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.