Fouling characterization of TFC forward osmosis membrane in a novel dynamic sludge anaerobic digestion reactor.

The low-solid sludge concentration in reactors limited application of anaerobic digestion. Forward osmosis technology could be innovatively used for adjusting total moisture content of anaerobic digestion (AD) process in order to achieve a higher solid concentration and smaller reactor volume of AD reactor, for which membrane fouling is a crucial problem and determines the water flux and system performance. Many factors such as flux and composition of feed solution might have influence on the membrane fouling. In high-solid anaerobic digester, total solid could be critical to membrane fouling. A simulative anaerobic digestion forward osmosis membrane bioreactor (adFO-MBR) system was designed for fouling investigation of thin-film composite (TFC) forward osmosis membrane. Anaerobic digestion sludge samples with different total solid (TS) content or with different particle size was used as feed solution in this study. Water flux, adsorption capacity of protein and polysaccharose, SEM-EDX and AIR-FTIR were used for characterization of the pristine and fouled membranes. Experimental results showed that feed solution with TS at 5.5–8.0% had the highest and relatively stable water flux (5.5–7.3 L/m² /h) because of the skeleton support and water passage in sludge with high TS. Water flux with smaller particulates and narrow particle size distribution had a slow decline trend. Adsorption capacity of protein and polysaccharose were positively related with total solid content of AD sludge. The results of this study can suggest us the appropriate parameters of AD sludge in adFO-MBR in terms of membrane fouling control. [ABSTRACT FROM AUTHOR]