Cost analysis of recirculating pre-treated backwash water from sand filters into drinking water treatment: trial results

Effective water resource management and reduction of water consumption require water utilities to minimize losses during the treatment process. As a result, backwash water produced during filtration is often the subject of research focused on its reuse within the water treatment system. This study was conducted at two large water treatment facilities, each with a capacity of 100,000 m3/day. The research focused on backwash water produced during the cleaning of sand filters. Before being reintroduced into the treatment process, the backwash water underwent pre-treatment involving UV disinfection followed by ultrafiltration. The effectiveness of various processes, including coagulation with sedimentation, microfiltration, ultrafiltration, and UV disinfection was assessed under optimal conditions, based on their ability to remove organic matter and microorganisms, which pose health risks when backwash water is recirculated. Additionally, the operational and capital costs of selected pre-treatment approaches were evaluated. The findings revealed that pre-treating backwash water with ultrafiltration membranes (UF), followed by UV disinfection, and reusing it in the treatment systems can reduce environmental impacts.