Ecological Restoration Effect Assessment And Improvement Methods For The Urban River

At present,the treatment of urban river mainly is by the methods of sewage interception along the river bank,collection and replenishment of sewage water,etc.and improves the water quality and environment of the river to a certain extent.However,due to the significant difference in the flow during the dry season in the rainy season,the limited interception capacity and the overflow of the culvert in the rainfall,the water quality of the river is unstable and the ecological restoration effect of the urban river is affected.In this paper,the urban river supplemented with wastewater treatment plant effluent was the research object,and the ecological restoration effect assessment index system was constructed and applied to an example of an urban river in Southern China.Ecological restoration effect assessment was carried out under the conditions of dry season and rainy season respectively,and the main factor of the result i s studied.Aimed at improving water quality,a hydrodynamic water quality model was constructed.And based on different scenarios,the ecological restoration measures based on water quality,water amount and water supply were studied to provide technical s upport for ecological restoration effect assessment and ecological restoration of similar river.Construct the index system of the ecological restoration effect of the urban river supplemented with wastewater treatment plant effluent.Through the combination of frequency analysis and theoretical analysis,the key ecological factors of the urban river were identified,and the weight of each index was determined by the combination weighting method of analytic hierarchy process and entropy weight method.According to the existing standards norms and data normalization method,the evaluation criteria was established,and the comprehensive evaluation criteria are divided into 1 to 5 levels.Evaluation results are as follows: better,good,fair,slightly worse,worse.Taking an urban river in the south as the research object,the physical and chemical characteristics and aquatic biota of the water body were monitored and analyzed in the dry season and the rainy season respectively.The assessment results show that the ecological restoration effect in the upper and middle reaches of the river is a little worse,the ecological restoration effect in the lower reaches is poor,and the ecological restoration effect in the rainy season is better than in the dry season.The main factors affecting the ecological restoration of dry season were nitrogen and phosphorus,while the main factors affecting the ecological restoration effect in rainy season were COD,DO,TP and current speed.A hydrodynamic water quality model for an urban river in southern China is established.The fitting degree is good,and the calculation error is basically in the 20% range,so it is available.Based on the study of the evaluation results and the hydrodynamic water quality model,water qu ality improvement measures based on water quality,water quantity and water supplement method is simulated and the results show that with the improvement of discharge standard of tail water in sewage plant to standard A in Beijing(DB11/890-2012),improvement is most effective,and the COD and NH4+-N improvement is better,improvement is poor for the effect of TN and TP,three kinds of water quality improvement measures can not make the concentration of TN reach the grade V of surface water.Water quality improvement measures based on water quality,quantity and the type of water supply make the ecological restoration effect of the upstream from the "general" into "good" and that of the downstream from the "general" into "good" nearly.However,the effect of water quality improvement on ecological restoration is limited,and comprehensive measures must be taken from many aspects.