Black odorous water concentrating by forward osmosis (FO) with aquaporin biomimetic membranes: Pollutants concentrating and membrane fouling characteristics

摘要

This study aimed to investigate pollutant concentration and membrane fouling characteristics of a forward osmosis (FO) process using aquaporin biomimetic membrane (ABM) for concentrating black odorous water. The membrane cells were operated in active layer facing feed solution (ALFS) mode with 2 M NaCl solution as the draw solution. The system was continuously performed for 64 batch cycles, and each cycle duration was 24 h. At the end of each cycle, physical cleaning with deionized water was employed as the membrane recovery strategy. The results showed that the rejection ratios of chemical oxygen demand (COD), total phosphorus (TP) and nitrate (NO3-N) could reached 97.2%, 98.0%, and 85.0%, respectively, while most NH4+-N penetrated into the draw solution due to cation exchange. The total nitrogen (TN) rejection ratio was largely dependent upon the NH4+-N/TN ratio. At high NH4+-N/TN ratio, the successions of ammonia oxidizing bacteria (AOB) communities enriched in the biofouling layer in different experimental stages would affect the transformation degree of NH4+-N, and thus lead to much fluctuations of TN rejection. The average initial water flux reached 9.84 L/(m(2).h), and the average water flux of each cycle kept stable especially in the later stage of the experiment. In the biofouling layer, polysaccharides enhanced while proteins decreased in the later period. P, Mn, Fe and Na also accumulated on the surface. Noranki Reyranellaceae, Erythrobacter, SM1A02, Pirellula, and Hydrogenophaga were the predominant genera enriched in the fouling layer, which would lead to complex pollutants transformations, especially nitrogen transformation, during the FO process.