Assessment of biological activated carbon treatment to control membrane fouling in reverse osmosis of secondary effluent for reuse in irrigation

Biologically treated secondary effluent (BTSE) is being used increasingly as a source of water for irrigation purposes. Biological activated carbon (BAC) was investigated as a pre-treatment to reduce the organic fouling and biofouling potential of reverse osmosis (RO) membranes for the desalination of a moderately saline BTSE to be used for agricultural purposes. The BAC reduced the organic content through biodegradation by the microorganisms and adsorption by the activated carbon, and subsequent microfiltration (0.1 μm PVDF) further reduced the organic content and thus fouling of the RO membrane. The BAC treatment was shown to effectively reduce the biodegradable dissolved organic carbon and assimilable organic carbon contents, and the bacterial regrowth potential, thus confirming its potential for mitigating biofouling of the RO membrane. The improved RO performance demonstrated that this process was effective for reducing the fouling propensity of the BTSE to enable its sustainable application for producing an effluent with a high reuse potential for irrigation purposes. The RO permeate can then be blended with untreated water to produce a product with a suitable inorganic content for irrigation.