The aim of this work was to investigate the effect of different feeding times (2, 4, and 6 h) and organic loading rates (3, 6 and 12 gCOD l(-1) day(-1)) on the performance of an anaerobic sequencing batch reactor containing immobilized biomass, as well as to verify the minimum amount of alkalinity that can be added to the influent. The reactor, in which mixing was achieved by recirculation of the liquid phase, was maintained at 30 +/- 1 degrees C, possessed 2.5 l reactional volume and treated 1.5 l cheese whey in 8-h cycles. Results showed that the effect of feeding time on reactor performance was more pronounced at higher values of organic loading rates (OLR). During operation at an OLR of 3 gCOD l(-1) day(-1), change in feeding time did not affect efficiency of organic matter removal from the reactor. At an OLR of 6 gCOD l(-1) day(-1), reactor efficiency improved in relation to the lower loading rate and tended to drop at longer feeding times. At an OLR of 12 gCOD l(-1) day(-1) the reactor showed to depend more on feeding time; higher feeding times resulted in a decrease in reactor efficiency. Under all conditions shock loads of 24 gCOD l(-1) day(-1) caused an increase in acids concentration in the effluent. However, despite this increase, the reactor regained stability readily and alkalinity supplied to the influent showed to be sufficient to maintain pH close to neutral during operation. Regardless of applied OLR, operation with feeding time of 2 h was which provided improved stability and rendered the process less susceptible to shock loads.

The aim of this work was to investigate the effect of different feeding times (2, 4 and 6 h) and applied volumetric organic loads (4.5, 6.0 and 7.5 gCOD L(-1) day(-1)) on the performance of an anaerobic sequencing batch biofilm reactor (AnSBBR) treating effluent from biodiesel production. Polyurethane foam cubes were used as inert support in the reactor, and mixing was accomplished by recirculating the liquid phase. The effect of feeding time on reactor performance showed to be more pronounced at higher values of applied volumetric organic loads (AVOLs). Highest organic material removal efficiencies achieved at AVOL of 4.5 gCOD L(-1) day(-1) were 87 % at 4-h feeding against 84 % at 2-h and 6-h feeding. At AVOL of 6.0 gCOD L(-1) day(-1), highest organic material removal efficiencies achieved with 4-h and 6-h feeding were 84 %, against 71 % at 2-h feeding. At AVOL of 7.5 gCOD L(-1) day(-1), organic material removal efficiency achieved with 4-h feeding was 77 %. Hence, longer feeding times favored minimization of total volatile acids concentration during the cycle as well as in the effluent, guaranteeing process stability and safety.

Currently, there is an increasing demand for the production of biodiesel and, consequently, there will be an increasing need to treat wastewaters resulting from the production process of this biofuel. The main objective of this work was, therefore, to investigate the effect of applied volumetric organic load (AVOL) on the efficiency, stability, and methane production of an anaerobic sequencing batch biofilm reactor applied to the treatment of effluent from biodiesel production. As inert support, polyurethane foam cubes were used in the reactor and mixing was accomplished by recirculating the liquid phase. Increase in AVOL resulted in a drop in organic matter removal efficiency and increase in total volatile acids in the effluent. AVOLs of 1.5, 3.0, 4.5 and 6.0 g COD L(-1) day(-1) resulted in removal efficiencies of 92%, 81%, 67%, and 50%, for effluent filtered samples, and 91%, 80%, 63%, and 47%, for non-filtered samples, respectively, whereas total volatile acids concentrations in the effluent amounted to 42, 145, 386 and 729 mg HAc L(-1), respectively. Moreover, on increasing AVOL from 1.5 to 4.5 g COD L(-1) day(-1) methane production increased from 29.5 to 55.5 N mL CH(4) g COD(-1). However, this production dropped to 36.0 N mL CH(4) g COD(-1) when AVOL was increased to 6.0 g COD L(-1) day(-1), likely due to the higher concentration of volatile acids in the reactor. Despite the higher concentration of volatile acids at the highest AVOL, alkalinity supplementation to the influent, in the form of sodium bicarbonate, at a ratio of 0.5-1.3 g NaHCO(3) g COD (fed) (-1) , was sufficient to maintain the pH near neutral and guarantee process stability during reactor operation.

The main objective of this work was to investigate the effect of volumetric loading rate (VLR), shock load, and alkalinity supplementation on the efficiency and stability of an Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR) containing polyurethane foam cubes. Mixing in the reactor, which was kept at 30 +/- 1 degrees C, occurred by recirculating the liquid phase. The reactor treated 2.5 l cheese whey in 8-h cycles, at concentrations of 1, 2, and 4 g COD l-1, which corresponded to VLRs of 3, 6, and 12 g COD l-1 day-1, respectively. Application of single-cycle shock loads of 6, 12, and 24 g COD l-1 day-1 did not impair reactor performance. In addition, for VLRs of 3, 6, and 12 g COD l-1 day-1, alkalinity supplementation to the influent, at the end of each assay, could be reduced to 75, 50, and 50%, respectively, in relation to supplementation at the beginning of the assay. During reactor operation a viscous polymer-like material was formed between the polyurethane foam cubes, which increased at higher VLR. Finally, addition of salts to the influent improved reactor efficiency.

The stability and efficiency of an anaerobic reactor containing biomass immobilized on polyurethane foam were assessed. The reactor with mechanical stirring of 500 rpm and maintained at 30+/-1 degrees C treated synthetic wastewater with a concentration of approx 500 mg of chemical oxygen demand/L and was fed with different influent volumes and cycle times maintaining organic load. Operation was in batch mode with renewal of only part of the volume of wastewater to be treated; that is reactor discharge was not complete, but partial. The main operational characteristic investigated was the ratio of the volume of wastewater fed per cycle (VA) to the volume of wastewater in the reactor (VA) maintaining the same volumetric organic load. This way, operating flexibility could be verified in relation to the volume of treated wastewater at each cycle and the cycle time for the same organic load. The results indicated that the reactor was able to operate with different VA/Vu ratios with no significant loss in performance, thus allowing increased operational flexibility. For conditions in which VA was >or=50% of VA, removal efficiencies of filtered and nonfiltered organic matter were about 84 and 79%, respectively, whereas at conditions of higher initial influent dilution, these efficiencies were slightly lower, about 80 and 74%, respectively. At higher initial influent dilutions, it became difficult to maintain a constant reactor medium volume, owing to a high formation rate of viscous polymer-like material, likely of microbiologic origin.

RESUMO -Neste trabalho avaliou-se o desempenho de um reator anaeróbio operado em batelada seqüencial e contendo biomassa imobilizada (Anaerobic Sequencing Batch Biofilm Reactor -AnSBBR) em espuma de poliuretano. Com a finalidade de contribuir para a resolução dos problemas de aspecto tecnológico que esse tipo de sistema ainda apresenta, como controle de alcalinidade e concentração de sais no tratamento de efluentes com alta biodegradabilidade, o presente trabalho teve como objetivo principal a avaliação da influência da suplementação de sais sobre a eficiência e a estabilidade do reator para o tratamento de soro de queijo, no intuito de colaborar para a correta operação deste tipo de reator. Os resultados mostraram um aumento nos valores de eficiência de remoção de matéria orgânica, ou seja, um aumento no desempenho do reator nas condições em que houve a suplementação de sais no afluente; no entanto, verificou-se que a concentração desses sais não influenciou o desempenho do reator. Os valores de eficiência de remoção de matéria orgânica para a primeira condição, sem adição de sais, ficaram em torno de 81 % e 85 %, para amostras não filtradas e filtradas do efluente, respectivamente. Para as condições com adição de sais, estes valores subiram para 89 % e 92 %, respectivamente. Além disso, foi verificado que não houve acúmulo de ácidos, o reator manteve sua estabilidade em todas as condições estudadas, mantendo o pH do meio próximo da neutralidade.

No abstract

RESUMO-O Reator Anaeróbio Operado em Batelada Seqüencial e Contendo Biomassa Imobilizada (AnSBBR-Anaerobic Sequencing Batch Biofilm Reactor), quando utilizado para tratamento de soro de queijo, tem mostrado diferentes desempenhos em função da concentração de sais no meio. Assim, o presente trabalho teve como objetivo principal a avaliação da influência da suplementação de sais sobre a eficiência e a estabilidade do reator para o tratamento de soro de queijo, sob carga orgânica volumétrica de 2,0 gDQO/L.d. Os resultados mostraram um aumento nos valores de eficiência de remoção de matéria orgânica e carga orgânica removida com o aumento da concentração de sais no afluente do reator. Além disso, o aumento da concentração de sais no meio também resultou em um aumento da alcalinidade a bicarbonato no efluente do reator, concomitante a uma diminuição da concentração de ácidos voláteis totais no efluente, conferindo ao sistema uma maior estabilidade operacional.