Optimum Operation Conditions of Direct Capillary Nanofiltration for Wastewater Treatment

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 paper, Direct CNF has been applied (for the first time) for wastewater treatment under continuous and stable process conditions and to acceptable cost. An important aspect was to determine the optimum operation conditions of the pilot plant. The optimum conditions for Direct CNF when applied to domestic wastewater are 15 minutes filtration time, 20 l/m.h flux rate with undiluted domestic wastewater. The filtration can operate continuously under stable process conditions for approximately 8 hours. Subsequently, the pilot plant must be chemically cleaned due to contamination of the membrane fibres.