River Network Area Research Articles

Water Quality Improvement Effective Analysis for Artificial Groundwater Recharge in Urban River Network System

With increase of population and urbanization, the persistent deterioration of urban rivers has become the most intractable problem for environment management agency. After the boom of pollution control projects implementing such as sewage system and sewage treatment plants building to decrease the pollution load, there is a growing interest on increasing ground water discharge with artificial groundwater recharge work and improving load capacity of target river. Under this background, it is important to study the exact effect of water artificial groundwater recharge work on water quality improvement, especially in the river network area, to give support on exact designment. In this study, the river network in Hanjiang district featured with complex river network has been selected as study area. Based on water quality monitoring result and current load statistical result, a one-dimensional mathematic model of target river network has been set up and the water quality has been simulated with different water artificial groundwater recharge schemes, which considering both river supplementary discharge and water quality factors. Then the simulation results under different effects have been analysed and the optimal scheme has been selected to meet the goals. The analysis results indicate that qualified option is recharging 2 m3/s fresh water of level III, under which, the water quality of study area can achieve the basic standard of Level V as qualified scenic water.

Calculation of environmental capacity and pollutant discharge in Changxing county based on sustainable development

Due to the improvement of the understanding of the natural environment and social service function of rivers, many countries in the world have started the research and practice of water environment protection. Lots of Chinese cities also paid most of their attentions to the water environment especially in the river network area. Systematic calculation and analysis of the water environment status becomes famous in most of the Chinese cities, which not only shows the current status of water environment but also indicates the methods to reduce the domestic pollution. In this study, Changxing county is selected as a typical Chinese city, COD (Chemical Oxygen Demand) and TN (Total Nitrogen) are considered as two typical pollutants, both water environmental capacity and current pollution are calculated. From the comparison between the present pollution load and the discharge limit into the river, it can be seen that TN is the key influencing factor of the water environment carrying capacity in Changxing County, and its overload ratio is up to 5.0. A series of measures to reduce the pollution load into the river are put forward in order to provide an auxiliary decision-making basis for further protecting “clear water and green mountains”.

Study on the Construction of Water Environment Promotion Joint Control and Joint Regulation System in Plain River Network Area

There are many river networks in Southeast plain cities of China, such as dense river network, many water projects, poor connectivity, strong pollution load into the river, and difficulty in regulation and control. The water environment problem of river network has become the bottleneck restricting the sustainable economic and social development of plain river network area. In order to improve the river water environment, it is very important to carry out reasonable intelligent regulation of regional river system. In view of the current situation that the water environment regulation is mainly based on manual operation and has not formed intelligent dispatching decision-making, this paper integrates the technology of water power and water quality joint control of urban river network, researches and develops the joint control and joint dispatching system of water environment improvement in plain river network area, and establishes a full coverage, full element three-dimensional monitoring and warning, dispatching and intelligent decision-making system, driven by monitoring data, with model as the core and remote control as the core with the goal of hydrodynamic, water level and water quality as the target, relying on the model cloud, the intelligent one click precise scheduling is realized.

Key technologies and equipment for contaminated surface/groundwater environment in the rural river network area of China: integrated remediation

To realize the integrated remediation of SW/GW and soil in the rural river network area, the integrated remediation in rural river network area project (IR-RRNA), funded by the Ministry of Science and Technology of the People’s Republic of China, has been launched. In eastern China, the rural river network area (RRNA) is an anthropic active area characterized by its rapid economic development and high gross national product. However, the water environmental pollution in these areas is increasingly severe, which has greatly hindered their sustainable development. Especially, the frequent interactions between surface/groundwater (SW–GW) have intensified the pollution migration and transformation in RRNA. The IR-RRNA (2019–2022) will apply the related interdisciplinary and methodological knowledge to elucidate the transportation and transformation of pollutants in water and soil during SW–GW interaction and develop remediation technologies of surface water, groundwater, and soil suitable for the RRNA. In this way, to realize the remediation technologies integration for surface/groundwater and soil in RRNA and implementing application demonstration. Meanwhile, a technical guideline will be compiled for the integrated remediation suitable for the RRNA. This project is conducive to addressing the urgent environmental problems as well as promoting rural economic revitalization and ecological environment optimization.

Impacts of land use at multiple buffer scales on seasonal water quality in a reticular river network area

The assessment and prediction of regional water quality are fundamental inputs to environmental planning and watershed ecological management. This paper explored spatiotemporal changes in the correlation of water quality parameters (WQPs) and land-use types (LUTs) in a reticular river network area. Water samples of 44 sampling sites were collected every quarter from 2016 to 2018 and evaluated for dissolved oxygen (DO), total phosphorus (TP), ammonia nitrogen (NH3-N), and permanganate index (CODMn). A redundancy analysis (RDA) and stepwise multiple linear regression (SMLR) were applied to analyze the land-use type impacts on seasonal WQPs at five buffer scales (100, 200, 500, 800, and 1000 m). The Kruskal–Wallis test results revealed significant seasonal differences in NH3-N, TP, CODMn, and DO. The area percentages of farmland, water area and built-up land in the study area were 38.96%, 22.75% and16.20%, respectively, for a combined total area percentage of nearly 80%. Our study showed that orchard land had an especially favorable influence on WQPs. Land-use type impacts on WQPs were more significant during the dry season than the wet season. The total variation explained by LUTs regarding WQPs at the 1 km buffer scale was slightly stronger than at smaller buffer scales. Built-up land had a negative effect on WQPs, but orchard and forest-grassland had a positive effect on WQPs. The effects of water area and farmland on WQPs were complex on different buffer scales. These findings are helpful for improving regional water resource management and environmental planning.

Spatiotemporal heterogeneity of hydrodynamic forces and water quality in typical lakeside river networks in Taihu Basin

基于中国太湖梅梁湾东部的无锡市滨湖区河网29个监测点在丰水期、平水期和枯水期的流速和水质监测数据，将河网分为梁溪河、曹王泾、骂蠡港、城市河网南区以及城市河网北区5个区域，对流速和典型水质指标的时空异质性进行分析，结合主成分分析和相关性分析，得到各区域水动力与水质现状及其成因.结果显示：梁溪河和曹王泾的水质条件和水动力条件较好，多数水质因子与流速表现出了强相关性；骂蠡港的水质和流速区域变化明显，表现弱相关性；城市河网北区和南区的流速较缓，河道污染负荷较大，流速与水质因子之间的相关性较低.通过在滨湖河网开展流速和水质的野外监测，分析流速对于河网水环境的实际效果，验证不同水质指标与流速之间的响应关系，为滨湖河网区水质保护和科学的水污染治理技术提供基础支撑.;Based on the flow velocity and water quality monitoring data in three periods: flood season, dry season and normal season from 29 river network monitoring stations in Wuxi Binhu region, which is located in eastern part of Meiliang Bay, Lake Taihu in China, the river network can be divided into five regions. After analyzing the spatial and temporal heterogeneity of flow velocity and the typical water quality indexes and combining the principal component and correlation analysis, the current situation and causes of different regional hydrodynamic and water quality can be understood. The results show that the water quality and hydrodynamic conditions in Liangxi River and Caowangjing River are good, and most of the water quality factors show strong correlation with the flow rate. The regional variation of water quality and flow velocity in Mali Port is obvious, showing weak correlation. In the north and south of the urban river network, the flow rate is slow, the river pollution load is heavy, and the correlation between the flow rate and water quality factors is low. Through the field monitoring of flow velocity and water quality in the Binhu River network, the actual effects of flow velocity on the water environment of the river network can be analyzed, and the response relationship between different water quality indexes and flow velocity have been verified, which provides basic support for the water quality protection and scientific water pollution treatment technology in the Binhu River network area. Thus, it is of great significance to improve the water ecological environment.

Evaluation of the effect of water diversion on improving water environment in plain river network under the multi-objective optimization

引调水是改善平原河网地区水环境的重要方法之一，通过构建太湖流域走马塘东南片平原河网区一维水动力水质数学模型，研究不同引调水方案对区域水环境改善效果，确定引调水过程中的异质性因子.从决策目标、水质指标、空间指标3个层面综合考虑，构建环境效益与经济效益结合的多目标函数及评价体系，对引调水方案进行评估优选.结果表明：引调水流量较大时，能够在一定程度上改善区域水环境状况，规划方案下引调水5 d后，高锰酸盐指数、氨氮、总磷的平均改善率分别为30.7%、22.2%、26.4%；引调水时，区域河网中不同空间点位、不同水质指标之间的水质改善过程与效果都存在一定异质性；引调水水量、调度模式及污染源分布都会对调水后的河网区水质产生差异性影响；本研究建立的多目标评价体系较现有方法能够有效涵盖引调水中存在的异质性因子，从多个目标层面优选引调水方案，实现水量水质综合优化调控，为平原河网地区水环境长效管理与科学决策提供理论参考.;Water diversion is a significant method to improve the water environment in the plain river network area. Through building up the one-dimensional hydrodynamic and water quality model of the plain river network area of southeast Zoumatang of Taihu Basin, the effect on water environment of different water diversion schemes was simulated, and the heterogeneous factors in the process were determined. A multi-objective function and evaluation system combining environmental benefits and economic benefits were constructed from three aspects, including decision-making, water quality indexes and spatial indexes, and the water diversion schemes were evaluated and optimized. The results show that: (1) With a larger flow, water diversion can improve the regional water environment to some extent. After 5 days of water diversion under the planning schemes, the average improvement rates of COD_Mn, ammonia nitrogen and total phosphorus were 30.7%, 22.2% and 26.4%, respectively. (2) Heterogeneity existed in the process and effect of water quality improvement in different spatial points and water quality indexes in the river network during water diversion. (3) The water quantity and dispatching mode of water diversion as well as distribution of pollutants all have different effects on the water quality in the river network. (4) Compared with the existing method, the multi-objective evaluation system of water diversion established in this research can effectively cover the heterogenous factors and evaluate and optimize different water diversion schemes from multiple objectives, therefore can achieve comprehensive optimization and control of water quantity and quality, and provide theoretical reference for long-term management and scientific decision-making of water environment in the plain river network area.

The impacts of water diversion on hydrodynamic regulation of plain river network

平原河网多存在河道流动性不强，河道生态流速难以保障的问题，以典型平原河网地区——宁波市海曙区为例，开展野外原型同步监测，以河道分流比、换水率及槽蓄量为研究对象，系统分析引调水工程对河网水动力的调控效果.结果表明：平原河网水动力改善效果与引排水口分布、引水流量密切相关，为保证河网区水体交换良好，引排水口的连线应尽可能贯通整个区域；平原河网换水率在空间分布上具有很强的异质性（4种调水方案下河道换水率极差，最大为190%，最小为75%），引调水工程能够改善分流能力大的支汊的水动力特征，对分流能力小的支汊及断头河的水动力状况帮助不大；河网换水率提高、槽蓄量变化率减小是区域水动力改善的必要条件，海曙区较小的槽蓄量变化率为0.2%左右.本研究分析了河网区的河道输水能力以及换水率，对优化河网概化密度以减小模拟偏差有参考意义，为进一步探究平原河网水动力改善促进水环境质量提升提供基础，利于特殊水动力特征河道治理和区域水环境管控.;In the plain river network area, the mobility of rivers is usually poor and the ecological flow velocity of rivers is difficult to be guaranteed. Taking Haishu District of Ningbo City, a typical plain river network area, as an example, a field prototype synchronous monitoring experiment was carried out. The effect of water diversion on hydrodynamic regulation was systematically studied with the river diversion ratio, water exchange rate and storage capacity as the research objects. The results showed that:The hydrodynamic improvement effect of plain river network was closely related to the position of water inlets and outlets and water diversion flow. To ensure a good water exchange rate, the connection of water inlets and outlets should run through the whole area as far as possible. The water exchange rate of plain river network area had strong heterogeneity in spatial distribution (under the four schemes, the maximum range of water exchange rate was 190% and the minimum was 75%). The water diversion project could improve the hydrodynamic characteristics of the branches with large diversion capacity, but it was not helpful for the branches with small diversion capacity and truncated creek. The improvement of regional hydrodynamic needed to increase the water exchange rate and decrease the change rate of storage capacity, the smaller change rate of storage capacity in Haishu district was about 0.2%. The study analyzed the water conveyance capacity and water exchange rate, which has reference value for optimizing the generalized density of river network to reduce the simulation deviation and provides a basis for exploring the improvement of water dynamics in plain river network and promoting the water environment quality. It will also be conducive to river regulation with special hydrodynamic characteristics and regional water environment control.

Improved method for identifying Manning’s roughness coefficients in plain looped river network area

Manning’s roughness coefficient(n) is considered a key parameter in a one-dimensional (1D) hydrodynamic model. However, it is highly variable and time- and site- dependent. Further, identifying proper n values is not easy, especially in plain looped river network areas. Therefore, a more systematic approach is needed. This study proposes a coupled optimization-simulation model to systematically estimate the spatial distribution of n values. The particle swarm optimization (PSO) algorithm and InfoWorks Integrated Catchment Modelling (ICM) software were integrated to solve the objective function and hydraulic process, respectively. Crisscrossing rivers were partitioned into river reaches that were each assumed to have a uniform and constant Manning’s roughness coefficient according to their network topology and cross-section variation. In addition, a sensitivity analysis was implemented to determine the weights of measured data from different gauging stations, and a large difference in the spatial distribution of the sensitivity index illustrated the importance of identifying the weights of multiple stations. Then, a systematic approach was applied to estimate the n values in the Changshu Grand Polder Area (CGPA), which is crisscrossed by 150 rivers, under the water diversion stage. The calculation statistics and efficiency indicated that the proposed method performs well for model calibration.

Effect of Heavy Rainfall on Nitrogen and Phosphorus Concentrations in Rivers at River-net Plain

To understand the quantitative effect of heavy rain on nitrogen and phosphorus pollution in river-net plain, daily observations of nutrient concentrations in two rivers, flowing into Lake Taihu, were conducted from 1st September, 2017 to 31st August, 2019. The daily rainfall was recorded by auto-recording meteorological stations located on the two rivers and the Taihu Laboratory for Lake Ecosystem Research. Intensive sampling in different sections of the two rivers during Super Typhoon Lekima was also conducted in August 2019. Using these datasets, the influence of heavy rainfall on various forms of nitrogen and phosphorus concentrations in the rivers, and its environmental effects, were analyzed. The results showed that 16 heavy rainfall events (19 d) were observed in two years, 50% of which occurred in the summer season. In addition, heavy rainfall accounted for as much as 41.33% of the total rainfall over the entire year. After the period of heavy rainfall, the concentrations of various forms of nitrogen and phosphorus increased, and the particulate P generally exhibited the fastest response, usually peaking on the day of heavy rainfall. In contrast, the peaks of N were delayed for 2-5 days with the occurrence of heavy rain. In general, the duration of the increase in the concentration of nutrients in the study river caused by heavy rainfall was short (usually 1-2 days), and sometimes was lower than the concentration before the rains. The Dapu River exhibited a slower response to heavy rains than the Yincun River because it has a larger and longer catchment area than the Dapu River. In addition, the effect of heavy rain on N and P concentrations was also strongly influenced by the land-use situation around the river basin. The increase of nitrogen in the reach, affected by agricultural non-point sources, was dominated by granular nitrogen, and the increase of nitrogen in the reach affected by urban non-point sources was dominated by dissolved nitrogen. The increase of phosphorus was dominated by granular phosphorus in the entire process. The conclusions of this study are as follows:In the plain river network area, the fluctuations of nitrogen and phosphorus concentrations in the river water body caused by heavy rainfall are small, and the response of various forms of nitrogen and phosphorus are significantly affected by the local environmental background. Therefore, the water quality generally exhibited limited variation. Due to the large proportion of water entering the lake during heavy rainfall events, a high level of the nutrient loading was also observed, and the occurrence of heavy rainfall was occasional. The short-term effect of heavy rainfall on the nitrogen and phosphorus loading entering the lake in the river channel in the plain river network area is therefore, also significant, and requires further investigation.

Impact of rapid urbanization on the threshold effect in the relationship between impervious surfaces and water quality in shanghai, China

The threshold effect in the relationship between impervious surfaces and water quality has been a focus in past decades, but little attention has been paid to how the threshold effect changes during a rapid urbanization period. This study reveals the temporal variation of threshold effect in the relationship between the percentage of total impervious area (PTIA) and water quality indicators in a reticular river network area in Shanghai, China. The PTIA was surveyed and defined using the ISC method (impervious surface coefficients). A segmented regression model was used to disclose the non-linear relationship between PTIA and water quality. It is confirmed that the threshold effect was different in terms of water quality indicators, but the effect size became smaller as the threshold increased with urbanization level during the period of 1989–2010. Meteorological conditions make influence on the threshold effect, it can be found that the effect is more significant under higher air temperature conditions, while in the lower temperature situation, there is no significant threshold effect.

The EMR-rural project: key techniques and devices development for rural environmental monitoring and remediation in China

Rural development, as one of the biggest challenges facing human beings recently, has attracted widely attention in the world, among which rural environment protection is essential for sustainable development. In response to the call to build “green livable villages”, the environmental monitoring and remediation in rural project (EMR-rural project) is launched. EMR-rural (2019 to 2022) is funded by the Ministry of Science and Technology of the People’s Republic of China (MOST). The project aims to develop key techniques and devices for contamination classification, risk assessment, pollution sources tracing and environmental remediation with regard to soil, underground and surface water quality in rural area. To this end, a new generation of physical, chemical and biological tools is integrated with intelligent management platform. The project follows a problem-oriented approach by in situ investigation, lab/pilot-scale mechanism exploration and field determination. EMR-rural takes advantage of the access to the applicable techniques and devices to investigate and to restore soil and water pollution in river network areas, mountainous areas as well as cold areas of China.

Performance assessment of coupled green-grey-blue systems for Sponge City construction

In recent years, Sponge City has gained significant interests as a way of urban water management. The kernel of Sponge City is to develop a coupled green-grey-blue system which consists of green infrastructure at the source, grey infrastructure (i.e. drainage system) at the midway and receiving water bodies as the blue part at the terminal. However, the current approaches for assessing the performance of Sponge City construction are confined to green-grey systems and do not adequately reflect the effectiveness in runoff reduction and the impacts on receiving water bodies. This paper proposes an integrated assessment framework of coupled green-grey-blue systems on compliance of water quantity and quality control targets in Sponge City construction. Rainfall runoff and river system models are coupled to provide quantitative simulation evaluations of a number of indicators of land-based and river quality. A multi-criteria decision-making method, i.e., Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is adopted to rank design alternatives and identify the optimal alternative for Sponge City construction. The effectiveness of this framework is demonstrated in a typical plain river network area of Suzhou, China. The results demonstrate that the performance of Sponge City strategies increases with large scale deployment under smaller rainfall events. In addition, though surface runoff has a dilution effect on the river water quality, the control of surface pollutants can play a significant role in the river water quality improvement. This framework can be applied to Sponge City projects to achieve the enhancement of urban water management.

Performance of water transfer in response to water environment issues in Wuxi, China

The continuous development of industrialization and urbanization resulted in increased pollution in plain river network areas. In response to water environment issues, water transfer can be a countermeasure to improve water environment. There are five basic elements to be determined of water transfer, i.e., water sources, water transfer patterns, regulating rules, water transfer routes, and flow rate of water transfer. In Wuxi City, needs for water transfer were analyzed from the five aspects above. The former three elements were determined based on the results of water transfer measurements. The water source was Yangtze River, the pattern was continuous water transfer, and regulating rules were water transferred by pumping stations and drained by sluices and pumping stations. Besides, a water quantity and quality coupling model was constructed to analyze routes and flow rate of water transfer. Different flow rate of water transfer, from 80 to 130m3/s, were analyzed. According to the characteristics of regional river system and the requirements of flood control, the Baiqugang River was taken as the clean water route, and the urban flood control enclosure was taken as the clean water transfer station. In the end, it was concluded that the optimal flow rate is 110m3/s based on the results of different schemes. It indicates that a proper scheme of water transfer can better improve the water environment in plain river network areas.

Unraveling the nexus of multi-environmental factors and benthic macroinvertebrates in typical inflow river of Taihu Lake in China.

The objective of this study is to examine the relationship between benthic macroinvertebrates and various environmental factors (i.e., physicochemical properties of sediment and hydromorphological condition) in the typical inflow river sediments of the Taihu Basin in China. Pearson correlation and redundancy analysis (RDA) were used to investigate associations between environmental factors and benthic macroinvertebrate community structure. The RDA results indicated that the environmental factors account for 58.6% of the spatial differentiation of benthic macroinvertebrate community. High density of Oligochaeta species, which were potential indicators of heavy metal pollution within sediments, was observed as the pollution-tolerant species in the study area, indicating that the benthic community was seriously polluted by heavy metals and nutrients. Moreover, the variation in benthic macroinvertebrate community structure and trait composition were mainly explained by physicochemical properties of sediment (e.g., Pb, temperature, and phosphate), whereas hydrological condition (e.g., turbidity) alterations played a less important role. Thus, the environmental factors are significantly correlated with the abundance and biomass of benthic macroinvertebrate by taking interacts of multi-environmental factors into account. These results provide scientific basis for water environment health management and pollution control in Taihu Basin river network area.

Stream order and connectivity affect phosphorus distribution in plain river network

ABSTRACT The order and connectivity of streams influence phosphorus distribution extensively. In this work, the space-and-time variabilities of total phosphorus (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP), dissolved reactive phosphorus (DRP), and dissolved unreactive phosphorus (DUP) in streams of three orders (Ⅰ, Ⅱ, ⅡⅠ) were analyzed during each spring of 2016-2018 in a plain river network area, China. The results show that: ① PP was the main form of TP and DRP was the main form of TDP. ② The average concentrations of phosphorus in the order Ⅰ streams were significant larger than those in the order ⅡⅠ The concentrations of TP, PP, TDP, and DRP in the poor-connected streams were considerably higher than those in the well-connected streams. Therefore, it is essential to implement effective practices to improve the protection and appropriate connectivity of small streams in plain river network areas.

Elevated manganese concentrations in shallow groundwater of various aquifers in a rapidly urbanized delta, south China

High concentration of manganese (Mn) in groundwater is a major concern because of its harmful to human health, and the origin of which in urbanized areas is often complicated. The present study aims to delineate spatial distributions of groundwater Mn in various aquifers and in areas with different urbanization levels in the Pearl River Delta (PRD), and to identify the origins of groundwater Mn in this region. Nearly 400 groundwater samples collected, and 14 chemicals were analyzed. The results show that approximately 20% groundwater in granular aquifers showed elevated-Mn (>0.4 mg/L), and was more than two times of that in fissured aquifers, while that in karst aquifers was absent. The proportions of elevated-Mn groundwater in urbanized areas and peri-urban areas were higher than that in non-urbanized areas. The decomposition of organic matter and reduction of Fe (hydr)oxides in sediments with reducing condition was likely to be the main factor controlling elevated-Mn groundwater in granular aquifers at a regional scale. By contrast, elevated-Mn groundwater in fissured aquifers was likely mainly affected by the urbanization accompanied with the leakage of low-oxygen domestic sewage and the industrialization accompanied by the leakage of industrial wastewater. In addition, Mn-rich surface water was also probably an important source for groundwater Mn in river network areas. Therefore, it is necessary to make a long-term monitoring for groundwater Mn in granular aquifers, especially in urbanized areas and river network areas, because of the high proportion of elevated-Mn.

Occurrence and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in water resources of the typical plain river network area

Drinking water sources play a significant role in providing water for urban residents and public services. The pollution and health risk of polycyclic aromatic hydrocarbons in drinking water sources have attracted extensive attention. In this study, river water samples were collected from two drinking water resources of the typical plain river network area in eastern China, and tap water samples were collected from public places. The concentration of the 16 priority PAHs in river water and drinking water were determined by SPE-GC-MS. The results indicated that the concentrations of Σ16PAHs ranged 128-183 ng/L in the autumn and 61.3-87.3 ng/L in the winter, respectively. The cancer risks and non-cancer risks of adults associated with drinking water intake were low, but it still deserved more attention.

Water Environmental Capacity Calculation and Allocation of the Taihu Lake Basin in Jiangsu Province Based on Control Unit.

The water quality target management of the control unit is a convenient and direct technology for water environment management and the development direction of water environment management in China, involving control unit division and water environment capacity calculation. Taking the Taihu Lake Basin in Jiangsu Province as an example, we propose herein the basic principle of the division of a regional control unit in a plain river network and the method of analyzing the rationality of the control unit division. On this basis, the Taihu Lake Basin in Jiangsu Province was divided into 70 control units. To calculate the water environmental capacity in the plain river network area, we established a water environmental capacity calculation framework based on multiple targets of lakes and rivers, and proposed the goal of water quality “double compliance” of the water environmental functional zone and the assessment section. For this study, we calculated the regional water environmental capacity using the mathematical model of the Taihu Lake Basin’s water environmental capacity, and the water environmental capacities of the 70 control units were allocated by the weight coefficient method, which established water area and functional division length. The research results described herein were applied to the pollution permit management of the Taihu Lake Basin in Jiangsu Province. It provides important technical support for the establishment of a pollution permit system based on the total capacity to improve environmental quality.

Removal of Microplastics by Different Treatment Processes in Shanghai Large Municipal Wastewater Treatment Plants

Wastewater treatment plants are important sources of microplastics (MPs) in aquatic environments. The present study was conducted to investigate the number concentration, removal rate, and fate of MPs in two large municipal treatment plants in Shanghai. The MPs number concentration in the influent water of WWTP1 and WWTP2 were (226.27±83.00) piece·L-1 and (171.89±62.98) piece·L-1, respectively. WWTP1 had a MPs removal efficiency of 63.25%, which is slightly higher than that of WWTP2, at 59.84%. The removal efficiency during the primary treatment process of the two sewage treatment plants on MPs accounted for 70%-80% of the whole treatment process. The primary treatment process and secondary treatment process transferred (48.10%±1.62%) and (12.97%±0.05%) of MPs in the sewage to the sludge, respectively. As a whole, (38.82%±1.55%) of MPs in the sewage treatment plants were finally discharged into natural waters, and the remaining (61.18%±1.55%) entered the sludge. This study shows that the removal rate of MPs in Shanghai's municipal treatment plants is low and that after treatment, large amounts still enter the natural waters with the final effluent, which causes significant ecological risks. This study provides basic data of MPs removal and trends of large urban sewage treatment plants in a plain river network area, which can provide reference for further design of MPs removal processes.