1. Introduction
Globally, with the boom in agricultural and industrial activities, about 80% of the wastewater generated by human activities is discharged without any treatment [1,2]. Domestic wastewater with high levels of nitrogen, phosphorus, organic pathogens and other pollutants [3,4] is usually discharged directly into nearby rivers and lakes in most areas, which has led to a series of environmental and ecological crises, especially in developing countries [5,6]. Eutrophication of rivers and lakes, due to the discharge of domestic sewage containing excessive nitrogen and phosphorus, has become a major environmental problem [7,8]. These problems are exacerbated in rural areas where funding and research are lacking [9]. Rural domestic sewage discharges without effective treatment can pollute local waters and pose potential ecological and health risks in the aquatic environment [10,11].
In 2021, the World Health Organization (WHO) and the United Nations International Children’s Emergency Fund (UNICEF) jointly reported that 616 million people worldwide live in environments without sanitation, of which about 90% live in rural areas [12]. In rural areas, the coverage of domestic wastewater treatment facilities is substantially lower than those in urban areas, due to a lack of investment and research in rural areas [9]. Direct discharge of human excreta and domestic sewage can seriously affect surface water and groundwater, leading to ecological degradation of the regional environment [13,14,15]. According to a survey conducted by the Ministry of Ecology and Environment of the People’s Republic of China [16], the volume of rural wastewater in China in 2020 accounted for 40% of the country’s total wastewater, including 51% of chemical oxygen demand (COD), 30% of total nitrogen (TN) and 39% of total phosphorus (TP). Indeed, only 25–30% of rural domestic sewage (RDS) in China is effectively treated [17]. RDS treatment is, therefore, a priority for improving rural habitats and preventing local watershed environments from point and nonpoint pollution, thereby achieving global sustainable development goals. Compared to municipal domestic wastewater, RDS can result in larger polluted areas, intermittent discharge and high variability in water quality and quantity [18]. Therefore, unlike municipal wastewater treatment technologies, RDS may require diverse collection modes and different treatment technologies [19].
RDS discharge has become increasingly important in the Yangtze River basin in recent years, due to the increase in the economic development and living standards of rural areas that affect negatively the environment of the physical components of the watershed (e.g., rivers, lakes and drinking water sources) [20,21,22,23]. In this regard, in December 2016, the State Council of the People’s Republic of China issued the 13th Five-Year Plan for Ecological Environmental Protection, highlighting the importance of promoting a comprehensive environmental improvement of 130,000 administrative villages, and enhancing rural domestic sewage treatment [7,24]. In February 2017, the Ministry of Environmental Protection of the People’s Republic of China and the Ministry of Finance jointly issued the Thirteenth Five-Year Plan for Comprehensive Improvement of the National Rural Environment, indicating that 130,000 new villages will achieve comprehensive environmental improvement in 2020 [25]. In February 2019, the No. 1 document of the Central Committee of the Communist Party of China (CPC) highlighted the importance of agricultural development in rural areas, indicating that considerable attention should be paid to the improvement of the rural habitat environment, enhancing the degree of resource utilization of rural livestock, and controlling poultry pollution and sewage discharge to ensure effective sustainable development of rural areas [26,27,28]. The release of the above-mentioned documents provides a policy and scientific basis for ensuring efficient treatment of RDS. Indeed, the local government implemented several investment projects for rural sewage treatment.
Wuhan City is a mega-city located in the middle reaches of the Yangtze River Basin. The three-year action plan for rural domestic sewage management, issued in 2018 [29], aims to carry out a three-year rural domestic sewage management action to achieve a coverage rate of domestic sewage management in village areas of 100%. Previous studies have shown that the consideration of districts as basic planning units can ensure effective management of various village areas [30,31].
In this context, this paper aims to propose a system and technical route for ensuring effective RDS management by category at the district levels in Wuhan Jiangxia District. In total, through the above system and technical route, more than 2000 villages in the study area were classified in this study, and the order of successive sewage treatment was set according to the importance of the villages. The classification and ranking of villages can help the local wastewater management department to design and implement specific domestic wastewater treatment projects for each village, leading to an economic and scientific implementation of domestic wastewater projects, and providing a model for rural domestic wastewater management in the Yangtze River basin.
As a rural wastewater treatment work to be carried out in the Yangtze River basin in a comprehensive manner with administrative districts as the unit, the theoretical significance of this study is to propose a kind of rural wastewater treatment project prep work, i.e., the construction of rural wastewater special planning methods and ideas. The specific categories include the following: firstly, the villages in the region are classified according to the classification criteria in the article; secondly, several new wastewater collection models are established; then, the sequential treatment order of rural domestic wastewater treatment for the results of different village classifications are determined; finally, the rural sewage treatment in the whole administrative region are collected scientifically and orderly.
The specific objectives of the present study are: (Ⅰ) to establish a more suitable model for domestic sewage collection in rural areas; (Ⅱ) to classify the rural areas in Jiangxia District and carry out sewage treatment actions according to the importance of the classified villages; (III) to analyze the problems and solutions in the planning process of district-level rural domestic sewage.
2. Literature Review
The treatment of rural domestic sewage is a major problem that puzzles the whole world, and it is also an important obstacle to sustainable development. On the issue of rural domestic sewage treatment, different countries have different plans on what kind of collection system and treatment methods should be adopted. Therefore, this study begins by analyzing the relevant literature concerning rural domestic sewage collection mode and treatment technology.
2.1. Collection Mode of Rural Domestic Sewage
At present, the reported collection modes of rural domestic sewage mainly include centralized collection and decentralized collection. Due to the distribution of residents in rural areas, the common collection mode is the centralized system [32]. Asano [33] pointed out that the centralized system is a sewage treatment system suitable for cities. It needs a long pipeline network to transport the collected wastewater to the central device for treatment, and then discharge or reuse. Globally, the centralized system is not suitable for rural areas, due to the residents’ distribution characteristics, terrain characteristics and financial problems in rural areas. Therefore, it is necessary to explore the domestic sewage treatment mode suitable for rural areas. Giulia [34] found that the decentralized system can not only help alleviate the water security problems in arid areas, but also create a sustainable framework in circular economy, which is conducive to saving construction funds. Muzioreva [35] revealed that the decentralized wastewater system may replace the centralized system as a sustainable scheme. The decentralized wastewater system is the most commonly used wastewater treatment technology in developing countries, but it is not efficient in the research of wastewater treatment technology [19]. Generally speaking, the research conducted is limited to simpler technologies. It can be seen from the above literature that the centralized mode is mainly used in urban areas, while the decentralized collection mode is mainly used in rural domestic sewage treatment. However, at the boundary between urban and rural areas, it is difficult to achieve the ideal sewage treatment effect by using the above-mentioned collection mode alone. Therefore, this article has established a more perfect collection system for rural domestic sewage (e.g., collection at the town level (CT), centralized collection (CC), decentralized collection (DC) and combined CC and DC (CCD), so that rural domestic sewage can be better collected and further treated.
2.2. Treatment Process of Rural Domestic Sewage
At present, rural sewage treatment technologies mainly include constructed wetlands, stabilization ponds and integrated rural sewage treatment process, as well as many other treatment technologies. In developing countries, most rural areas are widely distributed. These rural areas have great cultural differences, diversified living forms, and are scattered. In addition, rural areas have limited financial budgets. Except that domestic sewage in rural areas around cities can be directly discharged into urban sewage treatment plants, sewage pipe networks and centralized sewage discharge systems cannot be built in most rural areas [36]. Therefore, the above-mentioned treatment methods have developed rapidly in rural areas.
On the road of rural sewage treatment, many countries have carried out research on relevant treatment methods and promoted specific cases; here are a few examples: Jóźwiakowski [37] summarized the research and experience of constructed wetland systems (CWs) in southeast Poland in urban sewage treatment from 1992 to 2016 and thought that one-stage CWs could be used on a large scale in scattered rural areas. On the other hand, the hybrid system can be successfully applied to entertainment centers or protected areas, especially national parks. It has been shown that the use of hybrid CWs conforms to the concept of sustainable development. Marzec [38] analyzed the removal effect and reliability of pollutants in vertical and horizontal flow composite-constructed wetlands planted with Phragmites australis, manna grass and mallow. By measuring several water pollution indexes and using the Weibull probability model for reliability analysis, the results show that all pollution indexes of wastewater discharged into the receiving water body are obviously lower than the limits required by Poland. Chen [36] summarized the process flow, operation effect and engineering applicability of typical integrated sewage treatment processes in different countries; the results are helpful in fully understanding the development status, evaluation method and operation mode of rural sewage treatment technology. It is also helpful to clarify the optimization and development direction of rural sewage treatment technology in developing countries in the future. The above research shows that, different from urban sewage treatment technology, constructed wetland plays an important role in rural sewage treatment. There are also some related studies in China, Cheng [39] which revealed that the biogas project for domestic sewage treatment (BPDST) is a promising facility for wastewater management in rural areas of China, and that, compared with centralized sewage treatment plants, the development of a decentralized sewage treatment system is conducive to achieving sustainable development goals and meeting the demand of resource reuse.
There is also corresponding research on the treatment of rural domestic sewage in the Yangtze River basin. Chai [40] revealed that different forms of constructed wetland treatment processes are selected for rural domestic sewage according to the village scale, and livestock breeding wastewater is fermented by biogas digesters and then put into farmland for secondary utilization. It is revealed that Huang’s [30] comprehensive treatment project of rural domestic sewage in Suzhou can alleviate the present situation of rural domestic pollution, help to achieve the goal of total amount control of regional pollutants, effectively reduce the pollution degree of Taihu river network, and have great significance for ensuring the safety of drinking water and the sustainable development of rural areas.
However, for a large administrative region (e.g., the whole city, the whole district), there is still a lack of corresponding cases on how to scientifically implement the sewage treatment plan to save investment and achieve the sewage treatment goal. Therefore, before the design and construction of sewage treatment, it is necessary to study the special planning scheme of sewage treatment to guide the orderly rural sewage planning in this area.
3. Materials and Methods
3.1. Study Area
Wuhan City is located in the central part of China, while Jiangxia District is located in the southern part of Wuhan City in China (114°01′–114°35′ E, 29°58′–30°32′ N), on the south bank of the middle and lower reaches of the Yangtze River (Figure 1). The study area is limited by Hongshan District in the north, Ezhou City (Hubei Province) in the northeast, Daye City (Hubei Province) in the southeast, Xianning City (Hubei Province) in the south, Jian County of Xianning City in the southwest, and Caidian and Hannan districts of Wuhan City in the northwest. Jiangxia District is 63.2 km long from north to south and 54.17 km wide from east to west, covering a total area of 2018 km2 and a planning area of 1650 km2 [41]. Jiangxia District has a strategic geographic location and convenient transit access area. In the “1 + 8” Wuhan City Circle approved by the China government, Jiangxia is at the center of the “1 + 3” connecting part and is an important channel for Xianning, Huangshi and Ezhou into Wuhan. In addition, the study area has unique ecological, economic and industrial development patterns.
3.1.1. Meteorological Data
In this study, the meteorological data used were derived from the monitoring data released by the Wuhan Meteorological Bureau. Jiangxia District has a humid monsoon climate with a subtropical transition. The mean annual temperature and mean annual precipitation range from 15.9 to 17.9 °C and 889.2 to 1862.6 mm, with average values of 16.8 °C and 1347.7 mm, respectively, whereas sunshine hours range from 1450 to 2050 h. In addition, the study area experience rainfall events and high temperature in the same season. The prevailing winds throughout the year are in southeast and northeast directions, with an average relative humidity of 70% and short extreme cold and heat periods, indicating obvious characteristics of subtropical continental monsoon climate in the study area.
3.1.2. Hydrology and Geomorphology
Jiangxia District has a unique geographic location, as shown in Supplementary Materials (Figures S1 and S2) showing the distribution of Lakes and topographic characteristics of Jiangxia District. The study area is limited by the Yangtze River to the west and lakes to the northeast and southwest. In addition, reservoirs, fishponds, weirs and dams are widely distributed in the study area. Due to the narrow and slopping topography from the northern to southern parts, and from the eastern to western parts of the study area, the water system in the study area is fan-shaped. The larger rivers in Jiangxia District are the Yangtze River and Jinshui River, flowing over 32.6 and 45.9 km, respectively. In addition, there are four large lakes in the study, namely, Tangxun Lake, Liangzi Lake, Futou Lake and Lu Lake. Rivers, lakes, riverbanks and reservoirs in Jiangxia District cover a total area of 64,670 hectares, accounting for one-third of the district’s surface area. 38,400 hectares of the water surface can be cultured in the district, which is the largest district in Wuhan. The rich water system of Jiangxia District is an important component of Wuhan’s ecological pattern.
Jiangxia District is a transitional section between Jianghan Plain and the hills of southern Hubei. The topography of the district is characterized by a high central part and a flat alluvial plain on both sides. The hilly area is distributed mainly in the northern part of Jiangxia District, forming an east-west belt across the alluvial plain. The eastern and western parts of the study area are covered by plains, with an altitude range of 20–40 m, while the central and northern parts are covered by hilly areas, with an elevation of about 150 m.
3.1.3. Distribution of Villages
Rural sewage treatment planning in Jiangxia District involves 13 streets, 257 administrative villages, 2156 villages and 90,190 households. According to the local agricultural department statistics of Jiangxia District in 2018–2020, sewage treatment systems need to be implemented for about 2156 villages and domestic sewage systems of 38 villages can be directly connected to the constructed sewage treatment plant pipeline, while those of 505 villages need to be improved. In addition, 1613 villages need new sewage treatment facilities. See Supplementary Figure S3 and Supplementary Table S1.
3.2. Methods
3.2.1. Principles of Rural Domestic Sewage Collection Mode
In order to better establish a model of rural domestic sewage collection in Jiangxia District, we set the following principles:
(1) Distribution of rain and sewage: The sewage collection method adopts a diversion system, allowing the collection of rainwater from each village by ditches, pipes, or discharging it on site to reduce the load on the sewage treatment facilities, while domestic sewage is collected and transported to the sewage treatment facilities through pipes;
(2) Sewage collection: All sewage types should be collected by the sewage collection pipeline. Village domestic sewage includes toilet sewage, bathing sewage, kitchen sewage and other washing sewage. Among them, bathing sewage, kitchen sewage and other washing sewage can be directly connected to the sewage collection network, while toilet sewage must be pretreated by a septic tank before entering the sewage collection pipeline;
(3) Adaptation of measures to local conditions: Due to the low population densities of villages and the wide area of domestic sewage discharge, the urban sewage centralized collection mode cannot be considered in rural areas. Therefore, domestic sewage can be transported from villages located in the collection area of the urban sewage treatment plant pipeline network to urban sewage treatment plants for treatment, whereas other sewage collection modes can be used in other villages to collect domestic sewage according to local conditions, such as topographic characteristics and geographic locations of villages;
(4) Economical and reasonable: The village domestic sewage collection system should consider the topographical characteristics and landscape of villages to facilitate the gravity-driven sewage flow to the sewage treatment plant without using lift pumps, thereby reducing the energy consumption in the sewage collection process.
3.2.2. Technology Line
The technical route of rural domestic sewage treatment plan in Jiangxia District is shown in Figure 2.
(1) Data collection: The information (e.g., district master plan, environmental protection plan, water development plan, agricultural development plan, urban and rural tourism plan and national land plan) collected should include planning documents related to rural domestic wastewater, as well as the corresponding maps. Researchers should collect information on existing sewage stations in each street and township at the district level, as well as information on rural sewage water quality, rural demographics and village geography;
(2) In situ investigation: Researchers need to assess the accuracy of the collected information by investigating the operation of existing rural domestic facilities, villagers’ re-flections on the current problems of domestic wastewater treatment in villages, and sources of problems related to domestic wastewater treatment through in situ investigations. In addition, researchers need to determine the number of inhabitants, village categories, and the pattern of domestic sewage discharge in villages with different levels of aggregation, providing insights into the development of the village classification plan;
(3) Analysis of the collected data: The researcher needs to carry out the planning with reference to the Guidelines for the Preparation of the Special Plan for the Treatment of Domestic Sewage in Rural Villages in Wuhan City, before which, the following issues need to be studied: defining the objectives of treatment, classifying the villages, and determining specific discharge standards for different categories of villages. In the planning process, researchers need to be responsive to the views of relevant government departments by writing the preliminary plan, which can be subsequently revised and improved before evaluating it by a jury composed of experts in the field of rural domestic sewage treatment.
3.2.3. Establishment of Rural Sewage Collection Mode
The topography of the terrain varies greatly in Jiangxia District, due to the high number of villages. In addition, there is great variation in the degree of households in the study area. Rural domestic wastewater collection modes, such as the single mode, may result in excessive investment in the pipe network, making the project expensive. Therefore, the village domestic sewage collection mode was classified in this study, based on the local topographic features and population information, into four scenarios, namely, collection at the town level (CT), centralized collection (CC), decentralized collection (DC) and combined CC and DC (CCD) (Figure 3).
(1) Collection at the town level (CT): Wastewater is collected from villages within 0.5 km of the township. The village sewage network is connected to the township sewage network through small pipe networks, ensuring the flow of the rural domestic sewage flows into the township sewage treatment plant without requiring additional sewage treatment plants in villages, making this collection scenario cost-effective;
(2) Centralized collection (CC): The centralized collection mode is a sewage collection mode in which domestic sewage from a village or several nearby villages is collected by a single pipe, then discharged to a sewage treatment plant for subsequent treatment. The centralized collection mode and treatment system of village wastewater should be designed according to the topographical characteristics to ensure an effective collection of domestic wastewater;
(3) Decentralized collection (DC): The decentralized collection model is a sewage collection model that collects the septic tank supernatant and domestic wastewater from scattered rural areas and discharges it to the decentralized treatment plants near households. This scenario is applicable to the collection of domestic sewage from a single detached single house or several neighboring farm households. In addition, this scenario does not require the construction of a large number of sewage networks, making it cost-effective;
(4) Combined centralized collection and decentralized collection (CCD): A single centralized collection mode or decentralized collection mode cannot ensure efficient sewage collection due to the complex topographical characteristics of some village areas. Therefore, a combination of centralized and decentralized collections can be used to collect domestic sewage. Indeed, the centralized sewage collection mode can be used to collect wastewater from the majority of households living in the village in a centralized manner, while the decentralized collection mode can be used only for a few households in the village far from the centralized area.
3.2.4. Calculation of the Total Amount of Rural Domestic Sewage
(1) Estimation of the total volume of rural domestic sewage in Jiangxia District
In this study, the total volume of village sewage was estimated according to the Wuhan Rural Village Domestic Sewage Treatment Technology and Construction Guidelines, taking into account the amount of domestic sewage generated by rural villages, foreign populations and public service facilities [42,43]. The total amount of rural domestic sewage discharge was estimated in this study using Equation (1). It should be noted that 70~80% of the water quota was used to determine the rural domestic sewage volume in areas without survey data (see Supplementary Table S2).
(1)
where Q denotes the daily treated sewage volume (L/d); q denotes the per capita daily domestic water consumption (L/d); n denotes the local resident population; r denotes the drainage coefficient; k denotes the domestic sewage volume variation coefficient. The coefficient of change in the domestic sewage volume k was set with reference to CJJ 124-2008 [44] and GB 50014-2006 [45]. When selecting the coefficient of variation of sewage k, the rural holiday domestic sewage discharge should be considered. In addition, when there is actual information on the change in domestic sewage volume, the actual data are used.(2) Rural Domestic Sewage Water Quality Analysis
Village domestic wastewater water quality (e.g., acidity (pH), suspended solids (SS), chemical oxygen demand (COD), biological oxygen demand (BOD), ammonium (NH4+-N), total nitrogen (TN), total phosphorus (TP)) was determined using the results of field investigation. However, values reported in Supplementary Table S3 were considered for areas with a lack of data.
(3) Functional Classification of Surface Water
According to the environmental functions and protection objectives of surface waters, Environmental quality standards for surface water is divided into five categories in order of function [46]:
I: It mainly applies to source water and national nature reserve;
II: It is mainly applicable to the first level protection zone of centralized drinking water sources, rare aquatic habitats, fish and shrimp spawning grounds, juvenile fish baiting grounds, etc.;
III;: It is mainly applicable to the secondary protection zone of centralized living drinking water sources, fish and shrimp overwintering grounds, water plant breeding areas and swimming areas;
IV: It is mainly applicable to general industrial water and human non-direct contact water;
V: It is mainly applicable to agricultural water and landscape water.
3.2.5. Rural Domestic Wastewater Treatment
To determine the priority of rural domestic sewage management, the following order was considered: key villages, featured villages, ordinary villages for treatment, priority treatment of key villages and featured villages. The key villages denote villages around town, large villages and villages around rivers, lakes and drinking water sources (VRLS). Featured villages denote villages with developing rural tourism. Ordinary villages, except for key villages and featured villages, are all ordinary villages (see Supplementary Table S4 for a detailed description).
4. Research Results and Discussion
According to our site survey, there are 1613 villages that need new sewage facilities, 38 villages that can be connected to urban sewage treatment plants, and 505 villages that need to repair or renovate existing sewage facilities. See Supplementary Figure S3 and Supplementary Table S1 for specific data.
4.1. Rural Domestic Sewage Emission Standard
At present, unified discharge standards are still lacking for rural domestic wastewater treatment facilities in China. In addition, meeting the urban sewage treatment plant pollutant discharge standards (GB18918-2002) (level B or A standard) in the construction of sewage treatment facilities is still challenging [47,48]. Therefore, the drainage characteristics of different categories of villages and the current economic status of various wastewater treatment technologies are considered in Wuhan city. The effluent concentrations of rural village wastewater treatment plants are assessed using seven indicators, namely, chemical oxygen demand (COD), acidity (pH), suspended solids (SS), ammonium (NH4+-N), total phosphorus (TP), total nitrogen (TN), animal fats and vegetable oils. It should be noted that TN and TP are considered only for the VRLS areas, while animal fats and vegetable oils are considered for the featured villages involved in tourism catering services [42] (Table 1).
4.2. General Analysis of Rural Domestic Sewage Management in Jiangxia District
According to the Jiangxia District Government’s goal: in 2020, the district’s administrative sewage treatment had a coverage rate of more than 80%, and the village sewage treatment had a rate of more than 70%. In addition, some administrative villages with conditions need to achieve full collection and treatment of sewage and to establish a long-term mechanism for the management and operation of village sewage treatment facilities. The guiding principle of rural life sewage treatment in Jiangxia District for the 2018–2020 period highlighted the importance of sewage treatment plans for the administrative villages to achieve a household water treatment rate of over 85%, taking into account the order of key villages, featured villages and ordinary villages, as well as the ecologically sensitive areas and large villages.
4.3. Cost-Effectiveness Analysis
The three-year sewage treatment in rural Jiangxia District can effectively improve the appearance of villages in Jiangxia District, solve the problem of arbitrary discharge of rural sewage, improve the ecological environment and living environment in rural Jiangxia District, and play an important role in the protection of water resources in the region. In addition, after the implementation of the three-year action plan for the management of domestic sewage in rural villages in Jiangxia District, 24,334 m3 of domestic sewage from 2156 villages can be treated every day, benefiting 90,190 households, and reducing the total amount of pollutants entering the lake system, thereby ensuring effective protection of the quality of water bodies in Jiangxia District. Moreover, it addresses the problem of arbitrary discharge of rural domestic sewage, restores the ecological function of rivers, ditches and ponds, and improves the self-purification capacity of water bodies, providing local farmers with a good living environment. Table 2 shows the reduction rates of pollutants in rural villages’ domestic sewage effluents.
Figure 4 shows the temporal changes in the quality of water bodies in Jiangxia District. The water quality was classified in this study based on the surface water environmental quality standards [49]. It can be seen from Figure 4 that, before the implementation of the special plan for rural domestic sewage, 8.7% of the water surface showed poor water quality (V) in Jiangxia District, which was improved following the implementation of the special plan, increasing gradually the proportions of water II and III quality classes. Therefore, the implementation of the special plan for rural domestic sewage is conducive to improving water quality in Jiangxia District.
The results demonstrated that the implementation of rural village domestic sewage management in Jiangxia District plays a positive role in reducing regional soil erosion, suppressing surface source pollution, improving sanitary conditions, and raising public awareness of environmental health protection, with good social and environmental benefits.
4.4. Existing Problems and Analysis
Combined with the rural domestic wastewater treatment planning in other areas, the following main problems were identified in rural domestic wastewater treatment in Jiangxia District, Wuhan City, in this study [50,51,52,53].
4.4.1. Rural Domestic Sewage Is Commonly Discharged without Restriction
Most villages in Jiangxia District lack sewage discharge pipes, treatment systems and old public restroom renovation projects. In addition, sewage is discharged from the VRLS areas into rivers without restriction, resulting in water pollution of lakes.
4.4.2. Complexity of Village Domestic Wastewater Treatment
Rural sewage treatment is complex due to the complex topographical characteristics, the degree of settlement and the characteristics of receiving water bodies in Jiangxia District. For instance, Jiangxia District is characterized by low and high topography, with the presence of plains in the eastern and western parts and hills in the central and northern parts, resulting in considerable variation in the topography in Jiangxia District.
4.4.3. Lack of Sewerage Network in Rural Areas
The sewage collection rate in the villages is generally low. In addition, some of the domestic sewage drainage networks are exposed and deteriorated. The combined rainwater and sewage collection mode and the overflowing sewage phenomenon in the rainy season lead to more serious secondary pollution, affecting negatively the effects of domestic sewage management in these villages.
4.4.4. Problems Related to The Construction of New Sewage Treatment Facilities
Generally, it is challenging to construct sewage networks in villages with high population density and complex topography. In addition, some septic tanks used by rural residents do not meet the requirements and need to be rectified, while other septic tanks of rural residents are buried directly below the house foundation, making it difficult to connect to the sewage network.
4.4.5. Problems Related to The Operation and Management of Domestic Sewage Treatment Facilities
(1) Low-level Operation Maintenance and Management of Domestic Sewage Treatment Facilities
The lack of professional technical and management personnel has led to low levels of operation maintenance and management of some achieved domestic sewage treatment facilities (e.g., weeds growing in the artificial wetlands, lack of dredging of the pipe networks, and absence of daily operation-related information on facilities);
(2) Lack of Funding for Operation and Maintenance
As in other areas, the Jiangxia District Government’s financial assistance funds can only cover part of the maintenance costs. In addition, the standards of long-term management and maintenance funding sources are not proposed.
4.5. Solutions
The current problems and targeted measures are shown in Table 3.
According to the existing land planning of Jiangxia District, and combined with the results of in situ investigations conducted in villages of Jiangxia District, specific measures and annual implementation plans were proposed for each type of village. The principles used in the proposition of specific measures are as follows:
4.5.1. Systematic Coordination of Work and Classification Guidance
Government planning should be coordinated with water environment protection, new rural construction and village layout planning. According to the environmental standards of rural sewage receiving water bodies and the overall goal of “increasing II, preserving III, reducing IV and eliminating V” of water quality of Wuhan lakes [30], the village sewage collection mode, discharge standards and discharge volume are determined by the collected in situ investigation-derived data and existing research results.
4.5.2. Adaptation to Local Conditions, Economic Rationalization and Flexible Planning
According to the existing wastewater treatment projects, the implementation cost of pipe networks is often more than two times that of wastewater treatment facilities. Therefore, it is of great importance to achieve cost-effective sewage treatment and pipe network implementations. The administrative village should be first considered as a unit according to the topographical characteristics, size and discharge requirements of the village, then selecting the appropriate sewage collection and treatment mode, taking into account the capacity of the township sewage treatment plant.
4.5.3. Sewage Treatment According to the Importance of Villages
The government should give priority to the treatment of “VRLS”, key villages, and special villages. In addition, villages to be demolished and merged should be included in the list of villages where septic tank renovation and toilet conversion projects are expected to be implemented. The government needs to focus on key villages and coordinate the management of domestic sewage in rural villages.
4.5.4. Rural Sewage Management Team Was Established by Way of Cross-Departmental Coordination
The government needs to integrate the resources of the environmental protection department, the agricultural commission department, the sanitation department and other areas, coordinate the relevant project funds and implementation plans of various departments, coordinate the relevant work of various departments, develop a unified rural domestic sewage remediation work and coordination program, to avoid the phenomenon of new facilities without management.
4.5.5. Interdepartmental Rural Sewage Management Team
The government needs to involve professional environmental protection enterprises to evaluate and supervise the operation of domestic sewage, and to establish reward and penalty schemes to ensure the effective operation of sewage facilities.
5. Conclusions and Prospects
In summary, this paper illustrates a way of collecting and treating rural domestic wastewater, using Wuhan Jiangxia District as an example. The rural areas in the region are divided into key villages, characteristic villages and ordinary villages, and the domestic sewage treatment projects are carried out for them in order of priority. At the same time, different collection modes are adopted for villages according to their distribution. After the implementation of the rural domestic sewage treatment project, not only has the volume of direct discharge of domestic sewage and the discharge of pollutants in the water body been greatly reduced, the water quality indicators of the surrounding lakes in Jiangxia District have also improved significantly, with the proportion of Class II and Class III quality water bodies rising significantly, the proportion of Class IV water bodies decreasing, and the disappearance of poor Class V water bodies. Therefore, the special planning of domestic sewage in Jiangxia District has achieved better results.
Along with the construction of a suitable environment and precision poverty alleviation in the Yangtze River Basin in China, rural domestic sewage treatment is required in various villages. The special action plan for rural domestic sewage treatment at the district and county levels requires the coordination and guidance of relevant departments to ensure comprehensive local rural domestic sewage treatment. The planning process conducted in Jiangxia District, Wuhan, provided further insights into the local actual situation to ensure a continuous improvement of the quality of the living environment and water bodies for rural residents based on government management at the district and village levels by improving rural domestic sewage treatment. This study explores a reproducible and sustainable rural domestic sewage treatment mode adapted to China’s rural area characteristics. In the past two years, the planning ideas and classification model proposed in this paper have been widely used in other administrative districts of Wuhan, such as Huangpi district and Xinzhou District, which are located in suburban or rural areas. Many families in these rural areas need sewage treatment, and the overall scale is equivalent to Jiangxia District. The method of this paper has achieved good results in the special sewage treatment in administrative areas of this scale and has played a positive role in the treatment of rural domestic sewage and the improvement of surface water quality.
There is still a long way to go for rural domestic sewage treatment in the Yangtze River Basin, and the compilation of special plans for rural domestic sewage treatment in districts and counties can effectively solve the problem of disunity of planning in many departments. This study, guided by the actual situation of local rural areas and scientific norms, leads the rural sewage treatment work by strengthening the overall planning of urban and rural areas, selecting the appropriate sewage treatment mode and technical route, as well as strengthening the management and protection mechanism. This research has far-reaching significance for improving rural sewage treatment levels, protecting rural water environment, and building a beautiful and livable new countryside.
Although this study has made achievements in the management of rural domestic sewage in Jiangxia District and successfully extended it to the management of rural domestic sewage in other administrative regions of Wuhan, there are still some limitations, including the following two main aspects:
(I) Limitation of the geographical area. Since the cases in this study are from the Yangtze River basin, which is relatively rich in water resources, humid climate, relatively dense population and relatively developed agriculture, the methods mentioned in the article may not apply to those areas with arid and sparsely distributed populations. Therefore, the relevant planning ideas and management objectives developed in this study cannot be directly replicated in other watersheds or administrative regions located in different physical geographic conditions. It is necessary to combine the physical geographic factors, population and socio-economic conditions of the study area and modify the methods of the article accordingly to meet the realistic requirements of the study area;
(II) Limitation of time. The rural domestic wastewater planning in the article is short-term planning of three years, which may not apply to those areas that require long-term planning of rural domestic wastewater (five, ten, or even longer years). This is because changes in the population base will be an important influencing factor in long-term planning. The rural population can fluctuate greatly, including population migration and population misrepresentation, which can lead to large differences between the total calculated rural domestic wastewater discharges and the actual discharges generated, seriously affecting the effectiveness of the planning.
At present, we only apply GIS to the survey and study of the study area. In the future, on the one hand, we can use more analytical tools, such as big data and artificial intelligence, to predict the change in the population base and the development of the economy in the study area, to get more accurate raw data. On the other hand, rural domestic sewage treatment should be combined with new technologies. Developing a set of low-cost and high-efficiency domestic sewage treatment technologies suitable for rural areas according to the actual situation is the way to build a resource-saving and environment-friendly rural environment.
Conceptualization, N.D., Q.F. and J.X.; methodology, N.D. and Q.F.; software, L.W., J.X. and F.Y.; validation, N.D., F.Y. and H.D.; formal analysis, Q.F., N.D. and J.X.; investigation, F.Y., L.W. and Q.F.; resources, N.D., Q.F. and H.D., data curation, F.Y., N.D. and J.X.; writing—original draft preparation, Q.F.; writing—review and editing, N.D. and J.X.; visualization, N.D. and F.Y.; project administration, Q.F.; funding acquisition, N.D. and Q.F. All authors have read and agreed to the published version of the manuscript.
Not applicable.
Not applicable.
Data is contained within the article.
The present research was conducted at the College of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China. The first author acknowledges the technical support for this research from Innovation Academy of Precision Measurement Science and Technology, CAS, Wuhan 430071, China and Wuhan Zhi Huiyuan Environmental Technology Co., Ltd., China.
The authors declare no conflict of interest.
Footnotes
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Enlarge this image.Figure 2. The technical route of rural domestic sewage treatment plan in Jiangxia District.
Threshold concentration standards of domestic sewage discharge from villages in Wuhan City.
| Index | SS | COD | Animal and |
pH | NH4+-N | TN b | TP b | |
|---|---|---|---|---|---|---|---|---|
| Key Villages | Villages around Town | CJ343-2010 C [ |
||||||
| VRLS | GB18918-2002 1A [ |
|||||||
| Large Villages | GB18918-2002 1B [ |
|||||||
| Featured Villages | GB18918-2002 1B [ |
|||||||
| Ordinary Villages | Medium-sized villages | GB18918-2002 1B [ |
||||||
| Small Villages | GB18918-2002 2 [ |
|||||||
a: Applicable only to the featured villages sewage treatment facilities. b: Applicable only to the sewage treatment facilities in the VRLS areas.
Summary of Pollutants Reduction for Domestic Sewage Treatment in Rural Villages of Jiangxia District.
| Sub-District | Sewage Collection Volume (m3/a) | Emission Reduction of Pollutants (m3/a) | ||||
|---|---|---|---|---|---|---|
| COD | SS | NH4+-N | TN | TP | ||
| Wulijie | 410,639.6 | 98.6 | 53.4 | 6.2 | 8.2 | 1.6 |
| Shuan | 598,235 | 143.6 | 77.8 | 9 | 12 | 2.4 |
| Fasi | 728,540 | 174.8 | 94.7 | 10.9 | 14.6 | 2.9 |
| Zhengdian | 1,388,957.1 | 333.3 | 180.6 | 20.8 | 27.8 | 5.6 |
| Wulongquan | 824,653.6 | 197.9 | 107.2 | 12.4 | 16.5 | 3.3 |
| Shanpo | 1,131,865 | 271.6 | 147.1 | 17 | 22.6 | 4.5 |
| Anshan | 542,390 | 130.2 | 70.5 | 8.1 | 10.8 | 2.2 |
| Jinkou | 1,562,684 | 375 | 203.1 | 23.4 | 31.3 | 6.3 |
| Jinshui | 268,640 | 64.5 | 34.9 | 4 | 6.6 | 1.3 |
| Zhifang | 164,980 | 39.6 | 21.4 | 2.5 | 3.3 | 0.7 |
| Husi | 765,770 | 183.8 | 99.6 | 11.5 | 15.3 | 3.1 |
| Liangzihu | 164,980 | 39.6 | 21.4 | 2.5 | 3.3 | 0.7 |
| Jiangxia | 329,595 | 79.1 | 42.8 | 4.9 | 6.6 | 1.3 |
| Total | 8,881,929.3 | 2131.7 | 1154.6 | 133.3 | 177.6 | 35.6 |
Current problems and measures.
| Current Status and Problems | Main Measures |
|---|---|
| Villages to be demolished and annexed | Not included in sewage management planning |
| Villages within 0.5 km of the urban areas or township sewage treatment plants with suitable topographical conditions and sufficient sewage influent capacity | Construction of sewage network and septic tank (if necessary) only |
| Villages with damaged facilities, unstable operation or water output that does not meet current standards | Facility improvements to ensure that the effluent meets existing discharge and utilization standards |
| Villages with blocked, damaged, or poorly covered sewage collection pipes and separate rainwater and sewage pipes | Maintenance, repair and expansion of pipe network, rainwater and sewage diversion |
| Villages with high population densities or located in the VRLS areas with the potential for developing agricultural tourism | Classification according to as the priority |
| Villages located in non-ecologically sensitive areas, as well as scattered and likely demolished villages | Classified as a backward treatment plan, and adopting an economical sewage treatment model |
| Villages where the public restroom improvement project is implemented, with comprehensive environmental improvement, beautiful country-side construction, and complex field construction | If the domestic sewage treatment project meets the requirements of the special plan, no adjustment is required; otherwise, the project needs to be adjusted according to the actual situation of the villages |
| Villages with inappropriate maintenance of sewage treatment facilities and pipe networks | Professional team is needed to ensure effective maintenance. Establish reward and punishment methods, and implement maintenance funds |
Supplementary Materials
The following supporting information can be downloaded at:
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; Ding, Hua 3 1 College of Resource and Environmental Engineering, School of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
2 Innovation Academy of Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China
3 Wuhan Zhi Huiyuan Environmental Technology Co., Ltd., Wuhan 430000, China