Affiliations: Department of Environment and Resource, Zhejiang
University,Hangzhou 310029, China. E-mail: shends@mail.hz.zj.cn
Abstract: Population development of key groups of anaerobic and aerobic
bacteria involved in municipal refuse decomposition under laboratory landfill
bioreactors with and without leachate recycle adinoculation was measured since
modeling municipal refuse was landfilled in bioreactors for about 210 days.
Hydrolytic fermentative bacteria (HFB), hydrogen-producing acetogenic bacteria
(HPAB), methane-producing bacteria (MPB), sulfate-reducing bacteria (SRB),
anaerobic and aerobic cellulolytic bacteria and denitrabacteria were enumerated
by the most probable number technique. The results showed that the dominant
microorganismgroups were the methanogenic bacteria including hydrolytic
fermentative, hydrogen-producing acetogenic and methane-producing bacteria.
They were present in fresh refuse but at low values and positively affected by
leachate recycle and refuse inoculation. The amounts of HFB or HPAB in
digesters D4 and D5 operated with noculation and leachate recycle reached their
maximum values of10^10-10^12 cells/g dry refuse for HFB or 10^5-10^6 cells/g
dry refuse for HPAB on day 60, in digester D3 operated with leachate recycle on
day 120 for HFB (10^9 cells/g dry refuse) or on day 90 for HPAB (10^5 cells/g
dry refuse), and in digesters D1 and D2 on day 210 for HFB (10^9 cells/g dry
refuse) or on day 90 for HPAB (10^4-10^6 cells/g dry refuse). The population of
methane-producing bacteria in digesters D4 and D5 sharply increased on days 60
and 90 respectively, however in digesters D1, D2 and D3 on day 120. Leachate
recycle and inoculation changed the cellulolytic microorganisms composition of
refuse ecosystem, the higher amounts of anaerobic cellulolytic bacteria were
measured in digesters D4 and D5 (10^7 cells/g dry refuse), followed by
digesters D3 (10^6 cells/g dry refuse), D2 or D1(10^4 cells/g dry refuse).
However, the amounts of aerobic cellulolytic bacteria were much lower than that
of anaerobic cellulolytic bacteria. And it was higher in digester D3 than those
in digesters D1, D2, D4 and D5. The amounts of SRB and denitrabacteria were
also higher in digester D5 than those in digesters D1, D2, D3 and D4. Refuse
decomposition could be accelerated by leachate recycle and inoculation in the
view of microorganism development.
Keywords: municipal refuse, landfill bioreactor, leachate recycle, inoculation, anaerobic bacteria
