| Ecological treatment process has caught more attentions in wastewater treatment as it has significant merits of low cost and suitable for slightly polluted water purification. However, ecological restoration technology is still immature in slightly polluted river water treatment, and more detailed studies must be carried out. Firstly, based on the water characteristic of slightly polluted river water, two sets of four chamber integrated vertical-flow filter and a set of Subsurface Vertical Flow Constructed Wetland were applied to purify the water, respectively. Nitrogen and phosphorus removal rates of each treatment system were analyzed, then the process which was more suitable for slightly polluted river water treatment was determined by comparison, and its optimum operating conditions were also determined. Secondly, the denitrification effect of the treatment system supplemented by external carbon source with wood was analyzed, which will provide a certain theoretical basis for design and operation of pilot system purifying river water. Finally, a Baffled Cyclic System and a Strengthened Constructed Wetland System, both filled with coal cinder and cement bricks, used wood as external carbon source, were set up in the downstream of Old Majia River in Kunming for the polluted river water treatment. Treatment efficiencies of the two systems were investigated, the method was also explored to resolve the problem of shortage about carbon source. The results could provide theoretical foundation for practical application of the bypass ecological purification process.The main results are as follows:(1) Nitrogen and phosphorus removal rates of the two sets of the four chamber integrated vertical-flow filter decreased as the hydraulic loading rate increased from 10 cm/d to 20 cm/d. As the average influent concentrations of TN, TP and COD were 17.40 mg/L, 1.13 mg/L and 39.98 mg/L, respectively. The TN removal rates of Device(A) under different conditions were 36.34% and 28.53%, respectively. And the average effluent concentrations of TN were 6.15mg/L and 12.45 mg/L, respectively; while the average TP removal rates were respective 90.86% and 64.15% with the average effluent concentrations of 0.05 mg/L and 0.42 mg/L, respectively; and the average effluent concentration of COD was 38.88 mg/L. The TN removal rates of Device(B) under different conditions were 35.63% and 11.30% respectively, and the average effluent concentrations of TN were 10.95mg/L and 15.26 mg/L, respectively; while the average TP removal rates were 92.37% and 52.91% with the average effluent concentration of 0.08mg/L and 0.53 mg/L, respectively; and the average effluent concentration of COD was 42.27 mg/L.(2) In device A, nitrogen was mainly removed in the first and second chamber, and phosphorus was mainly removed in the third and fourth chamber. However, nitrogen was mainly removed in the third chamber, and phosphorus was mainly removed in the second and fourth chamber in device B. Conclude could be drawn that the first and second chamber of device A and the third chamber of device B were filled with zeolite which can adsorb ammonia nitrogen effectively; while the third and fourth chamber of device A and the second and fourth chamber of device B filled with cement bricks which was effective for phosphorus removal. Besides, it was necessary to change the filler medium in time as the TP removal rate gradually decreased as to ensure the efficient and stable operation the device.(3) In the first 38 days, the ammonia nitrogen and total nitrogen removal rates of Subsurface-Vertical Flow Constructed Wetland were better as hydraulic loading rate was 12 cm/d, with the average removal rate of 92.14% and 89.37%, whereas total phosphorus removal rate was only 27.00%. However, in the next 54 days, total phosphorus removal rate increased to 42.15%, and the nitrogen removal rate deteriorated, which may be caused by desorption of the zeolite.(4) The pilot test supplemented with wood as the external carbon source indicated that the wood released phosphorus with the concentration of 0.03 mg/g, total nitrogen with the concentration of 0.81 mg/g, in which the concentration of ammonia and nitrate nitrogen were 0.13 mg/g and 0.26 mg/g, and it released COD with the concentration of 27.80 mg/g.(5) Pilot study showed that in the course of running about systems that Baffle Cycle Flow Process and Constructed Wetland Process were filled wood, it would release a certain amount of nitrogen phosphorus, later this phenomenon no longer appear.(6) As the hydraulic loading rate of 20 cm/d. The average removal rates of TN in Baffle Cyclic Flow Process and Strengthen Artificial Constructed Wetland were 79.29% and 70.63% when the influent concentration of TN, TP, COD were 11.78mg/L, 0.39mg/L, 36.77 mg/L, respectively, In addition, ammonia nitrogen removal rate were 73.97% and 71.21% respectively, and total phosphorus removal rate were 82.80% and 81.16%, respectively. |
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