INTRODUCTION
Background and rationale
The rapid economic growth since the 18th century has led to a significant water crisis and pollution, particularly in developing countries reliant on natural resources In Thailand, a prominent Southeast Asian economy, water quality has deteriorated, posing serious health risks, with approximately 43 million people consuming contaminated water, leading to diseases like diarrhea and typhoid The situation is particularly dire in Chiang Mai, where the Mae Kha canal suffers from severe pollution due to industrial, domestic, and agricultural waste, as well as littering by residents Despite various projects aimed at addressing these issues, local communities continue to face challenges, and the canal remains in poor condition, reflecting a broader environmental policy failure.
2 with city aesthetics rather than environmental rehabilitation or protection (Ribeiro & Srisuwan, 2005)
Figure 1.1: Mae Kha canal in city moat
Constructed wetlands (CWs) are an effective method for achieving high pollutant removal rates while enhancing aesthetic appeal Unlike conventional wastewater treatment plants, which require significant capital investments, high operating costs, and large physical space, CWs provide a cost-effective solution with low operational and maintenance needs, as they do not rely on mechanical components or external energy (Sohair, 2013) In this study, four small-scale constructed wetlands planted with Hedychium coronarium were established under greenhouse conditions at the Department of Biology, Faculty of Science, Chiang Mai University, utilizing domestic wastewater sourced from municipal pipe systems along the canal.
Objectives
This study has two objectives, they are:
1 To introduce CWs to resident who live along Mae Kha canal bank
2 To evaluate the percentage removal of pollutant factors in domestic wastewater after treated by CW models using Hedychium coronarium.
Research questions and hypotheses
❖ Question 1: How well local resident accepted the idea of building CWs in their community to treat domestic wastewater?
❖ Question 2: Would the Constructed wetland models used Hedychium coronarium achieve good percentage removal like other wetland plants?
In this study, question 1 was expected to receive various responses whereas question 2 was expected to test two hypotheses below
Question 2: Would the Constructed wetland models used Hedychium coronarium achieve good percentage removal like other wetland plants?
- Null hypothesis (Ho): There is no significant between Hedychium coronarium percentage removal and that in other wetland plants
- Alternative hypothesis (Ha): There is a significant between Hedychium coronarium percentage removal and that in other wetland plants
LITERATURE REVIEW
Water pollution in Mae Kha canal
The Mae Kha Canal marks the historical outer boundaries of Chiang Mai and continues to run alongside sections of the ancient outer wall, serving as a significant historical monument Currently, the canal stretches approximately 16 km in length, with its width varying seasonally and regionally between 1 and 2 meters.
The Mae Kha Canal, with an average depth of 2.5 meters and a length of 10 meters, has historically served as a vital resource for drinking, fishing, and daily activities Prior to the 1950s, it was a pristine and vibrant waterway, surrounded by rice paddies and forests, highlighting its significance in the local ecosystem and community life (Ribeiro & Srisuwan, 2005).
The Mae Kha canal, a crucial water resource for agriculture, irrigation, and drinking, has faced significant pollution issues since a 1978 report classified its water quality as unsuitable for drinking or bathing This degradation has been attributed to urban drainage discharges and informal settlements along the canal's banks Research from Buffalo State University and Chiang Mai University in 2006 confirmed that water quality deteriorated as it flowed through Chiang Mai, with seasonal variations affecting pollution levels; the dry season showed higher pollution rates due to reduced water flow, while the rainy season initially helped flush pollutants but saw a resurgence of pollution towards the end.
A Why water in the city center could be that serious degraded?
Since urbanization, Chiang Mai has seen an influx of poor rural migrants settling in informal areas, particularly along the banks of the Mae Kha canal, which has resulted in the canal becoming narrower over time and increased flooding during the rainy season (Gustavo, 2005) Furthermore, the direct discharge of wastewater into the canal, combined with runoff from commercial and industrial activities, has exacerbated the flooding issue, as illustrated in Figure 2.1 below (Sunantana, 2016).
Figure 2.1: Wastewater sources to Mae Kha canal source: Sunantana, 2016
B Domestic wastewater versus industrial wastewater
Domestic wastewater typically contains a higher ratio of biodegradable organic matter compared to industrial wastewater While industrial factories treat their wastewater before discharging it into the sewer system, domestic wastewater includes all materials added during use, such as human waste and water from personal hygiene, laundry, food preparation, and cleaning This results in a diverse range of chemicals entering the sewage system To improve water quality in the Mae Kha canal, collaboration between local authorities and the community is essential to reduce both domestic and industrial wastewater contributions.
How about solutions?
Conventional wastewater treatment systems require extensive chemical and energy inputs, operate best with specially-trained personnel, and have a limited lifespan of 25 to 40 years The high costs associated with replacing or retrofitting outdated facilities make these systems impractical, especially in tropical countries where many developing nations lack adequate wastewater treatment and disposal infrastructure.
The water treatment plant in Chiang Mai faces significant challenges, as highlighted by Sunantana in 2016, due to its combined drainage system for wastewater and runoff During the rainy season, the plant experiences an overload, compromising the purification process With only one treatment facility serving the entire city, the capacity to clean water before it is released into the natural river is inadequate Although the Mae Kha project, supported by the Overseas Economic Cooperation Fund in the 1990s, aimed to enhance water flow and reduce erosion by expanding the canal's dimensions, it has struggled with long-term management and maintenance effectiveness.
In developing countries, the primary purpose is to protect the public health through control of pathogens to prevent transmission of waterborne diseases (Kivaisi,
2001) For this purpose, simple and cost-effective technologies are suitable and should
8 be encouraged in developing countries in general and tropical developing countries in particular
In today's climate of heightened environmental awareness and corporate social responsibility, biological treatment methods are emerging as effective solutions for addressing environmental degradation Among these methods, Constructed Wetlands have gained global recognition as a viable option for sustainable environmental management.
The first constructed wetland, established in Australia in 1904, was designed to replicate the natural processes of ecosystems like lakes and wetlands for pollutant treatment, often referred to as “natural wastewater treatment systems” (Vassiolios, 2017) According to Dr Kadlec and Mr Wallace, these modern treatment wetlands are engineered to enhance specific features of wetland ecosystems, thereby improving their treatment capacity and can be built in various hydrologic configurations.
According to Torczon, the basis Constructed wetland structure includes:
A basin can be effectively created by utilizing the land's topography along with various grading techniques The substrates employed in a constructed wetland (CW) vary based on the specific site location and the intended function of the wetland, incorporating materials such as soil, gravel, sand, rock, and organic matter.
The choice of substrate is crucial for the dominant plant life in constructed wetlands (CW), as it influences the types of species that thrive Common wetland plants found in these systems include Canna, Heliconia, Spartina alterniflora, Elodea canadensis, and Azolla caroliniana.
In Thailand, the adoption of CW systems is currently limited; however, their recognition is anticipated to grow due to their sustainable and energy-saving benefits.
Constructed wetlands (CWs) have demonstrated superior performance in tropical regions, where the warm climate fosters year-round growth of macrophytes and increased microbiological activity (Karin & Hristina, 2007) Notable examples of CWs in Thailand include the Ban Pru Teau in Phang-nga Province and the Koh Phi Phi Integrated Wastewater Management System, renowned for its unique design featuring a flower and butterfly park, which has drawn tourists back to the island following the 2004 tsunami (Brix, 2011).
B How wetlands improve water quality?
Wetlands play a crucial role in the secondary treatment of municipal and certain industrial wastewaters, effectively polishing secondary effluent and runoff that may carry pollutants from diffuse sources (Norio, 2011) Wastewater treatment involves four key stages: Primary treatment eliminates solid matter; Secondary treatment employs micro-organisms to break down and remove remaining dissolved wastes and fine particles; Nutrient removal addresses nitrogen and phosphorus to prevent algal blooms that threaten aquatic life; and Disinfection targets disease-causing micro-organisms (Queensland Government, 2017).
Constructed wetlands (CWs) are effective in treating a variety of wastewater types, such as domestic, industrial, and agricultural sources (Vassilios, 2017) Their treatment performance is influenced by factors like design, organic loading rate, and hydraulic retention time (Karpiscak, 1999) Pollutant removal in CWs occurs through physical, chemical, and biological processes, including sedimentation, precipitation, absorption by soil, plant tissue assimilation, and microbial transformations (Davis, 2006) The most successful treatment wetlands enhance these mechanisms for optimal performance.
Constructed wetlands are categorized into two types as:
Subsurface flow constructed wetlands (CWs) can be categorized into two main types based on flow direction and substrate saturation: horizontal subsurface flow (HSF) and vertical flow (VF) Additionally, more variations such as tidal flow, upflow, and downflow have been identified by Vassilios in 2017 The choice of constructed wetland type depends on specific objectives According to the EPA in 2000, subsurface flow wetlands offer significant benefits, including the prevention of mosquitoes and odors, as well as reducing public contact with partially treated wastewater In contrast, free water surface (FWS) wetlands expose water surfaces to the atmosphere, increasing the risk of mosquito breeding and public access.
Research indicates that both Horizontal Subsurface Flow (HSF) and Vertical Flow (VF) constructed wetlands produce high-quality effluent, with VF being particularly recommended for wastewater treatment due to its compact size, superior effluent quality, and lower evapo-transpiration rates A study by Sohair in 2013 demonstrated that VF is an effective technique for reducing Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), and Total Suspended Solids (TSS), achieving removal rates exceeding 90% These findings align with similar research conducted by Haritash et al (2015) and Konnerup (2008).
From all reasons above, in this study, VF constructed wetland models were selected
Plants in constructed wetlands (CWs) serve crucial ecological functions beyond their aesthetic appeal According to a 2013 USDA Natural Resources Conservation Service research poster, vegetation in CWs primarily enhances microbial habitats, as the stems and leaves slow water flow and promote sedimentation, providing ample surface area for microbial attachment This increased vegetation fosters a more aerobic microbial environment in the substrate, helping to prevent erosion, mitigate pollutant entry, and maintain water quality in natural waterways Consequently, plant species thriving in the wettest conditions demonstrate the most significant ecological benefits.
Wetlands are dynamic ecosystems characterized by their unique adaptations to wet conditions, particularly in the root zone or rhizosphere, which serves as the active reaction zone This critical area facilitates essential physiochemical and biological processes driven by interactions among macrophytes, microorganisms, soil, and pollutants.
Tropical conditions can significantly enhance the performance of constructed wetlands (CWs) in addressing climate-related challenges (Norio, 2011) While CWs are recognized for their multiple benefits, they are not without limitations, the most notable being clogging due to the accumulation of organic and inorganic materials, biomass production, and dense root systems (Stefanakis et al., 2014) Additionally, the implementation of CWs in tropical regions poses environmental concerns, particularly regarding the breeding of disease-carrying insects like mosquitoes, which require standing water for reproduction To mitigate these risks and reduce the incidence of diseases such as malaria, it is crucial to design and operate constructed treatment wetlands effectively (Norio et al., 2011).
Hedychium coronarium (White Ginger)
In this study, Hedychium coronarium J Koenig, an uncommon wetland plant, was chosen for its favorable geographical distribution and morphology, which align with the examiners' criteria Additionally, this plant is significant for its potential in reducing mosquito larvicidal populations.
Firstly, H coronarium (syn H flavescens Carly; H flavum Roscoe; H sulphureum Wall) is a rhizomatos flowering plant popularly called white ginger lily
Hedychium coronarium, a member of the Zingiberaceae family, originates from regions such as China, Taiwan, Myanmar, and the Indian Subcontinent, including India and Nepal This plant thrives in shaded or semi-shaded areas that experience waterlogging, often found along riverbanks and in shallow waters, but it avoids completely submerged locations Additionally, H coronarium can grow at the edges of shaded secondary forests Its rhizomes are fleshy, branched, and knotty, featuring numerous nodes and reaching diameters of 2.5 to 5 cm as they spread horizontally beneath the soil surface.
& Dixit, 2017) Therefore, it could adapt to the substrate of CWs
The essential oil, methanolic, and aqueous extracts from the leaves and rhizomes of H coronarium were evaluated for their antimicrobial, mosquito larvicidal, and antioxidant properties A study identified 46 compounds in the rhizome oil, with key components including linalool, limonene, trans-metamentha, 2,8 diene, γ-terpinene, and 10-epi-γ-eudismol Additionally, the essential oil extracted from the flowers revealed a total of 29 components.
The study identified 14 main constituents in H coronarium, including β-transocimenone, linalool, 1,8-cineole, α-terpineol, 10-epi-γ-eudesmol, sabinene, and terpinen-4-ol (Chaithra, 2017) Notably, α-pinene, β-pinene, and 1,8-cineole demonstrated larvicidal effects on Aedes aegypti larvae, with LC50 values of 15.4, 12.1, and 57.2 ppm, respectively (Lucia, 2007) Additionally, H coronarium serves various purposes in daily life, including its use as a source of paper pulp, high-grade perfumes, and medicinal applications (Duke et al., 1985; Chopra et al., 1986; Uphof).
1959) Therefore, H coronarium was expected to reduce significantly mosquito larvicidal in CW models
MATERIALS AND METHODS
Surveying
To gain insights into the contamination of the Mae Kha canal from the residents' perspective, a survey was conducted from March 18 to 20 Questionnaires were distributed to residents living along three study plots: upstream, middle, and downstream of the canal Respondents shared their awareness of water pollution in the Mae Kha canal and its impact on their daily lives Additionally, the researcher proposed an alternative solution involving the creation of constructed wetlands, categorized into household and community scales, to mitigate the issue For detailed information, refer to Appendix 1.
For selecting survey area, a three-mile canal corridor that in urban Chiang Mai City were observed following the research area in a research of Sunantana in 2016:
The studied site begins at a 12-lane super-highway, marking the urban boundary, and extends through a bustling residential and tourist-business area It continues south towards the city center, where Mae Kha Canal converges with Lumkuwai Creek in a local community setting.
In this study, three selected plots were visualized in Figure 3.1
Figure 3.1: Study sites source: Sunantana, 2016
Domestic wastewater treatment using CW models with Hedychium coronarium 16 1 Materials
- Gravel (fine and medium side)
- Plant: Hedychium Coronarium (White Ginger)
All of the materials were carefully washed before the experiments were set up
From April 20 to June 5, 2018, CW replicates were established at the Department of Biology, Faculty of Science, Chiang Mai University under greenhouse conditions The experiment involved four tanks with Hedychium Coronarium and four control tanks Water samples collected from municipal sewer were divided into two buckets, treated with and without oxygen addition over a six-week period Each tank measured 54.7 cm in height and 27 cm in diameter, filled with 16 cm of sand, 22 cm of fine gravel, and 14.5 cm of medium gravel.
Figure 3.2: Designing constructed wetland models
A study was conducted to investigate the impact of nitrogen transformation on the pollutant uptake ability of H coronarium by treating water samples with and without oxygen Initial analyses revealed that wastewater samples from households were significantly contaminated, exceeding safety standards set by the Thailand Ministry of Natural Resources and Environment in 2010, which stipulate that total suspended solids (TSS) should not exceed 30 mg/L, total phosphorus should not exceed 2 mg-P/L, and total nitrogen should not exceed 20 mg-N/L The results, presented in Table 3.1, illustrate the changes in domestic wastewater parameters following treatment.
18 added oxygen Overall, all parameters had reduced compare with those in none oxygen addition bucket except for the increase in NO₃-N
Table 3.1: The difference between before and after domestic wastewater was added oxygen Parameters
The most significant change observed is the sharp increase in NO₃-N levels and a noticeable reduction in NH₄-N, attributed to nitrogen transformations occurring in the oxygen addition tanks As noted by Stefanakis et al (2014), key removal mechanisms include ammonification, nitrification, denitrification, plant uptake, and adsorption The introduction of oxygen into wastewater enhances the conversion of ammonia to nitrate, resulting in higher nitrate concentrations, which subsequently serve as essential nutrients for plant growth.
Under low dissolved oxygen (DO) conditions, denitrifying bacteria utilize nitrate-nitrogen as an electron acceptor, converting it into nitrogen gas once the DO levels decrease (Pai et al., 2013).
In week zero, all tanks were filled with clean water to facilitate system acclimatization over the course of one week Beginning in week one, wastewater was introduced daily to the tanks, both with and without oxygen addition, on days three and seven, following the weekly water drainage for analysis Water samples were collected at both the inlet and outlet points of the constructed wetlands (CWs) on day zero and subsequently every seven days to measure the percentage removal of COD, DO, TSS, NH4-N, NO3-N, and PO4-P, with each CW replicate being analyzed.
A total of 23 sample bottles were collected and analyzed to evaluate effluent and influent parameters Specifically, 800 ml of water samples were divided into two bottles for effluent assessment For influent measurements, four bottles containing 1,600 ml of wastewater with oxygen addition were collected, along with three bottles containing 1,200 ml of wastewater without oxygen addition.
Table 3.2 below presents analysis methods in this study which followed APHA stadard methods for the Examination of Water and Wastewater (23 nd edition) published in 2017
Table 3.2: Water analysis using standard methods
Total Dissolved Solids (TDS), pH Measured by a multi-parameter analyzer
Disolved Oxygen (DO) Azide modification method (4500-O C)
Chemical Oxygen Demand (COD) Analyzed by a close reflux, titrimetric method
Total Suspended Solids (TSS) Standard method (2540 D)
Ammonium nitrogen (NH4-N) Modified salicylate method
Nitrate nitrogen (NO3-N) UV-method
Orthophosphate (PO4-P) Stannous chloride method (4500-P D)
Statistical analysis of the collected data from both the survey and experiment was conducted using Microsoft Excel 2010 The percentage removal of influent and effluent mass was calculated using a specific equation.
Where Ci is the influent mass in mg/week; Co is the effluent mass in mg/week (Sohair, 2013)
The influent mass refers to the total water accumulated in the tanks, including daily additions on days three and seven, while the effluent mass is the total water remaining in the tanks after one week Although influent and effluent water were collected on the same day, the influent water measurement pertains to the week following the collection.
RESULTS AND DISCUSSION
Surveying results
4.1.1 General background of the communities
A total of 82 households, comprising 319 inhabitants, participated in the interview, with 22 respondents from the upstream area and 30 each from the middle and downstream areas Notably, 68% of participants reside within 5 meters of the Mae Kha canal The average household size in these communities is 3.89 individuals, and 59% of respondents report a monthly income ranging from THB 10,000 to THB 50,000 The majority of respondents are of working age, with 33% between 21 and 40 years old, followed by 31% aged 41 to 60, while only 18% are under 20 years old.
Residents utilize water daily for activities such as cooking, washing clothes and dishes, and gardening A significant portion of this water, nearly 70 percent, is reported to be drained out, with each household using approximately 300 gallons.
Many individuals are unaware of the destination and treatment of their wastewater, despite each person using approximately 600 liters of water daily A survey revealed that 22% of respondents directly drain wastewater into the Mae Kha Canal, while 20% dispose of it onto the soil, as illustrated in Figure 4.1 Most participants mistakenly believe their wastewater is directed to municipal sewers or septic tanks According to Unchulee (2014), residents perceive that they discharge wastewater through their plumbing systems.
The municipality's pipe network is responsible for collecting all community wastewater and discharging it directly into the Mae Kha canal Unfortunately, the existing water treatment system is inadequate for properly cleaning the wastewater before it is released into the natural river (Sunantana, 2016).
Figure 4.1: Domestic wastewater effluents in resident’ view
4.1.3 How can water pollution in Mae Kha canal affect resident’ lives?
Residents living along the Mae Kha canal identify household waste as the primary cause of severe pollution, with 24% of respondents attributing it to this source Markets and hotels contribute to the issue as well, with 16% and 17% of respondents respectively citing their impact Interestingly, only 15% believe that ineffective wastewater treatment from industrial plants is a significant factor The adverse effects of this pollution are evident, as nearly 60% of residents report being unable to tolerate the bad odor, particularly from afternoon to late night, while 25% express concerns about an increase in mosquito populations.
A recent survey revealed that while only 3 percent of respondents expressed discomfort due to the dark color of the Mae Kha canal, there is a strong consensus among all participants for effective solutions to address water pollution in the area.
Figure 4.2: Main sources of wastewater before drained out
4.1.4 How resident think about Constructed wetlands?
The survey introduced an alternative solution to address the issue of wastewater management through the creation of Constructed Wetlands, which can be categorized into household and community scales Results indicated that a higher number of respondents believed community constructed wetlands would be more effective, as shown in Figure 4.3 However, the preference for household constructed wetlands was also significant Those favoring community options argued that larger constructed wetlands could perform better, though this presents challenges for construction in the densely populated area near Mae Kha canal Conversely, a group of respondents expressed support for household constructed wetlands.
24 constructed wetland idea, believed that the wetland will be better conserved if it belongs to a particular individual than a whole community
Figure 4.3: Resident’ preference towards two constructed wetland size
Domestic wastewater treatment using CW models with Hedychium coronarium 24 1 Removal of COD
This study marks the first global application of H coronarium in constructed wetlands (CWs), aiming to evaluate its effectiveness in comparison to other common wetland plants The comparison of effectiveness was determined by analyzing the average percentage of pollutants removed by H coronarium, focusing on parameters such as COD, TSS, PO4-P, NH4-N, and NO3-N.
Chemical Oxygen Demand (COD) is a crucial metric that indicates the ability of water to utilize oxygen for the decomposition of organic materials and the oxidation of inorganic substances, including ammonia and nitrite, as defined by Science Encyclopaedia.
Commonly, COD measurements are made on samples of waste waters or of natural waters contaminated by domestic or industrial wastes
The study illustrated in Figure 4.4 shows a significant increase in the percentage removal of COD in constructed wetland (CW) models, rising from 54.3% to 95.3% over six weeks Control tanks, which did not receive oxygen addition, achieved the highest average removal rate of 85.8% Interestingly, the presence of H coronarium did not significantly impact COD removal, contradicting Akratos and Tsihrintzis' 2007 findings that indicated higher COD removal in planted beds compared to unplanted ones However, this observation aligns with Konnerup's 2008 research, which acknowledged the potential role of plants in COD removal, noting that the effect is often minimal and varies by species.
In treatments involving H coronarium, an average COD removal rate of 83% was achieved, as illustrated in Figure 4.4 and Table 4.1 This effectiveness is lower compared to other wetland plants, such as Canna lily, which demonstrated a 92.8% removal rate (Haritash et al., 2015), and a combination of Canna, Phragmites, and Cyperus, which reached a removal efficiency of 92.9% (Sohair et al.).
Figure 4.4 illustrates the percentage removal of Chemical Oxygen Demand (COD) by mass, with dotted lines indicating the weekly average influent mass of wastewater and solid lines representing the average effluent mass of treated water The space between the dotted and solid lines reflects the average percentage mass removal of COD across all tanks.
Table 4.1: COD removal mass in percentage after each week
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6
Control tanks with oxygen addition 72.50 57.06 90.96 93.92 93.28 92.90 83.44 Control tanks without oxygen addition
Total Suspended Solids (TSS) refers to all particles captured by filtering a sample through a specific pore size filter, encompassing a variety of materials from silt and sediment to larger debris.
27 of plant material such as leaves or stems and even insect larvae and eggs can fall in the general category of TSS
In constructed wetland (CW) systems, total suspended solids (TSS) are primarily trapped as sludge on the surface of the vertical flow (VF) CW bed, while some TSS infiltrates the porous medium for oxidation (Stefanakis et al., 2014) As illustrated in Figure 4.5 and Table 4.1, TSS mass removal percentages significantly increased across all systems after six weeks, ranging from a low of 18.3% to a high of 100.0% Notably, the control tank with oxygen addition achieved the highest average mass removal rate at 94%.
Figure 4.5 illustrates the percentage removal of total suspended solids (TSS) by mass, highlighting the average influent mass of wastewater each week with dotted regression lines The solid lines depict the average effluent mass of treated water after one week The difference between the dotted and solid lines indicates the average percentage mass removal of TSS across all tanks.
In H coronarium treatments, a significant reduction in total suspended solids (TSS) was observed across all planted tanks, achieving an average removal rate of 82.6% This finding aligns with Ye & Li's 2009 study on Schoenoplectus trigueter, although it is less efficient compared to Canna and Heliconia, which demonstrated removal rates of 96% and 97%, respectively, as noted by Konnerup in 2008.
2008 and Kadlec, 2003 that solids are mainly removed by a physical filtration mechanism thus there is no difference in removal of TSS between planted and unplanted beds
Table 4.2: TSS removal mass in percentage after each week
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6
Control tanks with oxygen addition 85.24 92.76 93.48 100.00 96.42 96.16 94.01 Control tanks without oxygen addition
Orthophosphates (PO4-P) in natural water serve as a key indicator of phosphorus availability for algae and plant growth, being the most accessible form for biological uptake They can enter streams and lakes via runoff and are subject to transformation through microbial uptake, chemical precipitation, or absorption by plants (Soltis-Muth, 2003).
After six weeks, PO₄-P levels significantly decreased across all systems, with reductions ranging from 88.6% to 99.5% The highest average percentage removal was observed in control tanks with added oxygen, achieving a remarkable 97.8% These findings are illustrated in Figure 4.6 and detailed in Table 4.3.
In treatments involving H coronarium, the average effectiveness reached 93%, significantly surpassing the combined effectiveness of Canna, Phragmites, and Cyperus at 63% Additionally, it outperformed Cyperus papyrus, which showed an effectiveness of 89%, and Miscanthidium violaceum, which had a lower effectiveness of 31% (Sohair et al., 2013).
Research by Kyambadde et al (2004) indicates that the phosphate (PO₄-P) removal efficiency of H coronarium is somewhat lower than that observed in control tanks with oxygen supplementation This observation aligns with Vassilios (2017), who noted that the effectiveness of plants in vertical flow constructed wetlands (VF CWs) is often constrained by the limited contact time of the percolating wastewater.
Figure 4.6 illustrates the percentage removal of PO₄-P by mass, with dotted lines indicating the regression lines for the average influent mass of wastewater each week In contrast, the solid lines represent the average effluent mass of treated water after one week The difference between the dotted and solid lines highlights the average percentage mass removal of PO₄-P across all tanks.
Table 4.3: PO₄-P removal mass in percentage after each week
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6
90.55 99.11 94.52 92.99 94.11 92.37 93.94 Control tanks with oxygen addition 97.18 99.52 98.25 97.78 97.40 96.70 97.80
Control tanks without oxygen addition
4.2.4 Removal of NH 4 -N and NO 3 -N
Nitrogen (N) is a crucial nutrient for the biological development of organisms, yet it is a significant pollutant in wastewater that poses toxicity risks to aquatic life (Sohair, 2013) Excess nitrogen concentrations, ranging from 0.1 to over 1.6 mg/L, can lead to eutrophication in surface waters, resulting in excessive algae growth that depletes dissolved oxygen and affects other aquatic species (Grace et al., 2010) This is supported by data indicating a dissolved oxygen level of 0 mg/L alongside high NH₄-N and NO₃-N concentrations Nitrogen exists in various forms, including inorganic (ammonia, nitrate) and organic (amino acids, nucleic acids), and undergoes numerous transformations in the ecosystem as organisms utilize it for growth and energy (Bernhard, 2010).
CONCLUSION
To identify the primary causes of water issues in Mae Kha Canal, the author aims to distribute a questionnaire to gather insights about the daily lives of local residents Your participation in this study will aid scientists in their efforts to restore the cleanliness of Mae Kha Canal.
1 How many people are there in your family?
2 Please give us the age of each members in your family?
3, Do you know about the severe contamination in Mae Kha Canal?
4, What do you think is the main source of wastewater poured into Mae Kha Canal? (you can choose more than 1 option)
5, Do you think the water pollution in Mae Kha Canal can affect you?
6, How it affect you? (you are allowed to choose various answers)
7, What time of a day does the smell annoy you most?
8, Do you want water quality in Mae Kha Canal to be improved? Why?
9, How far is it from your house to the Mae Kha Canal?
10, Do you have a house filter?
B - No, I would like to have
C - No, I don’t like using it
11, How about pipe system in your house? Is water directly drained into the canal?
12, How you use water in daily life? (you are allowed to choose various answers)
13, How much water you drain into the canal?
A - Less than 100 liters per day
D - More than 600 liter per day
14, How much is your total income per month?
15, How do you prefer the methods below?
Methods No at all A little Medium A lot