Chemical cleaning of biologically fouled membranes

Abstract

Microorganisms tend to attach to a solid surface in natural and engineered environment and can further grow into a gel layer known as biofilm, which is the main cause of membrane biofouling. This study investigated the chemical treatment of biologically fouled membranes. Biofilm was grown on nylon membranes to stimulate biofoul conditions, which was then treated by 6 different types of chemicals, namely sodium hydroxide, sodium hypochlorite, sodium chloride, Ethylenediaminetetraacetic acid (EDTA), citric acid and hydrogen peroxide. The effects of chemical concentrations were also studied in the range of 0.5-5%. The removal efficiency of biofims by 6 chemicals was determined in terms of fixed biomass, extracellular proteins (PN) and extracellular polysaccharides (PS).

Removal of biofilm by sodium hydroxide and hydrogen peroxide were shown to be substantial, with the highest removal efficiency of fixed biomass of 68% and 70% at the concentration of 0.5% respectively. Similar phenomena were also observed for extracellular polymetric substances(EPS). Citric acid has the lowest fixed biomass removal efficiency of 39.6%. However, in the concentration range of 0.5% to 5% studied, the concentration effect of chemicals on biofim detachment was not clearly demonstrated.