Anaerobic Treatment of Brackishwater Aquaculture Sludge: An Alternative to Waste Stabilization Ponds

Environmental pressure, land utilization, and economic feasibility have resulted in the development of recirculating aquaculture systems (RAS). For many RAS, sludge is collected and washed from the system to waste stabilization ponds (WSPs). However, disposal of brackishwater aquaculture sludge into WSP is often prohibited because the high salinity can interfere with treatment. Moreover, there are problems associated with WSPs because of elevated salt content, such as the common practice of reusing treated water and land application of stabilized sludge. We tested and compared the treatment of brackishwater aquaculture sludge in an upflow anaerobic sludge blanket (UASB) reactor as an alternative to a WSP. In UASB, wastewater flows upward through a blanket of granular sludge and is treated by anaerobic micro-organisms. Reduction in organic matter and 5-d biochemical oxygen demand by 97 and 91%, respectively, was achieved in a UASB as compared to corresponding reductions of 22 and 41% in a WSP. During the UASB digestion process, methane is produced and recovered. Overall, a reduction in potential environmentally harmful factors such as salinization, land requirements, greenhouse gas emissions, as well as transportation costs are achieved, making the UASB reactor an attractive possible alternative for saline aquaculture sludge management.