Texture and type of polymer fiber carrier determine bacterial colonization and biofilm properties in wastewater treatment

•Biofilm properties were studied in a cascade system treating municipal wastewater.•Carrier type and wastewater matrix both affected biofilm structure and activity.•In the first 2–3weeks, bacterial taxonomic diversity of biofilm reached its maximum.•Proteobacteria, Synergistetes, Bacteroidetes and Firmicutes dominated the biofilm. Effect of carrier texture and type on biofilm development and maturation were studied on an eight-reactors-containing pilot-scale cascade system which treated municipal wastewater under aerobic conditions and various system operational characteristics. Dissimilarities in the biofilm structures grown on four types of polymer fiber-based carriers placed in the reactors having different role during wastewater purification and compositional changes of bacterial communities during biofilm maturation were clearly observable. In the first 2–3weeks, taxonomic diversity of biofilm bacterial communities increased and reached their maximum values. Carrier type and texture had comparable effect on the weight, activity and composition of biofilms as the wastewater matrix. Biofilm community grown on the carrier having the best colonization properties were dominated by Proteobacteria, Synergistetes, Bacteroidetes and Firmicutes. In the nascent 7-days-old biofilm, aerobic chemoorganotrophic genera, while in the mature 45-days-old biofilm anaerobes, such as sulfate-reducer and fermentative genera were the major members of the bacterial communities.