| It's cold in winter of northeast in our country and sometimes the lowest temperature of sewage can reach to 4～7℃. It's disadvantage for biological treatment of sewage. At present, we have taken some measures to make low- temperature sewage conform to the discharging standards, but the measures increased project investments. Moreover, the processing effect of sewage could't conform to the discharging standards.We adopted cold-adapted microorganisms and sued biological aerated filter to treat the low-temperature sewage. The experiment investigated many problems such as start-up of biological aerated filter by cold-adapted microorganisms, the treatment efficiency for pollutants and some effect factors. At last, the study found the best controlling parameters and the dynamics model. The experiment also made the comparision between cold-adapted microorganisms and natural microorganisms, and investigated biofilm pattern and characteristics of microorganism population in BAF.The experiment demonstrated that it took about 18 days to complete the start-up under the condition of about 13℃with the cold-adapted microorganisms as seed. When the removal efficiency of CODcr and NH4+-N respectively reached to about 77% and 31%, and the removal efficiency of NH4+- N growing with Linear, the start-up of BAF have been completed. The concentration of pollutants in effluent completely excelled the requirement of discharging standards, under the condition that the influent temperature varied between 9～13℃, the hydraulic load was 1.6 m3/(m2·h), the proportion of aerated intensity and sewage intensity was 5:1. The experiment demonstrated that it was suitable that the hydraulic load was about 1.6 m3/(m2·h), the organic load was at the scope of 3.71～15kgCODcr/(m3·d)and the NH4+-N load varied between 0.61～0.70 kgNH4+-N/(m3·d).And we found the dynamics model equation of BAF that treated domestic sewage by using cold-adapted microorganisms, which expressed ln. The removal rules of pollutants varied following the water flow direction in BAF, under different hydraulic load conditions. The removal efficiency of CODcr and NH4+-N have positive correlation with the height of filter, for hydraulic load being 2.4 m3/(m2·h).When hydraulic load was 1.6 m3/(m2·h), the removal efficiency of CODcr only have positive correlation with the height of lower section in filter and the great mass of CODcr were removed at this section. However, the removal efficiency of NH4+-N have no correlation with the height of filter. Under all hydraulic load operated during the experiment, removal efficiency of SS have no correlation with the height of filter, and up to 70%～80% of SS was captured in the first 900mm. BAF adopted air-water backwash, the backwashing parameters had been decided during the experiment.The experiment demonstrated that the concentration of pollutants in effluent was similar in the two filters. The experiment studied biofilm pattern and the characteristics of microorganism population in BAF. The thickness of biofilm in BAF is thiner, the surface of biofilm is smoother, the extension and fluctuation of biofilm becomes smaller and the colour of biofilm changes shallower following the water flow direction, when the reactor was at the state of stable operating. There were many kinds of microorganism in BAF, such as bacterium, fungi, protozoan, metazoan, and oligochaetes. And the characteristics of microorganism population changed gradually along reactor height.With the example of 10000m3/d sewage treatment project, the results of the economic analysis showed that the total investments and the operating cost of BAF was excelled the biological oxidation.
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