Zone I in the reactor acted as a buffer zone in which the
inhibitory material in the wastewater could have been
degraded thus allowing the zone II to be loaded with a relatively
harmless and mostly acidified influent. So that, there
was much active populations of the relatively sensitive methanogenic
bacteria in zone II and explained why the higher ethane
yield was obtained in zone II. The acid-producing bacteria
would be reproduced quickly in the reaction zone I and the
activity of the ancient bacteria would be stronger in the
reaction zone II. The integrated two-phase anaerobic reactor
with the obvious phase separation feature could make acidproducing
bacteria and methanogen to be rationally distributed
during the anaerobic digestion processes. It was a benefit
to form a well distribution condition of the microbe to start up
the reactor. But it is unlikely that a complete separation of