A UVC-assisted photo-Fenton process was applied to hospital wastewater that had been submitted to anaerobic treatment. Low iron (10 μM; 0.56 mg L −1) and H 2 O 2 (500 μM; 17 mg L −1) concentrations were used at the natural pH of the effluent (pH ≈ 7.4). Citric acid was employed as a complexation agent, at a 1:1 ratio, in order to maintain Fe 3+ soluble at this pH, avoiding extra procedures and costs associated with acidification/basification of the final effluent. The anaerobic process quantitatively reduced the biochemical oxygen demand (BOD 5), chemical oxygen demand (COD) and total organic carbon (TOC), with low removal of antibiotics present in the wastewater. Degradation of the antibiotics ciprofloxacin, amoxicillin, sulfathiazole, and sulfamethazine was studied by spiking the anaerobic effluent at initial concentrations of 200 μg L −1. The antibiotics were efficiently degraded (80-95%) using UVC radiation alone, although under this condition, no DOC removal was observed after 90 min. Further additions of H 2 O 2 and iron citrate increased the degradation rate constant (k obs), and 8% of DOC was removed. A lower pH resulted in higher k obs , although this was not essential for application of the photo-Fenton process. Irradiation with a germicidal lamp resulted in greater degradation of the antibiotics, compared to use of a black light lamp or sunlight, since the overall degradation was influenced by photolysis of the antibiotics, photolysis of H 2 O 2 , and the Fenton reaction. The photo-Fenton treatment could also be applied directly to the raw hospital wastewater, since no significant difference in degradation of the antibiotics was observed, compared to the anaerobic effluent. The photo-Fenton process under UVA and solar radiation reduced total coliforms and E. coli after 90 min. However, quantitative disinfection of these bacteria present in the Hospital effluent was only accomplished under UVC radiation.
The use of reclaimed wastewater in agriculture can be a solution for regions with water shortages or low rainfall periods; besides fulfilling the crop's water needs, it would also promote the recycle of nutrients. However, care should be taken regarding soil salinization, especially in closed environments such as greenhouses for the cultivation of ornamental plants. The domestic effluents are rich in sodium which can accumulate on soil and cause soil sealing. This study evaluated the use of effluents from anaerobic filters and intermittent sand filters in the production of rosebushes (Rosa hybrida “Ambiance”). The crop yield of the rosebushes irrigated with reclaimed wastewater exceeded the one obtained with traditional cultivation, reaching a value 31.8 % higher when employing nitrified effluent originated from intermittent sand filters, with no difference in the product quality. The salinity levels are below the critical limits found in the literature; however, there was a significant increase compared to the irrigation with drinking water.
Nesta pesquisa estudou-se um sistema composto pela combinação de filtro anaeróbio com filtro de areia para o tratamento de esgoto. Para isso, foram avaliados três filtros anaeróbios operados com tempo de detenção hidráulica de nove horas, que tinham o efluente disposto sobre quatro filtros de areia em distintas taxas de aplicações. No primeiro filtro de areia aplicaram-se 50 L.m-2 uma vez por dia. No segundo, terceiro e quarto filtros, essa mesma carga foi disposta em dois, três e quatro horários, espaçadas entre às 9:00 e às 16:00 horas. O sistema apresentou um efluente final com qualidade que atendia os padrões para reúso e demanda bioquímica de oxigênio abaixo do limite para o lançamento em corpos hídricos (Decreto de Paulista nº 8.468/1976), indicando a viabilidade de disposição de taxas superiores às sugeridas pela NBR 13969/1997, a qual orienta os aspectos construtivos para esta forma de tratamento.
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