Abstract: When municipal solid waste (MSW) with high content of food waste is
landfilled, the rapid hydrolysis of food waste results in the imbalance of
anaerobic metabolism in the landfill layer, indicated by accumulation of
volatile fatty acids (VFA) and decrease of pH value. This occurrence could lead
to long lag time before the initiation of methanogenesis and to the production
of strong leachate. Simulated landfill columns with forced aeration, with
natural ventilation, and with no aeration, were monitored regarding their
organics degradation rate with leachate recirculation. Hydrolysis reactions
produced strong leachate in the column with no aeration. With forced aeration,
the produced VFA could be effectively degraded, leading to the reduction in COD
of the leachate effluent since the week 3. The CH_4 in the
landfill gas from the column with aeration rate of 0.39
m^3/(m^3· d) and frequency of
twice/d, leachate recirculation rate of 12.2 mm/d and frequency of twice/d,
could amount to 40% (v/v) after only 20 weeks. This amount had increased up to
50% afterward even with no aeration. Most of COD in the recirculated leachate
was removed. Using natural ventilation, CH_4 could also be
produced and the COD of the leachate effluent be reduced after 10 weeks of
operation. However, the persistent existence of oxygen in the landfill layer
yielded instability in methanogenesis process.
