Effect of operating conditions on the separation of ammonium and nitrate ions with nanofiltration and reverse osmosis membranes

This paper presents the pilot scale membrane separation studies on the Elmali Lake raw water in Istanbul, which is highly polluted by discharging of sewage waters. Low pressure nanofiltration (NF) and reverse osmosis (LPRO) membranes having the surface area of 2 m² have been used during the experimental runs. Experiments were conducted at different pressures, temperature and pH ranges. Feed flow rate was about 300 L/h. As a result, flux values increased linearly with increasing pressure. Ammonia and nitrate ion rejections also increased with increasing pressure and characteristics of rejection were similar for the both types of membranes. Permeate flux value increased proportionally with the temperature. The temperature changing has also influenced the rejection rate of ammonia and nitrate ions. Both ammonia and nitrate ion rejections at neutral pH values were very high. Therefore, neutral pH value is suitable for TFC-S and TFC-HR membranes to remove ammonia and nitrate ions.