During the first seven days,all bioreactors displayed poor performance under a high influent COD concentration of 1262 mg/L,resulting in the low removal efficiencies.During this stage,most quality parameters of the treated effluent from all bioreactors did not comply with the standard limits set by Malaysian legislation regarding industrial wastewater treatment (table 5).During the following several days,the removal efficiencies increased gradually but were still found to fluctuate,as the system was not fully acclimatised.The data listed in table 4 and 5 include all data recorded after NH3-N removal achieve some stability on day 49.Meanwhile,the colour parameter was recorded only after the system was completely acclimatised starting on days 152,as depicted in Fig.6 .The discussion in this section relates to the data collected after the start-up period,comprising data from days 49-300.