Valorization of drinking water treatment residuals-based granules: a techno-economic analysis for pollutant control

The management and disposal of drinking water treatment residuals (DWTR) cause high economic costs and negative impacts on the quality of the receiving environment. This study proposed a replicable framework for estimating DWTR production, evaluating the technical and economic implications, and assessing the potential application of DWTR granules across selected scenarios in Chile as a case study. A production of 24,500 metric tons (t) of DWTR per day was estimated for drinking water treatment plants located in the Metropolitan Region of Santiago, Chile, which collectively produce 23.6 m³s^-1 of treated water. The techno-economic analysis estimated DWTR conditioning costs between 50 and 80 USDt^-1, depending on the dewatering technology employed. DWTR granulation costs ranged from 90 to 140 USDt^-1. Costs vary mainly due to heat treatment (calcination) and the use of raw materials (binder), which account for over 70% of operational costs. The application scenarios showed that systems based on DWTR granules could remove arsenic and copper at costs of 0.10-0.19 and 0.10 USDm^-3 of treated water, respectively, and phosphorus at costs of 370-530 USDkg^-1 of P removed. These costs were economically favorable and competitive compared to DWTR disposal in landfill and other sorbents and treatment technologies. The sensitivity analysis illustrated that a ±30% variation in the costs of natural gas (calcination) and binder (bentonite) modified the DWTR granulation cost by up to ±24%. The results indicated that applying DWTR granules for the removal of aqueous contaminants constitutes an economically competitive strategy for managing waste within the urban water cycle.