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.