The Sustainable Development Path of Ecological Treatment Technology for Rural Sewage: A Bibliometric Perspective

Abstract

Due to the promotion of sustainable development goals and rapid economic development, the problem of rural sewage treatment is becoming increasingly severe. In order to understand the research hotspots, progress, and trends of ecological treatment technology for rural sewage at home and abroad, this article analyzes relevant literature published between 2000 and 2023 based on the core collection databases of China National Knowledge Infrastructure (CNKI) and Web of Science (WOS) using VOSviewer and CiteSpace visualization software. The research results indicate a continuous increase in attention to ecological treatment technologies for rural sewage, both domestically and internationally. Although China started relatively late in this field, it has developed rapidly. “China Water & Wastewater” has had a significant impact in related fields domestically, and a top-tier journal has not yet been founded by China internationally. The collaboration between research authors and institutions is evident, with CNKI focusing on exploring specific governance technologies, while WOS pays more attention to the overall governance framework and critical technologies. The research hotspots of ecological treatment technology for future village and town sewage include specific treatment technologies, treatment efficiency, overall treatment strategies, and environmental impact assessments. At the same time, cross-regional and cross-border cooperation should be strengthened, interdisciplinary collaboration should be promoted, open cooperation platforms should be established, diversified publishing channels should be supported, and research on microbial communities and non-point source pollution should be deepened.

1. Introduction

Urban sewage treatment has garnered significant focus due to its advanced technologies and infrastructure, while rural sewage treatment continues to pose considerable challenges [1]. Rural areas typically encounter more complicated wastewater management issues, such as insufficient infrastructure, limited resources, and varied pollution sources [2]. These challenges make it essential to explore more adaptable and sustainable treatment solutions, particularly ecological treatment technologies. Ecological treatment technology refers to the use of natural processes and systems, such as wetlands, microbial communities, and aquatic plants, to treat and manage wastewater [3]. These technologies offer an environmentally friendly, cost-effective, and sustainable approach to wastewater treatment, especially in rural areas. Ecological treatment technology can convert nutrients in sewage into fertilizer resources, effectively solving the problem of incomplete sewage treatment in villages and towns [4]. Traditional rural domestic sewage treatment mainly includes two methods: centralized and decentralized. Ecological treatment technology, as a sustainable treatment method, can be integrated into centralized and decentralized treatment systems. In centralized systems, ecological treatment technology can be used for deep treatment of wastewater to improve effluent quality [5,6]. In a decentralized system, it can fully leverage the advantages of low investment and low operating costs to better meet the actual needs of rural areas [7,8,9]. Compared with traditional centralized treatment methods, decentralized sewage ecological treatment technology has the advantages of low investment and operation costs and muscular flexibility. It can better cope with the problem of incomplete sewage treatment in rural areas, reduce pollutant emissions, protect the local water environment, promote sustainable utilization of water resources, and provide economically practical sewage treatment solutions for rural areas [10]. With the rapid progress of the times and continuous technological innovation, using advanced visualization software and bibliometric methods, we can break through the thinking limitations in traditional research and provide a new perspective and method for studying ecological treatment technology for rural sewage. By visualizing the ecological treatment technology of rural sewage, not only can we deepen the systematic understanding of this field and promote the depth and breadth of research, but we can also reveal the current development core and trends, provide strong support for predicting future technological reform directions, and accelerate the sustainable development of rural sewage treatment technology.

Bibliometrics is a method of studying literature’s quantity, distribution, and relationships through statistical analysis of literature data (such as publication quantity, citation frequency, and journal impact factor) to evaluate scientific research achievements, influence, and field development trends [11]. Zhang, Y. [12] was the first in China National Knowledge Infrastructure (CNKI) to combine bibliometric methods with sewage treatment and pollution prevention, providing a good reference and inspiration for subsequent researchers. In the earlier phase of research, conducted a visual analysis of pharmaceuticals and personal care products (PPCPs) based on the Web of Science (WOS) database, predicted the future development trend of PPCPs, and provided a reference for future researchers. The existing bibliometric literature mainly focuses on pollutant prevention and control, while quantitative analysis of rural sewage’s ecological treatment technology system is still insufficient. Therefore, this study conducts a bibliometric analysis of the ecological treatment technology of dispersed sewage in villages and towns, which has profound significance for promoting research progress in advancing technological development.

Building on the research of Chen, C. M. (2005) and Bukar U A et al. (2023), this study uses CiteSpace [13,14] and VOSviewer [15] visualization analysis software to sort and analyze high-frequency keywords, prominent trends, and cluster visualization of relevant literature in CNKI and WOS, and draw relevant maps. This study adopts a bibliometric perspective to analyze the literature on rural sewage treatment, focusing on trends in publication volume over time and geographic distribution of research. This helps to see the development trend of ecological treatment of rural sewage, comprehensively understand the research hotspots and development trends in the field of rural sewage ecological treatment technology, provide a reference for future research directions, and provide scientific policy suggestions and practical guidance for decision-makers, promoting the promotion and improvement of rural sewage ecological treatment technology in practical applications.

2. Data Processing and Methods

This article was retrieved on 1 April 2024. The literature search criteria for CNKI were set as “Topic = Sewage Ecological Treatment Technology AND Topic = Rural + Countryside + Village AND Publication Time 1 January 2000 to 31 December 2023 (exact match)”, and a total of 1653 literature were retrieved. The literature search criteria for WOS were set as “Topic = Sewage Ecological Treatment Technology AND Topic = Rural + Countryside + Village AND Year Published = 2000–2023”, and 804 articles were retrieved.

After retrieving relevant literature, we conducted a manual screening process. The screening criteria were as follows: We checked their treatment areas for papers on sewage ecological treatment technology to ensure they pertained to rural areas. Since many rural sewage ecological treatment methods originated from urban sewage treatment research, we retained papers covering urban and rural sewage treatment technologies. Through this screening, we excluded 28 and 19 articles from the CNKI and WOS databases, respectively. In the end, 1625 articles from CNKI and 785 from WOS remained, amounting to 2410 articles for subsequent analysis.

We employed VOSviewer 1.6.20 and CiteSpace 6.31 (including CiteSpace V) to analyze rural sewage ecological treatment technology literature visually. As Chen (2004, 2005) [13,14] demonstrated, CiteSpace is highly effective in literature co-occurrence, frequency, and clustering analyses. In this study, CiteSpace was used to conduct keyword co-occurrence analysis on literature in CNKI and WOS databases to identify research hotspots; by analyzing the co-occurrence of countries and institutions, the geographical distribution and cooperation network of the research are revealed; by utilizing its generated visual knowledge graph, the structure and development trajectory of the research field of rural sewage ecological treatment technology can be visually presented, providing strong support for subsequent research. Similarly, as Bukar [15] described, VOSviewer excels at creating co-occurrence and density maps. In this study, VOSviewer was utilized to perform collinear graph analysis on the keywords of ecological treatment technology for village and town sewage in CNKI and WOS. Through its density visualization function, nodes were presented with different colors based on the density of items at their locations, clearly showing the distribution of research hotspots. The complementary features of these two tools enable a comprehensive and in-depth analysis of rural sewage ecological treatment technology literature, enhancing the reliability of our research methods.

In our study, “centrality” refers to intermediary centrality. It measures how often a node lies on the shortest path between other nodes in a network formed by keyword co-occurrence. Keywords with high centrality act as crucial connectors in the research field, linking different research directions. They not only represent research hotspots but also indicate potential future research paths. We calculated centrality using the formula:

$$C_B(n)={\sum }_{s\ne t\ne n}{\displaystyle \frac{g_{st}(n)}{g_{st}}}$$

$g_{st}$: The number of shortest paths between nodes s and t;

$g_{st}(n)$: The number of shortest paths between nodes s and t that pass through node n.

3. Results and Discussion

3.1. Research Status

3.1.1. Analysis of Publication Volume

In the hot field of ecological treatment technology for rural sewage, the number of publications can reflect the research status, trends, and activity, reveal this field’s development status and achievements, and provide a basis for evaluating the research heat and dynamics. Import the annual publication volume and cumulative publication volume of the WOS database and CNKI database into an Excel spreadsheet and generate a statistical chart of the annual publication volume of rural sewage ecological treatment technology literature from 2000 to 2023 (Figure 1).

According to Figure 1, CNKI data showed a slow growth trend from 2000 to 2005, a sudden increase in 2006, and a fluctuating growth trend from 2006 to 2014. It showed a downward trend from 2014 to 2016; although it grew again in the following two years and reached the highest annual publication volume in 2018, it still showed a fluctuating downward trend after that. Before 2008, the growth and fluctuation of WOS data were relatively small, and the number of publications was also deficient. In 2009, there was a sudden slight increase, followed by a slow growth trend until 2014, and after 2014, it showed a rapid growth trend.

The annual publication volume of CNKI and WOS showed a fluctuating upward trend before 2014, but different changes occurred after 2014. CNKI began to show a fluctuating downward trend while WOS steadily increased. There are two possible reasons for the occurrence. Some conference papers were not added to the CNKI database but entered other databases such as Wanfang Data and VIP journals, and the other is that many domestic scholars switched to English SCI source journals. The reason for this may be that domestic scholars are paying more and more attention to SCI journal publications, so they have switched to English SCI journals, decreasing the number of papers in the CNKI database [16].

Simultaneously conducting a trend analysis on the annual cumulative publication volume, CNKI’s annual publication volume shows a linear upward trend. In contrast, WOS’s annual cumulative publication volume shows an exponential upward trend. As of 2023, domestic attention to ecological treatment technology for rural sewage is gradually increasing, while international attention is significantly increasing. Overall, the research attention in this field is steadily increasing.

3.1.2. Analysis of Author

Conducting statistical analysis on the authors of ecological treatment technology for rural sewage can help identify critical scholars and their research networks in the field. Two thousand four hundred ten research articles from 6870 authors from 79 countries and regions were compiled into the WOS and CNKI databases, and the publication data of the top ten authors were selected for analysis (

Table 1. Author’s publication volume and institutions of ecological wastewater treatment research in WOS and CNKI.

Order Number	Author	Number of Posts	Unit	Author	Number of Posts	Unit
1	Lu Xiwu	11	Southeast University	Xu Weiliu	9	Jiangsu Shuangdeng Paper Industry Co., Ltd.
2	Yang Jian	9	China University of Geosciences	Li Fengzhu	9	Jiangsu Shuangdeng Paper Industry Co., Ltd.
3	Xie Xianjun	8	China University of Geosciences	He feng	6	Institute of Hydrobiology, Chinese Academy of Sciences
4	Xu Rui	8	China University of Geosciences	Li Jinzhong	6	Tianjin Water Conservancy Research Institute
5	Wang Kun	7	China University of Geosciences	Wu Yuhui	5	Jiangsu Shuangdeng Paper Industry Co., Ltd.
6	Liang Yujun	6	China University of Geosciences	Zhai Jun	5	Chongqing University
7	Yang Gui	6	China University of Geosciences	Liu Wei	4	School of Environment, Tsinghua University
8	Liu Xiaohui	6	Tsinghua University	Liu Xiang	4	School of Environment, Tsinghua University
9	Liu Ying	6	Chinese Research Academy of Environmental Sciences	Xu Kangning	4	School of Environment, Tsinghua University
10	Lu Shaoyong	6	Chinese Research Academy of Environmental Sciences	Wang Chengwen	4	School of Environment, Tsinghua University

). Perform visual clustering analysis on the co-authors in the literature of WOS and CNKI and create co-occurrence word graphs for CNKI and WOS authors, as shown in Figure 2 and Figure 3.

The data in the table showed that authors with high publication volumes are generally from the same school/institution. For example, Yang Jian, Xie Xianjun, Xu Rui, and other scholars who have published multiple articles in WOS are all scholars from China University of Geosciences; Xu Weiliu, Li Fengchong, and Wu Yuhui, who have published multiple papers in CNKI, are all employees of Jiangsu Shuangdeng Paper Industry Co., Ltd. Generally, the number of articles published by authors does not exceed 5. For the same research area, studies with around 3–4 articles are already very comprehensive, and the practical significance of further research may be relatively limited.

Due to the large number of co-authors and the complexity of the collaboration, both WOS and CNKI authors were set to appear at least three times during the drawing process. As shown in the above figure, the time scale graph in the lower right corner is the time limit automatically selected by VOSviewer, which conforms to the author’s publication time. The circle size in the figure represents the number of articles published, the sphere’s color represents the author’s publication time, the line’s color represents the start time of the collaboration, and the thickness of the line represents the collaboration strength [17]. A node connected by several lines represents how many people have collaborated with the author. From the period in the bottom right corner, it can be seen that the authors who published three or more related field literature on CNKI began to appear in 2005, which is an extended period. However, WOS indicates that very few authors published three or more related field literature before 2017.

From 2000 to 2023, CNKI published more than three research papers on ecological sewage treatment technology in China, and the cooperation among scholars is relatively scattered. There are 3761 scholars involved in this related research, but more than half of them have independently published papers. Research on sewage ecological treatment is often conducted precisely for a specific region or through a literature review, and scholars tend to focus more on independent research. However, most scholars who have published three or more articles in WOS have cooperative relationships. This may be due to the need for multiple scholars to conduct research together in a specific direction of sewage ecological treatment, ultimately forming a collaborative network among scholars. However, the scope of cooperation is mainly limited to the same unit. For example, scholars Yang Jian and Xu Rui from the China University of Geosciences and Lu Ying and Lu Shaoyong from the China Academy of Environmental Sciences.

The figures and table show that the author exhibits a phenomenon of regional clustering cooperation, which may lead to slow research progress and long research cycles in their article. The top ten authors are all Chinese, which indicates that China has a high degree of research activity in ecological treatment technology of rural sewage, and Chinese scholars occupy an essential position in this field. Domestic scholars publish independently, while foreign scholars publish in groups within the same organization. It is suggested that domestic scholars consider increasing collaborative research to enhance the comprehensiveness and influence of their research. By collaborating with other scholars or institutions, resources can be better integrated, perspectives can be expanded, and research results’ quality and publication opportunities may be improved. Foreign scholars can consider strengthening interdisciplinary and transnational cooperation, expanding their research fields and application scope. Although internal collaboration within a unit has advantages, collaborating with researchers from different backgrounds can help introduce new perspectives and methods, promoting more comprehensive and innovative research outcomes.

3.1.3. Analysis of Issuing Countries

The publishing country reveals the geographical distribution of global scientific research forces, reflecting differences in international cooperation and regional research. CNKI is China’s largest comprehensive literature database, mainly collecting academic literature and research results from China. There are relatively few publications by foreign authors, so we only analyzed the literature retrieved by WOS between countries. Seventy-nine countries, including China, the United States, India, Canada, and South Korea, published research articles on sewage ecological treatment technology.

Analyze the publication situation of different countries from 2000 to 2023. As shown in

Table 2. Top 10 countries in terms of publication volume of sewage ecological treatment technology from 2000 to 2023.

Country	Post Volume	Percentage	Time for the First Post
China	502	63.95%	2004
India	50	6.37%	2007
USA	47	5.99%	2000
Poland	42	5.35%	2003
Japan	25	3.18%	2007
South Korea	23	2.93%	2008
Canada	21	2.68%	2009
Germany	20	2.55%	2006
England	16	2.04%	2000
Spain	14	1.78%	2007

, among the top 10 countries in terms of published papers, China ranks first with 502 papers. India ranks second with 50 published articles. In the time scale of this study, the earliest publication by the United States and England was in 2000; China first published relevant research literature in 2004, but the number of publications has since proliferated, significantly surpassing other countries. This phenomenon indicates that although China started relatively late in this field, it has rapidly progressed and achieved a leading position. Currently, the proportion of publications in China has reached 63.95%, exceeding the total of other countries, demonstrating China’s in-depth research and rich experience in rural sewage treatment technology. Given the complex terrain and numerous rural areas in our country, with a wide variety of technologies, there is still ample space for comprehensive and sustained research in the future.

Use CiteSpace to graph the cooperation relationship between sewage ecological treatment technologies in various countries from 2000 to 2023 (Figure 4). The circle size in the graph represents the activity level and number of publications of a particular country, and the color from light to dark represents the publication time of the country. The color of the connecting line between countries represents the time of cooperation. The color from red to blue is from 2000 to 2023, and the bluer the color, the later the cooperation time between countries. The purple outer circle represents its high centrality; China, the United States, South Korea, India, England, and Germany have strong centrality. Among them, the circle of China is particularly prominent, indicating that China leads in the number of publications in each publication year and has close ties with other countries. The intricate connections between countries indicate that research in this field is closely linked, and cooperation spans a long time. In future research, scholars worldwide should cooperate closely on rural sewage ecological treatment. This collaboration will advance such technologies at home and abroad, contributing to global rural sewage treatment and environmental protection.

3.1.4. Analysis of Published Journals

Journal analysis of published articles helps identify major academic exchange platforms and high-impact publishing channels, providing essential references for the dissemination and quality evaluation of research results [18]. We analyzed the relevant information from 1772 academic journals collected from CNKI and WOS. According to the eight items of “ranking”, “institution name”, “publication cycle”, “founding time”, “host unit or region”, “composite impact factor”, “publication volume”, and “proportion”, the top 10 journals with the highest publication volume were counted and compiled into

Table 3. Information table of top 10 research journals on ecological wastewater treatment technology in villages and towns in CNKI.

Order Number	Organization Name	Publication Cycle	Founding Time	Sponsor Unit or Region	IF	Post Volume	Percentage
1	China Water and Wastewater	semimonthly	1985	China Municipal Engineering North China Design Research Institute Co., Ltd.; National Engineering Research Center for Urban Water and Wastewater	1.554	48	2.95%
2	Journal of Anhui Agricultural Sciences	semimonthly	1961	Anhui Academy of Agricultural Sciences	0.9	28	1.72%
3	Water and Wastewater Engineering	monthly	1964	Asia-pacific Institute of Construction Science and Technology Information; China Civil Engineering Society	1.434	28	1.72%
4	Resources Economization and Environmental Protection	monthly	1983	Tianjin Energy Conservation Association	0.9	23	1.42%
5	Environmental Engineering	monthly	1982	Central Research Institute of Building and Construction Co., Ltd.; Environmental Engineering Branch of Chinese Society for Environmental Sciences	2.83	19	1.17%
6	Environmental Science and Management	monthly	1975	Heilongjiang Provincial Research Institute of Environmental Sciences	0.702	19	1.17%
7	Guangdong Chemical Industry	semimonthly	1974	Institute of Chemical Engineering Guangdong Academy of Sciences	0.496	17	1.05%
8	Technology of Water Treatment	monthly	1975	Hangzhou Water Treatment Technology Development Center Co., Ltd.	1.933	14	0.86%
9	Environment and Development	bimonthly	1989	The Inner Mongolia Autonomous Region Research Institute of Ecological and Environmental Sciences	0.729	13	0.80%
10	Water Purification Technology	monthly	1982	Shanghai Water Purification Technology Society; Shanghai Urban Water Resources Development and Utilization National Engineering Center Co., Ltd.	1.348	12	0.74%

and

Table 4. Information table of top 10 research journals on ecological wastewater treatment technology in villages and towns in WOS.

Order Number	Organization Name	Publication Cycle	Founding Time	Sponsor Unit or Region	IF	Post Volume	Percentage
1	Ecological Engineering	semimonthly	1996	Holland	3.8	75	9.55%
2	Science of The Total Environment	semimonthly	1972	Holland	9.8	56	7.13%
3	Environmental Science and Pollution Research	bimonthly	1994	Germany	5.8	42	5.35%
4	Water Science And Technology	semimonthly	1981	England	2.7	30	3.82%
5	Chemosphere	weekly	1972	England	8.8	25	3.18%
6	Environmental Pollution	monthly	1987	England	8.9	24	3.06%
7	Environmental Science and Technology	biweekly	1967	America	11.4	23	2.93%
8	Journal of Ecological Engineering			Poland	1.3	22	2.80%
9	Journal of Environmental Management	semimonthly	1973	England	8.7	20	2.55%
10	Journal of Hazardous Materials	semimonthly	1975	Holland	13.6	18	2.29%

.

The journals with the highest number of research papers published in sewage ecological treatment technology are “China Water & Wastewater” and “Ecological Engineering”, ranking first in CNKI and WOS. From 2000 to 2023, 48 and 75 journal papers were included, accounting for 2.95% and 9.55%, respectively. Ranked in the top two on CNKI, “China Water & Wastewater” and “Water & Wastewater Engineering” are both academic journals with high visibility and recognition in sewage ecological treatment. The former topic includes columns on environmental science and resource utilization, architectural science and engineering, water conservancy and hydropower engineering, organic chemical engineering, and light industry handicrafts. It publishes new technologies and achievements in domestic sewage treatment for ecological environment workers and introduces new methods, trends, and development directions of sewage treatment technology. As a magazine closely related to sewage treatment, “Water & Wastewater Engineering” provides more targeted research in sewage. It focuses on introducing relevant research on urban water supply and drainage, describing comprehensive industry information on water supply and drainage, and providing reports and introductions on the attention paid to sponge city construction and the construction plan of sewage treatment plants. These two journals have become the first choice for many scholars when publishing relevant literature, making significant contributions to developing research related to sewage ecological treatment, and providing a reference for subsequent researchers to choose journals for study and submission.

“Ecological Engineering”, WOS’s most widely published journal, covers bioengineering, restoration ecology, ecological protection, and biological system restoration. It provides reference and guidance for many scholars in current research on sewage ecology internationally. From the perspective of impact factors, Chinese literature generally ranges from 0.5 to 3, while English journals generally range from 5 to 10. Some articles can achieve even higher impact factors, such as the “Journal of Hazardous Materials”, which has a composite impact factor of 13.6. The top ten founding countries of journals in WOS include the United Kingdom, the Netherlands, the United States, Germany, and Poland, with no founding in China. It is recommended that domestic journals strengthen cooperation with international research institutions, improve the quality and innovation of articles, focus on the accuracy of English abstracts and keywords, actively participate in international conferences and collaborative projects, and enhance the visibility and influence of journals.

3.1.5. Analysis of Issuing Institutions

Analyzing the collaborative network of publishing institutions can provide insights into the contribution levels of various research institutions and their influence on the academic community [19]. The processed text data is imported into CiteSpace 6.3.1 software. Due to the large amount of data, the analysis is divided into two time periods for observation, specifically from January 2000 to December 2011 and from January 2012 to December 2023.

According to Figure 5, although there are many nodes and connections between them, most institutions still publish papers independently. Node connections mainly exist among large research groups composed of universities such as Beijing University of Chemical Technology, Southeast University, and Beijing Forestry University. This indicates that although a sizeable collaborative network emerged from 2000 to 2011, many individual papers were still published by other institutions. This led to drawbacks such as a single research perspective, outdated technology, and results that failed to meet expectations. Secondly, it can be seen from Figure 6 that from 2000 to 2011, in addition to the cooperation network formed by the Chinese Academy of Sciences, the rest of the nodes forming the connection were mainly composed of foreign countries, institutions, and universities. During this period, China did not send many papers on WOS, and the links between them were relatively loose. This indicates that Chinese scholars have had relatively few international collaborations and published articles in foreign journals during this stage. Domestic journals dominate in publishing, resulting in relatively loose international connections.

It can be seen from Figure 7 that from 2012 to 2023, there will be large cooperation networks centered on Southeast University, Xi’an University of Architecture and Technology, Central South University of Forestry and Technology, and other schools, as well as medium-sized cooperation networks centered on the University of Chinese Academy of Sciences and the Ecological Environment Research Center of the Chinese Academy of Sciences, and other small cooperation networks. Selecting an extensive collaborative network consisting of Southeast University and others separately, it can be seen that not all institutions collaborated simultaneously. We first need to know that the “circles” in the graph represent nodes, and the larger the circle, the more times the institution appears. The wider the circular wheel rim of the node in the figure, the more times it appears in its year. The color of the circular wheel rim represents the distribution of appearance time, and the yellow-white color in the node represents the earlier appearance time [20]. There was a collaboration between Shanghai Jiao Tong University and the Chinese Academy of Forestry in 2012. However, Shanghai Jiao Tong University also collaborated with other colleges by publishing relevant literature in 2017. This large-scale collaborative network is generally divided into two parts. In the right half of the figure, colleges such as Shanghai Jiao Tong University, Donghua University, Ocean University of China, and China Academy of Forestry mainly cooperated before 2015, while in the left half, colleges such as Southeast University, Central South University of Forestry and Technology, Yunnan University, and Lanzhou Jiaotong University mainly published articles after 2017 and cooperated with other schools and institutions in their research, with closer connections and more connections between nodes than in the right half. It can further promote the development of sewage treatment technology-related fields.

Figure 8 shows that, compared with 2011, an extensive cooperation network centered on the Chinese Academy of Sciences will be formed from 2012 to 2023, except for a certain number of independent and small publishing institutions. We draw it separately because it is too dense, as in Figure 9. The nodes with purple outer circles in the figure have high centrality. In the picture, only the Chinese Academy of Sciences has a purple outer circle, meaning the academy has a very high centrality. The two most prominent nodes in the Chinese Academy of Sciences composition chart and the University of the Chinese Academy of Sciences constitute this complex, large-scale cooperation network, taking them as the central institutions to create with other institutions and publish articles on WOS jointly. The lines in the figure show that most of the collaborations took place after 2017, which was also the beginning of a rapid increase in the number of WOS literature. This means that more and more authors and institutions in China are willing to publish articles related to sewage ecological treatment on WOS. Therefore, based on several graphs, it is necessary to strengthen the cooperation between research institutions in sewage ecological treatment, with the intense driving the weak and jointly promoting the development of sewage ecological treatment research.

3.2. Research Hotspots

A research hotspot refers to a set of scientific research questions discussed in the literature that have connections between a specific period. The hot topics in a research field can be determined by analyzing high-frequency keywords [21]. Overlaying keywords can present the hot research topics in this field to obtain high-frequency keywords. It uses VOSviewer to perform collinear graph analysis using the keywords ecological treatment technology for village and town sewage in CNKI and WOS. In density visualization, nodes are represented by labels like network visualization and over-visualization. Each node presents a different color based on the density of items at its location, transitioning from blue to green and, ultimately, to yellow. The higher the display frequency of a node, the more its color tends to be yellow. On the contrary, the fewer times a node appears, the closer its color is to blue.

Figure 10 and Figure 11 show that CNKI has formed a region with high hotspot density centered on artificial wetlands, and the words on the edges are a series of keywords such as stable ponds, rural domestic sewage, and domestic sewage. This indicates that in CNKI’s research, artificial wetland technology is mainly used for sewage ecological treatment, with attention focused on rural domestic sewage, forming the density map shown in the figure. WOS has formed a hotspot density formed by keywords such as removal, wastewater, and sewage drain, indicating that a large number of relevant literature found in the search focuses on the treatment methods, treatment results, and causes of sewage problems, such as personal care products (PPCPS). Based on the data provided in VOSviewer, merge similar items in WOS, such as sewage slide and sewage sludge, heavy metals and heavy metals, and compile

Table 5. Top 30 high-frequency keywords related to sewage treatment technology by CNKI and WOS from 2000 to 2023.

Order Number	Database	Keyword	Frequency	Centrality	Database	Keyword	Frequency	Centrality
1	CNKI	Constructed wetland	626	0.35	WOS	Sewage sludge	146	0.03
2	CNKI	Sewage disposal	176	0.25	WOS	Removal	113	0.06
3	CNKI	Rural domestic sewage	161	0.15	WOS	Sewage treatment	109	0.14
4	CNKI	Stabilization pond	128	0.22	WOS	Wastewater	103	0.07
5	CNKI	Domestic sewage	108	0.11	WOS	Heavy metals	95	0.04
6	CNKI	Artificial wetland technology	57	0.1	WOS	Performance	79	0.09
7	CNKI	Rural sewage	47	0.1	WOS	Personal care products	66	0.02
8	CNKI	Ecological treatment	44	0.04	WOS	Sewage treatment plants	65	0.04
9	CNKI	Processing technology	42	0.04	WOS	Pharamaceuticals	57	0.09
10	CNKI	Rural area	40	0.02	WOS	Nitrogen removal	55	0.04
11	CNKI	Apply	40	0.07	WOS	Ecological risk	49	0.01
12	CNKI	Ecological remediation	38	0.03	WOS	Sewage	46	0.12
13	CNKI	Nitrogen and phosphorus removal	34	0.04	WOS	Nitrogen	45	0.05
14	CNKI	Handle	25	0.02	WOS	Fate	44	0.02
15	CNKI	Sewage	23	0.03	WOS	Treatment plants	42	0.02
16	CNKI	Wetland plants	23	0.03	WOS	Antibiotics	41	0.03
17	CNKI	Effluent disposal	23	0.06	WOS	Soil	41	0.07
18	CNKI	Advanced Treatment	22	0.02	WOS	Constructed wetlands	40	0.11
19	CNKI	Removal rate	21	0.11	WOS	Water	40	0.04
20	CNKI	Base material	20	0.06	WOS	Pollution	39	0.04
21	CNKI	Eutrophication	20	0.02	WOS	Sewage treatment plants	37	0.01
22	CNKI	Non-point source pollution	20	0.01	WOS	Sludge	37	0.01
23	CNKI	Purification effect	19	0.06	WOS	Aquatic environment	33	0.05
24	CNKI	Phosphorus	18	0	WOS	Surface water	33	0.03
25	CNKI	Microbe	17	0	WOS	Activated sludge	33	0.14
26	CNKI	AHP	17	0.02	WOS	Degradation	33	0.01
27	CNKI	Hydrophyte	16	0.01	WOS	Temperature	32	0.04
28	CNKI	Vertical flow constructed wetland	16	0.02	WOS	Constructed wetland	32	0.11
29	CNKI	Combined process	15	0.01	WOS	System	32	0.08
30	CNKI	Nunja	15	0	WOS	Domestic sewage	31	0.07

.

From the final results, high frequency does not necessarily mean high centrality. High centrality means it can be more important in research hotspots. By comparing the centrality of keywords, there are some significant differences between CNKI and WOS in the research direction of ecological treatment technology for rural sewage. In CNKI, keywords with centrality greater than 0.1 and frequency ranking in the top thirty, such as “constructed wetland”, “sewage disposal”, “rural domestic sewage”, “stabilization pond”, “domestic sewage”, “artificial wetland technology”, “rural sewage” and “removal rate”, indicate that the research focus of this database is more on specific technologies and effects. In particular, although the frequency of the “removal rate” is not high, its high centrality indicates that this field may receive more attention in the future, reflecting the emphasis on processing efficiency. In contrast, keywords with centrality greater than 0.1 and frequency ranking in the top thirty in WOS, such as “sewage treatment”, “sewage”, “constructed wetlands”, and “activated-sludge”, are mainly focused on overall governance and key technical aspects. This indicates that research in WOS focuses more on overall treatment strategies for wastewater treatment, the impact of pollution sources on the environment, and corresponding remediation technologies. Overall, CNKI tends to delve into specific treatment techniques in researching ecological treatment technology for rural sewage, such as substrate selection and plant selection in artificial wetlands. On the other hand, WOS focuses more on the impacts caused by pollution sources and their remediation, reflecting its attention to the overall governance framework and critical technologies.

Based on Figure 10 and Figure 11 and Table 5, the four hotspots for future research on ecological treatment technology for rural sewage include specific treatment technologies, in-depth exploration of specific technologies such as the size and scale of artificial wetlands and stable ponds, and plant selection; processing efficiency, focusing on removal rate and its impact on processing efficiency, reflecting the importance of improving governance effectiveness; overall governance strategy, studying the overall governance framework of sewage treatment, emphasizing the control and remediation technology of pollution sources; environmental impact assessment, analyzing the impact of pollution sources on the environment, and focusing on corresponding remediation and management measures.

3.3. Research Trends

The advantage of understanding the research trend of ecological treatment technology for rural sewage is that it can reveal the hot topics, technological progress, and changes in research focus in the field, allowing researchers to track current development directions and predict future research trends. This helps identify areas that have not been fully explored and guide the effective allocation of resources and energy [14]. By using CiteSpace V software to integrate and analyze the keywords of CNKI and WOS and sorting them according to the onset time, Figure 12 is obtained. According to this chart, the emergence time can be roughly divided into two stages: initial research and stable development.

3.3.1. Initial Research Stage

The initial research stage refers to the seven emerging terms from 2000 to 2007, namely: “stabilization pond”, “effluent treatment”, “closed cycle”, “papermaking wastewater”, “ecological treatment”, “ecological engineering”, and “environmental impact.” These hot topics were found to exist in the early stages of ecological treatment technology for rural sewage. Select “stabilization pond” and “ecological treatment” as the initial research topics based on their prominence, intensity, and duration (Figure 13).

The emergence time of “stabilization pond” was between 2000 and 2004, with an intensity of 9.9855. Except for 2020, when no articles explicitly targeted the term “stabilization pond”, 124 articles were published at other times containing the keyword “stabilization pond”. As one of the three major technologies in sewage ecological treatment, stabilization ponds have always been a hot topic of discussion among scholars in sewage treatment. Since 2000, attention has been paid to sewage treatment, and related research has gradually increased. The number of publications has remained stable, focusing on different types of stabilization ponds. After 19 years, the number of publications gradually decreased because a single stable pond technology may not meet the current sewage treatment needs. More and more scholars have turned their attention to composite treatment technology.

The emergence time of “ecological treatment” was from 2002 to 2005, with an intensity of 4.5486. Between 2000 and 2023, 44 articles appeared using it as a keyword. Ecological treatment emerged as a prominent keyword from 2002 to 2005, and it is more likely to be understood as an ecological treatment measure rather than simply an ecological treatment technology. As literature related to rural sewage treatment technology, scholars generally focus on the types of sewage, treatment methods, and removal effects during the research process.

3.3.2. Stable Development Stage

The stable development stage refers to the 12 emerging terms from 2008 to 2023, namely “eutrophication”, “research progress”, “handle”, “removal rate”, “processing technology”, “processing processes”, “rural sewage”, “biofilm”, “non-point sources”, “rural area”, “rural domestic sewage”, and “microbial community.” Based on the intensity and duration of highlighting, two prominent words were selected as the themes for the stable development stage: “treatment technology” and “rural sewage” (Figure 14).

The emergence time of “processing technology” is from 2015 to 2019, with an emergence intensity of 4.4471. The number of articles published is 39. In the 5 years when the keyword appeared in this keyword cluster, the number of times it appeared was 21, reaching its peak of 5 times in 2017 and 2019. Processing technology often refers to the primary method of sewage treatment. For example, treatment methods include activated sludge, biofilm, artificial wetlands, and stable pond technology. While scholars are researching them, they also point out their advantages and disadvantages, as well as the treatment issues that should be paid attention to in the implementation process, providing reference and inspiration for subsequent researchers in the study of sewage treatment technology.

The emergence time of “rural sewage” is from 2017 to 2023, with an intensity of 3.8619. According to the 2022 Urban and Rural Statistical Yearbook, urban sewage treatment has been largely completed. However, there are still some remote villages in rural areas whose sewage still needs to be treated. The term “rural sewage” appeared in 2007, and since then, Chinese scholars have recognized that rural sewage treatment is an indispensable part of environmental remediation. After 2017, the country began to vigorously rectify the problem of rural sewage pollution, which has attracted increasing attention from scholars.

The trend in the two stages reflects the continuous evolution of sewage treatment and environmental protection technologies, especially their increasing importance in rural areas. Meanwhile, the application of ecological treatment methods and microbial technology has become increasingly important in recent years [22]. Overall, the emergence and changes of these keywords reveal the development of research directions in environmental protection over time, reflecting the continuous exploration and application of new technologies and methods in response to social, economic, and technological changes and environmental challenges.

4. Conclusions

This research conducts a bibliometric analysis of literature from the CNKI and WOS databases spanning 2000–2023 to comprehensively explore the ecological treatment technology for rural sewage.

The research attention towards this technology has been on a steady rise both domestically and internationally. In recent years, a trend shift has been observed in publication patterns. Domestic scholars have shown a reduced inclination towards domestic journals, while there has been a notable increase in submissions to international journals. China has been actively involved in this research field, with Chinese scholars making substantial contributions. Although collaboration among researchers is evident, it may potentially lead to knowledge and resource concentration issues.

China initiated its research in this area in 2004, later than the US and UK, which started in 2000. However, China has not only caught up but also outpaced other countries in terms of the number of publications, and international cooperation in this field is also significant. Domestically, China Water and Wastewater has exerted a certain influence, yet China has limited representation in top-tier international journals.

Regarding research foci, CNKI-sourced studies mainly concentrate on specific treatment technologies, such as those related to artificial wetlands. In contrast, WOS-based research places more emphasis on the impacts of pollution sources and corresponding remediation strategies, highlighting the overall governance framework and key technologies. Future research hotspots in the ecological treatment technology for rural sewage are expected to include specific treatment technologies, treatment efficiency, overall treatment strategies, and environmental impact assessments.

It should be noted that this study has its limitations. Relying solely on the quantitative analysis of Chinese and English literature might cause the neglect of technical characteristics in non-English-speaking countries. Moreover, the lack of quantitative indicators like impact factors and citation frequencies may affect the comprehensiveness of the research evaluation.

5. Recommendations for Future Works

Future research on rural sewage ecological treatment should focus on the following aspects:

Optimizing Specific Treatment Technologies: Specific treatment technologies are a crucial aspect of future research. Future studies could focus on optimizing the design parameters of constructed wetlands. This may involve determining the optimal ratio of different substrates and selecting the most suitable wetland plants according to the characteristics of rural sewage, with the aim of enhancing treatment efficiency. Enhancing Treatment Efficiency: Given that treatment efficiency is a significant research area, developing real-time monitoring systems for treatment processes is advisable. These systems can provide timely data on pollutant removal rates, enabling timely adjustments to treatment processes in constructed wetlands and stabilization ponds, thereby improving overall treatment efficiency.

Addressing Methodological Shortcomings: Future research should seek to expand literature sources to reduce the over-reliance on Chinese and English literature. This can be accomplished through collaboration with researchers from non-English-speaking countries, accessing local databases, and translating relevant studies. Incorporating quantitative indicators such as impact factors and citation frequencies into the analysis can contribute to a more accurate evaluation of the influence and quality of research papers.

Promoting Interdisciplinary and International Collaboration: With the growing importance of ecological treatment methods and microbial technology, cooperation among environmental engineering, microbiology, and social sciences is essential. Social scientists can assist in understanding the acceptance and implementation of new treatment technologies in rural communities, while microbiologists can contribute to improving microbial-based treatment systems. Chinese researchers could strengthen international cooperation, learn from advanced treatment technologies and management models in developed countries, and share China’s successful large-scale rural sewage treatment cases.

Establishing Open Platforms and Diversifying Publications: Establishing open research platforms can help break down institutional and regional barriers, facilitating knowledge sharing. Researchers are recommended to diversify publication channels. Besides high-impact international journals, specialized regional journals and open-access platforms can be considered to increase the visibility of research findings and promote academic exchanges.