Influence of biofilm thickness and microbial community of the MABR in its performance removing organic micropollutants

Presence of organic micro pollutants in natural water bodies is an increasing concern due to their detrimental impact to ecosystems and human health. In this study, membrane aerated biofilm reactor (MABR) is evaluated for its ability to remove OMPs by correlating its removal efficiency with the MABR biofilm thickness and microbial community diversity. MABR demonstrated high efficiency in the removal of ammonium and COD even at early stages of biofilm development (thickness 0.21 mm) and in the presence of ammonia oxidizing bacteria (Nitrosomonas 1.1%), nitrite oxidizing bacteria (Nitrospira 0.3%) and heterotrophs with nitrogen-species removal abilities (i.e. Zoogloea- 4.4%, Acinetobacter- 7.7%, Rhizobium- 5.8%, Protochlamydia- 0.7%, Methylorenera- 2.4%, and Azospirillum- 1.9%). With the increase of biofilm thickness through time, relative abundance of bacterial groups shifted. Bacteria supporting nitrogen removal increased (Runella- 2.3%, Paludibaculum- 1.7%, Leucobacter- 1.4%), enhancing OMPs removal and ammonium removal with complete conversion into N2 gas. Removal of OMPs by MABR were divided in 3 groups according to the removal flux obtained through the MABR: Group 1 > 1mg OMP/m2d; Group 2: 0.15 > J > 1mg OMP/m2d; and Group 3 < 0.15mg OMP/m2d. Specifically, over 90% removal efficiency was obtained for OMPs of group 1 including: acetaminophen, bisphenol A, estrone, ethinyl estradiol and ibuprofen at biofilm thickness of 1.94 mm. MABR demonstrated potential to treat water contaminated with OMPs, COD and ammonium with an optimal biofilm thickness and microbial community based on Zoogloea- 6.1%, Runella- (1%), Paludibaculum (1.2%), Leucobacter (0.9%), Aquabacterium (1.9%), Protochlamydia (4.4%) and Hirschia (0.8%).