A pilot-scale wastewater reclamation system based on direct descending filtration and chlorine disinfection

Abstract

The development of cost-effective technologies for treating and disinfecting wastewater to a level that makes it economically valuable, environmentally sustainable, and health-safe for reuse is of utmost importance. In this study, a direct descending filtration pilot unit was designed, assembled, and tested within a municipal wastewater treatment plant to produce nonpotable reclaimed wastewater. Bench-scale tests were performed to define the optimum coagulant type and dosage (Poly aluminium chloride, 15 mg L−1). The pilot plant performed best at a filtration rate of 15 m h−1 in a bed of commercial building silica sand with an average particle size of 0.93 mm, resulting in a net production of 0.103 m3 h−1 of treated water. The removal efficiencies for apparent color, E. coli, turbidity and total suspended solids were 86.8 ± 2.3%, 86.8 ± 3.6%, 76.9 ± 6.9% and 68.7%, respectively. After a final stage of chlorine disinfection, the E. coli removal was higher than 99.7%. All the resulting parameters were within the recommended standards for nonpotable uses, such as landscape irrigation, dust and fire control, soil compaction, and street cleaning.