Abundance and composition of indigenous bacterial communities in a multi-step biofiltration-based drinking water treatment plant Karin Lautenschlager a,b , Chiachi Hwang c , Fangqiong Ling c , Wen-Tso Liu c , Nico Boon d , Oliver K € oster e , Thomas Egli a,b , Frederik Hammes a,* a Eawag, Swiss Federal Institute for Aquatic Science and Technology, U ¨ berlandstr. 133, CH-8600 Du ¨ bendorf, Switzerland b ETH Zu ¨rich, Institute of Biogeochemistry and Pollutant Dynamics, CH-8092 Zu ¨ rich, Switzerland c Department of Civil and Environmental Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA d Ghent University, Faculty of Bioscience Engineering, Laboratory of Microbial Ecology and Technology (LabMET), Gent, Belgium e Zu ¨ rich Water Supply (WVZ), Hardhof 9, P.O. Box 1179, CH-8021 Zu ¨ rich, Switzerland article info Article history: Received 24 February 2014 Received in revised form 5 May 2014 Accepted 19 May 2014 Available online xxx Keywords: Adenosine tri-phosphate (ATP) Biofilter Drinking water Microbial communities 454 pyrosequencing abstract Indigenous bacterial communities are essential for biofiltration processes in drinking water treatment systems. In this study, we examined the microbial community composition and abundance of three different biofilter types (rapid sand, granular activated carbon, and slow sand filters) and their respective effluents in a full-scale, multi-step treatment plant (Zu ¨ rich, CH). Detailed analysis of organic carbon degradation underpinned biodegradation as the primary function of the biofilter biomass. The biomass was present in concentra- tions ranging between 2e5  10 15 cells/m 3 in all filters but was phylogenetically, enzy- matically and metabolically diverse. Based on 16S rRNA gene-based 454 pyrosequencing analysis for microbial community composition, similar microbial taxa (predominantly Proteobacteria, Planctomycetes, Acidobacteria, Bacteriodetes, Nitrospira and Chloroflexi) were present in all biofilters and in their respective effluents, but the ratio of microbial taxa was different in each filter type. This change was also reflected in the cluster analysis, which revealed a change of 50e60% in microbial community composition between the different filter types. Abbreviations: AOC, assimilable organic carbon; ATP, adenosine tri-phosphate; BDOC, biodegradable organic carbon; DGGE, dena- turing gradient gel electrophoresis; EBCT, empty bed contact time; FCM, flow cytometry; GAC, granular activated carbon; HPC, het- erotrophic plate count; L-DOPA, L-3,4-dihydroxyphenylalanine; MUB, methylumbelliferone; PPO, polyphenol oxidase; PO, peroxidase; RSF, rapid sand filter; SSF, slow sand filter; TCC, total cell concentration; TOC, total organic carbon; UPGMA, unweighted pair group method with arithmetic mean. * Corresponding author. Tel.: þ41 44 823 5350; fax: þ41 44 823 5547. E-mail address: Frederik.Hammes@eawag.ch (F. Hammes). URL: http://www.eawag.ch Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/watres water research 62 (2014) 40 e52 http://dx.doi.org/10.1016/j.watres.2014.05.035 0043-1354/© 2014 Elsevier Ltd. All rights reserved.