Deep Purification of Contaminated River Water with High-rate Algal and Aquatic Combined Pond

The effect of deep purification of a river in Shenyang with high-rate algal and aquatic combined pond was investigated by analyzing COD_Cr, NH₄⁺-N, TP and DO, etc.. The results showed that when the concentrations of DO, COD_Cr, NH₄⁺-N, TN and TP in contaminated river water were 0.89-1.65 mg/L, 70-100 mg/L, 1.6-2.9 mg/L, 2.3-4.5 mg/L and 0.6-1.2 mg/L, respectively under HRT of 4 d and water depth of 0.5 m, by using the combined ponds, the average concentrations of DO increased to 5.88 mg/L, and the average concentrations of COD_Cr, NH₄⁺-N, PO₄^3--P, TN and TP in the treated river water decreased to 35.40 mg/L, 0.66 mg/L, 0.17 mg/L, 1.51 mg/L and 0.16 mg/L, respectively, which reached the Grade V standard of Environmental Quality Standard for Surface Water. On the other hand, the aquatic pond had high efficiency to remove algae from the outlet of algal pond and the average removal rate was 94.5%. The descending order of the purification of COD_Cr, NH₄⁺-N and PO₄^3--P was first-order high-rate algal pond, second-order high-rate algal pond, and aquatic pond; furthermore, the high-rate algal pond played a major role.