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Article

Impacts of Wastewater Management and Enhancing the Landscape of the Mae Kha Canal: A Quasi-Experimental Study

by
Vongkot Owatsakul
1,
Prajuab Panput
1,
Punyaphol Jaisuda
1 and
Damrongsak Rinchumphu
2,*
1
Public Works Bureau, Sanitary Engineer Division, Chiang Mai Municipality, Chiang Mai 50300, Thailand
2
Faculty of Engineering, Chiang Mai University, Chiang Mai 50200, Thailand
*
Author to whom correspondence should be addressed.
Water 2025, 17(7), 1105; https://doi.org/10.3390/w17071105
Submission received: 18 February 2025 / Revised: 3 April 2025 / Accepted: 3 April 2025 / Published: 7 April 2025
(This article belongs to the Special Issue Driving Water Reuse by New Technologies, Land Use and Infrastructure Planning, and Legislation Policies)
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Abstract

:
The Mae Kha Canal in Chiang Mai, Thailand, has long suffered from severe water quality deterioration due to rapid urbanization, population growth, and inadequate waste management practices. This article describes an integrated water resource management approach, started in February 2018, with the goal of guaranteeing sustainable urban living conditions and improving the water quality of the canal. This study was a quasi-experimental study, with key interventions including garbage net installation, coconut-fiber mattress weir installation, and Free Water Surface Wetland treatment using vetiver grass. An interrupted time-series analysis of the monthly biochemical oxygen demand (BOD) and dissolved oxygen (DO) levels were applied to examine the trends and changes after the full implementation of wastewater management in March 2021. The results demonstrated significant improvements in water quality, indicated by reduced BOD levels (from 17.00–38.70 to 9.00–12.67 mg/L) and increased DO levels (from 0.00–2.40 to 0.80–6.00 mg/L). However, the decreases in BOD and increases in DO levels were not stable during the year. The post-intervention trend of BOD level decreased after the wastewater management implementation at SriDonChai Road (coefficient of trend: = −0.75 [95% confidence interval: −1.44 to −0.06]). This project highlights the effectiveness of integrated management strategies in addressing urban water quality issues and emphasizes the importance of community involvement in sustainable environmental management. The findings underscore the necessity for integrated approaches to wastewater management in urban environments to address both ecological health and public welfare.

Graphical Abstract

1. Introduction

Basic requirements for good health include having a safe place to live and access to clean drinking water for households, industry, and agriculture [1]. Even though more than 70% of the world is covered with water, only 3% is freshwater and less than 0.01% of the world’s freshwater sources are suitable for human consumption [1,2,3]. The world’s population growth brings with it fierce competition for the planet’s resources, especially water and energy; these are at grave risk due to water pollution and global warming, respectively [4]. Moreover, increased water use by industry and agriculture, as well as unsustainable urbanization and industrialization, has resulted in water contamination from the release of wastewater, toxic effluents, and chemicals into water bodies [4,5,6], which could lead to marked water shortages. Contaminated water and wastewater consequently have negative impacts on public health, economy, agricultural security, drinking water supply, and biodiversity [7]. Wastewater remains a problem in several parts of the world. Hence, appropriate water utilization and wastewater management, including treatment, filtration, and reuse, have been studied and discussed for sustainable development.
There are various strategies for treating wastewater [1,8], such as adsorption [2,9,10], membrane filtration [11], coagulation/flocculation [12,13,14], oxidation [15,16,17], and biological treatment [14,18,19]. In addition, new wastewater treatment techniques and strategies have been forthcoming. For example, Muthukumaran and Ambujam [20] proposed strategies for improving wastewater management in Tiruchirappalli City, Tamil Nadu, India, and made recommendations for the use of treated wastewater in agriculture. Del Villar and García-López [21] studied the potential of reusing water from the Canal de Isabel II in Madrid, Spain, using water stress data and wastewater reuse to aid decision-making. Frascari et al. [22] investigated integrated technology and management solutions for efficient agricultural wastewater treatment and reuse in Egypt, Morocco, and Tunisia. Iqbal et al. [23] presented a water quality management modeling approach to control the concentration of pollutants in the Ravi River, Punjab, Pakistan. The application of vetiver grass is one approach to treat organic matter in contaminated surface water, and has been applied to treat polluted water and for environmental protection [24,25,26,27]. The findings of a recent experimental study in Vietnam show that vetiver grass application in vertical-flow constructed wetlands achieves a removal efficiency of 90% for biochemical oxygen demand (BOD) and >80% for chemical oxygen demand (COD) [28].
Thailand’s rapid economic and social expansion is causing many egregious environmental problems. At present, risk factors affecting water management comprise natural disasters and human actions, including encroachment on public water sources, increasing population, the expansion of urban communities, the creation of water barriers, the release of pollutants into rivers and canals, etc. All of these negatively affect water resources, both qualitatively and quantitatively, and this is an important national problem that affects the living conditions of the people, as well as the economic and social stability, of Thailand. In 2022, the Pollution Control Department of Thailand measured the quality of surface water in 49 major rivers throughout Thailand using the water quality index; they found that the water quality was good, fair, and deteriorated in 43%, 41%, and 16% of them, respectively [29]. Thus, Thailand faces problems with water quality in many areas, especially in urban areas with large populations, such as Bangkok and the surrounding area, as well as locations of industrial plants, such as Chiang Mai, Rayong, Nonthaburi, and Samut Prakan. There are several water resources in Thailand faced with wastewater issues. For example, Saen Saep Canal in Bangkok has had problems with wastewater for a long time. Many researchers have studied and attempted to mitigate these issues. Techapichetwong and Phasukphan [30] proposed the application of pollution flow diagrams to manage the water quality of the canal, while Somsuk and PilaiLa [31] studied the impact of population growth on the water quality therein and methods to improve it.
The Mae Kha Canal in Chiang Mai Province is another canal that has experienced deteriorating water quality for a long time. In 2017, the Chiang Mai Provincial Office reported that the biochemical oxygen demand (BOD) and the dissolved oxygen (DO) levels in this canal were 4.58–8.39 and 0.17–3.1 mg/L, respectively, which do not meet the good surface water quality standards [32]. This canal is strategically important for draining water from the urban area into the Ping River. In the past, it was a water source that was used for agriculture, consumption, and water transportation. However, population growth in Chiang Mai has led to communities becoming densely located on both sides of the Mae Kha Canal along its length—more than 20 communities out of a total of 99 [32,33]. Many residences, small businesses, and factories have been constructed along and encroach on the Mae Kha Canal, with the people therein dumping garbage, and wastewater from the buildings and establishments draining into it. This economic and residential zone has deteriorated both physically and ecologically, which has impacted the city by causing water quality problems [14]. In 1997, a wastewater collection system was constructed, covering 40 km2 of Chiang Mai Municipality, to collect and transfer wastewater to the wastewater treatment plant. However, the collection system did not cover both sides of the Mae Kha Canal. Therefore, the Chiang Mai Municipality Office aimed to conduct a Mae Kha Canal development project to improve the quality of this canal with integrated water resource management.
After examining the dumping of wastewater into the Mae Kha Canal, the Chiang Mai Municipality arranged to dredge it and construct drainage and wastewater collection pipes on both sides of it. In addition, the municipality has provided knowledge and understanding to the community by organizing activities and encouraging participation by the community to conserve and maintain the Mae Kha Canal sustainably and improve the landscape of the public walkways on both sides of the Mae Kha Canal. Therefore, we aimed to investigate the impact of the wastewater treatment system of the Mae Kha Canal development project, which was implemented from February 2018 to December 2022, to ensure that the canal has good water quality and that people have suitable housing.

2. Materials and Methods

2.1. Location and Communities of the Mae Kha Canal

The Mae Kha Canal is the oldest in Chiang Mai Province. It originates in Doi Suthep-Pui National Park in Mae Rim District, Chiang Mai Province, and its endpoint is in Hang Dong District, Chiang Mai Province, the total length of which is approximately 30 km [32]. The Mae Kha Canal is divided into three sections [32]: the first section is in the Mae Rim District (~8.19 km), the second is in the Mueang District, Chiang Mai Municipality (~10.20 km), and the third is from the Pa Daet Subdistrict Municipality in Mueang District to the Sop Mae Kha Subdistrict in Hang Dong District (~12.00 km), where the water then runs into the Ping River. There are 6 communities in the first section, 25 in the second section (known for its dense population of 25,352 in July 2024, which has resulted in slum settlements), and 11 in the third section [33]. This study was focused on the second section (see Figure 1).

2.2. The Mae Kha Canal Development Project

The Mae Kha Canal development project had a quasi-experimental design, with integrated water resource management conducted with five procedures: (1) demolishing houses and buildings straddling the Lam Mueang branch and dredging out sediment from the canal; (2) laying drainage pipes to collect wastewater from buildings, businesses, and the drainage system in the area to manage sewage and solid waste in the canal; (3) creating a weir to slow down the water flow with coconut-fiber mattresses; (4) testing the use of the wastewater management and treatment system in the Mae Kha Canal; and (5) constructing a wall to prevent soil slides, a sanitary sewerage system, and a public walkway on both sides of the Mae Kha Canal. Details of the Mae Kha Canal development project, such as the participating organizations, objectives, work procedures, and indicators, are provided in Table 1.

2.2.1. Demolishing Houses and Buildings Encroaching on the Mae Kha Canal and Dredging out the Sediment

Before the development project, 57 out of 1207 households located along the Mae Kha Canal in the Srimongkhon and Paphaeng communities were encroaching on the Mae Kha Canal (Figure 2A). These households were built in the direction of the flowing water, resulting in the area being at risk of flooding because they were preventing rainwater from flowing into the canal. Moreover, these households were releasing wastewater into the canal, thereby lowering the water quality. After demolishing them and dredging out the sediment, the drainage into the canal and the look of the area were greatly improved (Figure 2B).

2.2.2. Managing Sewage and Solid Waste in the Mae Kha Canal

The Mae Kha Canal area was unattractive before this effort to control garbage and solid waste was started. It was filled with a great deal of trash, and the residents living nearby complained about the stench emanating from the solid waste therein (Figure 3A). Following the commencement of this task, garbage was collected from sewer pipes using nets in predetermined locations. The garbage nets were made from Nylon with a 2.5 cm hole size; they were 4 m wide and 10 m long, and fixed to a steel frame over a drainpipe (Figure 3B). At first, the Chiang Mai Municipality was gathering up to 500 kgs of rubbish per week from the nets, which was reduced to just 200 kgs of garbage per week. This is a result of local businesses and residents working together to prevent trash from being dumped into the canal. As a result, the Mae Kha Canal has stunning scenery, and the water flow has been greatly improved (Figure 3C).

2.2.3. Creating a Weir to Slow Down the Water Flow with Coconut-Fiber Mattresses

For this procedure, we aimed to reuse leftover materials—coconut-fiber mattresses—to construct a weir as a filter, using a bamboo structure with sandbags. This was installed in an optimal location, and is a strong and stable long-term installation (Figure 4). The drainage rate depends on the natural drainage rate in each season. In addition, it also prevents the erosion of the canal bank.

2.2.4. Testing the Wastewater Management and Treatment System of the Mae Kha Canal

A FWS wastewater treatment system for the Mae Kha Canal was constructed using vetiver grass (Figure 5). An FWS wastewater treatment system using vetiver grass is a widely recognized and accepted method. Vetiver grass is effective in treating wastewater in rivers, canals, and industrial settings, and it can be applied in various areas, including narrow spaces, uneven terrain, and sloped regions. We continuously checked the condition of the treatment system and provided maintenance guidelines from October 2019 to February 2021.

2.2.5. Constructing a Retaining Wall to Prevent Land Slides, and Implementing a Sanitary Sewerage System and a Public Walkway on Both Sides of the Mae Kha Canal

For this phase, we created 1.5 km of wastewater pipelines on each side of the Mae Kha Canal to protect the banks on both sides of the canal, prevent flooding during the rainy season, collect and treat wastewater from households and establishments, and encourage people within the community to use the public walkway by including an area for trading, recreation, and exercise (Figure 6).

2.3. Water Quality Evaluation Methods

DO and BOD were measured to evaluate the water quality in Mae Kha Canal. The DO (mg/L) level for the wastewater was measured using Azide Modification [34]. This approach calculated the DO level from the sodium thiosulfate (Na2S2O3) titration of 200 mL water samples, as follows:
1 mL 0.0025M Na2S2O3 = 1 mg DO/L
BOD (mg/L) is a measure of the amount of DO consumed by microorganisms during the decomposition of organic matter in water. The BOD test typically involves measuring the amount of oxygen consumed over a specific period (5 days in the present study). It is calculated as follows [34]:
BOD = D O 0 − D O 5 P
where D O 0 and D O 5 are the initial and final DO concentrations in the water sample, respectively (mg/L), and P represents the fraction of the BOD bottle that is represented by the sample. The criteria for interpreting water quality are provided in Table 2.
The evaluations of water quality using the BOD and DO indices were conducted monthly from water samples at three locations, including Mae Kha Bridge (Atsadathon Road), Klong Ngern Community Bridge (Klang Stream), and Mae Kha Bridge (SriDonChai Road), 40 times from October 2019 to January 2023 (Figure 7). The BOD and DO evaluations may be unavailable for some months due to drought or severe contamination.

2.4. Statistical Analysis

The missing BOD and DO levels were imputed via linear interpolation using the nearest available values. The BOD and DO levels of sampled water were summarized using descriptive statistics as means, standard deviations, and ranges for each location. An interrupted time-series analysis of the monthly BOD and DO levels was applied to examine the trends and changes after the full implementation of wastewater management (garbage net installation, coconut-fiber mattress weir installation, and FWS treatment using vetiver grass.) in March 2021. A p-value < 0.05 was considered statistically significant. All of the analyses were performed using Stata version 17.

3. Results

3.1. BOD and DO Levels

BOD and DO levels were measured monthly from October 2019 to January 2023. The averages and ranges of levels at each location are provided in Table 3. The average BOD level at SriDonChai Road was the lowest (16.83 (range: 4.00–49.00) mg/L). Meanwhile, the average DO levels at Atsadathon Road and SriDonChai Road were similar (1.73 (range: 0.00–6.50) and 1.58 (range: 0.00–9.50) mg/L, respectively), and higher than those in the Klang Stream.

3.2. Impact of the Coconut-Fiber Mattress Weir

Prior to installing a weir comprising coconut-fiber mattresses, the Mae Kha Canal was suffering from bank erosion and harsh conditions because of material flowing into the river. The BOD values in the Klang Stream decreased from 46.67 mg/L in September 2020 to 8.17 mg/L in November 2022, while at SriDonChai Road, the values declined from 8.50 mg/L in September 2020 to 5.00 mg/L in November 2022. Although the BOD values still did not meet the target value of less than 2.0, implementing the weir comprising coconut-fiber mattresses significantly improved the water quality. As presented in Figure 8, the BOD and DO levels also improved at the Atsadathon Road and SriDonChai Road stations.

3.3. Impact of Vetiver Grass in the Wastewater Management and Treatment System

During the installation and subsequent testing of the FWS wastewater treatment system comprising vetiver grass in the Mae Kha Canal from October 2019 to February 2021, the BOD levels decreased from 17.00–38.70 to 9.00–12.67 mg/L and the DO levels increased from 0.00–2.40 to 0.80–6.00 mg/L. However, the average BOD levels increased (Figure 9A), while the DO levels decreased (Figure 9B) compared to the levels measured during the installation and testing period.

3.4. Impact of the Wastewater Management and Treatment System

As presented in Figure 10, after the full implementation of the wastewater management and treatment system (procedures 2, 3, and 4) in March 2021, there was no significant change in BOD levels at any of the locations, and in particular, the coefficient of the trend negatively changed at SriDonChai Road (−0.96 [95% confidence interval (CI): −1.92 to −0.005]; p-value = 0.049). Meanwhile, the DO levels significantly decreased at SriDonChai Road (−3.98 [95% CI: −6.96 to −1.00]; p-value = 0.010) and decreased at Atsadathon Road (−2.34 [95% CI: −4.92 to 0.25]; p-value = 0.076). The post-intervention trend estimates show that the BOD level significantly decreased at SriDonChai Road (−0.75 [95% CI: −1.44 to −0.06]; p-value = 0.033) and DO levels increased at Atsadathon Road (0.15 [95% CI: −0.003 to 0.31]; p-value = 0.054) and SriDonChai Road (0.07 [95% CI: −0.007 to 0.15]; p-value = 0.072) (Table 4).

3.5. Advantages of Retaining Wall, Sanitary Sewerage System, and Public Walkway

The retaining walls help prevent soil erosion during the rainy season. The sanitary sewerage system avoids the drainage of household wastewater into the canal and redirects it into the Chiang Mai Municipality Wastewater Treatment Plant before being released into water sources. In addition, the public walkway along both sides of the Mae Kha Canal provides local people with a place to rest and exercise. It has become a new tourist attraction in Chiang Mai city, with more than 1000 tourists visiting it per day and generating an income of more than THB 36,000,000 per year. Therefore, the quality of water in Mae Kha Canal is a key factor that should be monitored to improve both environmental and economic scenarios.

4. Discussion

The development of the Mae Kha Canal, in cooperation with the community and government agencies, involved the implementation of a project aimed at making the canal sustainable in terms of water quality and the quality of life for the residents. Dredging and removing structures around the Mae Kha Canal enhanced the aesthetics of the surrounding environment by improving water drainage, eliminating pollutants, and addressing housing encroachment, which has caused environmental damage, wastewater problems, and significant littering. It improved the water quality and reduced waste and water flow. Socially, it has provided clean water sources, a novel tourist attraction, and a space for the public to exercise and relax along the canal. Economically, it has boosted income for the community through tourism. According to water management evaluations, the DO levels at Atsadathon and SriDonChai Road fell within the moderate-to-good water quality range at the end of the project. Although the BOD and DO values after the wastewater management implementation were not stably improved, the post-intervention trend of decreasing BOD (−0.75 [95% CI: −1.44 to −0.06] at SriDonChai Road) and increasing DO values (0.15 [95% CI: −0.003 to 0.31] at Atsadathon Road and 0.07 [95% CI: −0.007 to 0.15] at SriDonChai Road) suggested an improvement in water quality.
The problem of trash in the Mae Kha Canal, primarily caused by people dumping waste therein, has significantly affected the local community, aquatic life, and the surrounding environment. To tackle this issue, trash nets were employed to capture waste dumped into the canal. This approach has been successfully employed in other countries, such as in the City of Kwinana in Western Australia, where deployed trash nets capture 370 kg of waste every four months [35]. In addition, Hariyadi et al. [36] studied the use of trash nets in the Citarum River in Indonesia to effectively capture many forms of plastic waste. Similarly, Morritt et al. [37] reported that although trash nets deployed on the Thames River effectively trapped plastic waste, a large amount of submerged plastic waste was still flowing into the marine environment. This is also one of the challenges for the Mae Kha Canal, where some submerged trash still flows into the canal. In Thailand, trash nets have been introduced in various areas, such as in the Rayong Municipality, where nets have been placed over the ends of drainage pipes to prevent trash from entering canals and the sea [38], capturing 2–3 tons of waste per day across 15 locations. The adoption of this concept to address the trash problem in Mae Kha Canal at four locations, where 70 kgs of trash is captured daily, has had a positive impact both environmentally (making the canal cleaner and allowing the local ecosystem to thrive) and socially (the local people in the community are no longer affected by foul odors from the canal and the surrounding environment is aesthetically pleasing).
To address riverbank erosion and wastewater from trash in the Mae Kha Canal, semi-permanent check weirs were constructed using coconut-fiber mattresses to help slow down the water flow, retain water, and filter out debris. Typically, the water quality standards for surface water sources require that the DO level is at least 4.0 mg/L and that BOD does not exceed 2.0 mg/L for water bodies receiving effluent from certain activities [39]. Before the installation of the weirs, the average BOD level at Atsadathon Road was 18.11 mg/L, and afterward it was reduced to 7.50 mg/L. Meanwhile, the DO level increased from 1.79 to 5.40 mg/L after the weir installation. Although these indices did not meet the surface water quality standards, a trend of improvement was suggested. This improvement has positively impacted on the environment (improving the water quality and decreasing erosion of the riverbanks), as well as socially (the local community now has access to clean water for domestic use and agriculture), and economically (the better water quality has improved the quality of agricultural produce and increased income).
A recent study in Vietnam conducted an experiment that involved applying vetiver grass in vertical-flow constructed wetland management, and found that it efficiently reduced BOD by 90% and COD by >80% [28]. An FWS wastewater treatment system using vetiver grass was implemented in this study. In this project, vetiver grass was planted on floating platforms, which improved the water quality in the Mae Kha Canal. The average BOD was reduced by 58.82% (from 25.23 mg/L at the beginning in October 2019 to 10.39 mg/L at the end of installation in February 2021), which is consistent with previous studies involving vetiver grass systems in other countries. For example, an 80–85% BOD reduction was experienced in an institutional kitchen [40], a 71.03% BOD reduction was found in the Bagmati River, Nepal [41], and a 91.9% BOD reduction was recorded in industrial wastewater in Ethiopia [42]. The vetiver grass floating platform technique has been deployed in Thailand, leading to 77% removal of BOD from textile factory wastewater [43], as well as an 87.85% reduction in BOD in pig farm wastewater [44]. The trends of BOD and DO levels after the implementation tended to improve at SriDonChai Road. However, the decreases in BOD and increases in DO levels were not stable during the year. The BOD and DO levels fluctuated during the study period. The average BOD levels increased after the FWS installation, while the DO levels decreased compared to the levels measured during the installation and testing period. This might result from other factors, such as drought in winter and summer, or differences in contamination with living patterns and festivals. In addition, it might be related to the maintenance of the FWS after installation. According to a qualitative study about the integrated water resource management of the Mae Rim sub-watershed in Chiang Mai province, the researchers stated that the problems of water resource management in the Mae Rim sub-watershed resulted from an inefficient management process and a lack of correct integration processes between the government and the community [45]. Therefore, for sustainable development, additional wastewater management and community approaches should be provided and examined for their effectiveness in further studies.
In addition to the pollutants in water resources, environmental factors might be related to BOD and DO levels. A previous study about BOD and DO levels in Quelimane, Mozambique, suggested that BOD and DO levels might be influenced by the tides [46]. The study stated that the DO levels during August were more than 2 mg/L, whereas the values were lower than this critical value during September and October. A study on the mathematical modeling of BOD and DO levels also suggested the influence of time at measurement [47]. They performed a series of space–time numerical simulations and found that the model allows the analysis of regions with higher and/or lower DO and BOD concentrations, as well as the temporal variation in concentrations at specific time points. Additionally, the model of BOD and DO measurement might influence the stability of measurements. There are several models which could provide more stable estimations of BOD and DO levels, such as Chebyshev orthogonal polynomial modeling [48] and the Streeter–Phelps equation [49]. Further studies to compare the simplified model used in this study and these complex models could provide more insightful results.
In an area where houses were encroaching on the Mae Kha Canal and causing water pollution and foul odors, one of the tasks of the project was to develop the area into an attractive tourist destination. This involved enhancing the area alongside the canal by constructing retaining walls to prevent landslides, creating a drainage system to stop households from discharging wastewater directly into the canal, and building public walkways on both sides of the canal. These walkways provide residents and tourists with a place to relax and exercise, thereby benefiting approximately 865 households living along the canal. The development of this area has had several positive impacts, including economically (the Mae Kha Canal has now become a new tourist attraction in Chiang Mai, drawing more than 1000 visitors daily and generating over THB 1,530,000 per month for the local community), socially (the project has provided Chiang Mai residents and tourists with a beautiful public space for relaxation and exercising), and environmentally (the canal now has clean water, is free of trash and foul odors, and the local ecosystem has now been restored). The project’s success led to it receiving a national award from the Prime Minister’s Office of Thailand for excellence in municipal management under the “Beautiful Canal, Clear Water” category, earning second place at the national level [50].
The development of the Mae Kha Canal in collaboration with the community and government agencies has yielded significant improvements in water quality, local scenery, and Chiang Mai’s status by becoming a prominent tourist attraction. The five procedures in the project collectively enhanced the canal’s environmental, social, and economic conditions. Dredging improved water drainage and aesthetics, trash nets have reduced pollution and improved the ecosystem, check weirs have slowed the water flow, the vetiver grass-based FWS wastewater treatment system has effectively reduced BOD, and the development of the canal into a recreational area has boosted local tourism and economic activity. However, there are still some challenges. Dredging and removal activities can disrupt aquatic habitats and incur high initial costs. Trash nets may require ongoing maintenance and may not be able to capture all of the waste. Check weirs made from coconut-fiber mattresses might degrade over time, and the vetiver grass in the FWS wastewater treatment system needs adequate space and regular maintenance. Furthermore, while the canal’s development into a tourist spot has revitalized the area economically, it could lead to environmental degradation if not properly managed and could also affect residents through increased living costs or displacement. To address these issues, it is crucial to implement phased construction, conduct regular maintenance, explore alternative materials, and develop sustainable tourism practices that involve and benefit the local community. Since the FWS system in this quasi-experimental study was conducted in the real setting, in which water flow changed throughout the study period, the retention time and water flow could not be controlled. In addition, there was no industrial plant related to heavy metal pollutants in the study area. Thus, this study evaluated only the quality of water based on BOD and DO levels. Chemical oxygen demand and total organic carbon are suggested as suitable and stable indices for refused water resources. Therefore, chemical oxygen demand, total organic carbon, other water quality indices (e.g., water quality index, total coliform bacteria, fecal coliform bacteria, nitrate, total nitrogen, phosphate, and total phosphorus), and heavy metal pollutants are of interest, and should be included in future investigations.

5. Conclusions

The comprehensive development of the Mae Kha Canal achieved through the collaboration of the community and government agencies has significantly enhanced both the canal’s environment and the quality of life of residents. This initiative involved five tasks in an integrated project aimed at making the canal sustainable and transforming it from a polluted waterway into a vibrant and attractive area. These tasks included dredging and removing obstructions to improve the water flow and reduce pollution, installing trash nets to capture waste and prevent further pollution, constructing semi-permanent check weirs to combat erosion and treat wastewater, using an FWS wastewater treatment system comprising vetiver grass on floating platforms to further improve water quality, and developing the canal area to provide a popular tourist destination. The results of these efforts have been overwhelmingly positive, with improved water quality, reduced pollution, enhanced aesthetics, increased community income through tourism, and the creation of public spaces that benefit both residents and visitors. BOD levels decreased from 17.00–38.70 to 9.00–12.67 mg/L and DO levels increased from 0.00–2.40 to 0.80–6.00 mg/L. Although the BOD and DO values after wastewater management implementation were not stably improved, the post-intervention estimates of the BOD level at SriDonChai Road decreased (−0.75 [95% CI: −1.44 to −0.06]) and the DO levels at Atsadathon Road and SriDonChai Road seemed to increase (0.15 [95% CI: −0.003 to 0.31] and 0.07 [95% CI: −0.007 to 0.15], respectively). The transformation of Mae Kha Canal has not only revitalized the local environment, but has also made it a significant tourist attraction, garnering national recognition for its successful management and development.

Author Contributions

Conceptualization, V.O. and D.R.; methodology, V.O. and D.R.; validation, V.O., P.P. and P.J.; formal analysis, V.O.; investigation, V.O.; resources, V.O., P.P. and P.J.; data curation, V.O., P.P. and P.J.; writing—original draft preparation, V.O.; writing—review and editing, V.O., P.P., P.J. and D.R.; project administration, V.O. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding. This research was partially supported by Chiang Mai University.

Data Availability Statement

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Acknowledgments

We acknowledge the Sanitary Engineer Division, Chiang Mai Municipality, Chiang Mai, Thailand.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. A map showing the locations of Chiang Mai Province (A) and the Mae Kha Canal (B).
Figure 1. A map showing the locations of Chiang Mai Province (A) and the Mae Kha Canal (B).
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Figure 2. Comparison of before (A), during (B), and after (C) demolishing houses encroaching on the Mae Kha Canal and dredging out sediment.
Figure 2. Comparison of before (A), during (B), and after (C) demolishing houses encroaching on the Mae Kha Canal and dredging out sediment.
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Figure 3. The Mae Kha Canal (A) before and (B) after initiating the solid waste and sewage management system and (C) examples of garbage that can be captured.
Figure 3. The Mae Kha Canal (A) before and (B) after initiating the solid waste and sewage management system and (C) examples of garbage that can be captured.
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Figure 4. Constructing the water-slowing weir using coconut-fiber mattresses.
Figure 4. Constructing the water-slowing weir using coconut-fiber mattresses.
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Figure 5. The FWS wastewater treatment system using vetiver grass platforms.
Figure 5. The FWS wastewater treatment system using vetiver grass platforms.
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Figure 6. The public promenades and walls prevent soil erosion on both sides of the Mae Kha Canal.
Figure 6. The public promenades and walls prevent soil erosion on both sides of the Mae Kha Canal.
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Figure 7. Maps of the locations of water quality measurements and five procedures of the Mae Kha Canal development project.
Figure 7. Maps of the locations of water quality measurements and five procedures of the Mae Kha Canal development project.
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Figure 8. Comparison of (A) biochemical oxygen demand (BOD) and (B) dissolved oxygen (DO) values before, during, and after constructing the bamboo-structured weir filter containing coconut-fiber mattresses to slow down the water flow.
Figure 8. Comparison of (A) biochemical oxygen demand (BOD) and (B) dissolved oxygen (DO) values before, during, and after constructing the bamboo-structured weir filter containing coconut-fiber mattresses to slow down the water flow.
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Figure 9. Comparison of (A) biochemical oxygen demand (BOD) and (B) dissolved oxygen (DO) values before and after installing and testing the FWS wastewater treatment system.
Figure 9. Comparison of (A) biochemical oxygen demand (BOD) and (B) dissolved oxygen (DO) values before and after installing and testing the FWS wastewater treatment system.
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Figure 10. Interrupted time-series analysis of (A) biochemical oxygen demand (BOD) and (B) dissolved oxygen (DO) values before and after full wastewater management and treatment system implementation.
Figure 10. Interrupted time-series analysis of (A) biochemical oxygen demand (BOD) and (B) dissolved oxygen (DO) values before and after full wastewater management and treatment system implementation.
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Table 1. Details of the Mae Kha Canal development project.
Table 1. Details of the Mae Kha Canal development project.
ProcedurePeriodParticipating OrganizationsObjectivesWork ProcessesIndications
1. Demolishing buildings encroaching on the canal and dredging out sedimentFebruary
2018		Municipality,
The 33rd Military District,
Marine Office,
Provincial Land Office		To drain water; reduce environmental problems such as wastewater, garbage, and sewage; and improve the sceneryDemolishing buildings encroaching on the canal
(1) Meeting with the local community to discuss the requirement for dismantling the buildings.
(2) Signing an agreement.
(3) Dismantling houses and buildings encroaching on the Mae Kha Canal under the supervision of sanitary engineers.
Dredging out sediment
(1) Determining the scope of the work.
(2) Undertaking a public relations exercise with the affected communities in the work area.
(3) Producing guidelines for water management.
(4) Determining the location for bringing machinery into the area.
(5) Removing sediment from the area.
(6) Determining where to dispose of the sediment.		(1) The Mae Kha Canal’s drainage rate increased more than five times from before the project began, from less than 5 cubic meters per second to 25 cubic meters per second.
(2) The water quality, as indicated by the dissolved oxygen (DO) levels, showed a statistically significant improvement, with DO values rising from 0 mg/L to over 2 mg/L.
2. Managing sewage and solid wasteJanuary 2021 to March 2022MunicipalityTo reduce the amount of solid waste and improve the water flow(1) Planning appropriate locations to install garbage nets and sewage barriers.
(2) Determining the size of the nets and panels.
(3) Installing them under the supervision of a sanitary engineer.
(4) Inspecting after installation and planning scheduled maintenance and removal of garbage from the nets.		(1) Reduce garbage collection in Ma Kha canal from 4 times per month to 1 time per month.
(2) The water flow rate was constant during the project operation.
3. Creating a weir to slow down the water flow with coconut-fiber mattressesOctober 2020 to October 2022MunicipalityTo trap sediment, increase the dissolved oxygen (DO) content, reduce erosion of the riverbank, and store groundwater above the weir(1) Reusing leftover materials (coconut-fiber mattresses) from establishments.
(2) Determining the optimal location for their installation.
(3) Inspecting and improving the condition of the original soil under the weir base to make it strong and stable.
(4) Constructing a weir using coconut-fiber mattresses as filters in a bamboo structure with sandbags.
(5) Setting the height of the weir ridge to drain water efficiently and prevent flooding in the area above the weir.
(6) Checking the results after construction.		After building a weir with mattresses made of coconut fiber, the increase in oxygen and DO was higher than or equivalent to 4 mg/L.
4. Testing the use of a wastewater management and treatment systemOctober 2019 to February 2021MunicipalityTo improve the water quality, reduce the amount of organic pollution, and increase the DO content(1) Drafting a plan and determining the steps for installation in the operational area.
(2) Creating a Free Water Surface Wetland (FWS) wastewater treatment system using vetiver grass.
(3) Carrying out the installation.
(4) Continuously checking the condition of the treatment system and providing maintenance guidelines.		The quantity of nitrogen and phosphorus, or organic matter, has reduced, and the DO value is more than or equal to 4 mg/L and the BOD value is less than or equal to 2 mg/L
5. Constructing a retaining wall and a public walkway on both sides of the canalApril 2021 to September 2022MunicipalityTo protect the banks on both sides of the canal, prevent flooding during the rainy season, collect and treat wastewater from households and establishments, and encourage people within the community to use the public walkway by including an area for trading, recreation, and exercise(1) Building 1.5 km of wastewater pipelines on each side of the Mae Kha Canal.
(2) Enhancing the landscape, covering a distance of 0.785 km.		(1) The Do value is more than 2 mg/L.
(2) There is no wastewater pipe connection into the Mae Kha Canal.
(3) Reduce overflow flooding from more than 10 times per year before construction to not happening at all in 2023.
Table 2. Criteria for interpreting water quality [29].
Table 2. Criteria for interpreting water quality [29].
Water QualityDO (mg/L)BOD (mg/L)
Good>4.0–6.00.0–1.5
Moderate>2.0–4.0>1.5–2.0
Degenerate0.0–2.0>2.0–4.0
Note(s): BOD, biochemical oxygen demand; DO, dissolved oxygen.
Table 3. Biochemical oxygen demand (BOD) and dissolved oxygen (DO) levels at various locations.
Table 3. Biochemical oxygen demand (BOD) and dissolved oxygen (DO) levels at various locations.
LocationsBOD (mg/L)DO (mg/L)
Means (SDs)RangesMeans (SDs)Ranges
Atsadathon Road22.68 (17.91)2.50–102.001.73 (1.85)0.00–6.50
Klang Stream21.84 (12.16)5.50–48.000.94 (1.04)0.00–4.00
SriDonChai Road16.83 (10.14)4.00–49.001.58 (1.93)0.00–9.50
Note(s): BOD, biochemical oxygen demand; DO, dissolved oxygen.
Table 4. Interrupted time-series analysis of biochemical oxygen demand (BOD) and dissolved oxygen DO levels by location.
Table 4. Interrupted time-series analysis of biochemical oxygen demand (BOD) and dissolved oxygen DO levels by location.
ParametersAtsadathon RoadKlang StreamSriDonChai Road
Coef.p-Value95% CICoef.p-Value95% CICoef.p-Value95% CI
BOD
Intercept (β0)21.31<0.001 *11.4031.2213.810.001 *6.2021.4213.20<0.001 *7.0719.34
Trend (β1)−0.240.616−1.230.740.700.202−0.391.780.210.544−0.480.89
Level change after March 2021 (β2)10.920.358−12.8434.682.490.773−16.6122.199.480.181−4.6223.58
Trend change after March 2021 (β3)0.010.988−1.761.79−1.240.074−2.600.13−0.960.049 *−1.92−0.005
Post-intervention trend estimates−0.230.746−1.671.21−0.540.158−1.300.22−0.750.033 *−1.44−0.06
DO
Intercept (β0)1.360.104−0.293.011.210.006 *0.382.041.140.168−0.502.78
Trend (β1)0.050.583−0.140.24−0.010.853−0.090.080.160.157−0.070.39
Level change after March 2021 (β2)−2.340.076−4.920.25−0.690.162−1.680.29−3.980.010 *−6.96−1.00
Trend change after March 2021 (β3)0.100.411−0.150.350.050.402−0.060.15−0.090.445−0.330.15
Post-intervention trend estimates0.150.054−0.0030.310.040.271−0.030.110.070.072−0.0070.15
Note(s): BOD, biochemical oxygen demand; DO, dissolved oxygen; Coef., coefficient; CI, confidence interval. * p-value < 0.05.
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Owatsakul, V.; Panput, P.; Jaisuda, P.; Rinchumphu, D. Impacts of Wastewater Management and Enhancing the Landscape of the Mae Kha Canal: A Quasi-Experimental Study. Water 2025, 17, 1105. https://doi.org/10.3390/w17071105

AMA Style

Owatsakul V, Panput P, Jaisuda P, Rinchumphu D. Impacts of Wastewater Management and Enhancing the Landscape of the Mae Kha Canal: A Quasi-Experimental Study. Water. 2025; 17(7):1105. https://doi.org/10.3390/w17071105

Chicago/Turabian Style

Owatsakul, Vongkot, Prajuab Panput, Punyaphol Jaisuda, and Damrongsak Rinchumphu. 2025. "Impacts of Wastewater Management and Enhancing the Landscape of the Mae Kha Canal: A Quasi-Experimental Study" Water 17, no. 7: 1105. https://doi.org/10.3390/w17071105

APA Style

Owatsakul, V., Panput, P., Jaisuda, P., & Rinchumphu, D. (2025). Impacts of Wastewater Management and Enhancing the Landscape of the Mae Kha Canal: A Quasi-Experimental Study. Water, 17(7), 1105. https://doi.org/10.3390/w17071105

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