The anaerobic biofilter (AF) is a k

The anaerobic biofilter (AF) is a kind of anaerobic reactor
filled with fillers, with most of the microorganisms in the form
of a biofilm growing on the surface of the fillers. In principle,
vulnerable bacteria for the degradation of toxic pollutants in
CGWcan be efficiently retained in AF by growing on the surface
of the fillers (Wang et al., 2013). Moreover, the mixed liquor
suspended solids (MLSS) of AF can reach as high as 30 g VSS/L
(Wang et al., 2014; Xu et al., 2015). High biomass and long SRT
(Sludge Retention Time) could greatly alleviate the inhibiting
effects of toxic pollutants in CGW. Finally, the spatial distribution
of microorganisms in an AF is conducive to reducing the
effects of toxic pollutants on vulnerable bacteria. That is,
bacteria for toxic pollutant degradation could be accumulated
at the inlet end of the AF under the selection pressure of
high-concentration toxic pollutants, while vulnerable bacteria,
such asmethanogens, could be enriched at the outlet end of the
AF, where there is a low concentration of toxic pollutants and
abundant volatile fatty acids. For example, Chen et al. (1994)
obtained COD removal rate of 90% in treating pharmaceutical
wastewater by AF. Yang et al. (2012) used a new AF reactor to
treat terephthalic acidwastewater, obtaining effluent with COD
of less than 60 mg/L. Therefore, AF should have great potential
in treating CGW, although there are few reports of its use.