Bioremediation of vegetable oil and grease from polluted wastewater in dairy factory

Vegetable oil and grease polluted wastewater caused many problems in wastewater plan such as physical blockages in sewer, pump, screens and filter distributor arms. Its occurrence in effluent increase COD significantly even its amount is not high. In this paper, bioremediation was investigated to remove vegetable oil and grease. Four strains were positive with lipid degrading test. Cell morphology and optimal conditions such as pH, temperature anf lipid concentration was found. The lipid-degrading activity of A12, B13 and D15 was highest at 30 o C and pH 7 while that of D14 is at 34 o C and pH 7.5 . The result also showed that the highest lipase production of strains A12, B13 and D14 were observed at 0.1 %w/v of lipid, but for strain E15 concentration of lipid was 0.15 %w/v. Addition of antifoam and surfactant was studied. The optimal concentration of antifoam (CF-18) and surfactant (PVA) was found as 0.4%w/v and 0.2 %w/v respectively. 10% w/v of straw in the best ration of support particle, at which the cell density of bioremediatior was 2x10 8 cfu/g. The best temperature for storage was 5-7 o C, even so at the conditioned temperature (20-25 o C) the bioremediation was good until 20 weeks. At optimal moisture 10% and under low temperature (5-6 o C) the bioremediator was still as good as its initial after 20 weeks. Application of bioremediator in 25 m 3 /day wastewater treatment plan indicated that COD removal yield increased s6-7% compared with normal case (no bioremediation).