Start-up phase of a UASB-septic tank used for high strength municipal wastewater treatment in Mexico

The objective of this work was to assess the performance during the start-up phase of a Upflow anaerobic sludge blanket (UASB)-septic tank for municipal wastewater treatment in Mexico City. A lab scale UASB-septic tank (62 L total volume, acrylic), consisting of three chambers treated high strength municipal wastewater at ambient temperature (16 °C–24 °C), under 72 h Hydraulic retention time (HRT) during three months. Total and soluble chemical oxygen demand (COD), total biological oxygen demand (BOD₅), total solids and total suspended solids (TSS) removals were 75.2 ± 6.5%, 54.8 ± 6.7%, 64.2 ± 4.8%, 25.9 ± 5% and 82.9 ± 5%, respectively. These results are comparable with the removals reported in other works with similar arrangements; and are similar even with average removals of COD, BOD and TSS in UASB reactors installed in Latin America. The good performance obtained showed that it is possible to achieve a short start-up period with UASB-septic tank if it is inoculated with anaerobic sludge. These findings also evidenced the feasibility and reliability of the UASB-septic tank system for decentralized wastewater management in Mexico.