Production of Drinking Water from Domestic Wastewater Using Capillary Nanofiltration

Direct Capillary Nanofiltration (Direct CNF) is a new technique used for surface water and wastewater treatment in one step without pre-treatment. The CNF membrane module combines the favourable cleaning properties of capillary ultrafiltration membranes with the favourable separation properties of nanofiltration membranes in terms of removal of DOC, colour, bacteria, viruses and pesticides. Direct CNF was applied to Twente Canal surface water to produce high quality permeate in a single step. In this study, Direct CNF has been applied (for the first time) to wastewater treatment under continuous and stable process conditions. The optimum conditions for Direct CNF when applied to domestic wastewater were 15 minutes filtration time, 20 l/m.h flux rate with undiluted domestic wastewater during 8 hours and 40 minutes filtration time. Direct CNF showed high removal for bacteria, heavy metals, COD, BOD5, DOC and medium removal for manganese, calcium and magnesium while lower removal was detected for mono ions such as sodium and chloride. The permeate of CNF was high quality water but it was still not drinkable because of high ammonia, total nitrogen concentrations as well as the residues of bacteria. Accordingly, the permeate was treated with granular activated carbon followed by low doses of chlorine for disinfection to produce drinking water.