USING AMMONIUM BICARBONATE AS DRAW SOLUTION IN FORWARD OSMOSIS PROCESS FOR REMOVAL OF p-CHLOROPHENOL IN DISCHARGED WATER FROM COOLING SYSTEM

Abstract

This study examined the optimal condition of forward osmosis process (FO process) for remove p-chlorophenol in discharged cooling water. The lowest applied pressure for operate the filtration process was 0.1 MPa. Two draw solutions (e.g. sodium chloride (NaCl) and ammonium bicarbonate (NH4HCO3)) were applied in this study. The same concentration of 0.5 M of two draw solutions (NaCl and NH4HCO3 ) produced osmotic pressure 2.49 and 3.735 MPa, respectively. Hence, the NH4HCO3 was selected to be draw solution in FO process for further study. Concentration of NH4HCO3 solution as draw solution was varied as 0.05, 0.1, 0.5 and 1.0 M for remove p-chlorophenol in synthetic wastewater (NaCl 0.017 M), the concentrations of p-chlorophenol were decreased from the initial state 5.14 %, 5.72 %, 10.19 % and 15.32 %, respectively. In case of real discharged cooling water, the concentrations of p-chlorophenol were decreased from the initial state 4.19 %, 4.39 %, 7.83 % and 9.72 %, respectively. The concentration of p-chlorophenol in draw solution cannot be detected. Hence, p-chlorophenol was rejected by size exclusion mechanism. However, the concentration of p-chlorophenol in feed solution might be reduced due to evaporation and photodegradation. Separation of ammonia (NH3) in NH4HCO3 solution as draw solution was operated by distillation process in order to obtain a good quality of water. At the low concentration of draw solution (e.g., 0.05 M), NH3 can be separated easily and the quality of obtained water was appropriate to return to cooling system. In the contrast, some of NH3 still remained in the draw solution at the high concentration of draw solution e.g., 0.5 and 1.0 M. which caused the high electrical conductivity and was not appropriate to return into cooling system. The increasing of temperature and the distillation time can enhance NH3 separation efficiency.