Suitable redox potential is a basic condition for methane production in
normal activity. Microorganisms can grow under a relatively wide facultative
condition in an AD reactor. In our experiments, the redox potential
of acidifiers gradually decreases with acidification HRT Fig. 2(b). The
reason may be that oxygen content decreases with vegetable waste
decomposition, with the low point at −395 mv on day 9. NH4
+-N level
in the acidifier also gradually decreases from 1498 mg·L−1 to
387 mg·L−1
. The cause may be the continuous conversion of NH4
+-N,
nitrate or N2 by nitrobacteria and denitrifying bacteria. In studying
bio-denitrification, Mulder et al. have found anaerobic ammonium
oxidate, and anammox. When the microbes are under anaerobic
conditions, they use NH4
+ as electron donor and NO3 or NO2 as electron
acceptor, and then transfer ammonium nitrogen and nitrate nitrogen to
N2.