ENVIRONMENTAL ASSESSMENT OF WATER TREATMENT SLUDGE DISPOSAL

Abstract

Sludge disposal is often overlooked when performing a Life Cycle Assessment (LCA) of water treatment plants (WTP). This study considered two common WTP sludge disposal methods (dehydration-landfilling and direct discharge to the water bodies) to determine their contribution to the overall WTP impact. The WTP LCA model, including the sludge disposal, was built in SimaPro 9.4.0.1, and the environmental impact was calculated using the ReCiPe 2016 method. The results indicate that landfilling can contribute 9.29-86.8% and 39.31-52.66% of the impact in all midpoint and endpoint categories, respectively. On the contrary, the discharge system contributes only to 5 out of 18 considered midpoint categories. Still, it is responsible for at least 93.6% of the endpoint impact in damage to human health and ecosystems categories. The sensitivity analysis revealed that the share of WTP sludge disposal can fluctuate significantly for the landfill system but remains the same for discharge cases under varying input parameters. The main reason for such high impact scores for both cases can be the contaminants in sludge, namely Arsenic, Zinc, and Nickel. Generally, the findings of this study indicate that sludge treatment and disposal is the vital element of the WTP life cycle inventory.