in case of the 2nd experimental run the temperature conditions were the same as the first run. The temperature range was mesophilic (35–37 ◦ C). The pH in the reactor was measured during these experiments and it was observed that it varied from 7.6 to 8 so there was no requirement for pH adjustment as, reported in a previous study [ 1 ]. In the 2nd experimental run the slaughterhouse waste sample employed had a COD level of 100,972 mg / l, the sludge sample had the same COD level of 42,024 mg / l as in the 1st run. Waste sample was sufficiently diluted in order to remove the discrepancy observed in the 1st run. The first reading, i.e. on 5th day, indicated a decrease of 67% in the COD level. The following readings indicated further de- crease in COD levels to 73% and 80%. These results indicate that by increasing the amount of the inoculum the efficiency of the system in COD removal may be increased. The reduction in COD levels during experimental runs is shown in Fig. 2