Treatment of landfill leachate using modified anaerobic baffled reactor

Abstract

Landfill leachate is highly concentrated organic wastewater with complex composition. It is a major source of pollution potentially threatening the quality of groundwater, surface water and life forms. Leachate needs to undergo a series of treatment prior to discharge into soil, ground water and surface water bodies. Current biological treatment of landfill leachate using aerobic ponds has some drawbacks such as low removal of organic matter and heavy metals. As a result, further treatment of the effluent from the aerobic ponds is required. Hence, chemical and physical treatments are provided which in turn increase the cost of treatment. In this study, raw leachate was subjected to an anaerobic treatment using a modified anaerobic baffled reactor (MABR). In phase I of the study, the design, development and start-up of the MABR system were accomplished. The synthetic feed which was used in the start-up of the reactor was meat extract. When the chemical oxygen demand (COD) removal efficiency reached up to 99%, leachate was gradually introduced until 100% COD. In phase II of the study, a full treatment of the landfill leachate was carried out by maintaining the hydraulic retention time (HRT) and gradually increasing the organic loading rate (OLR). In phase III of the study, the effect of variation of OLR on the treatment performance of the MABR was investigated by reducing the HRT. Results showed that the COD, As, Cr, Fe and color removal values during the treatment of landfill leachate at an OLR of 1.4 kgCOD/m3/d were 79.3%, 87.5%, 88.8%, 87.8% and 78.2%, respectively. In decreasing the HRT (4, 3, 2 and 1 days) and subsequently increasing the OLR (1.4, 1.86, 2.8 and 5.6 kgCOD/m3/d), the efficiency of the MABR showed reduction in the treatment performance. At an OLR of 5.6 kgCOD/m3/d and HRT of 1 day, the COD, As, Cr, Fe and color removal values were found to be 71%, 8.3%, 59.3%, 63.5% and 37.1%, respectively. In addition, the stable population of bacteria has tolerated the heavy metals when the OLR was gradually increased from 1.4 - 5.6 kgCOD/m3/d. The efficient removal of the heavy metals provides evidence that heavy metals can be degraded in anaerobic environments using the MABR. In sum, the MABR may be an efficient solution for the treatment of leachate at the site of a sanitary landfill.