RESULTS AND DISCUSSION
Initial loading phase Over the first 50 days of operation, the organic loading rate was gradually increased to 2 g VS/1/day,where it was maintained until day 60. The objective
of this low loading rate was to develop a suitable biomass of flocculent organisms in the reactor before higher loading rates were tried (Fischer et al., 1981). The success of the low loading in achieving its objective was indicated by the appearance of floc in all chambers of the reactors. During this start-up phase of operation, days 1-60, gas production
increased from 0.8 to 5.2 l/day in the three-chamber ABR. Similar increases in gas production were observed in all the other reactors.