In this study it was evaluated the effects of hydraulic retention time (HRT) and Organic Loading Rate (OLR) on the performance of UASB (Upflow Anaerobic Sludge Blanket) reactors in two stages treating residual waters of swine farming. The system consisted of two UASB reactors in pilot scale, installed in series, with volumes of 908 and 188 L, for the first and second stages (R1 and R2), respectively. The HRT applied in the system of anaerobic treatment in two stages (R1 + R2) was of 19.3, 29.0 and 57.9 h. The OLR applied in the R1 ranged from 5.5 to 40.1 kg COD total (m 3 d) -1 . The average removal efficiencies of chemical oxygen demand (COD) and total suspended solids (TSS) ranged, respectively, from 66.3 to 88.2% and 62.5 to 89.3% in the R1, and from 85.5 to 95.5% and 76.4 to 96.1% in the system (R1 + R2). The volumetric production of methane in the system (R1 + R2) ranged from 0.295 to 0.721 m 3 CH 4 (m 3 reactor d) -1 . It was found that the OLR applied were not limiting to obtain high efficiencies of COD total and TSS removal and methane production. The inclusion of the UASB reactor in the second stage contributed to increase the efficiencies of COD total and TSS removal, especially, when the treatment system was submitted to the lowest HRT and the highest OLR.KEYWORDS: anaerobic digestion, swine excrements, methane gas, UASB reactors in series, two stage treatments. DESEMPENHO DE REATORES UASB EM DOIS ESTÁGIOS SOB DIFERENTES TDH E COV TRATANDO ÁGUAS RESIDUÁRIAS DE SUINOCULTURARESUMO: Neste trabalho, avaliou-se o efeito do tempo de detenção hidráulica (TDH) e da carga orgânica volumétrica (COV) no desempenho de reatores UASB (Upflow Anaerobic Sludge Blanket), em dois estágios, tratando águas residuárias de suinocultura. O sistema foi constituído por dois reatores UASB em escala-piloto, instalados em série, com volumes de 908 e 188 L, para o primeiro e segundo estágios (R1 e R2), respectivamente. Os TDH, aplicados no sistema de tratamento anaeróbio, em dois estágios (R1 + R2), foram de 19,3; 29,0 e 57,9 h. As COVs aplicadas no R1 variaram de 5,5 a 40,1 kg DQO total (m 3 d) -1 . As eficiências médias de remoção de demanda química de oxigênio total (DQO total ) e sólidos suspensos totais (SST) variaram, respectivamente, de 66,3 a 88,2% e de 62,5 a 89,3% no R1, e de 85,5 a 95,5% e de 76,4 a 96,1% (no sistema R1 + R2). A produção volumétrica de metano no sistema R1 + R2 variou de 0,295 a 0,721 m 3 CH 4 (m 3 reator d) -1 . Verificou-se que as COVs aplicadas não foram limitantes para a obtenção de altas eficiências de remoção de DQO total e SST e produção de metano. A inclusão do reator UASB no segundo estágio contribuiu para o aumento das eficiências de remoção de DQO total e SST, sobretudo quando o sistema de tratamento foi submetido aos menores TDHs e maiores COVs. PALAVRAS-CHAVE: digestão anaeróbia, dejetos de suínos, gás metano, reatores UASB em série, tratamento em dois estágios.

In this work it was evaluated the performance of two systems of swine wastewater treatment consisting of two-stage upflow anaerobic sludge blanket (UASB) reactors, with and without post-treatment in sequencing batch reactor (SBR), fed continuously, with aerobic phase. The UASB reactors in the first stage had 908 L in the sets I and II, and in the second stage 350 and 188 L, respectively. In the set II the post-treatment was performed in a SBR of 3,000 L. The hydraulic detention times in the anaerobic treatment systems were 100, 75 and 58 h in the set I; 87, 65 and 51 h in the set II; and 240 and 180 h in the SBR. The volumetric organic load applied in the first stage UASB reactors ranged from 6.9 to 12.6 g total COD (L d) -1 in the set I and 7.5 to 9.8 g total COD (L d) -1 in the set II. The average removal efficiencies of total COD, total phosphorus (P total ), and Kjeldahl and organic nitrogen (KN and N org ) in the anaerobic treatment systems were similar and reached maximum values of 97%, 64%, 68%, and 98%. In the SBR, the removal efficiencies of total COD and thermotolerant coliforms were up to 62 and 92% resulting, respectively, in effluent concentrations of 135 mg L -1 and 2x10 4 MPN (100 mL) -1 . For P total , total nitrogen (TN) and N org , the average removal efficiencies in the SBR were up to 58, 25 and 73%, respectively. Anaerobic-aerobic treatment of swine wastewater in UASB and batch reactors in series Eng. KEYWORDS