Abstract
A hybrid membrane bioreactor (HMBR) employing activated sludge and biofilm simultaneously is proved to represent a good performance on membrane fouling control compared to conventional membrane bioreactor (CMBR) by reducing extracellular polymeric substances (EPS), especially bound EPS (B-EPS). In order to better understand the mechanism of membrane fouling control by the HMBR in regard of microbial community composition, a pilot scale HMBR operated to treat domestic wastewater for six months, and a CMBR operated at the same time as control group. Results showed that HMBR can effectively control membrane fouling. When transmembrane pressure reached 0.1 MPa, the membrane module in the HMBR operated for about 26.7% longer than that in the CMBR. In the HMBR, the quantity of EPS was significantly lower than that in the CMBR. In this paper, soluble EPS was also found to have a close relationship with cake layer resistance. The species richness and diversity in the HMBR were higher than those in the CMBR, and a certain difference between the compositions of microbial communities in the two reactors was confirmed. Therefore, the difference in microbial community compositions may be the direct reason why EPS in the HMBR was lower than that in the CMBR.
Highlights
In recent years, submerged membrane bioreactors (MBRs) have been more frequently used for wastewater treatment and reclamation
Due to the introduction of biofilm and low DO of about 1.0 mg/L, hybrid membrane bioreactor (HMBR) represents better performance on organic and nutrients removals compared to conventional membrane bioreactor (CMBR) (Table 2)
Particular attention has been paid on the mechanism of membrane fouling control by HMBR in regard of microbial community composition
Summary
In recent years, submerged membrane bioreactors (MBRs) have been more frequently used for wastewater treatment and reclamation. They possess many advantages over conventional activated sludge treatment processes including biostability, high effluent quality, small footprint, and low sludge production rate [1,2,3,4,5]. Membrane fouling is still the major obstacle preventing the universal application of MBR. Organic foulants generated from biological process have been the main focus for previous studies, and extracellular polymeric substances (EPS). Extracellular polymeric substances are a complex high molecular-weight mixture of polymers excreted by microorganisms. There are soluble cellular components as the dissolution products of the B-EPS, which are generally called soluble EPS (S-EPS) or soluble microbial products (SMP) [13]
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