Grey water treatment and simultaneous surfactant recovery using UF and RO process

The membrane-based grey water treatment for grey water reuse and surfactant recovery is presented in this research paper. Grey water from washing machine discharges having turbidity and used surfactant was processed through the polymeric ultrafiltration (UF) membrane to remove the turbidity. The UF treated grey water is further purified by reverse osmosis (RO) membrane for surfactant recovery and water reuse. The surfactant trapped inside the RO spiral wound membrane module is recovered through various membrane physical regeneration techniques such as backwashing, simultaneous backwash–back-flush and ozone back-flush. Among this, backwash–back-flush is found to be effective process for surfactant recovery. The methodology for optimising surfactant recovery is captured by studying effect of various operating parameters such as feed detergent concentration, backwash pressure, backwash temperature and back-flush flow rate. By implementing optimal process conditions, the integrated UF and RO membrane process is able to produce 300 L of reusable pure water and 80 L of concentrated detergent solution and 20 L of turbid water while treating 400 L of grey water discharges. Maximum surfactant recovery of 82% is obtained while treating grey water which consists of 720 ppm of total dissolved solids (detergent) and 45 ppm of surfactant. The extent of UF and RO membrane fouling is determined by measuring the pure water flux before and after the grey water treatment. The membrane performance is found to be stable when membrane is regenerated by backwash–back-flush technique for RO and gravity backwash for UF membrane.