To improve the capacity of present drinking water purification process on the removal of soluble pollutants and solve the problem of large area requirement and single function existing in the application of horizontal sedimentation tank, a novel biological settling tank was developed based on the designing concepts of rotating biological disk and sedimentation tank. Experimental results showed that the usage of rotating biological disk did not have notable effects on the turbidity removal capacity of the horizontal sedimentation tank. When the organic loading rate was 0.46 g·(m2·d)-1, the removal rates of organic pollutants, NH4+-N, TN, and TP were determined to be 81.4%, 95.0%, 21.1% and 86.0%, respectively. Further study showed that denitrification and dephosphorization processes competed for the limited carbon source existing in the water phase. With the increase of organic loading rate in the raw water, the removal rate of TP was improved. Meanwhile, the concentrations of organic matters and NH4+-N in the settled water were not affected, which indicated that the biological settling tank showed a capacity in resisting organic loading rate shock and could be used in the enhanced pollutant removal in treating micro-polluted water.
Keywords: denitrification; micro-polluted water; nitrification; organic loading rate; rotating biological disk; settling tank.