Experimental and Economic Evaluation of Nitrate Removal by a Nanofiltration Membrane

Abstract

Abstract Membrane nanofiltration (NF) process was employed to remove nitrate from synthetic and natural waters. The optimum technical and economical ranges of governing parameters for the water treatment process were determined using Central Composite Design method and Verbernen's economic model. The results of nitrate removal from synthesized water showed the minimum and maximum rates of permeation were 16.5 and 84.3 L/m2h (Lmh), respectively. The minimum and maximum nitrate rejection were 44.1% and 78.4%, respectively. Increasing pH had no significant effect on permeation flux but increased the nitrate removal rate. In the case of natural water, the minimum and the maximum flow rate were 7.7 and 68.1 Lmh. Furthermore, the minimum and maximum rejection rates of nitrate were 22.1% and 74.8%. The effects of variables on the permeation flux and nitrate removal for natural water were similar to those for synthetic water. However, by increasing pH, the amount of water passing through the membrane decreased. In all experiments, natural water had less permeation flux and less nitrate rejection than synthesized water. Moreover, the total investment cost reduced as the pressure increased. The cost per m3 of treated water decreased from 3 to 7 bars, then increased as the pressure increased.