Kee Kean Chin

Energy yields from anaerobic digestion of palm oil mill effluent

Abstract Three different suspended-growth anaerobic digestion configurations—the mesophilic one-stage, the mesophilic two-phase and the thermophilic one-stage, were used to treat palm oil mill effluent (POME) and their performances compared. The mesophilic two-phase process showed the highest energy yields which reached 20 542 J g−1 COD utilized at a hydraulic retention time of 31 days. However, high energy yields did not coincide with high TCOD removals. The latter was a characteristic of the thermophilic process. The relatively poor TCOD removal in the two-phase system was due to its lower efficiency in VSS removal. At hydraulic retention times of 25 days and more the mesophilic one-stage process had higher energy yields than the thermophilic process. Anaerobic digestion was found to be an effective means for POME treatment.

Treatment of piggery wastewater by expanded-bed anaerobic filters

Abstract Anaerobic fermentation of pig-farm wastewaters was studied on a laboratory scale with continuous, expanded-bed filters. Bed media investigated were graded sand and activated carbon. The 4 litre effective volume reactors were successfully operated over eight different hydraulic retention times. These were 6, 5, 4, 3, 2, 1 days and 18 and 14 h. The diluted wastewater was effectively treated by the two filters with COD and VSS removals ranging from 27 to 90% and 15 to 93% respectively. The activated-carbon filter was marginally better in performance.