Abstract
Ultra-low pressure reverse osmosis with suction filtration below 0.06MPa was applied to ground water treatment. The volume flux of 0.030m/d and the rejection of chloride ion of 90%, was achieved in this experiment. 60 days operation of the volume flux of 0.021m/d was possible without membrane cleaning. The rejection of heavy metals in this system was higher than that of chloride ion. Color substances like humic acid and micropollutants like bisphenol A were detected in the permeate of the reverse osmosis. Diffusion or penetration through defective pores other than convection would be a mechanism for the transport of these organic solutes judging from the experimental results of decrease in the rejections with low pressure operation. The decrease in ion rejection was analyzed by the solution diffusion model and by the extended Nernst Planck equations. The results showed that the selectivity of ionic species was well characterized by the extended Nernst Planck equations, though the estimated value of effective electric charge in the model was lower than that in the case of higher pressure operation.
