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

Thesis (M.Sc.) - Asian Institute of Technology, 1976

Designing appropriate wastes treatment systems needs detail survey of local environmental conditions and in-plant conditions. An appropriate treatment systems recommended should take advantage of local environmental conditions. Treatability evaluation of the feasible methods is also necessary. At D.P.O. Dairy Plant, large land area, wind, sunlight are available. Furthermore the plant locates rather far from the stream. In summer time, large amount of water is needed for grassland irrigating purpose. Thus the three recommendable alternatives in treating and disposing the dairy waste at D.P.O. Dairy Plant are: Alternative C: Dairy wastes treatment by facultative stabilization pond. With loading of 28 gBOD/m2 /day (250 lb BOD/ acre/day). Alternative B: Dairy wastes treatment by series stabilization ponds, facultative pond follows by aerobic pond, with loading of 33.6 and 16.8 gBOD/m2/day (300 and 150 lb BOD/acre/day) respectively. Alternative E: Combination of dairy wastes treatment by oxidation ditch and disposal by irrigation areas. The recommended loading for oxidation ditch is 0.4 kgCOD/Kg MLSS/day with detention time of 1.5 days. The dosing of 19.l and 4.9 l/m2 /day (17,000 and 4,350 gal/acre/day) are recommended for irrigation areas by ridge-furrow method and spray method, respectively. The alternatives are arranged from the least operating cost to the highest operating cost and also ranging from the least efficient to the highest efficient treatment. Alternative E is recommended only if the cost of the soil excavation is very high.