Effect of Biofilm on Inorganic Suspended Solids Accumulation on Reverse Osmosis Membranes

Abstract

Particles and colloids in feedwater for reverse osmosis (RO) processes are typically removed by pretreatment to silt density index allowable levels to prevent accumulation on membranes. However, the accumulation is mostly caused due to combined biofouling-particulate accumulation and it is important to quantitatively understand particle accumulation as affected by biofilm. This study aims to determine the effect of biofilm on the accumulation of inorganic suspended solids on RO membranes. With the same kaolin concentration contained on the feedwater, the amount of inorganic material deposited was greater by 0.16 mg/cm² when secondary effluent water was used in contrast to pure water, signifying quantitative enhancement of accumulated suspended solid (SS) on the membrane. Amount of glucose in feedwater did not result in a related increase in inorganic material since deposition seemed to be influenced by biofilm coverage on a preformed biofilm, as indicated by similar biofilm percentage coverage with and without glucose in feedwater. Micrographs indicated the preferential deposition of SS on the spacer filaments and membrane areas that were covered with biofilm. This effect of biofilm on inorganic SS accumulation will be highly useful in designing pretreatment strategies by addressing biofilm control to prevent both biofilm formation and SS accumulation.