Potential of nanofiltration for phosphate removal from wastewater

Experimental investigations were conducted to evaluate the performance of nanofiltration for tertiary level phosphate removal from wastewater. A flat sheet type Desal-5 thin film nanofiltration membrane in a plate and frame module was used. The influence of pressure, initial feed concentration, competing compounds, on nanofiltration performance were determined. The experimental study range of pressure and concentration were 400-1000 kPa and 2-10 mg l(-1) P respectively and ammonium sulphate was used as the competing compound. Results showed that phosphorus removal efficiency for nanofiltration is high (> 95%) and it can produce an effluent containing less than 0.1 mg l(-1) P as a tertiary level treatment. Higher pressure and concentration showed positive response, while presence of competing compound showed negative response on phosphorus rejection. A numerical equation relating osmotic pressure and permeate flux has also been developed based on the experimental results.