Study on the suitable thickness of a PAC-precoated dynamic membrane coupled with a bioreactor for municipal wastewater treatment

The membrane bioreactor (MBR) is an important process widely used in wastewater treatment. However, membrane flux declines rapidly due to membrane fouling, which limits the application of MBR. In order to alleviate membrane fouling, a precoated dynamic membrane (PDM) was studied systematically. The membrane module consisted of of 56-μm terylene filter cloth as the support membrane and powder-activated carbon (PAC) as the precoating reagent. The precoated dynamic membrane bioreactor (PDMBR) was used in municipal wastewater treatment practice. Meanwhile, from the viewpoint of retention capacity, flux recovery and alleviating membrane fouling, the suitable thickness of the PAC dynamic membrane was also investigated. The experimental results showed that the formation of PDM from PAC on a support membrane belonged to the cake filtering model, and the relationship of PDM resistance (Ra) and its thickness (D) was in accord with log-function; the suitable thickness was controlled around 0.3 mm. It was found that while the flux of PDM was kept at a high value, the operating pressure of PDM rose to 42 kPa after 43 days of stable operation of the PDMBR, and the removal efficiency of effluent COD and NH4+-N were as good as traditional hollow membrane bioreactors. Furthermore, the flux of the fouled membrane could be totally recovered just after being cleaned by brushing, and it did not consume any chemical reagents. Moreover, it was also found that the PDM could prevent biomass contaminations diffusing from the surface inwards by scanning electron microscopy (SEM).