High Loaded Bioflocculation Membrane Reactor of Novel Structure for Organic Matter Recovery from Sewage: Effect of Temperature on Bioflocculation and Membrane Fouling

The effect of temperature on the efficiency of high loaded bioflocculation membrane reactor (HLB-MR) flocculation and concentration of organic matter in municipal wastewater was analyzed using parallel comparative experiments. The study investigated organic matter recovery efficiency, bioflocculation effect, and membrane fouling status of the reactor at 8 °C and 15 °C. It was observed that at a low temperature of 8 °C, the organic matter recovery efficiency of HLB-MR was 80%, which was equivalent to that at 15 °C. However, the bioflocculation efficiency at 8 °C was only 65%, which was significantly lower than that of 85% achieved at 15 °C. The poor flocculation effect was related to the low yield of the extracellular polymer under low-temperature conditions and the low content of cations (sodium, calcium, and aluminum) in the sludge matrix. At the low temperature of 8 °C, the membrane fouling of the HLB-MR was more serious than that at 15 °C. Poor bioflocculation effect led to an increase in the number of fine particles (≤1 μm) in the reactor, which might be the main reason for the aggravation of membrane fouling. To overcome the adverse effects of low temperature on membrane fouling, it is recommended to adopt engineering measures, such as an appropriate increase in the solid retention time, increase in the aeration intensity, using powdered activated carbon, or enhancing the intensity of backwashing.