Removing trace-level organic pollutants in a biological filter

Laboratory-scale biofilm reactors simulating a full-scale nitrification filter were challenged with xenobiotic contaminants frequently encountered in water supplies. Phenol and mono- and dichlorophenols were removed immediately (by up to 92 percent), with increasing influent concentration reducing the percentage removal. Trichlorophenols were not biodegraded. Mono- and dichlorobenzenes were also removed (up to 81 percent), but an enzyme-induction period of 8-20 h was required biodegradation became significant. In many cases, feeding of an easily degraded organic substrate (acetate) increased removals of the xenobiotics by a relatively small amount. This result suggests that unidentified background organic material and soluble microbial products generated by nitrifying bacteria allow the accumulation of bacteria able to degrade a range of xenobiotic compounds.