| In the Bohai Rim, there are 35 prefecture level cities and 356 county-level administrative regions under the jurisdiction of the three provinces and two municipalities. Since the end of 1970’s, along with the rapid development of social economy, the concentration of COD and especially DIN in Bohai Sea showed a trend of continuous increase. Monitoring shows that, the DIN concentration in Bohai Sea has exceeded the water quality criteria seriously. The area which exceeds the national water quality standard level Ⅱ accounts for about 30%, while the polluted area along the coastline was uneven distributed.Since the 2000’s, China has explored a series of Bohai Sea comprehensive environmental remediation measures. According to the "across-the-board" pollutant reduction policies, governments of three provinces and two cities in Bohai Rim launched land-based COD and ammonia-nitrogen (NH3-N) total loads control programs in 2006 and 2011 respectively. According to the "China coastal environment quality bulletin", only the COD exceeding standard area has been decreased. But the DIN and COD concentration is still increasing, especially in the estuary area. It is indicated that the reduction plan does not achieve the expected effect, which is mainly due to the "across-the-board" pollutant reduction policies are seriously deviated from the uneven distribution characteristics of water quality along the seacoast. At present, the high speed of economic growth and urbanization causing increasing pollution sewage pressure. Under this condition, if it still uses the "across-the-board" pollutant reduction policies, it is difficult to form the most effective mechanism in the seriously polluted area. And also, it is possible to hinder the social and economic development of some administrative regions which do not exceed the water quality standard. Therefore, there is an urgent need for the conversion of pollutant reduction policies from "across-the-board" into the differential reduction plans.At present, whether the total loads control programs in USA (TMDL), Japan (TPLCS), European (WFD), and the United Nations Environment Programme (UNEP) (GPA), they are all focusing on the region especially the administrative area’s differential reduction plans of land-based pollutants, to establish and perfect the numerical test relationship between the administrative region discharge pressure and response of water quality. But at present, there is no calculation method of water quality-based allocated capacity index system of land-based pollutants for the administrative districts.In the sewage chain of land-based pollutants from the river basin of pollution source, public sewerage processing system to the sewage estuary and the offshore, due to the difference in the transport path, land types, and the distance from the sea, there are significant difference influences of pollutants load from different administrative districts on water quality. Therefore, in order to make the differential reduction plans matching with the best improvement of offshore water quality, on the one hand, the source regions of land-based sewage should take responsibility for the emission reduction targets. It needs to take into account the sewage overload condition of county level regions and above level administrative regions rather than only the outlets. On the other hand, in order to realize the administrative regions’ pollutant reduction targets, it needs the scientific definition of the production pollution control standards from the source. Aiming at the point source, it also needs to design the reducing capacity reasonably. It may also need a scientific planning on environmental remediation goals. In this way, administrative region’s land-based pollutants allocated capacity index system should include production pollution allocated capacity and engineering reduction allocated capacity, when necessary, it should also include the transport reduction allocated capacity.Therefore, the purpose of this study is to focus on the environmental goals in "Water Pollution Control Action Plan (ten water items)". The "across-the-board" pollutant reduction policies are seriously deviated from the uneven distribution characteristics of water quality along the seacoast. Through the establishment the calculation method of the land-based pollutants allocated capacity index system, and then taking the TN and COD pollutant allocated capacity index system of 356 county-level administrative regions as quantitative scientific basis, the differential reduction plans of the 35 prefecture level cities are established. Therefore, the research content of this paper mainly contains three aspects:(1) Establishment of calculation method for the water quality-based allocated capacity index system of source unit; (2) Calculation of TN and COD allocated capacity index system of 356 county-level administrative regions in Bohai Rim. (3) Optimization design of the differential reduction plans for 35 cities in Bohai Rim.Using a combination of laboratory experiments, marine water quality model, optimal allocation, theoretical analysis and other methods, the main results are obtained as follows:(1) Water quality-based method for Land-based pollutants allocated capacity calculation. On the basis of optimized water quality simulation mathematical programming method, pollutant transport process and quantity relation were analyzed, and allocated capacity calculation method for source unit was built. The results of the new method include production pollution allocated capacity and engineering reduction allocated capacity, when necessary, it also include the transport reduction allocated capacity.(2) The calculation of TN and COD water quality-based allocated capacity index system for 356 county-level administrative regions in Bohai Rim. In the application of the method mentioned above, the accuracy and reliability of calculation are affected by the matching relationship between the county administrative region and the source unit boundary, optimization and simulation accuracy, quality controlling standard setting, the upper and lower limit value of the constraint conditions, and the mathematical programming method of operation. ① The matching degree between the 356 county-level administrative regions and source units is controlled through dividing the source region into suitable scale. ②For the COD and DIN optimized simulation calculation:according to laboratory degradation experiment of typical pollutant sources pollutant, COD and DON first order degradation kinetic equation is modified; according to the difference between the degradation rate constant of COD and DON, the state variables are divided into 4 and 3 from 1; With these results of laboratory degradation experiment, the standard deviation of simulation calculation results decreased by 30%. ③For the method of mathematical program model, due to too much calculation units, the traditional simplex method computation time is too long, which is difficult to converge. So it adopts interior point method which has higher computational efficiency. ④ After testing by water quality model, the relative standard deviation of allocated capacity is about 37%. According to the theory of the relationship between the water quality over-criteria rate and the over-load rate of land-based pollutants, the result of allocated capacity is reasonable.(3) Distribution characteristics of the TN and COD pollutant allocated capacity index system in the 356 county-level administrative regions of Bohai Rim. The calculation results show that there are great differences in the allocated capacity of production pollution, engineering reduction and discharge pollution. There are three grade of allocated capacity:high, middle, and low. For TN and COD, the area proportion of the three grade of production pollution allocated capacity is 22%and 29%、51% and 53%、27% and 18%; the area proportion of engineering reduction allocated capacity 8% and 18%、36% and 42%、56% and 40%; the area proportion of discharge pollution allocated capacity 22% and 27%、49% and 47%、39% and 26%. The distribution characteristic of discharge pollution allocated capacity is similar with production pollution allocated capacity. While it is different between discharge pollution allocated capacity and engineering reduction allocated capacity.(4) Optimization design of the differential reduction plans for 35 cities in Bohai Rim. Currently, it only announced the pollution source census data at the prefecture level administrative region. Therefore, only differential reduction plans for prefecture level administrative region could be built. In order to make the pollutant reduction plan match with the improvement of water quality which has been over-criteria seriously, the over-load condition should including production pollution, engineering reduction and discharge pollution. The 35 prefecture level cities analysis showed that: ① For discharge pollution condition, the number of TN and COD over load cities are 26 and 19, respectively; Flat-load cities are 8 and 14; less-load cities are 1 and 2. For over-loaded Cities, they are mainly distributed in the area of Liaohe River watershed like Panjin, Anshan, Yingkou, and the area of Haihe River watershed like Beijing, Tianjin, Cangzhou. It should increase the pollutant reduction targets about 75%(TN) and 74%(COD). For less-load cities, they are mainly distributed in Chengde city and Huludao City, the pollutant reduction targets should be decreased by an average of about 75%(TN) and 66%(COD). ② For production pollution condition, the number of TN and COD over-load cities are 23 and 19, which over-load rate is 272% and 367%, respectively; Flat-load cities are 8 and 13; less-load cities are 4 and 3, which less-load rate is 77% and 62%. ③ For engineering reduction pollution, the number of TN and COD in short cities are 16 and 9, respectively; Flat-load city is 10 for both TN and COD. With comparison of production pollution over-load condition and engineering reduction shortage conditions, it showed that, in 23 TN and 19 COD pollution overload cities, there are 13 and 9 citis’ engineering reduction are short, but there are 10 enough for engineering reduction. It is indicated that, for the former, it is probably the main point source pollution. The pollutant reduction can be realized by expansion or new public sewage treatment system technical measures. However, for the latter, it is probably the main non-point source pollution. It should adopt non-point source pollutant reduction measures like reducing fertilizer, livestock and poultry breeding intensive.The main innovation of this thesis is to establish the calculation method of land-based pollutants allocated capacity index system for source unit. Especially on the basis of water quality simulation mathematical programming method, through establishing quantitative relationship among the land-based production pollution, engineering reduction pollution, discharge pollution and water quality response of Bohai Sea, the optimization calculation of land-based pollutants allocated capacity of source units is realized, which includes discharge pollution allocated capacity, engineering reduction pollution allocated capacity, and discharge pollution allocated capacity. The distinctive point of this thesis is establishment of the differential reduction plans of the 35 prefecture level cities. It can adjust the target according to the over-load condition to increase or decrease prefecture level cities’pollutant reduction targets. And also, according to the over-load condition, it can improve the public sewerage system, to make polluant reduction in Bohai Rim effect matching with the water quality improvement. Compared with the "across-the-board" pollutant reduction policies, it is more targeted in the reduction technical measures. |
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