ORIGINAL PAPER 2,4,6-trichlorophenol (TCP) photobiodegradation and its effect on community structure Yongming Zhang • Xuejing Pu • Miaomiao Fang • Jun Zhu • Lujun Chen • Bruce E. Rittmann Received: 2 August 2011 / Accepted: 2 January 2012 / Published online: 20 January 2012 Ó Springer Science+Business Media B.V. 2012 Abstract The mechanisms occurring in a photolytic circulating-bed biofilm reactor (PCBBR) treating 2,4,6-trichlorophenol (TCP) were investigated using batch experiments following three protocols: photo- degradation alone (P), biodegradation alone (B), and intimately coupled photodegradation and biodegrada- tion (P&B). Initially, the ceramic particles used as biofilm carriers rapidly adsorbed TCP, particularly in the B experiments. During the first 10 min, the TCP removal rate for P&B was equal to the sum of the rates for P and B, and P&B continued to have the greatest TCP removal, with the TCP concentration approach- ing zero only in the P&B experiments. When phenol, an easily biodegradable compound, was added along with TCP in order to promote TCP mineralization by means of secondary utilization, P&B was superior to P and B in terms of mineralization of TCP, giving 95% removal of chemical oxygen demand (COD). The microbial communities, examined by clone libraries, changed dramatically during the P&B experiments. Whereas Burkholderia xenovorans, a known degrader of chlorinated aromatics, was the dominant strain in the TCP-acclimated inoculum, it was replaced in the P&B biofilm by strains noted for biofilm formation and biodegrading non-chlorinated aromatics. Keywords Biodegradation Á Biofilm Á Photolysis Á Community structure Á Trichlorophenol Introduction Trichlorophenol (TCP), one of most recalcitrant chlorinated phenols organics, is a main raw material for production of a wood-preservative agent, fungi- cides, defoliants, and herbicides (Chu and Law 2003; Tan et al. 2009; Jesu ´s et al. 2009). TCP also is produced in the processes of pulp and paper bleaching and drinking water chlorination (Ali and Sreekrishnan 2001; Keith and Telliard 1979). Even more alarming is that TCP has been detected in soil, surface water, and even groundwater (Boyd S et al. 1989; Ramamoorthy 1997; Chang et al. 1999; Gardin et al. 2001) due to its widespread use in the production of a variety of biocides and as a biocide itself (Ha ¨ggblom 1992). Because TCP is listed as one of the toxic pollutants most needing control (Xia and Zhang 1990; USEPA 1991), treatment of the polluted wastewater and ground water containing TCP has been a focus of Y. Zhang (&) Á X. Pu Á M. Fang Á J. Zhu Department of Environmental Engineering, College of Life and Environmental Science, Shanghai Normal University, 200234 Shanghai, People’s Republic of China e-mail: zhym@shnu.edu.cn L. Chen School of Environment, Tsinghua University, 100084 Beijing, People’s Republic of China B. E. Rittmann Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, Tempe, AZ 85287-5701, USA 123 Biodegradation (2012) 23:575–583 DOI 10.1007/s10532-012-9534-0