An innovative solution for managing waterworks sludge : developing an alum sludge-based multi-stage constructed wetland system for wastewater treatment

Waterworks sludge continues to be an inescapable by-product of the potable water treatment process. Accordingly, final disposal of the sludge remains one of the most significant pressing problems for the potable water treatment industry. The possibility of reusing the sludge as a main substrate in a novel constructed wetland system was investigated in this study. Results show that significant phosphorus (P) and other pollutants removal were achieved in the system. With a mean influent BOD5 (5-day biochemical oxygen demand) and COD (chemical oxygen demand) levels of 392.7 mg/l and 579.8 mg/l, respectively, a removal efficiency of 90.6 % and 71.8 %, respectively, was obtained. P removal was however exceptionally high despite the high influent mean P level of 45.3 mg-P/l, which is about 2-3 times the level of P commonly found in sewage. This is attributable to the P adsorption capacity of the alum sludge and this highlights the benefits of its reuse in the system. The paper presents and discusses the findings from a laboratory scale research, which has potential for further large scale implementation.