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Water pollution is a globally significant issue. Water environment simulation is an important tool to study water pollution. In order to investigate the impact of hydrological periods, water quality indicators and cross-sections on the water environment capacity, we took the Luo River in Luoyang City as an example, and used MIKE21-coupled hydrodynamic and water quality model and the segmentation method to calculate the water environment capacity of COD, TP, and NH3-N in wet, normal, and dry periods under L1 (Gao Yazhai-Lilou), L2 (Li Lou-Baimasi), and L3 (Baimasi-G207 Highway Bridge) section. The results of the study showed that from the hydrological period, the water environmental capacity was the largest in the wet period due to the dilution effect caused by higher precipitation; from the water quality indexes, the COD concentration was the largest due to industrial pollution, but the higher degradation coefficients result in the largest water environment capacity for COD; from the cross-section, L1 has the longest channel, thus the highest capacity of the water environment was L1. This result can broaden ideas for the application of the MIKE21 model, provide a basis for the calculation of the dynamic water environment capacity and water pollution control in the river. HIGHLIGHTS Innovative hydrodynamic water quality model evaluates Luo River pollution across diverse flow scenarios.; Dry periods exhibit poorest water quality, while wet periods showcase the best.; Identified sections exceeding capacity emphasize pollution management during distinct hydrological conditions.;

In this paper, a coupling model of SWAT (Soil and Water Assessment Tool) and EFDC (Environmental Fluid Dynamics Code) was established, and the relationship between the pollution source and water quality response was identified. Based on the hydrodynamic water quality simulation results and the one-dimensional WEC (water environmental capacity) theoretical formula, the total nitrogen and total phosphorus WEC and the remaining WEC of the Yongzhou Section of Xiangjiang River Basin under the guaranteed rate of 90% and in 2017 were calculated, respectively. It can be seen from the results that the total nitrogen WEC of the Yongzhou Section of Xiangjiang River Basin in 2017 is 27,673.04 t, the total nitrogen WEC under the guaranteed rate of 90% is 19,497.61 t/a and the total phosphorus WEC of the Yongzhou Section of Xiangjiang River Basin in 2017 is 4,877.22 t. The total phosphorus WEC under the guaranteed rate of 90% is 2,936.64 t/a; in 2017, the remaining WECs of total nitrogen and total phosphorus in the entire basin are 14,646.69 and 3,358.67 t, respectively. HIGHLIGHTS A calculation method of water environment capacity was studied, which can provide a reference for the calculation of water environment capacity in large and medium-sized basins; The coupling model of SWAT and EFDC fix the lack of watershed sites and measured data, and inaccurate calculation of water environment capacity.; The coupling model identifies the relationship between pollution sources and water quality response.;

Economic development and large amounts of industrial production have led to environmental deterioration. The assessment and prediction of water environment capacity (WEC) are crucial supports for water quality target management. Therefore, this study aims to improve WEC via changes in the industrial structure and to analyze the economic changes. For this purpose, the economic efficiency (EE), water use efficiency (WUE), and water treatment efficiency (WTE) are estimated by the EE–SBM (slack-based measure)–DEA (data envelopment analysis) model. Based on the proposed model, the industry is divided into three types: green enterprises, yellow enterprises, and red enterprises. Yellow enterprises and red enterprises are the major supervision subjects, and the spatial distribution of different environmental risks is identified. The WECs of the main canals are analyzed based on dynamic changes in the industrial structure by integrating the 0-D and MIKE11 models. The results showed that after adjusting the industrial structure, the maximum added values of the WEC of chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH3–N), and total phosphorus (TP) are 1,744.66 t/a, 536.14 t/a, 24.81 t/a, and 4.16 t/a, respectively. The results show that the canals (R40, R41, R20, R19, and R17) are overloaded with pollutants and indicate that TN is included as a water environment quality assessment target. Furthermore, after the optimization of the industrial structure, the loss of industrial output value is 174.44 million yuan, and the added value of the environmental economy is 232.12 million yuan. The findings provide important technical support for achieving industrial upgrading and sustainable development.

There are many reservoirs in China, and the reservoir serves as an important source of drinking water. With the increasing pollution discharge upstream of the reservoir, the water quality of the reservoir is seriously threatened. Therefore, it is necessary to control the total amount of pollution and reduce the pollutants under the target water quality. In this paper, the upstream basin of the Yanghe Reservoir in Qinhuangdao City, Hebei Province was used as the study area, and the 0-D water quality model was used to estimate the water environment capacity of the study area under the Class II water quality target. And compared with the current pollutants, proposed reduction targets and measures. The results indicated that the water environmental capacity of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and ammonia–nitrogen (NH3-N) in the study area were 3226.9t, 264.6t, 71,200.6t, and 5575.7 t, respectively. The COD and NH3-N water environmental capacity cannot be fully utilized. The TN and TP exceeded the standard seriously, exceeding 1.47 times and 1.13 times of the TN and TP water environmental capacity under the water quality target of Class II, respectively. TN and TP need to be reduced by 57% and 53% for satisfying quality requirements, respectively. Through the analysis of pollutant sources, practical and feasible pollutant emission reduction measures are discussed. [ABSTRACT FROM AUTHOR]

Factors like intensive industrial and socio-economic development can lead to the deterioration of the water environment. At the same time, economic, social, and population sustainability rely on good water conditions in the river. Therefore, it is important to calculate the water environment capacity and allocate it accordingly. Our research selects the economic, social, and environmental factors to construct a water environment capacity allocation model using the analytic network process. Allocation results are as follows: there are Liaozhong County, Tiexi District, and Liaoyang County, where the water environment capacity allocation value exceeds 10 000 t/a at 18 336.25, 12 743.19, and 10 585.53 t/a, respectively. Dashiqiao City's water environmental capacity allocation is the least, at only 78.30 t/a. In the paper, the goal to allocate water environment capacity from the three major rivers to the administrative area is achieved in Liaoning Province, thus making the allocation result more comprehensive and fairer. It provides a scientific basis for controlling the water environment in Liaoning Province. [ABSTRACT FROM AUTHOR]

Protecting coastal area marine environments from pollution is critical to ensure sustainable development. However, the hydrodynamic and water environmental characteristics of many coastal waters are poorly understood. Furthermore, the levels of pollutants loading into coastal waters are rarely quantified. In this study, a hydrodynamic and pollutant transport model (based on MIKE 21 modules) was established in Qinhuangdao coastal waters, China. The simulated hydrodynamics and water quality parameters were highly congruent with measured values, exhibiting error levels below 20%. In Qinhuangdao coastal waters, the seawater flows primarily from southwest to northeast along the coast, with velocities in the range 0–0.4 m/s and 0–0.3 m/s during flood and ebb tides, respectively. Results from this study indicated that these waters were characterized by a weak tidal current, with mean velocities varying in the range 0–0.5 m/s. The chemical oxygen demand (COD) concentration of the coastal waters was in the range 0.1–3.7 mg/L, and the COD pollutants were diffused approximately 3–10 km off the coastline. The water environment carrying capacity (WECC) at each point source was also calculated based on the response coefficients; further, WECC in Qinhuangdao coastal waters was calculated at 544.01 t/a and 1088.02 t/a under two Chinese water quality levels (levels I and II), respectively. The results provided specific valuable information for controlling pollutants from rivers into coastal waters and managing the Qinhuangdao coastal waters environment. [ABSTRACT FROM AUTHOR]

The Shuangqiao river in Anhui Province is one of the main rivers entering to Chaohu Lake. The water quality of the Shuangqiao river has long been inferior to Grade V, which directly threatens the safety of drinking water for residents. The water environment capacity of Shuangqiao river basin was calculated using one-dimensional water quality model based on the current characteristics. The study showed that the environmental capacity of COD,NH3-N and TP of the basin were -755. 7 t/a,38. 42 t/a,and -3. 438 t/a, respectively. According to the Waste Load Allocations (TMDL) principle,the total load distribution of the various pollution sources within the basin was completed,and the point source and non-point source pollution load reduction plans was formulated based on the contribution rate of the pollution Ioad,respectively,which built a foundation for the full implementation of the water qualityobjective management system in Shuangqiao river basin,and provided reference and technical support for the water quality simulation of small watersheds with similar basic data. [ABSTRACT FROM AUTHOR]

Water flow and contaminant transport were simulatedby using MIKE11 based on the measured river discharge and concentration of CODMn and ammonia in the Shaying River basin of Anhui Province. The water environmental capacity of the Shaving River basin in this region was estimated by using the linear programming method with respect to the category III of the water quality target of Huaihe River. The results show that the water environmental capacities of CODMn and ammonia are 23 900 t/a and 7 600 t/a respectively. The water environmental capacities of CODMn and ammonia fluctuate dramatically with the changes of the discharge and water quality of the upstream. The maximum water environmental capacities of CODMn and ammonia appear in August, showing 3 558 t and 1 363 t respectively, while the minimum ones appear in March, showing 621.8 t and 180.6 t respectively. The water quality of the upstream has a significant influence to the environmental capacity of the downstream of the river in Anhui Province. [ABSTRACT FROM AUTHOR]

To protect aquatic environment and human health, determining the optimal sewage discharge standard for wastewater treatment plants (WWTPs) is important to reduce pollutant discharge into natural ecosystems. In this study, a novel quantitative assessment method combining water environment capacity (WEC) estimation and feasibility analysis was introduced for the selection of WWTP sewage discharge standard. A certain WWTP executing national Grade 1-B discharge standard in China’s southern coast was selected as a case study. First of all, pollution sources of receiving water were investigated. More than 69.0% of nutrients (nitrogen, phosphorus) came from WWTP effluent, while non-point pollution contributed 58.3% of organic pollutants. Next, the WEC of receiving water was estimated via multiple mathematical models. It was speculated that the WEC of TP may be completely depleted by 2020 if still executing national Grade 1-B discharge standard. The maximum acceptable pollutant concentration of WWTP effluent are determined with chemical oxygen demand (COD) 86.05 mg/L, total nitrogen (TN) 19.38 mg/L, ammonium (NH4+-N )4.87 mg/L, and total phosphorus (TP) 0.67 mg/L to maintain water self-purification. Finally, after further economic/technical feasibility analysis, an optimal sewage discharge standard was recommended: 40 mg COD/L, 15 mg TN/L, 4.0 mg NH4+-N/L, and 0.3 mg TP/L. [ABSTRACT FROM AUTHOR]

In view of the large spatial difference in water resources, the water shortage and deterioration of water quality in the Chang-Ji Economic Circle located in northeast China, the water resource carrying capacity (WRCC) from the perspective of time and space is evaluated. We combine the gray correlation analysis and multiple linear regression models to quantitatively predict water supply and demand in different planning years, which provide the basis for quantitative analysis of the WRCC. The selection of research indicators also considers the interaction of social economy, water resources, and water environment. Combined with the fuzzy comprehensive evaluation method, the gray correlation analysis and multiple linear regression models to quantitatively and qualitatively evaluate the WRCC under different social development plans. The developmental trends were obtained from 2017 to 2030 using four plans designed for distinct purposes. It can be seen that the utilization of water resource is unreasonable now and maintains a poor level under a business-as-usual Plan I. Plan II and Plan III show that resource-based water shortage is the most critical issue in this region, and poor water quality cannot be ignored either. Compared with Plan I, the average index of WRCC in Plan IV increased by 51.8% and over 84% of the regions maintain a good level. Strengthening sewage treatment and properly using transit water resources are more conducive to the rapid development of Chang-Ji Economic Circle.

In order to realize the sustainable economic and social development of the Jialu River basin in Zhengzhou, maximally optimize the emission rights of sewage outlets and rationalize industrial and agricultural distribution, a steady state water quality model was established to analyze the river water environment in Jialu River basin of Zhengzhou City, which was based on the cross section（COD and NH 4）being up to standard and the total within a given range. This model can optimize main sewage outlets in major rivers in the urban area by analyzing the optimal configuration of river water environment capacity（COD and NH4）in Jialu River basin of Zhengzhou City. This model could distribute and regulate the total amount of water environmental capacity of segmented rivers. The research shows that in accordance with the method of constraining and reducing the total amount of pollution that enters the river and the water environment capacity for cross-section standards, the Jialu River (municipal section) can not only achieve the water quality control objectives of the functional areas, but also can realize the optimal allocation of emission rights under the constraints of the compliance rate of the whole river reach. [ABSTRACT FROM AUTHOR]

Based on the principles of fairness and feasibility, a nonlinear optimization allocation method for pollutants was developed based on controlled section water quality standards, considering the synergetic influence of point and surface sources. The maximum allowable emission of pollutants from point and surface sources were taken as the objective function. The water quality attainment rate of controlled sections, the control requirements of pollution sources, and technical parameters of pollution control engineering were taken as constraints. A nonlinear optimization allocation model was established, and a genetic algorithm was used to solve the problem. As an example, the model was applied to a certain area in the Taihu Lake basin, southern Jiangsu province, China. The analysis results showed that the annual number of days for ammonia-nitrogen and total phosphorus meeting the standard were 334 and 332 days, respectively, under maximum allowable emissions for each pollutant, and the water quality compliance rates of the control section were 91.5% and 91%, respectively. The ammonia-nitrogen and total phosphorus concentrations in the controlled section achieved related water quality compliance rate targets of 90%. These all met the water quality compliance rate requirements of the control section. The results indicate that this method reflects the feasibility of optimizing the total allocation results systematically and intuitively, overcomes the insufficiency in the feasibility of the optimized allocation method, and provides effective and reliable technical support for control and management of the total pollutant amount based on water quality improvement.

Based on the one-dimensional water quality modelling theory, this paper discusses the impact of different calculation methods on water environment capacity in different water functional areas. Through a case study of the Yinma River in Jilin province, in the same condition, the influence of four calculation methods (1. section-beginning control and no pollution sources generalization; 2. section-beginning control and uniform pollution sources generalization; 3. section-end control and no pollution sources generalization; 4. sectionend control and uniform pollution sources generalization) on the calculated results of water environment capacity were analysed. The calculation results of four calculation methods from big to small are: 4,3,2,1. In the case of considering only one of the model parameters, control section or pollution source generalization, the percentage improvements of water environment capacity are the same. [ABSTRACT FROM AUTHOR]

Water environment capacity calculation is the foundation of basin environment management. Due to lack of basic materials and data, the water environment capacity in small basin was not massively researched with appropriate calculating method. This paper mentioned a water capacity calculating method suitable for environment management. The method was based on the study of Xuchang Section of Qingyi River and described with details as follows: Xuchang Section was divided into four control units with GIS technology. The river pollution loads of non-point source pollutants from farmland runoff, rural life, livestock and poultry were calculated with the in-site and statistical data of pollution resource. Meanwhile the calculated river pollution loads of non-point / point source pollutants were statistically analyzed on the basis of control units. Then a water quality module was tested and verified, in which the predicted value tallied with the measured value. The parameter of this water quality module corresponds to the in-site data within relative error ±14%. This module was used to estimate and calculate water environment capacity. With this module the available water environment capacity of each control unit and pollutant reduction amount can be earned through deducting the river pollutant load of point pollutant. The results showed that the utilized method in this paper can satisfy the requirement for the calculating accuracy of small basin water environment capacity.

Taking the section of Songhua River in Harbin for example in this paper, taking COD as evaluation factors, and using the economic utility model and AHP, the water environmental capacity value has been studied. The results show that, due to water capacity, the saved cost of wastewater treatment is 0.067 billion yuan/year, and the economic benefits is 9. 417 billion yuan/year. The total value of the environmental capacity is 9. 484 billion yuan/year. The economic benefits of the class II, III and IV are 3.483, 4.802 and 11.32 billion yuan respectively. The maximum value of the environmental capacity belongs to the Class III water body, and is about 51% of the total economic value. [ABSTRACT FROM AUTHOR]

According to the principle of the function division of surface water, the Songhua River basin is divided into 2 primary function regions and 3 secondary function regions by divided system of two grades based on the analysis and evaluation on the water quality and quantity. According to the practical situation that the amount of water reducing and the channel becoming shallow in dry season makes the channel water amount and velocity decrease, the paper employs one-dimensional calculation model and defines model parameters rationally to calculate the water environment capacity of every function zone and get the calculation result. Based on knowing the water environment capacity of the water function region, people should carry out the optimization distribution and management of water resources, ought to improve the benefit and efficiency of water utilization, strictly control developing the industries of highly water-consuming and high-polluting, and construct a water-saving and anti-pollution society extensively. [ABSTRACT FROM AUTHOR]

Abstract: Taking a certain large water supply reservoir as example, this paper applies homa solution of lake perfect mixing attenuation model to analyze lake volume, lake staying time and degradation coefficient''s effect on water environment capacity of total nitrogen and total phosphorus. The elastic coefficients are used as sensitivity indicators to discuss the above three model parameters’ contribution rates to environmental capacity. The contribution rates of lake volume, staying time and degradation coefficient to total nitrogen capacity are respectively 36%, 29% and 35%, and the contribution rates to total phosphorus capacity are respectively 26%, 43% and 31%. The results show that the variation of model parameters can change dramatically dilution, degradation and displace capacity, and the change will affect the total environmental capacity. From the average value of elastic coefficient, each model parameter has great contribution to total nitrogen and total phosphorus environment capacity. [Copyright &y& Elsevier]

Abstract: Estimating of the water environment capacity is an important content of the assessment of regional environmental impact. This article estimates the environmental capacity of surface water of the Yellow River basin, Haihe River basin, Huaihe River basin, Jiaodong Peninsula rivers basin in Shandong based on discussing the concept of water environmental capacity and estimation methods. This article selects the appropriate water quality model and determines the appropriate parameters looking the basin divided unit as the basic unit of the water environment capacity, based on the results of the division of surface water basin and the comprehensive comparison of the multiple water quality model. Then the author calculates the water environmental capacity and gets the control unit of the water environmental capacity, the results will be visualized feedback by GIS. The study has important reference value for assessment of regional environmental and a reasonable estimate of the water environmental capacity. [ABSTRACT FROM AUTHOR]

The tradable discharge permit is an efficient marketing twist to deal with negative externality of water pollution, and initial allocation discharge permits (IADP) is a tough prerequisite for a health tradable discharge permit system. However, the allocation rules focusing on both water environment quality attainment and economic-technical feasibility have not been achieved. Therefore, a three-tier analytical framework including control units, industries, and enterprises has been established for satisfying the requirements of water environment quality attainment and technical feasibility. The framework includes three calculation modules and one justification module. A case study of the framework is carried out in the Changzhou City of Taihu Lake, China. Through comparison of the results of industry IADP, the technology-based initial allocation discharge permits scheme in control unit 7 is adopted as the final initial allocation discharge permits scheme, and the reduction plan chemical industry is carried out in control unit 8; finally, the initial allocation discharge permits results after reduction are employed as the final initial allocation discharge permits scheme. This three-tier analytical framework could ensure environmental protection, equality, efficiency, and make the scheme be more acceptable for enterprise stakeholders. In addition, it could support for optimization of industrial layouts and industrial structure upgrading to some degree. [ABSTRACT FROM AUTHOR]

China has large population and wide territory, the natural conditions of different regions are complicated, water resources are distributed unblanced, economic developing states are unequal. For these reasons the variation of concerned water environment capacity has obvious character of regional differentiation. In this paper, from the economic development point of view, the regular pattern of regional differentiation of China's water environment capacity resources is analyzed, the concept of contradictory degree between water environment capacity and economic development is introduced, based on them, rivers in China are divided into three regions, and corresponding strategies to control water pollution are advanced. The aims are to use river water environment capacity resources effectively, to control pollution and to improve environmental quality. [ABSTRACT FROM AUTHOR]

In view of the large spatial difference in water resources, the water shortage and deterioration of water quality in the Chang-Ji Economic Circle located in northeast China, the water resource carrying capacity (WRCC) from the perspective of time and space is evaluated. We combine the gray correlation analysis and multiple linear regression models to quantitatively predict water supply and demand in different planning years, which provide the basis for quantitative analysis of the WRCC. The selection of research indicators also considers the interaction of social economy, water resources, and water environment. Combined with the fuzzy comprehensive evaluation method, the gray correlation analysis and multiple linear regression models to quantitatively and qualitatively evaluate the WRCC under different social development plans. The developmental trends were obtained from 2017 to 2030 using four plans designed for distinct purposes. It can be seen that the utilization of water resource is unreasonable now and maintains a poor level under a business-as-usual Plan I. Plan II and Plan III show that resource-based water shortage is the most critical issue in this region, and poor water quality cannot be ignored either. Compared with Plan I, the average index of WRCC in Plan IV increased by 51.8% and over 84% of the regions maintain a good level. Strengthening sewage treatment and properly using transit water resources are more conducive to the rapid development of Chang-Ji Economic Circle. [ABSTRACT FROM AUTHOR]

Based on the principles of fairness and feasibility, a nonlinear optimization allocation method for pollutants was developed based on controlled section water quality standards, considering the synergetic influence of point and surface sources. The maximum allowable emission of pollutants from point and surface sources were taken as the objective function. The water quality attainment rate of controlled sections, the control requirements of pollution sources, and technical parameters of pollution control engineering were taken as constraints. A nonlinear optimization allocation model was established, and a genetic algorithm was used to solve the problem. As an example, the model was applied to a certain area in the Taihu Lake basin, southern Jiangsu province, China. The analysis results showed that the annual number of days for ammonia-nitrogen and total phosphorus meeting the standard were 334 and 332 days, respectively, under maximum allowable emissions for each pollutant, and the water quality compliance rates of the control section were 91.5% and 91%, respectively. The ammonia-nitrogen and total phosphorus concentrations in the controlled section achieved related water quality compliance rate targets of 90%. These all met the water quality compliance rate requirements of the control section. The results indicate that this method reflects the feasibility of optimizing the total allocation results systematically and intuitively, overcomes the insufficiency in the feasibility of the optimized allocation method, and provides effective and reliable technical support for control and management of the total pollutant amount based on water quality improvement. [ABSTRACT FROM AUTHOR]