基于EFDC模型对入海排污选址方案的研究

发布时间：2018-08-29 14:22

【摘要】：入海排污是沿海地区污水处理厂尾水处置的主要途径,但不合理的排污口布设也会对海洋环境和敏感功能区造成不利影响。因此,如何科学合理地选取排污口位置是污水处理厂工程设计中的一项重要内容。大连长兴岛经济区计划新建的西部污水处理厂设计处理能力为8万t/d,处理后的污水将执行《城镇污水处理厂污染物排放标准》一级A标准,初步设计方案在近岸四类海洋功能区中拟选了离岸距离不同的三处排污口位置。本文选用近年来广泛应用于水动力和水质模拟的"环境流体动力学模型(EFDC)"商业化软件,分别预测各排污口尾水排放对受纳海域和功能区的水质影响,并综合相关指标构建排污口选址适宜性评价体系,以达到对排污口位置方案优选的目的。首先应用EFDC模型对长兴岛附近海域的水动力条件进行数值模拟,计算结果与监测站点的潮流和潮位实测数据吻合较好。然后针对三处入海排污口的设计位置,应用EFDC模型模拟计算了两个全潮周期的代表性污染物的最大浓度包络范围。得到在正常工况时,三处排污口的各污染物超四类水质标准值包络面积分别为 COD:0.04、0、0.03km~2,无机氮(DIN):1.57、0.76、0.47km~2,活性磷酸盐(AP):0.15、0.09、0.08km~2;在事故状态下污水直接排放时各污染物浓度超标的包络面积分别为 COD:2.49、3.78、2.30km~2,DIN:9.73、7.32、9.50km~2,AP:12.2、5.91、7.09km~2,且涨潮时会造成部分一类功能区内不同污染物浓度的超标,因此应避免在涨潮期直排。为综合比较不同排污口位置的环境影响和经济成本,基于海域受污染程度和工程建设费用相关指标,构建了排污口选址适宜性的综合评价体系。权重确定采用了比层次分析法更为简便实用的有序二元对比法,在对各指标进行重要性定性排序的基础上,通过依次两两对比,根据模糊比较结果获得权重。对三处候选排放口的综合分析结果表明,选择离岸距离适中且距一类功能区较远的一处作为排污口,在环境影响和成本费用方面具有相对最佳的综合适宜性。本文提出的研究方法和体系对于入海排污口的选址优化问题具有较好的推广应用价值。
[Abstract]:Sewerage into the sea is the main way to dispose the tail water of sewage treatment plants in coastal areas, but the unreasonable layout of sewage outlets will also have adverse effects on the marine environment and sensitive functional areas. Therefore, how to select the location of sewage outlet scientifically and reasonably is an important content in the design of sewage treatment plant. The designed treatment capacity of the western sewage treatment plant planned for construction in Dalian Changxing Island Economic Zone is 80,000 t / d. The treated sewage will comply with the "Municipal sewage treatment Plant Pollutant discharge Standard" Class A Standard. In the four coastal marine function zones, the preliminary design scheme selected three locations of sewage outlets with different distance from shore. In this paper, the commercial software "Environmental fluid Dynamics Model (EFDC)", which has been widely used in hydrodynamic and water quality simulation in recent years, is used to predict the effect of tail water discharge from each sewage outlet on the water quality of the receiving sea area and the functional area. The evaluation system of location suitability of sewage outlet is constructed by synthesizing relevant indexes to achieve the purpose of optimal selection of the location scheme of sewage outlet. Firstly, the EFDC model is used to simulate the hydrodynamic conditions in the sea area near Changxing Island. The calculated results are in good agreement with the measured data of tidal current and tidal level at the monitoring station. Then the EFDC model is used to simulate and calculate the maximum concentration envelope range of the representative pollutants in two full tidal periods according to the design location of the three sewerage outlets. At normal working conditions, The envelope area of the standard values of the four kinds of pollutants in the three sewerage outlets is COD:0.04,0,0.03km~2, inorganic nitrogen (DIN): 1. 57 7 0. 76% 0.47 km2, and the active phosphate (AP): 0. 15 0. 09 0. 08 km2. The envelope area of each pollutant concentration exceeding the standard when the sewage is discharged directly under the accident condition is COD:2.49,3.78,2.30km~2,DIN:9.73,7.32,9.50km~2,AP:12.2,5.91,7.09km~2, and rises respectively. The tide will cause the concentration of different pollutants in some functional areas to exceed the standard. Therefore, direct discharge should be avoided during the high tide period. In order to comprehensively compare the environmental impact and economic cost of different location of sewage outlet, a comprehensive evaluation system of site selection suitability of sewage outlet was established based on the indexes of pollution degree and construction cost. The weight is determined by using the ordered binary contrast method which is more convenient and practical than the analytic hierarchy process. On the basis of the qualitative ranking of the importance of each index, the weight is obtained according to the fuzzy comparison result by two and two comparisons in turn. The results of comprehensive analysis of three candidate discharge outlets show that the relatively optimal comprehensive suitability in terms of environmental impact and cost can be obtained by selecting a place with a moderate offshore distance and far from a class of functional areas as a sewage discharge outlet. The research method and system proposed in this paper have a good value in popularizing and applying to the location optimization of sewerage outlet.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

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