Membranes are prone to fouling due to several causes one of which is biofouling caused by bacteria. Biofouling can form foundation to collect other debris and lead to further problems. Fouled membranes decrease flow at constant rate, increase pressure to maintain permeate flow and decreased salt rejection. In order to prevent biofoulings use of biocides recommended. The RO Biocide should be dosed from beginning of using new and or clean membrane.