The experiment was investigated the ability of the natural sedimentation to reduce amount of organic compound in household wastewater including removal mechanisms of organic compound in household wastewater by sedimentation. Sedimentation used in this experiment were collected from klongpremprachakon in 2 locate are as follows; in front of Watsamiannari and in front of train station Bangkhen. The experimental sediment bring it from area actual and sediment has autoclaved for analysis organic compound included BOD value COD value and organic matter by variation of time testing 3 5 12 and 24 hour respectively. The research result found that the experimental 24 hour Amount of organic compound in terms of BOD COD concentration and organic matter retained in household wastewater quite low. The natural sediment redound to adsorption and biodegradation by microorganism was reduce amount organic compound included BOD value COD value and organic matter better than inactivated sedimentation by autoclave.

The objectives of this research were to study the reduction of organic compounds by the biological action substance of the effluents from palm oil mil to produce singe cell protein. The wastewater taken from the third pond of the wastewater treatment system which was already used for biogas production was found to have pH 6.5. The organic matter like COD (3679 mg/L) Oil& grease (133 mg/L) as well as the total solids and the minerals were much lower than those of the decanter effluent. The reduction of organic compounds by using the biological action by Candida tropicalis TISTR 5146 5045 and C. lipolytica TISTR 5151 were studied. The results indicated that C. tropicalis TISTR 5146 which was cultivated in palm oil mill at initial pH 5.5 and diluted with water to the ratios of 1:5 at agitation on the shaker of 150 rpm at room temperature gave the highest yield of biomass of 2.52 g/L and COD reduction of 94.38 % after 3 days of cultivation. The optimal condition for C. tropicalis TISTR 5146 cultivation was that the ratio of palm oil mill effluent to diluted water was 1:5 containing 10 g/l glucose and 10 g/l yeast extract at initial medium pH 5.5 in the shaking flask of 150 rpm at room temperature. The highest biomass obtained was 12.53 g/L while the cell consisted of protein and fat for 43.12 % and 0.34 % respectively.