Potential utilization of sewage sludge

Abstract

Singapore, a tropical-island city-state, is served by six modern sewage treatment plants with a combined design capacity of around 900,000 m3/day. Currently, 96.5 percent population of Singapore is served by sewer systems. Total production of raw sludge and digested dewatered sludge from six sewage treatment works in 1988 was about 2,546,000 m3 and 39,000 m3 respectively. Most of the dewatered sewage sludge is used as a soil conditioner and landfilling. Since land is limited in Singapore, alternative means of disposal of dewatered sewage sludge are essential. Therefore, studies were conducted to investigate the feasibility of using dewatered sewage sludge for producing building materials and products like aggregates, bricks, paving blocks, tiles, drain sections and pipes. Studies were also conducted to use sewage sludge as a conditioning additive to improve the characteristics of poor subgrade soils for road construction. Attempts were also made to utilize sewage sludge as a filler material in concrete and bituminous mixes. Findings of these investigations have shown encouraging results. This paper presents the results of these studies on potential application of sewage sludge for beneficial uses.