Analysis Of Water Environment Characteristics In Southeast Cities In China And Research On A Guiding Program For Comprehensive Remediation

In recent years,with the acceleration of urbanization,many environmental problems have appeared.The pollution of surface water is serious,and the water quality of most urban water bodies are inferior to class Ⅳ.The emissions of regional pollutant are huge.In 2017,the total amount of national wastewater discharge was 77.74 billion tons,of which industrial wastewater discharge was 18.29 billion tons,urban domestic sewage discharge was 58.81 billion tons,and domestic sewage became the main source of pollution.Non-point source pollution has become a major water environment problem in some cities,caused by changes in land use types.Although many water diversion projects were implemented,there is still a gap to meet the requirements of water body function standards,and ecological livable cities.Therefore,a guiding plan and technical roadmap is urgently needed to formulate for the comprehensive improvement of the urban water environment,so as to provide technical support for the overall regulation of urban water pollution and the improvement of the water environment.This study monitored and evaluated the water quality of major rivers and lakes in the southeastern region of China.The evaluation results show that the water quality in the southeastern region accounts for a large proportion of class Ⅳ as well as being inferior to class Ⅳ,and the overall water quality in the southeast region is poor.The spatial and temporal characteristics of the water pollution in rivers and lakes in the southeast region were analyzed separately.The results show that the water quality of rivers is gradually being improved in recent years;the water quality in the flood period is obviously better than other periods;and the water quality in summer is significantly better than winter.From a spatial perspective,the water quality deteriorated after running through the urban area;the water quality in the upstream of urban rivers is better than that in the downstream;and the water quality of tributaries has a great impact on urban rivers.According to the estimation and analysis of typical urban pollution sources,the major pollutants were total nitrogen and ammonia nitrogen.,which were brought by domestic sewage,and rainfall runoff pollution,the contaminants from upstream.Based on the analysis of the characteristics of water environment and the causes of pollution,a guidance plan for comprehensive improvement of the water environment in the southeastern region was proposed.Including the determination of the preparation target,the calculation of water environment capacity,the calculation of pollution load distribution and the guidance plan.Among them,the one-dimensional model of river water environmental capacity in the southeastern region is mostly used;when calculating the water environment capacity of lakes,the zero-dimensional model is mostly used for COD and ammonia nitrogen,and the allowable load model of nutrients is mostly used for TN and TP;the proportional distribution method is recommended for pollution load distribution;Detailed program method,case and technologies are introducted respectively from point source four aspects including pollution control,non-point source pollution control water body water quality improvement and promotion control,and water saving.Finally according to the time axis and staged objectives of the comprehensive improvement of urban water environment,a road map for the comprehensive improvement of the urban water environment in the southeast region has been established by strategic tasks,the priorities of technical development at each stage and aspects from which each stage to start work.