Assessing the feasibility of using ultrafiltration to recirculate backwash water in a surface water treatment plant

Abstract

The necessity of rational water resource management and reduction of water consumption demands that water utilities address water losses during water treatment. Therefore, the backwash water generated during the filtration process is often the focus of research aimed at its reuse within the water treatment system. The studies outlined here were conducted in a large water treatment plant (100,000 m3), focusing on the backwash water produced from sand bed filter flushing. Prior to its reintroduction into the treatment train, the backwash water underwent pre-treatment using ultrafiltration (UF) process with two different modules: a spiral module with a PVFD (200kDa) membrane and a capillary module with a PES (80kDa) membrane. The effectiveness of the process was evaluated based on the degree of retention of organic substances and microorganisms, which pose health risks in backwash water recirculation. The capillary membrane exhibited greater effectiveness in retaining these contaminants, thereby ensuring the complete elimination of pathogenic microorganisms. The study findings indicate that pre-treating backwash water using UF membranes and reintroducing it into the water treatment system before the ozonation process can lead to a reduction of environmental fees. However, this process results in a 1.5% increase in water treatment costs.