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Performance of a sequencing batch biofilm reactor for the treatment of pre-oxidized sulfamethoxazole solutions.

A combined strategy of a photo-Fenton pretreatment followed by a Sequencing Batch Biofilm Reactor (SBBR) was evaluated for total C and N removal from a synthetic wastewater containing exclusively 200 mg L(-1) of the antibiotic Sulfamethoxazole (SMX). Photo-Fenton reaction was optimized at the minimum reagent doses in order to improve the biocompatibility of effluents with the subsequent biological reactor. Consequently, the pretreatment was performed with two different initial H(2)O(2) concentrations (300 and 400 mg L(-1)) and 10 mg L(-1) of Fe(2+). The pre-treated effluents with the antibiotic intermediates as sole carbon source were used as feed for the biological reactor. The SBBR was operated under aerobic conditions to mineralize the organic carbon, and the Hydraulic Retention Time (HRT) was optimized down to 8h reaching a removal of 75.7% of the initial Total Organic Carbon (TOC). The total denitrification of the NO(3)(-) generated along the chemical-biological treatment was achieved by means of the inclusion of a 24-h anoxic stage in the SBBR strategy. In addition, the Activated Sludge Model No. 1 (ASM1) was successfully used to complete the N balance determining the N fate in the SBBR. The characterization and the good performance of the SBBR allow presenting the assessed combination as an efficient way for the treatment of wastewaters contaminated with biorecalcitrant pharmaceuticals as the SMX.

Can activated sludge treatments and advanced oxidation processes remove organophosphorus flame retardants

This study aims to determine the occurrence of 10 OPFRs (including chlorinated, nonchlorinated alkyl and aryl compounds) in influent, effluent wastewaters and partitioning into sludge of 5 wastewater treatment plants (WWTP) in Catalonia (Spain). All target OPFRs were detected in the WWTPs influents, and the total concentration ranged from 3.67 µg L(-1) to 150 µg L(-1). During activated sludge treatment, most OPFRs were accumulated in the sludge at concentrations from 35.3 to 9980 ng g(-1) dw. Chlorinated compounds tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP) and tris(2,3-dichloropropyl) phosphate (TDCPP) were not removed by the conventional activated sludge treatment and they were released by the effluents at approximately the same inlet concentration. On the contrary, aryl compounds tris(methylphenyl) phosphate (TMPP) and 2-ethylhexyl diphenyl phosphate (EHDP) together with alkyl tris(2-ethylhexyl) phosphate (TEHP) were not detected in any of the effluents. Advanced oxidation processes (UV/H2O2 and O3) were applied to investigate the degradability of recalcitrant OPFRs in WWTP effluents. Those detected in the effluent sample (TCEP, TCIPP, TDCPP, tributyl phosphate (TNBP), tri-iso-butyl phosphate (TIBP) and tris(2-butoxyethyl) phosphate (TBOEP)) had very low direct UV-C photolysis rates. TBOEP, TNBP and TIBP were degraded by UV/H2O2 and O3. Chlorinated compounds TCEP, TDCPP and TCIPP were the most recalcitrant OPFR to the advanced oxidation processes applied. The study provides information on the partitioning and degradability pathways of OPFR within conventional activated sludge WWTPs.

Bacterial community characterization of a sequencing batch reactor treating pre-ozonized sulfamethoxazole in water.

Antibiotics are pharmaceutical compounds widely used to treat a broad range of infections. These chemicals appear to be recalcitrant compounds when released to water systems, and their presence at the effluent of wastewater treatment plants and surface waters has been widely documented. Sulfamethoxazole (SMX), a sulfonamide commonly used to treat urinary infections, is one of them. Ozonation was proved to be a suitable method to remove SMX antibiotic in water. However, it is stated that a high ozone dosage would be necessary to achieve the complete mineralization of the intermediates. In this work, ozonation is coupled with a Sequencing Batch Biofilm Reactor (SBBR) in order to completely degrade SMX and its metabolites from water solutions. Moreover, a precise description of the microbial community in the bioreactor is provided by means of traditional microscopy and molecular biology techniques. The results obtained showed high Total Organic Carbon removals at the end of the biological treatment (89% removal). Furthermore, nitrates produced during the aerobic SBBRs performance were monitored and eliminated by adding an anoxic stage, achieving an overall nitrogen removal of 86%. A bacterial community analysis of the SBBR during aerobic and aerobic-anoxic conditions was performed, targeting the bacterial 16S ribosomal ribonucleic acid (rRNA) gene. These results revealed a dominant contribution of bacteria from the Proteobacteria class, with a major contribution from the Rhizobiales and Burkholderiales orders during the bioreactor performance, counting 52% of the total population.

Biological and photochemical degradation of cytostatic drugs under laboratory conditions

Cytostatic drugs, used in chemotherapy, have emerged as new environmental contaminants due to their recurrent presence in surface waters and genotoxic effects. Yet, their degradability and environmental fate is largely unknown. The aim of this study was to determine the degradation kinetics of 16 cytostatic drugs, prioritized according to their usage and occurrence in hospital and wastewater treatment plants (WWTP) effluents, through the following laboratory scale processes: hydrolysis, aerobic biodegradation, UV-C photolysis, UV-C/H2O2 and simulated solar radiation. Some drugs were unstable in milli-Q water (vincristine, vinblastine, daunorubicin, doxorubicin and irinotecan); others were photodegraded under UV-C light (melphalan and etoposide) but some others were found to be recalcitrant to biodegradation and/or UV-C, making necessary the use of advanced oxidation processes (AOPs) such as UV-C/H2O2 for complete elimination (cytarabine, ifosfamide and cyclophosphamide). Finally, radiation in a solar box was used to simulate the fate of cytostatic drugs in surface waters under natural radiation and complete removal was not observed for any drug. The degradation process was monitored using liquid chromatography coupled to high resolution mass spectrometry and pseudo-first order kinetic degradation constants were calculated. This study provides new data on the degradability of cytostatic compounds in water, thus contributing to the existing knowledge on their fate and risk in the environment.

Degradation kinetics and pathways of three calcium channel blockers under UV irradiation

Calcium channel blockers (CCBs) are a group of pharmaceuticals widely prescribed to lower blood pressure and treat heart diseases. They have been frequently detected in wastewater treatment plant (WWTP) effluents and downstream river waters, thus inducing a potential risk to aquatic ecosystems. However, little is known about the behavior and fate of CCBs under UV irradiation, which has been adopted as a primary disinfection method for WWTP effluents. This study investigated the degradation kinetics and pathways of three commonly-used CCBs, including amlodipine (AML), diltiazem (DIL), and verapamil (VER), under UV (254 nm) irradiation. The chemical structures of transformation byproducts (TBPs) were first identified to assess the potential ecological hazards. On that basis, a generic solid-phase extraction method, which simultaneously used four different cartridges, was adopted to extract and enrich the TBPs. Thereafter, the photo-degradation of target CCBs was performed under UV fluences typical for WWTP effluent disinfection. The degradation of all three CCBs conformed to the pseudo-first-order kinetics, with rate constants of 0.031, 0.044 and 0.011 min(-1) for AML, DIL and VER, respectively. By comparing the MS(2) fragments and the evolution (i.e., formation or decay) trends of identified TBPs, the degradation pathways were proposed. In the WWTP effluent, although the target CCBs could be degraded, several TBPs still contained the functional pharmacophores and reached peak concentrations under UV fluences of 40-100 mJ cm(-2).

Ozone/H2O2 Performance on the Degradation of Sulfamethoxazole

This work aims to analyze the contribution of H2O2 on ozonation of Sulfamethoxazole (SMX). A single ozonation was able to totally remove SMX. TOC and COD depletion rates after a transferred ozone dose of 60 mg/L was related to the formation and decomposition of H2O2. An increase on O3 gas inlet concentration from 10 g/m3 to 20 g/m3 improved COD abatement from 11% to 36%. When the presence of H2O2 at the beginning of ozonation was tested, it was verified that COD and TOC degradation were enhanced, attaining maximum values of 76% and 32%, respectively, when compared with 35% and 15% reached in a single ozonation.

Assessment of cationic surfactants mineralization by ozonation and photo-Fenton process.

Aqueous solutions of two important quaternary ammonium compounds--16-BAC (benzyl-dimethyl-hexadecylammonium-chloride) and 18-BAC (benzyl-dimethyl-stearylammonium-chloride)--were treated by the ozonation and photo-Fenton processes at different ozone doses and hydrogen peroxide concentrations, respectively. During the photo-Fenton experiments, two different types of lamps were used--a UV mercury vapor medium pressure lamp and a xenon lamp, which simulates solar radiation. The total organic carbon removal was monitored to follow the mineralization of the surfactants. According to the experimental results, after 90 minutes of treatment, the photo-Fenton process achieved up to 80% of mineralization when the UV lamp was used. The efficiency of the photo-Fenton with the xenon lamp was lower. The ozonation process reached, at most, 50% mineralization at the used conditions (ozone dose = 7.57 g/h).

Experimental design applied to photo-Fenton treatment of highly methomyl-concentrated water

This work is focused on the study of the suitability of the photo-Fenton process as a pretreatment for water highly contaminated with a methomyl commercial formulation in Advanced Greenhouses devices. Initial concentrations of reagents and pesticide were evaluated according to a central composite experimental design, with methomyl depletion and biocompatibility of the final effluent as response functions. A triad of optimal operation conditions could be determined, [Met.](0)=50 mg L(-1), [H(2)O(2)](0)=254 mg L(-1) and [Fe(2+)](0)=77 mg L(-1) for the best elimination yield and an acceptable BOD(5)/COD value, and initial concentration of methomyl can be established as the most important parameter for the performance of the treatment due to the limitations that impose on the hydrogen peroxide doses in the presence of the excipients of the commercial formulation.

Biodegradability Improvement of Aqueous 2,4-Dichlorophenol And Nitrobenzene Solutions By Means of Single Ozonation

The possibility of the integration of ozonation and biological processes as an economical way to treat biorecalcitrant organic compounds such as nitrobenzene and 2,4-dichlorophenol was investigated. In the pre-treatment step, stoichiometric coefficients and pseudo first-order kinetic constants were obtained. Biodegradability was monitored throughout the ozonation step, in order to evaluate the optimum ozone doses. The low TOC reduction after these ozone doses allowed much of the organic carbon to be removed in the biological stage. In the case of 2,4-dichlorophenol, the biodegradability improvement was checked in an aerobic bioreactor. By means of the combined ozonation-biological oxidation, up to 80% of the initial organic content was removed. Results presented in this study show the feasibility of using the combination of ozone and conventional biological treatments to treat wastewaters containing these pollutants.

Biodegradation of Photo-Fenton Pre-Treated Solutions of Sulfamethoxazole by Aerobic Communities. Molecular Biology Techniques Applied to the Determination of Existing Strains

Abstract This work is focused in the combination of a photo-Fenton process and biological treatments in different devices for the degradation of a 200 mg.L-1 Sulfamethoxazole (SMX) solution. Firstly, the combination of a photo-Fenton process, carried out with different initial H2O2 concentrations, with an aerobic biological treatment performed in a 1 L suspended biomass batch reactors was carried out. A relationship between the degree of pre-treatment and the overall TOC removals achieved was found. Secondly, a photo-Fenton pre-treatment carried out with an initial H2O2 concentration of 300 mg.L-1 and 10 mg.L-1 of Fe2+, was selected to feed a Sequencing Batch Biofilm Reactor (SBBR). It was possible to work with stable cycles of 24 hours, degrading 75% of the TOC contained in the initial SMX solution. Bacterial community located in the biofilm was successfully characterized by applying molecular biology techniques and Scanning Electron Microscopy (SEM).