Abstract: The application of water oligotrophic bacteria to the removal of low-concentration dissolved pollutants from slightly polluted water is a new research direction in the field of water supply treatment. The bacteria isolated from the eutrophic medium were inoculated on the oligotrophic medium with different dilution ratios, so as to screen out the facultative oligotrophic microorganisms. The results showed that Bacillus pumilus and Bacillus cereus were the two highly effective bacteria isolated from the water and sediment of the Second River in Huai’an, and the TOC in the low-concentration water could be removed more than 60% 7 days after dosing the stains. Both strains could use a variety of carbon and nitrogen sources to grow, and the concentration of 3% hydrogen peroxide and 10% ethanol could kill strains, Therefore, both of them could be safely and effectively used in the field of water treatment.

Key words: oligotrophic bacteria, slightly polluted water, nutritional properties, gradient nutrient dilution method