Nitrogen removal in a moving bed membrane bioreactor for municipal sewage treatment: Community differentiation in attached biofilm and suspended biomass

Moving bed membrane bioreactors (MBMBR) are advanced biological wastewater treatments combining suspended biomass (SB) and attached biofilms (AB). To evaluate the specific contribution of each biomass fraction to N removal, the abundances of gene markers of nitrifying and denitrifying bacteria were measured by quantitative PCR in a pilot-scale MBMBR treating municipal sewage. Eight experimental phases were conducted, combining different carrier filling ratios (20% or 35%, v/v), hydraulic retention times (10 h or 24 h) and mixed liquor total suspended solids (ca. 2500 mg/L or ca. 4500 mg/L). Under all the operating conditions tested, the abundance of the targeted bacterial groups was fairly similar in both SB and AB fractions, and the biofilm contributed >20% of the nitrifiers in the MBMBR. Mixed liquor volatile suspended solids, biofilm total solids, COD, temperature and carrier filling ratio significantly explained the changes of abundance of N-cycle bacteria, according to multivariate statistical analysis. In conclusion, the SB and AB fractions appeared to have equally relevant roles in the N removal process in a MBMBR. (C) 2015 Elsevier B.V. All rights reserved.