Robust biochar-assisted alleviation of membrane fouling in MBRs by indirect mechanism

Biochar is a low-cost by-product of biomass pyrolysis to obtain renewable energy, and is composed of carbon skeleton, oxygen-containing functional groups, and minerals. Herein a new environmental application of biochar is detailed, namely, alleviating membrane fouling in a membrane bioreactor (MBR) process by dosing the bioreactor with quantities of various modified biochars (alkali washed (AW-BC), hydrophobic (HB-BC), hydrophilic (HL-BC), and activated biochars (AC-BC)). Results of trans-membrane pressure (TMP) tests showed that with the exception of HB-BC, all the other modified biochars exhibited robust antifouling capability and the TMP was decreased by as much as 36.8% and 31.4% at 24 h and 10 d respectively for AW-BC (most easily prepared) compared to a control. This was comparable to the results obtained in the use of expensive activated carbon (AC). Instead of dealing with the large surface area and scouring effects of AC, it was found that the indirect effects of biochar on sludge may be the basis for the antifouling mechanism, where the hydrophilicity of the biochar improved the settling of sludge. In addition, it was speculated that the abundant functional groups of the biochar increased the adsorption of Extracellular polymeric substance (EPS) based on the characterizations of N2-adsorption-desorption, fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM). Compared to traditional antifouling materials, the results of this study may offer a low-cost alternate for alleviating membrane fouling in MBRs.