Abstract: At a low temperature (≤9 ℃), comparison experiments of 12 original strains of degrading organic pollutants were made in the laboratory. Three strains which can degrade BHC effectively were screened out, moreover, the optimal degradation conditions of the three strains were got though the orthog onal experiments. Furthermore, under the same degradation conditions (pH=65, 0.8 g/L NH ₄Cl, 0.6 g/L KH₂PO₄), degradation experiments were carried out by mixing the three strains, which were domesticated, in C²₃ and C³₃ ways, and the result shows that the C³₃ mixed strains had higher degradation rate of BHC than each of the three strains and the C²₃ mixed strains. The highest degradation rate was got when the incubation amounts of 1st stain, 2nd stain an d 3rd were at the ratio of 1 ∶5 ∶3, which was 63.27%.

Key words: biodegradation in low temperature, hexachlorocyclohexane, mixed microorganisms