Low flux sponge membrane bioreactor treating tannery wastewater

Abstract

Sponge membrane bioreactor (Sponge-MBR) has been proposed as an effective process to eliminate organic matters, nitrogen compounds and control fouling for domestic and hospital wastewater treatment. However, tannery wastewater with extremely organics and salt concentrations poses a great threat to the stability of biological treatment processes, rapidly increasing fouling and cost of physio-chemical treatment. This study examined the performance of Sponge-MBR to treat real tannery wastewater under organic loading rates of 1.38 ± 0.59 and 2.05 ± 0.61 kg COD m−3 d−1. The results showed that tannery wastewater vastly inhibited the growth of suspended biomass (MLVSS/MLSS ratio of 0.3). However, such ratio has been increased up to 24% in the attached biomass of sponge carriers. Up to 87 ± 14% of organic matters and 43 ± 10% of total nitrogen (TN) were eliminated even though the system suffered a high total dissolved solids (TDS) of 12,510 mg L−1. Using nitrogen balance analysis, the simultaneous nitrification-denitrification process occurred inside the sponges resulting in 21% TN removal via denitrification. Thanks to the dynamic movement of sponge carriers, the cake layer (i.e., solids and colloids) contributed only 28% of total resistance. This outcome resulted in decreasing 1.2-fold fouling rate as using sponge media in the MBR. Overall findings suggest that a low flux operation combined with sponge media (20%) in the MBR appears to be a viable option for real tannery wastewater treatment.