Eutrophication Prediction And Control Technologies Of The Source Water Reservoir

The Chanzhi Reservoir is located in the upper reach of the Dagu River , which is a typical water-type reservoir and the biggest reservoir of Qingdao. But the nitrogen and phosphorus in the reservoir have exceeded the environmental quality standards for surface water under the influences of agriculture cultivation and domestic sewage. With the rapid development of agriculture and industry and urban growth, the contradiction between water demand and supply is aggravating. Therefore, it is urgent to study the eutrophication prediction and control technologies of the Chanzhi Reservoir of Qingdao.Based on the natural environment investigation in the area of the Chanzhi Reservoir, spatial and temporal distribution of water quality in the Chanzhi Reservoir is analyzed. According to the existing water quality monitoring datas, a modified fuzzy comprehensive evaluation model is established to evaluate the eutrophication status of the Chanzhi Reservoir. According to unique environmental background of the Chanzhi Reservoir, the features of sediment pollution are studied. The equations of nitrogen and phosphorus flux and release time are established under circumstances of different temperatures and disturbances by indoor column test. In addition, a plane 2D water flow-water quality model with sediment release is developed to simulate the water quality distribution of the Chanzhi Reservoir in different hydrological years with the joint effects of different pollution sources. At last, the optimized condition and removal effect of the two-stage vertical-flow land system for input rivers water treatment, the effectiveness of using PSAFS to control phosphorus release from sediment and the feasibility of ecological operation to control nitrogen and phosphorus pollution in sediment are deeply studied by the lab test. The main conclusions of this paper are as follows:(1) The fuzzy comprehensive evaluation model is modified and employed to evaluate the eutrophication status of the Chanzhi Reservoir.Modified fuzzy comprehensive evaluation model is employed to evaluate the eutrophication status of the Chanzhi Reservoir. The evaluation results show that the reservoir is in eutrophication level and the input rivers are in heavy eutrophication level.(2) The equations of nitrogen and phosphorus flux and release time are established.The release regularity of nitrogen and phosphorus is studied and the equations of nitrogen and phosphorus flux and release time were established under circumstances of different temperatures and disturbances by indoor column test.. static release can be expressed by logarithmic equation: y = a+bln( x), the dynamic release can be expressed by power exponential equation: y = axb.(3) A plane 2D water flow-quality model with internal release is established.The internal release factors are coupled in the plane 2D water flow-quality model, and the plane 2D water flow-water quality model with internal release is established through determining of initial conditions, boundary conditions and parameters and the validation of model. The water quality distribution of the Chanzhi Reservoir is predicted in different hydrological years with the joint effects of different pollution sources. And the predicting results show that, the moderate nutrition accounts for 7.4%, moderate eutrophication accounts for 16.7%, and eutrophication accounts for 75.9%.(4) The two-stage vertical-flow land system which is suitable for input rivers treatment is proposed.The biological filter media, hydraulic retention time and hydraulic loading are optimized by indoor test. The optimized conditions of the system are as follows: the filler is bio-ceramic, HRT is144h, hydraulic loading is 0.139m/d. The removal rates of TN, TP, CODMn andChl a under the optimized condition are 60.2%, 69.3%, 56.8% and 70.6% respectively.(5) PSAFS is used to restrain phosphorus release of the sediment at the first time.The results show that the restraining result is significant as the cumulative release concentration of TP in blank test is more than twice compared to the test which is added PSAFS, and the volatility of the cumulative release concentration of TP in blank test exceeds the sample which is added PSAFS.(6) The new technology of ecological operation to control nitrogen and phosphorus pollution in sediment is proposed. The results show that when the water temperature is 25℃, the treatment effect of nitrogen and phosphorus pollution in sediment is better with shorter water- changing period and larger water-transferring proportion.