Investigation on the effective disposal of sludge from a water treatment plant


 Accumulation of water treatment sludge is a major environment problem in the water purification process. Recovery of waste constituents or reuse of sludge is a cost-effective method in handling this environmental dilemma. The present study investigates the suitability of sludge in the production of bricks and recovery of aluminum from the sludge accumulated at the Biyagama drinking water treatment plant (BDWTP) in Sri Lanka. The chemical parameters of total organic carbon, pH, total nitrogen content, total phosphorous content, heavy metals, and cation exchange capacity in samples were analyzed in different turbidity periods. The aluminum recovery was investigated both by acidic and by alkaline leaching processes. A mixing ratio of 3:1 (clay:water treatment sludge) was found to be suitable for manufacturing bricks having compressive strength, efflorescence, and water absorption parameters according to SLS 39:1979. The metal composition of manufactured bricks was compared with clay and water treatment sludge. The environmental impact of current landfilling was estimated by analyzing the leachate of this sludge for COD, NO3-, NO2-, PO43-, free NH3, SO42-, and metals. The heavy metal leachability of manufactured bricks was also analyzed to establish its suitability as an eco-friendly product.