Handling the Sludge When Using Polyaluminum Chloride as a Coagulant in the Potable Water Treatment Process

Abstract

The sludge produced in the treatment process depends on the type of coagulant and other chemicals used and the suspended particles present in raw water. Discarding this sludge in the landfills poses pollution of both ground and surface water, disturbing the lives in the water and the water quality. The primary potable water provider in Sri Lanka is the National Water Supply and Drainage Board. It focuses on finding ways of disposal, sustainable practices, and possible applications of the water treatment sludge. This research aims to identify the aluminum level in the potable water treatment sludge of the Konduwattuvana water treatment plant in Ampara and to utilize that sludge as an alternative raw material in burnt clay brick manufacturing. The national standards and limitations of the sludge content and the standard brick manufacturing process were followed. To reach the aim, a sequence of tests was conducted, and the brick characteristics are subjected to test for different sludge ratios according to the Sri Lankan Standard of 36:1978 for burnt clay bricks. Experimental results show that the aluminum content in liquid sludge and sludge cake was found to be 231.6 mg.L-1 and 54.9 mg.L-1, respectively, which implies that the sludge contains aluminum. The optimum sludge ratio to produce burnt clay bricks was found to be 10% of the total weight of the brick.