A bed weight of
3.2 kg of the seed sludge was used and the methane fermentation
was initiated by adding 80 g of TCM or the mixture of TCM and
RCM at the ratio of 1:1. The biogas recycling to the bottom of the
reactor was performed from the start of culture. When acetate concentration fell below 3 mmol kg1 new substrate was added. The
fermentation temperature was maintained at 55 ± 2 C and the
stirring velocity was 10 rpm. The gas volume and gas content were
measured every day. Samples were drawn periodically to analyze
for pH, ammonia, TKN and VFAs. Sulfuric acid samples were also
collected to analyze the trapped ammonia.