Chiang Mai Journal of Science

     The large volume of wastewater produced by food factories in western Thailand has increasingly impacted the ecosystem. This study aimed to isolate lipid-degrading bacteria from household and industrial wastewater in Nakhon Pathom Province, Thailand, and to treat oil-contaminated wastewater from a vitamin E manufacturing plant under aerobic conditions. Out of 120 isolates, two strains (1W51 and 1W52) were selected for their strong ability to degrade lipids, as demonstrated on tributyrin media. 16S rRNA sequencing identified strains 1W51 and 1W52 as closely related to Bacillus nitratireducens and Bacillus paranthracis, respectively. Both strains produced hydrolytic enzymes including amylase, protease, and lipase on selective media. They also demonstrated beta-hemolysis, positive drop collapse results, and clear halo zones in oil displacement tests. The emulsification index (E24) of both strains exceeded 50%. After treatment with these strains, the chemical parameters in wastewater showed notable improvement: total suspended solids (TSS) and chemical oxygen demand (COD) decreased by 50% and 75%, respectively, while dissolved oxygen (DO) and biological oxygen demand (BOD) increased by 67% and 73%, respectively. The addition of B. nitratireducens 1W51 and B. paranthracis 1W52 significantly improved wastewater quality, indicating their potential for use in environmentally friendly biological wastewater treatment.