A new reactor based on upflow sludge blanket technology (USB) for fermentation of both the particulate and soluble fractions of domestic wastewater is presented. The process is fed with the total wastewater flow, and carries out suspended solids (SS) retention, fermentation and clarification of the fermented effluent in a single reactor. The study was carried out using pilot scale reactors, under six different operating conditions with regards to hydraulic load (hydraulic retention time, HRT, varying between 1.1 and 4.3 hours) and at a constant temperature (20 ± 1°C). With regards to primary treatment, the process has been shown to ensure low SS residuals in the fermented effluent under all operating conditions tested. Very low residuals, with an average below 50 mg SS/l, were obtained with an upflow velocity of between 0.75 and 0.9 m/h. These trials have also highlighted the important role played by the adsorption of particulate organic matter on the biological flocs of the sludge blanket in the elimination of SS. Fermentation efficiencies are superior to those of existing fermenters, the results clearly proving that a majority of the volatile fatty acids produced originate from the soluble fraction of the wastewater. Under the optimum conditions tested, with an HRT = 2.8 hours, 0.17 mg HAc/mg total COD are produced, over 60% of which is generated by the fermentation of the influent soluble organic matter. Under these operating conditions, maximum solubilisation of the particulate fraction has been estimated at 0.13 mg of filtered COD/mg particulate COD (total COD-filtered COD).

Sludge samples from an upflow anaerobic sludge blanket (UASB) reactor and four submerged aerated biofilters (BFs) of a wastewater treatment plant (1,000 inhab.) were processed at bench scale by alkaline and acid hydrolysis with the objective to evaluate the organic matter solubilization, volatile solids (VS) destruction and the effect of hydrolytic processes on the extracellular polymeric substances (EPS) fraction of the sludge samples. The results showed that alkaline hydrolysis of sludge samples treatment with 1.0% total solids (TS) using NaOH 20 meq L(-1) was more efficient on organic matter solubilization and VS destruction than acid hydrolysis. The EPS sludge content was also affected by the alkaline treatment of anaerobic sludge samples. The EPS concentrations (mg EPS/gVSS) on the anaerobic sludge after the alkaline treatment were significantly lowered according to sample height in the UASB reactor. Data indicated that the EPS sludge fraction is the main component affected by the alkaline hydrolytic process of anaerobic sludge samples.

O reúso de águas tem sido considerado uma ferramenta estratégica para atenuar as pressões hídricas. No Brasil ainda não há uma legislação específica, de abrangência nacional, com a abordagem de padrões de qualidade de água para fins de reúso. Nesse estudo foram analisados 11 documentos reguladores (legais, normativos e norteadores) federais e sub federais, tanto em relação ao reúso de água como em relação aos usos múltiplos da água. Objetivou-se com isso estabelecer uma comparação entre os principais padrões de qualidade de água para contribuição à implementação e ao aprimoramento do instrumento de reúso no Brasil. Concluiu-se que os documentos legais que abordam o uso e o reúso de águas apresentam padrões sobrepostos e na maioria dos casos, com valores bastante discrepantes. Em relação à restrição de uso ou exposição ao risco para os casos de reúso urbano, há uma grande diversidade nas premissas conceituais entre os diferentes instrumentos avaliados. Os documentos legais específicos para reúso de águas no Brasil apresentam-se com restrições demasiadamente elevadas, podendo dificultar a implantação de ações efetivas de reúso no país. O padrão de qualidade de água específico para reúso deve ser condizente com a realidade socioeconômica do país, indicando principalmente o padrão microbiológico do efluente e os parâmetros que o representa. Avaliações de risco devem ser abordadas de maneira a respaldar os limites estabelecidos para padrões microbiológicos.

This paper presents exploratory results on the association of an Upflow Anaerobic Sludge Blanket - UASB reactor (46 L) and a submerged aerated biofilter – BF (6.3 L) for domestic sewage treatment. The experimental period extended for 322 days, during which the hydraulic and organic loads were gradually increased in both reactors. Having the UASB as a reference, the following hydraulic loads were tested: 0.4 m3/m2.h (θ = 16 h); 0.6m3/m2.h (θ = 10h); 0.8 m3/m2.h (θ = 8 h); 1.0 m3/m2.h (θ = 6 h) and 1.45 m3/m2.h (θ = 4h). During the experiments carried out with the UASB reactor operating at a hydraulic detention time of 6 hours, related to a θ < 11′ in the granular media of the BF, the mean removal efficiency in terms of SS, BOD5 and COD, in both reactors, were respectively 94%, 96% and 91%. The final effluent, related to the BF effluent, presented the following mean characteristics: SS = 10 mg/L, BOD5 = 9 mg/L and COD = 38 mg/L. The results obtained in the last phase of the experiments, when the hydraulic load in the UASB reactor reached 1.45 m3/m2.h (θ = 4h), were similar to those obtained in the previous phase. These results demonstrate that submerged aerated biofilters can be considered a viable alternative for the post-treatment of effluents from UASB reactors treating domestic sewage. These reactors are capable of being operated with very short hydraulic detention times.

Mechanisms for biological phosphorus removal from wastewaters in an upflow granular aerated filter are evaluated. The feasibility of excess phosphorus uptake on fixed bacteria is demonstrated on pilot scale and the limiting parameters are established. The influence of the duration of anaerobic and aerobic states and of substrate loadings on phosphorus removal is verified, as well as the impact of alternating aeration on nitrification. Because bacteria are attached, hydraulic retention time of biomass and water can be separated and the exposure of bacteria to anaerobic or aerated conditions can be optimised.

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The aim of this study was to evaluate the potential cultivation of lettuce (Lactuca sativa) with domestic wastewater effluents with different levels of treatment from a compact WWTP in Brazil. Vegetables were grown in five treatments: nutrient solution (control), secondary effluent diluted 50%, secondary effluent not diluted, tertiary effluent UV irradiated, and UASB effluent. Microbiological analyses from leaves showed low levels of contamination with E. coli, thermotolerant coliforms and total coliforms. Salmonella spp. and helminth eggs were not detected. However, roots showed hardly any concentration of these microorganisms. These results shows that it is possible to cultivate leafy vegetables in a hydroponic system with treated effluents, taking care at the moment of harvesting vegetables.

The aim of this study was to verify the efficiency of UV irradiation in the inactivation of Salmonella spp. in treated wastewater with different levels of turbidity and exposed to increasing doses of UV irradiation. Experiments were carried out in a batch reactor and in a real scale reactor. Salmonellae obtained from clinical samples were seeded into autoclaved wastewater collected from a wastewater treatment plant (WWTP) comprising an association of a UASB reactor followed by three submerged aerated biofilters (BAF) and one tertiary filter. The results showed that salmonellae were not inactivated in effluents from the UASB reactor indicating that the presence of suspended solids was an important obstacle to UV penetration in bacteria. However, UV irradiation was efficient in inactivating Salmonella of effluents from aerated secondary and tertiary biofilm reactors.