Incinerating Hong Kong water treatment sludge: the potential of ash reuse and recycling

Abstract

At present, landfilling is the only means to dispose of nearly 900 tonnes of dewatered waste sludge generated in Hong Kong everyday. The Environmental Protection Department of Hong Kong has chosen sludge incineration to resolve this issue, but it should be further noticed that this approach still results in residual ashes that require proper stabilization prior to be landfilled. A sustainable solution in waste management should develop a closed-loop for material flow by reusing and recycling. Current focuses on sludge incineration planning are largely the stringency of emission standards and the impact on the facility surrounding areas. However, potential reuse and recycling strategies for incineration ash should also be taken into account to be part of the sustainable waste management plan. This paper introduces the different types of sludge generated in Hong Kong; predicts the characteristics of their ashes after incineration; and evaluates the potential of ash reuse and recycling strategies, e.g. land applications and construction materials, in according to their unique nature and application goals. Although both scientific principles and engineering feasibility are core consideration factors for beneficial uses of incineration ash, rigorous campaign for the public acceptance will be essential toward the success of such implementation.