The granular sludge properties and performance evaluation of upflow anaerobic sludge blanket reactor as a pre-treatment for domestic wastewater

Abstract

Upflow Anaerobic Sludge Blanket (UASB) has traditionally being used in treating high strength wastewater to reduce the strength prior to the aeration treatment. The ability of UASB to reduce the strength of the wastewater via anaerobic mode help to reduce the aeration demand in the aerobic reactors, which in turn lower the energy demand for aeration. A pilot study of 131 m3 working volume capacity bioreactor has been conducted to assess the potential and benefits of UASB as pre-treatment for domestic wastewater prior the aerobic biological treatment system. Based on monitoring assessment, the results showed that the integration with UASB performance as a pre-treatment able to reduce organic and solid loading from incoming influent (Chemical Oxygen Demand (COD) ~ 50 % removal and Total Suspended Solid (TSS) ~ 60 % removal). Consequently, the downstream aerobic biological system will be able to operate efficiently with less aeration requirement, hence save energy consumption for overall plant and produce better quality of effluent. Furthermore, the formation of anaerobic granular sludge is also observed in the UASB reactor. The analysis proved that granules with size between 0.3 to 0.6 mm were obtained in the sludge bed of the UASB reactor, and the highest amount (volume) was obtained from bottom part. Based on physical properties analyses, these granules have an excellent settling ability and compact sludge settleability (SVI30 55–95 mL/g, SV 25–30 m/h). In conclusion, this study is significantly indicated that UASB can be deployed for enhancement of domestic wastewater treatment, by using anaerobic granular sludge as seed sludge for subsequent activated sludge process, thus will improve the overall sludge settleability performance of the plant.