Performance and biofilm-associated bacterial community dynamics of an upflow fixed-film microaerophilic-aerobic bioreactor system treating raw textile effluent

Textile wastewater contains numerous xenobiotic compounds which have several detrimental effects on aquatic and terrestrial ecosystems. Therefore, the adequate treatment of textile wastewater is essential. This study elucidated the biodegradation of raw textile effluent (RTE) in an upflow fixed-film microaerophilic bioreactor (UFMB) along with the characterization of its bacterial community dynamics at different hydraulic retention times (HRTs) and organic loading rates (OLRs). Among the various packing materials tested in the UFMB operation, wood charcoal was found to be the most suitable packing material for the establishment of biofilm and biodegradation of RTE. The steady-state performance of UFMB having wood charcoal as packing material achieved 81.97% of American dye manufacturers institute (ADMI) colour index removal, 73.08% of biochemical oxygen demand (BOD) removal and 80.47% of chemical oxygen demand (COD) removal at 2d HRT. Whereas, upon integration of the UFMB with the sequential aerobic bioreactor (UFMB-AB system), achieved better performances with 98.6% COD, 98% ADMI and 92% BOD removal from the RTE. Additionally, the combined UFMB-AB system effectively removed other contaminants such as sulphate, phenolics and nitrogenous compounds in the RTE. The biofilm was synergistically established by the bacterial community DR4 and the native community of RTE. In response to different HRTs and OLRs, the UFMB bacterial biofilm community experienced various shifts in its composition. However, a core microbiome persisted throughout the bioreactor operation. The imputed metagenome analysis of the established UFMB biofilm using phylogenetic investigation of communities by unobserved state reconstruction (PICRUSt), revealed the presence of several xenobiotic degradation and metabolism pathways with an abundance of various different oxidoreductase genes responsible for the biodegradation of dyes and other organic pollutants present in the RTE. •Integrated UFMB-AB system showed >98% ADMI and COD removal from the RTE.•Dynamics of the biofilm bacterial communities were observed at different HRT.•A core bacterial community persisted throughout the UFMB operation.•Sulfurospirillum and Macellibacteroides genera were abundant in the UFMB biofilms.•The genus Pseudomonas dominated the sequential aerobic bioreactor system.