Enhancing stormwater treatment through ultrafiltration: Impact of cleaning chemicals and backwash duration on membrane efficiency

Abstract

The effect of chemical cleaning and regular backwashing on the efficiency of an ultrafiltration membrane fouled during stormwater treatment was studied. Increasing backwash time from 30 to 60 s resulted in an increase in productivity by 20%. However, the productivity was highest when a backwash time of 45 s was used (3% higher than using 60 s). Chemical cleaning was carried out using an alkaline solution (NaOH with or without NaOCl) followed by acid washing with HCl. The addition of NaOCl to the cleaning chemical did not significantly increase the efficiency of chemical cleaning, and the average pure water permeability increase was 97 ± 13 LMH bar−1 after chemical cleaning with NaOH followed by HCl and 117 ± 15 LMH bar−1 after chemical cleaning with NaOH + NaOCl followed by HCl, on average. In addition, reversibility after chemical cleaning was 96 ± 67%, on average. The result from scanning electron microscopy showed that at the end of the experiments, inorganic foulants existed in both the inner layer (feed side) and the outer layer (permeate side) of the membrane. HIGHLIGHTS Longer backwash time resulted in higher permeability and backwash efficiency.; Chemical cleaning using NaOH with/without NaOCl followed by acidic cleaning by HCl could recover pure water permeability and reversibility of the ultrafiltration membrane.; A significant amount of inorganic material was found on the fouling layer.;

Keywords

• dead-end filtration
• fouling
• permeability
• pulsatile fluid flow
• runoff
• stormwater treatment