A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Eng.) - Asian Institute of Technology, 1974

The complexities of the disposal of petroleum refinery and petrochemical wastewaters behave for considerable study and evaluation of problems peculiar to each operation. Analyses of the three existing petroleum refineries in Thailand were conducted, Extensive study of one of these refineries was then performed. Daily grab and composited wastewater samples were collected and analyzed for physical, chemical and biological characteristics. Diurnal and daily flow fluctuations were recorded. Existing wastewater generation, collection and treatment systems were studied and wastewater segregation, reuse and effective treatment processes suggested. Chemical coagulation-precipitation was experimented with alum and ferric chloride with and without coagulant-aids, in the presence and absence of intermediate tray in the sedimentation tank for both petroleum refinery and synthetic petrochemical wastes. This resulted in 30-35 percent total COD (chemical oxygen demand) reduction and 90-95 percent insoluble COD reduction. Oil reduction was from 85 -90 percent. Activated sludge units both batch and continuous-fed were operated for both types of wastes. COD reduction of 40-45 percent; phenols reduction of 80-85 percent; sulphides reduction of 75-80 percent and phosphates reduction of 75-80 percent were achieved. Batch activated sludge units were run with pure and mixed culture, without any appreciable difference in the pollutants removal. Aeration lagoon was used to finish the wastewaters from the activated sludge units. Final effluent was having COD from 4045 mg/l; phenols 0.3-0.5 mg/l; sulphides 0.2-0.9 mg/l and phosphates 0.6-1.4 mg/l. This water was found to be non-toxic to fish based on the results of bioassay analyses.