The population of
these microorganisms increased in the biofilm when the influent
ethanol concentration was increased. However, the
effect on the chemical characteristics of the outlet water was
small. This bacterial group use 8042- as a terminal electron
aceeptor to generate H2S. The concentration of this anion,
which may be present in high or low concentrations in
groundwater, can increase substantially in the total absence
of oxygen and nitrate, elements from which bacteria obtain
more energy (28). Under these circumstances, proliferation
of this physiological group, which increases the H2S concentration
in the treated water, will affect the organoleptic
characteristics of the treated water.