently, alternative, innovative AOPs using nanoscale materials have been explored. Zero-valent metals including zero-valent iron (ZVI) and zero-valent aluminum (ZVAl) have received increasing research interest due to their ease of use, high activity, availability and remarkable treatment performance. Their large surface area and the high number of active redox sites render nZVI and nZVAl good candidates for water and wastewater treatment. In this chapter, the application of ZVI- and ZVAl-mediated treatment systems for the degradation of organic and inorganic micropollutants has been presented and reviewed.

H 2 O 2 /UV-C and Photo-Fenton treatment of a nonylphenol polyethoxylate surfactant was investigated in synthetic freshwater. H 2 O 2 /UV-C treatment outperformed Photo-Fenton treatment in terms of mother pollutant abatement kinetics as well as overall organic carbon removal efficiencies. Short polyethoxy-chain nonylphenol polyethoxylates, polyethylene glycols, formic acid, acetic acid and formaldehyde were identified as the common degradation products of the nonionic surfactant. Monocarboxylated polyethylene glycols and oxalic acid were detected during H 2 O 2 /UV-C oxidation, whereas a degradation product resulting from the hydroxyl radical attack of the tertiary alkyl chain and the aromatic ring was detected during Photo-Fenton treatment. Based on the liquid chromatography–mass spectrometry results, it was suggested that the polyethoxy chain of the surfactant was more susceptible to degradation with the H 2 O 2 /UV-C treatment process, while the alkyl chain and aromatic ring were more prone to Photo-Fenton oxidation. Acute toxicity analysis employing the photobacteria Vibrio fischeri indicated that the inhibitory effect of the surfactant increased from 10% to 30% and 19% during the early stages of H 2 O 2 /UV-C and Photo-Fenton treatment, respectively. At the end of the treatment period, the inhibitory effect of the surfactant dropped back to less than 10%. According to the umu-genotoxicity test conducted with Salmonella typhimurium TA1535/pSK1002 strain, the genotoxic effect followed an increasing trend during the course of H 2 O 2 /UV-C treatment. A positive correlation was evident between the intensity of the nonylphenol monoethoxylate product ion and the genotoxic effect observed during H 2 O 2 /UV-C treatment. The genotoxic effect of Photo-Fenton-treated degradation products appeared to be relatively low as compared with those of H 2 O 2 /UV-C treatment.

The organic matter content in original and chemically treated olive oil mill wastewater obtained from a three phase extraction plant was profiled by a resin fractionation procedure to evaluate changes in its characteristics after acid cracking as well as chemical treatment by FeCl3 coagulation, electrocoagulation with stainless steel electrodes, and an advanced oxidation processes (Fenton's reagent). For this purpose, untreated, acid-cracked, and chemically treated wastewater samples were fractionated into hydrophobic and hydrophilic (acid–base–neutral) structures using XAD-8, XAD-4, AG-MP-50, and Duolite A-7 resins. Structural distribution analysis of the untreated samples indicated that hydrophobic structures were the major (75–95%) components of the wastewater's organic matter content. For the total phenols parameter, a significant fraction (56%) appeared to be hydrophobic neutral coinciding with the acute toxicity of the olive oil mill wastewater. A significant amount of oil and grease as well as particulate organic matter could be removed by subjecting the original wastewater sample to acid cracking. FeCl3 coagulation appeared to be effective in the removal of hydrophobic fractions whereas electrocoagulation and the Fenton's reagent were also effective in the removal of hydrophilic organic matter. After chemical treatment of the olive oil mill wastewater, a significant shift in its structural distribution pattern was observed from mainly hydrophobic to more hydrophilic fractions.

In the present study the nonionic surfactant Triton ™ X-45 (TX-45), an octylphenol polyethoxylate, was treated by persulfate ( S 2 O 8 2 - )/UV-C process involving the intermediacy of sulfate radicals and the relatively well-known hydrogen peroxide (H 2 O 2 )/UV-C process. TX-45 removal occurred rapidly via both advanced oxidation processes. Complete oxidation was also achieved under the studied reaction conditions, however required extended treatment periods (>30 min) and high oxidant concentrations (⩾2.5 mM). Several degradation products could be qualified via GC–MS and HPLC analyses. Inspection of the identified degradation products indicated that the reaction mechanism of TX-45 was a combination of various pathways; (i) progressive shortening of the exhoxylate chain leading to relatively short-chain TX-45 and ultimately octylphenol, (ii) ω-carboxylation of the terminal alcoholic groups yielding octylphenol ethoxy carboxylates (OPECs) and (iii) central fission of the ethoxy chain resulting in the formation of polyethylene glycols (PEGs). Continued oxidation of the primary degradation products resulted in mono- and di-carboxylated PEGs. Degradation products bearing a smaller number of ethylene oxide units (⩽3) were generated during H 2 O 2 /UV-C treatment, whereas OPECs was only detected during S 2 O 8 2 - /UV-C treatment of TX-45. Acetic and succinic acids were quantitatively identified during S 2 O 8 2 - /UV-C treatment, whereas oxalic and fumaric acids were additionaly detected during H 2 O 2 /UV-C oxidation. Product identification suggested similar reaction pathways for the treatment of TX-45 by SO 4 - - and HO -driven oxidation processes.

The effect of acid cracking (pH 2.0; T 70 degrees C) and filtration as a pretreatment step on the chemical treatability of olive mill wastewater (chemical oxygen demand (COD) 150,000 m/L; total organic carbon (TOC) 36,000 mg/L; oil-grease 8,200 mg/L; total phenols 3,800 mg/L) was investigated. FeCl3 coagulation, Ca(OH)(2) precipitation, electrocoagulation using stainless steel electrodes and the Fenton's reagent were applied as chemical treatment methods. Removal performances were examined in terms of COD, TOC, oil-grease, total phenols, colour, suspended solids and acute toxicity with the photobacterium Vibrio fischeri. Significant oil-grease (95%) and suspended solids (96%) accompanied with 58% COD, 43% TOC, 39% total phenols and 80% colour removals were obtained by acid cracking-filtration pretreatment. Among the investigated chemical treatment processes, electrocoagulation and the Fenton's reagent were found more effective after pretreatment, especially in terms of total phenols removal. Total phenols removal increased from 39 to 72% when pretreatment was applied, while no significant additional (approximate to 10-15%) COD and TOC removals were obtained when acid cracking was coupled with chemical treatment. The acute toxicity of the original olive mill wastewater sample increased considerably after pretreatment from 75 to 89% (measured for the 10-fold diluted wastewater sample). An operating cost analysis was also performed for the selected chemical treatment processes.

The performance of S2O82-/UV-C and H2O2/UV-C treatments was investigated for the degradation and detoxification of Bisphenol A (BPA). The acute toxicity of BPA and its degradation products was examined with the Vibrio fischeri bioassay, whereas changes in estrogenic activity were followed with the Yeast Estrogen Screen (YES) assay. LC and LC-MS/MS analyses were conducted to determine degradation products evolving during photochemical treatment. In addition, BPA-spiked real freshwater samples were also subjected to S2O82-/UV-C and H2O2/UV-C treatment to study the effect of a real water matrix on BPA removal and detoxification rates. BPA removal in pure water was very fast (20 min) and TOC removals were considerably retarded (by 40%) in the raw freshwater matrix most probably due to its natural organic matter content (TOC = 5.1 mg L-1). H2O2/UV-C and S2O82-/UV-C treatment in raw freshwater did not result in toxic degradation products. (C) 2014 Elsevier Ltd. All rights reserved.

UV-A (near-UV), UV-C (short-UV) and visible-light assisted Fenton-like treatment of Bisphenol A (BPA) was investigated in pure water and raw freshwater samples spiked with BPA. Treatment performances were evaluated in terms of BPA degradation, dissolved organic carbon (DOC) removal and H2O2 consumption rates. Complete BPA degradation accompanied with significant DOC removal was achieved for all studied processes. Increasing the initial solution pH only exhibited a negative effect on treatment efficiencies when bicarbonate alkalinity was used for pH adjustment, whereas the raw freshwater matrix and irradiation type also influenced oxidation rates appreciably. Acute toxicity analysis employing Vibrio fischeri revealed that the inhibitory effect of BPA decreased significantly during the course of Photo-Fenton-like treatment. Several transformation products could be identified via HPLC and GC-MS analyses including hydroxylated phenolic compounds (hydroquinone; 2-methoxy, 1-4-benzenediol; 4-isopropenylphenol; 4'-hydroxy-acetophenone; 1-(4-cyclohexylphenyl) ethanone; 4-isopropylenecatechol; 4-4'-dihydroxybenzophenone; 4-ethyl,1,3-benzenediol), as well as the ring opening products hexanoic acid methyl ester, fumaric, succinic and oxalic acids. A reaction pathway featuring hydroxylation, dimerization and ring opening steps is proposed. (c) 2013 Elsevier Ltd. All rights reserved.

H 2 O 2 /UV-C oxidation and UV-C photolysis of 2,4-dichlorophenol (2,4-DCP) and the nonionic industrial surfactant nonylphenol decaethoxylate (NP-10) were comparatively studied in terms of changes in parent pollutant, total organic carbon (TOC), oxidation products and acute toxicity to the marine photobacterium Vibrio fischeri . The H 2 O 2 /UV-C process was superior over UV-C photolysis in terms of parent compound and TOC removals. After 90 min H 2 O 2 /UV-C treatment, complete degradation of both parent compounds accompanied with 95% and 78% TOC removals for 2,4-DCP and NP-10, respectively, could be achieved. The highest concentrations of oxidation products were obtained for carboxylic acids and aldehydes during H 2 O 2 /UV-C treatment and UV-C photolysis of 2,4-DCP, with 21 and 19 mg L −1 carboxylic acids and 0.96 and 0.77 mg L −1 aldehyde formation, respectively. In the case of NP-10, substantially higher concentrations of carboxylic acids (32 mg L −1 ) were formed throughout the course of H 2 O 2 /UV-C treatment as compared to UV-C photolysis alone (3.4 mg L −1 ). Although the original inhibitory effect of 75 mg L −1 2,4-DCP (99% relative inhibition) was reduced to 17% after 30 min H 2 O 2 /UV-C treatment, the toxic effect re-appeared after complete degradation of 2,4-DCP being measured as 75% after 90 min treatment. During UV-C photolysis of 2,4-DCP the relative inhibition decreased steadily to 34% after 90 min treatment. The inhibitory effect of NP-10 fluctuated during H 2 O 2 /UV-C ultimately resulting in a slightly higher toxicity value (16% relative inhibition) than the original pollutant (9% relative inhibition). The acute toxicity of NP-10 gradually increased to a relative inhibition of 36% throughout UV-C treatment.

UV-C photo-assisted persulfate (PS), hydrogen peroxide (H 2 O 2 ) and peroxymonosulfate (PMS) oxidation processes were evaluated and compared for aqueous phenol degradation. The effect of initial oxidant concentration on PS/UV-C, H 2 O 2 /UV-C and PMS/UV-C treatment efficiencies was examined on the basis of phenol and total organic carbon (TOC) removals. Complete phenol degradation could be achieved under all examined reaction conditions with apparent phenol degradation rate constants varying between 0.069 ± 0.002 – 0.382 ± 0.003 min −1 accompanied with complete TOC removals (⩾97%) under optimized PS (20 mM), H 2 O 2 (30 mM) and PMS (20 mM) concentrations. Hydroquinone, catechol and benzoquinone were quantified during H 2 O 2 /UV-C and PMS/UV-C treatment of phenol verifying a HO -dominated oxidation pathway. During PS/UV-C oxidation, the identification of benzoquinone and 3-phenoxyphenol verified the hydroxycyclohexadienyl radical and phenoxyl radical pathways in SO 4 - mediated phenol oxidation.

Aqueous Triton X-45 (TX-45; 20 mg/L; original total organic carbon (TOC) = 14 mg/L), a representative, commercially important alkylphenol polyethoxylate, was subjected to persulfate ( PS) oxidation activated with zero-valent iron (ZVI) nanoparticles. After optimization of the ZVI/PS treatment combination ( 1 g/L ZVI; 2.5 mM PS at pH5) in terms of pH (3-9), ZVI ( 0.5-5 g/L) and PS (0.5-5.0 mM) concentrations, TX-45 could be efficiently (>90%) degraded within short treatment periods (40%) TOC removals. The degree of PS consumption and Fe release was also followed during the experiments and a positive correlation existed between enhanced TX-45 removals and ZVI-activated PS consumption rates accompanied with a parallel Fe release. Acute toxicity tests were conducted using two different bioassays to examine the toxicological safety of the ZVI/PS oxidation system. Acute toxicity profiles significantly decreased from an original value of 66% relative inhibition to 21% and from 16% relative inhibition to non-toxic values according to Vibrio fischeri and Pseudokirchneriella subcapitata bioassays, respectively. The photobacterium V. fischeri appeared to be more sensitive to TX-45 and its degradation products than the microalgae P. subcapitata.

The organic matter content in original, untreated (COD=150,000mg/L; TOC=36,000mg/L; oil-grease=8,200mg/L; total phenols=3,800mg/L), and chemically treated olive mill wastewater was examined in detail by instrumental and analytical (resin fractionation) methods. For this purpose, two approaches were followed: (i) UV-fluorescence, FTIR, and GC-MS analyses as well as (ii) structural fractionation assessment employing XAD-8, XAD-4, AG-MP-50, and Duolite A-7 exchange resins to obtain hydrophobic-acidic, basic, neutral, and hydrophilic-acidic, basic, neutral fractions, respectively. Acid cracking (pH 2.0; T=70 degrees C), FeCl3 coagulation (pH 3.0; FeCl3=2,500mg/L) electrocoagulation with stainless steel electrodes (pH 2.0; T=65 degrees C; A=50mA/cm(2); t=120min), and the Fenton's reagent (pH 2.0; T=65 degrees C; 20mM Fe2+: 200mM H2O2; t=120min) were selected for convenient chemical treatment of the effluent. Resin fractionation analyses of the original wastewater sample indicated that the major organic content composed of hydrophobic moieties (75-95%). The percent relative inhibition of the original wastewater was concentrated in the hydrophobic neutral fraction (100%). By employing instrumental analyses, several organic compounds could be identified. Relatively low molecular weight chemicals were qualified via GC-MS analysis, whereas FTIR results revealed an appreciable loss of aliphatic moieties together with an increase in aromatic structures.

In the present study, hydrogen peroxide (HP) and persulfate (PS)-activated nanoscale zero-valent iron (nZVI) and zero-valent aluminum (nZVAl) heterogeneous treatment systems (nZVI/HP-PS and nZVAl/HP-PS) were investigated for the removal of 20 mg/L (88 mu M) aqueous Bisphenol A (BPA). Oxidation with HP and PS in the absence of nanoparticles did not cause BPA degradation, whereas the nZVI/O-2/H+ and nZVAl/O-2/H+ treatment systems resulted in 33% and 38% BPA removals at an initial reaction pH of 3, respectively. Activation of nZVI and nZVAl with HP or PS improved BPA and TOC removals due to the enhancement of hydroxyl and sulfate radicals generation. Removal efficiencies decreased upon increasing the reaction pH from 3 to 5, while a remarkable enhancement in BPA and TOC removals was evident when nZVI was activated with PS. Complete BPA removal was achieved by using 1 g/L nanoparticle activated with 2.5 mM HP or PS at pH 3 for the nZVI/HP and nZVAl/HP-PS treatment combinations, whereas 84% BPA removal was obtained for nZVI/PS treatment. Highest TOC removal was achieved as 90% for nZVI/PS treatment at pH 5 and nZVAl/PS treatment at pH 3. Treatment performances correlated with the HP/PS consumption and Fe/Al release rates.

Cost-effective methods are required to treat a wide range of wastewater pollutants in a diverse range of conditions. As compared with traditional treatment methods, electrocoagulation provides a relatively compact and robust treatment alternative in which sacrificial metal anodes initiate electrochemical reactions that provide active metal cations for coagulation and flocculation. The inherent advantage of electrocoagulation is that no coagulants have to be added to the wastewater and hence the salinity of the water does not increase after treatment. Electrocoagulation is a complex process involving a multitude of pollutant removal mechanisms operating synergistically. Although numerous publications have appeared in the recent past, the lack of a holistic and systematic approach has resulted in the design of several treatment units without considering the complexity of the system and process control mechanisms. Due to the fact that electrocoagulation is thought to be an enigmatic, promising treatment tech...

Ozonation of the commercially important, recalcitrant reactive dye intermediate 2-naphthylamine 3,6,8-trisulphonic acid (K-Acid) was investigated. Ozonation performance was examined by following ozone absorption rates and K-Acid, chemical oxygen demand and total organic carbon removals. Mean oxidation states and unidentified organic products were also determined. At pH 3, where direct ozone reactions are dominant, the second-order rate constant between K-Acid and molecular ozone was determined as 20 m−1 s−1 for steady-state aqueous ozone concentration. The competition kinetics approach was also adopted where a reference compound, phenol, and K-Acid were subjected to ozonation. By applying this method, the second-order reaction rate constant was found to be 76 m−1 s−1. Common oxidation products formed during ozonation at pH 3, pH 7 and pH 7 with 1 mm hydrogen peroxide were identified as methoxy-phenyl-oxime, phenol, benzene, benzaldehyde and oxalic acid via high-performance liquid chromatography and gas chromatography/mass spectrometry analyses. Continuous nitrate and sulphate evolution were observed during K-Acid ozonation as a consequence of the abrupt release and subsequent oxidation of its amino and sulphonate groups. The number and amount of reaction products were most intensive for K-Acid ozonation at pH 7 with 1 mm hydrogen peroxide. According to the acute toxicity tests conducted with Vibrio fischeri, ozonation products were not less toxic than the original K-Acid solution that caused only 15% inhibition.

The commercially important naphthalene sulfonate K-acid (C10H9NO9S3; 2-naphthylamine 3,6,8-tri sulfonic acid) was subjected to electrocoagulation employing stainless steel electrodes. An experimental design tool was used to mathematically describe and optimize the single and combined influences of major process variables on K-acid and its organic carbon (COD and TOC) removal efficiencies as well as electrical energy consumption. Current density, followed by treatment time were found to be the parameters affecting process responses most significantly, whereas initial K-acid concentration had the least influence on the electrocoagulation performance. Process economics including sludge generation, electrode consumption, and electrochemical efficiency, as well as organically bound adsorbable halogen formation and toxicity evolution were primarily considered to question the feasibility of K-acid electrocoagulation. Considering process economics and ecotoxicological parameters, process implementation appeared to be encouraging.

In the present study, H2O2/UV-C, Fenton and photo-Fenton treatment of 2,4-dichlorophenol was compared in terms of oxidation products and acute toxicity. The oxidation products were identified by gas chromatography-mass spectroscopy, high performance liquid chromatography and ion chromatography, whereas changes in acute toxicity were evaluated by the Vibrio fischeri luminescence inhibition assay. H2O2/UV-C and photo-Fenton processes ensured complete 2,4-dichlorophenolremoval, detoxification and significant mineralization. Hydroquinone and formic acid were identified as the common oxidation products of the studied advanced oxidation processes investigated. 3,5-dichloro-2-hydroxybenzaldehyde, phenol, 4-chlorophenol and 2,5-dichlorohydroquinone were identified as the additional H2O2/UV-C oxidation products of 2,4-dichlorophenol. Acute toxicity decreased with decreasing 2,4-dichlorophenol and increasing chloride release. (C) 2012 Elsevier B.V. All rights reserved.

In this study, the degradation of dimethyl phthalate (DMP), taken as model compound for phthalate esters, by the photo-assisted peroxymonosulfate (PMS) process was investigated. The high oxidation potential of hydroxyl and sulfate radicals generated by the activation of PMS under UV-C light irradiation was used to completely oxidize aqueous DMP solutions. Experiments were conducted at varying initial pH values (3.0, 6.0, and 9.0) and PMS concentrations (0-60 mM) to evaluate the effect of different reaction conditions on DMP treatment performance with the PMS/UV-C process. It was observed that lowering the initial reaction pH slightly improved the degradation rate of DMP. On the contrary, TOC abatements were slightly enhanced with increasing initial reaction pH. An adequate (optimum) PMS concentration of 40 mM resulted in the fastest and highest DMP degradation rates and efficiencies, respectively. At an initial concentration of 100 mg L(-1), more than 95% DMP removal was obtained after only 20 min under PMS/UV-C treatment conditions. For the proposed adequate PMS concentration (40 mM) the lowest electrical energy per order (EE/O) value was calculated as 2.9 kW h m(-3) order(-1).

In this experimental study, the treatability of the commercially most important naphthalene sulfonate H-acid that is frequently being used as a raw material for the production of textile azo dyes with the Photo-Fenton-like (Fe3+/H2O2/UV-A) advanced oxidation process was investigated. In the first part of the study, the above-mentioned model pollutant was subjected to Photo-Fenton treatment under different working conditions, e. g., different pH, Fe3+ catalyst and H2O2 oxidant concentrations. The treatment performance of the photocatalytic treatment process was examined on the basis of chemical oxygen demand and total organic carbon removal efficiencies. In the second part of the experimental work, untreated and Photo-Fenton-treated H-acid solutions were subjected to an activated sludge inhibition (toxicity) test using heterotrophic biomass to determine changes brought about in the acute toxicity of the naphthalene sulfonate during advanced oxidation treatment. For synthetic wastewater containing H-acid with an initial COD of 450 mg/l 82% COD and 51% TOC removals were obtained (optimized experimental conditionals: pH = 5.0; Fe3+ = 1.5 mM; H2O2 = 35 mM; reaction time = 24 min). In the case when only partial oxidation was targeted (experimental conditions: pH = 5.0; Fe3+ = 1.0 mM; H2O2 = 40 mM; reaction time = 12 min), for the same initial COD of 450 mg/l, COD and TOC abatements were obtained as 67% and 44%, respectively. Activated sludge inhibition experiments have demonstrated that no toxic advanced oxidation products were formed during Photo-Fenton oxidation.

The high solubility, polarity and recalcitrant nature of naphthalene sulphonates render their treatment by conventional physicochemical and biological methods a rather difficult task. The present study aimed at investigating the treatability of a commercially important naphthalene sulphonate, e.g. H-acid, using H2O2/UV-C and Fe2+/H2O2/UV-C photochemical oxidation processes. The H2O2/UV-C process was capable of 100% H-acid, 48% COD and 27% TOC removals 180 min under the experimental conditions of 468 mg/l initial COD, 60 mM initial H2O2 concentration and an initial pH of 5.9–6.0. A steady increase in the average oxidation state throughout the photochemical reaction revealed that more oxidized organic intermediates were formed during H2O2/UV-C treatment of H-acid. The effect of initial H2O2 concentration on H2O2/UV-C treatment efficiency was examined by conducting experiments at varying initial H2O2 concentrations up to 200 mM. An initial H2O2 concentration of 150 mM appeared to be the optimum where the hig...

In the present study, the treatability of aqueous DEP solution employing H2O2/UV-C oxidation and the changes in acute and/or chronic toxicity of untreated and H2O2/UV-C treated DEP solutions was investigated. For DEP removal and its ultimate oxidation (mineralization), an optimum initial H2O2 concentration of 40 mM was required. The HO• bimolecular reaction rate constant of DEP was found as 2.33 ± 0.27×108 M−1 s−1. Activated sludge inhibition experiments inferred that H2O2/UV-C treated DEP solutions were composed of a mixture of oxidation intermediates which exhibited higher degree of inhibition to heterotrophic biomass with respect to DEP. According to the results obtained in this work, the complete mineralization of DEP by H2O2/UV-C process would be a better option.

In the present study, Fenton's oxidation of a chromium complex disazo dye (Acid Blue 193) synthesis wastewater was evaluated, modeled and optimized by employing Central Composite Design. Within this context, the individual and interactive effects of critical process parameters such as Fe2 + , H2O2 concentrations, initial chemical oxygen demand (COD) and reaction time was assessed. The process response (output) variables were chosen as percent color, COD and total organic carbon (TOC) removal efficiencies. Optimum working conditions in terms of color and organic carbon removals were established to be Fe2 + = 3 mM; H2O2 = 25 mM; reaction time = 10 min at pH 3 and an initial COD content of 245 mg/L. Under these conditions, 96% color, 82% COD and 51% TOC removals were obtained. The established polynomial regression models describing color, COD and TOC removals satisfactorily fitted the experimental data and could be used to predict Fenton's treatment results at statistically significant rates. Optimized treatment results were compared with those obtained via electrocoagulation treatment under optimized conditions (applied current = 50 A/m2; reaction time = 15 min; initial pH = 7 for an initial COD content of 245 mg/L). The relative inhibition of heterotrophic oxygen uptake rate was measured to examine the inhibitory effect of azo dye synthesis effluent before and after Fenton's oxidation and electrocoagulation with respect to synthetic domestic wastewater. Untreated azo dye production wastewater exhibited a slightly inhibitory effect that was appreciably reduced but not entirely removed after Fenton's oxidation, whereas no inhibition of mixed bioculture was observed for azo dye synthesis effluent subjected to electrocoagulation treatment.