Comparative assessment of the degradation of 2-methylisoborneol and geosmin in freshwater using advanced oxidation processes.

Traditional methodologies of conventional drinking water treatment are unable to remove some chemical compounds, such as those that cause odor and taste in drinking water. The present work aims to evaluate the efficiency of advanced oxidations processes, using UV radiation, O3 and O3 + UV in the degradation of geosmin (GSM) and 2-methylisoborneol (2-MIB) in synthetic samples. The efficiency of the processes was monitored by Gas Chromatography coupled with Mass Spectrometry using solid phase microextration technique. Experiments were carried out for 45 min with samplings every 15 min. The degradation results showed that UV radiation alone was not efficient for the degradation of both compounds. The fasted decay was observed by the combined use of O3 and UV with an ozone concentration of 15.84 mg L-1. Under these conditions, the final concentration of GSM was below the limit of quantification, so that approximately 99% of the initial concentration was degraded, while 2-MIB was degraded by 95%. With the same O3 concentration without the use of UV radiation, 63% and 65.7% of MIB and GSM, respectively, were removed. Higher efficiency of the treatment was observed with a higher O3 concentration which allows a shorter reaction time.

Combined system for the treatment and reuse of urban wastewater: the efficiency of anaerobic reactors + hybrid constructed wetlands + ozonation.

The research developed a combined system in batch flow and in pilot scale for the treatment and reuse of urban effluents. The system was fed raw effluent from a university campus in Brazil and composed of four anaerobic reactors, three constructed wetlands (CWs) and an ozonation unit. The three sequential hybrid constructed wetlands were composed of a floating treatment wetland, an aerobic-anoxic baffled constructed wetland (CW) and a saturated vertifcal flow CW. Later, during the last trimester, weekly samples of the treated effluent were ozonated by bubbling with an application rate of 240 mg.h-1 O3. The system presented high removal rates efficiencies in terms of carbonaceous organic matter (78.9%), nitrogen (91.0%), color (96.7%) and turbidity (99.1%). In addition, it worked well for disinfection and acute ecotoxicity, but P was only efficiently (75%) removed in the first 8 months, with removing efficiency declining after this period. Ozonation provided significant color removal and an increased pH. The combination of floating, alternated upflow and downflow and saturated vertical flows improved the treatment of wastewater. This was due to the presence of both aerobic and anaerobic zones, as well as the filter substrate, through an integrated system with simple construction and operation and increased lifespan.

Sistema integrado com microalgas e wetland construído de fluxo vertical no tratamento de efluentes urbanos / Integrated system with microalgae and constructed wetland in vertical flow for urban wastewater treatment

RESUMO O sistema integrado com microalgas (MA) e wetland construído de fluxo vertical (wetland construído pós-microalgas - WCPMA) foi aplicado para a realização de ensaios de tratamento de efluentes no campus da Universidade de Santa Cruz do Sul, no Rio Grande do Sul (UNISC-RS). Águas negras e amarelas foram alimentadas para esse sistema em regime de batelada a partir de um tanque equalizador da estação de tratamento de efluentes da universidade, considerando tempo de detenção hidráulica (TDH) de três dias para cada unidade do sistema integrado. O comparativo de desempenho foi feito com unidades também envolvendo a sequência de tanque de armazenamento de efluentes (TAE) + sistema de controle (C), somente com suporte de areia e brita, em triplo estágio, bem como wetlands construídos de fluxo vertical, também em triplo estágio. O abastecimento utilizou fatores de carga em termos de demanda química de oxigênio (DQO) de 2,4±0,9 g m-1dia-1 para o TAE e de 26,7±11,2 g m-1dia-1 para as unidades de wetlands construídos, de MA+WCPMA e de C (sem o cultivo da Hymenachne grumosa). Em relação à unidade TAE+MA+WCPMA, as reduções dos parâmetros de cargas poluentes foram mais significativas em termos de demanda bioquímica de oxigênio (DBO5) (58%), fósforo total (63%) e, principalmente, nitrogênio amoniacal no sistema integrado, com redução de 100%. Em termos de toxicidade aguda com Daphnia magna, a detoxificação foi efetiva, com variações de valores de EC50 de 58 a 100%. O estudo obteve resultados expressivos que indicam que o sistema MA+WCPMA é uma alternativa promissora no tratamento de águas residuárias para unidades geradoras descentralizadas, possibilitando maior redução da ação eutrofizante.

ABSTRACT The application of integrated systems with microalgae (MA) and Vertical Flow Constructed Wetland Post Microalgae (CWPMA) was performed for campus wastewater treatment assays located in Santa Cruz do Sul (UNISC-RS). Black and yellow waters were fed to systems in batch regime from equalizer university wastewater treatment plant tank, considering hydraulic detention time (HDT) of three days for each unity of the integrated system (MA+CWPMA). The comparison of performances was also made with units involving storage tank wastewater (STW)+Control System (C), only supported with sand and gravel in triple stage, as well as CWs, also triple stage. The supply used load factors in terms of COD 2.4±0.9g m-1 day-1 (for STW) and 26.7±11.2 COD m-1day-1 for the units of CWs; MA+CWPMA and Control (without the cultivation of Hymenachne grumosa). Reductions of the parameters of pollution loads were more significant in terms of BOD5 (58%), total phosphorous (63%) and especially in terms of ammonia nitrogen in integrated STW+MA+CWPMA, with a reduction of 100%. In terms of acute toxicity with Daphnia magna, detoxification was effective, with EC50 values ranging from 58 to 100%. The study developed obtained significant results that indicate this is a promising alternative in the treatment of wastewater for decentralized generating units, allowing greater reduction in eutrophic action.

Ecotoxicological and genotoxic assessment of hospital laundry wastewaters.

The aim of the present study was to assess the ecotoxicity and genotoxicity of hospital laundry wastewaters generated from a regional hospital located in Rio Pardo Valley in the state of Rio Grande do Sul, Brazil. Physicochemical, microbiological, ecotoxicological, and genotoxic analyses were performed, and the results indicate that some parameters were not in accordance with the limit concentrations established by Brazilian and international guidelines for urban wastewaters. Daphnia magna (EC50 2.01%) and Danio rerio (LC50 29.25%) acute toxicity was detected, and sublethal effects were identified in Lactuca sativa (IC25 12.50%) and Allium cepa (IC25 51.25%). Cytotoxicity was observed at the five wastewater concentrations used yielding statistically significant differences (p < 0.05) in the meristematic cells of A. cepa compared with the negative control. The results obtained here warn about the necessity to develop treatment methods that can mitigate the environmental impacts caused by the ecotoxicity and genotoxicity of hospital laundry wastewaters.

Glutaraldehyde degradation in hospital wastewater by photoozonation.

In this paper, we assessed aqueous solutions of glutaraldehyde (GA), a chemical used for the disinfection of hospital materials, using advanced oxidative processes, O3, and UV, and the combination of the latter two. Assays with different ozone concentrations at distinct pH levels were conducted to determine the best treatment process. GA concentrations before and after each treatment were measured by spectrophotometry. The best treatment was that which combined O3 and UV, yielding a degradation of 72.0-75.0% in relation to the initial concentration with pH between 4 and 9. Kinetics demonstrated that GA degradation is not dependent on pH, as there was a first-order reaction with a rate constant of k = 0.0180 min(-1) for initial pH 9 and of k = 0.0179 min(-1) for initial pH 7, that is, the values are virtually the same. Secondary wastewater samples were also analysed using the septic tank/filter system of a regional hospital in Vale do Rio Pardo, state of Rio Grande do Sul, southern Brazil. In this case, the characteristics of the wastewater were described and, after treatment, a GA degradation rate of 23.3% was noted, with reductions of 75% for chemical oxygen demand, 81% for biochemical oxygen demand, 68% for turbidity, 70% for surfactants and total disinfection in terms of thermotolerant coliforms.