Avaliação da prática de retorno de lodo secundário sobre o desempenho de reatores UASB em escala plena: estudo de caso da ETE LABOREAUX - Itabira / MG

• Ano de defesa: 2015
• Autor(a) principal: Túlio Cesar Floripes Gonçalves
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: SANEAMENTO MEIO AMB RECURSOS HÍDRICOS; Engenharia sanitária; Saneamento
• Link de acesso: http://hdl.handle.net/1843/BUBD-A6EK4W

This research studied the effect of returning secondary sludge to UASB reactors for thickening and digestion in the full-scale sewage treatment plant (STP) Laboreaux in Itabira Minas Gerais. The effect of sludge return was evaluated based on COD, TSS and SSed removals through the operation of the reactors in 4 stages. The initial stage had an HRT of 18hours and the others had a mean HRT of 9 hours. During the research period, 636 days, the reactors received return sludge 24 hours per day, in 30 min cycles. The results show that during the phase when the reactor was operated at an HRT of 18 hours, removal efficiencies were high (73% for COD, 84% for TSS and 88% for SSed). However, it is not feasible to operate the reactors using such high detention time compared to 9 h, the design retention time commonly used in UASB reactors. Changing the HRT from 18 h to 9 hr resulted in the immediate decrease in the quality of the effluent from UASB reactors, with average removal efficiencies for COD, TSS and SSed of 38, 39 and 50%, respectively. It is believed that the higher influent flowrate used during operation with a lower HRT resuspended organic material from the bottom of the reactors). Another important factor leading to the worsening of the quality of the effluent sludge was the total mass of sludge present in the reactors, leading to a high concentration of solids (2%) at the highest point (close to the sedimentation chamber and baffles) which contributes to a great loss of particulate material in the reactor effluent. Among the operational phases with HRT of 9 h, the final phase, in which sludge was removed at height of 2 m and kept at 0.5% of the total volume, showed the best results, with removal efficiencies for COD, SSed and TSS of 75, 85 and 95%, respectively. The compliance analysis for UASB reactors showed that, for the stage where the reactors were operating with high HRT (18 h), 50% of the analyzed values of COD and 40% of SST values were below the values required by the environmental agency. As for the last phase of the research (HRT 9 h), 30% of the COD values and 70% of SST values remained below the required values by the environmental agency. Returning sludge proved to be an advantageous and applicable technique for anaerobic treatment plants (UASB+FBP). The observed operational problems were mainly caused by the inefficient management of sludge in the UASB.