Environmental and Economic Assessment of Sludge Reuse in a Conventional Drinking Water Treatment Plant

Drinking water treatment plants (DWTP) are crucial to protecting public health yet face environmental pressures because of chemical use, energy-intensive operations, and managing the challenges of treatment residuals. In India, alum-based coagulation continues to be widely used, causing production of huge amounts of alum sludge, which is discharged into water bodies. In this study, we performed life cycle assessment (LCA) and techno-economic assessment (TEA) of a DWTP to examine two alternative approaches of handling sludge: (i) the existing practice of direct disposal and (ii) the circular strategy of settled sludge reuse. Environmental impacts were evaluated using the ReCiPe 2016 (H) method, focusing on energy use, chemical inputs, and sludge generation. The results show that reusing sludge reduces alum consumption by 60% while the increase in energy demand remains minimal (0.83%). These operational changes led to notable improvements, including 25–40% lower eutrophication potential, reduced human toxicity, and reductions in end point damage to human health (80.6%) and ecosystem quality (50.4%). The TEA indicated sludge reuse decreases daily operating costs from INR 54 142.44 to 51 987.38, decreasing the unit treatment cost from INR 9.10 to 8.74 per cubic meter. Overall, the study demonstrates that incorporating sludge reuse is technically and financially feasible, offering a practical pathway toward sustainable drinking water treatment in India.