Treating wastewater from households along mae kha canal using hedychium coronarium a pilot study in thailand

Keywords: Constructed wetlands CWs, water quality, Hedychium coronarium, percentage removal... Domestic wastewater treatment using CW models with Hedychium coronarium.. Domestic wastewa

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURAL AND FORESTRY

NGUYEN MINH CHAU

TOPIC TITLE: TREATING WASTEWATER FROM HOUSEHOLDS

ALONG MAE KHA CANAL USING HEDYCHIUM CORONARIUM

A PILOT STUDY IN THAILAND

BACHELOR THESIS

Study mode : Full-time Major : Environmental Science and Management Faculty : International Program Office

Batch : 2014-2018

Thai Nguyen, 21/10/2018

DOCUMENTATION PAGE WITH ABSTRACT

Thai Nguyen University of Agriculture and Forestry

Degree Program Bachelor of Environmental Science and Management

Thesis title

Treating wastewater from households along Mae Kha

canal using Hedychium coronarium – a pilot study in

Thailand

Supervisors

Associate Prof Dr.Arunothai Jampeetong Department of Biology, Faculty of Science, Chiang Mai University

PhD Hoang Hai Thanh Advanced Education Program Office, Thai Nguyen University of Agriculture and Forestry

Supervisor’s signature

Abstract:

Chiang Mai, Thailand is one of the most famous destinations for tourists worldwide Unfortunately, the water pollution is a problem that has been interfering residents’ life and economic development due to rapid urbanization One of the most serious cases is Mae Kha canal which is an important feature in Chiang Mai's water system This research, therefore, aims to help local resident building cost-effective wastewater treatment models called Constructed Wetlands (CWs) in order to filter sewage at household level before it was release into the environment The experiment

consisted of four tanks covered with Hedychium coronarium and four control tanks, all

set up at Department of Biology, Faculty of Science - Chiang Mai University The water sample was collected from municipal sewer then separated by two different buckets in which it was treated with and without oxygen addition throughout six

weeks In this study, Hedychium coronarium – a non-common wetland plant, was

selected as it is recorded able to lessen mosquito appearance which certainly is one of the drawbacks of CWs The experiments goals were to estimate the average percentage

of parameters removed by Hedychium coronarium in terms of COD, TSS, PO4-P,

NH4-N, NO3-N The percentage removal in COD, TSS, PO4-P, NH4-N, NO3-N were

83%, 82.6%, 93%, 89%, 84.7% respectively It initially proved that the removal

efficiency of Hedychium coronarium is as high as others wetland plants and expected

to inspire future researchers in continuing to apply new plants to lessen CWs’

perennial problems and optimize its benefits in wastewater treatment

Keywords: Constructed wetlands (CWs), water quality, Hedychium

coronarium, percentage removal

Number of pages 48 pages

Date of submission 21/10/2018

ACKNOWLEDGEMENTFirst and foremost, I would like to thank my supervisor Assoc Prof Dr Arunothai Jampeetong for being supportive during my difficult time She had set an

example of excellence as a researcher, mentor, instructor, who always prioritize her students and science

I would like to thank my instructor, Tararag Pincam for always being so

patient with me even though I misunderstood and made troubles many times She always supported me with my works as well as treated me as a sister and gave me various valuable advices in life

I would like to thank my supervisor Dr Hoang Hai Thanh from Vietnam for

her constant support

I would like to say thank to all members in Biology laboratory of Faculty of Science, Chiang Mai University, they were always kind to me and never hesitated to give me a hand

Finally, I would like take this opportunity to extend my sense of gratitude to my family and friends who always believe in me and backing me unceasingly

NGUYEN MINH CHAU

TABLE OF CONTENTS

LIST OF FIGURES vii

LIST OF TABLES viii

LIST OF ABBREVIATION ix

PART I INTRODUCTION 1

1.1.Background and rationale 1

1.2.Objectives 2

1.3 Research questions and hypotheses 3

1.3.1 Research questions 3

1.3.2 Research hypotheses 3

PART II LITERATURE REVIEW 4

2.1 Water pollution in Mae Kha canal 4

2.2 How about solutions? 7

2.2.1 Previous solutions 7

2.2.2 Constructed Wetland 8

2.3 Hedychium coronarium (White Ginger) 12

PART III MATERIALS AND METHODS 15

3.1 Surveying 15

3.2 Domestic wastewater treatment using CW models with Hedychium coronarium 16 3.2.1 Materials 16

3.2.2 Experimental set up 17

3.2.3 Water Sampling and analysis 19

3.2.4 Statistical analysis 20

PART IV RESULTS AND DISCUSSION 21

4.1 Surveying results: 21

4.1.1 General background of the communities 21

4.1.2 Household’s wastewater management 21

4.1.3 How can water pollution in Mae Kha canal affect resident’ lives? 22

4.1.4 How resident think about Constructed wetlands? 23

4.2 Domestic wastewater treatment using CW models with Hedychium coronarium 24 4.2.1 Removal of COD 24

4.2.2 Removal of TSS 26

4.2.3 Removal of PO4-P 28

4.2.4 Removal of NH4-N and NO3-N: 30

PART V CONCLUSION 35

REFERENCES 36

APPENDIX 43

Appendix 1 44

Appendix 2 48

LIST OF FIGURES

Figure 1.1: Mae Kha canal in city moat 2

Figure 2.1: Wastewater sources to Mae Kha canal 6

Figure 2.2: Hedychium coronarium 13

Figure 3.1: Study sites 16

Figure 3.2: Designed constructed wetland models 17

Figure 4.1: Domestic wastewater effluents in resident’ view 22

Figure 4.2: Main sources of wastewater before drained out 23

Figure 4.3: Resident’ preference towards two constructed wetland size 24

Figure 4.4: Percentage removal in COD by mass 26

Figure 4.5: Percentage removal in TSS by mass 27

Figure 4.6: Percentage removal in PO₄-P by mass 29

Figure 4.7: Nitrogen transformation in nature 31

Figure 4.8: Percentage removal in NH₄-N by mass 32

Figure 4.9: Percentage removal in NO₃-N by mass 33

Figure A1: Residents worried when talking about Mae Kha canal 48

LIST OF TABLES

Table 3.1: The difference between before and after domestic wastewater was added

oxygen……… 18

Table 3.2: Water analysis using standard methods ……… 19

Table 4.1: COD removal mass in percentage after each week ……… 26

Table 4.2: TSS removal mass in percentage after each week……… 28

Table 4.3: PO₄-P removal mass in percentage after each week ……… 29

Table 4.4: NH₄-N removal mass in percentage after each week……… 32

Table 4.5: NO₃-N removal mass in percentage after each week……… 33

LIST OF ABBREVIATION

CWs Constructed wetlands FWS Free water surface

SSF Subsurface flow

PART I INTRODUCTION 1.1 Background and rationale

In this era, human being is facing water crisis and water pollution due to rapid economic growth since the First Economic Revolution in 18 century Water pollution

is not an unfamiliar topic nowadays, especially in the case of developing countries, where economic development is still depending significantly on natural resources Moreover, the anthropogenic pollutants from industrial, domestic and agricultural waste are ultimately absorbed by aquatic plants and animals Thailand, one of Southeast Asia’s tiger economies is facing the same environmental problem Water quality in Thailand has declined, alarming health risks if water is not purified before

consumption According to Brianna in 2017 there are approximately 43 million Thai

people drinking contaminated water, allowing diseases like diarrhea, typhoid and dysentery to enter their system; this water is contaminated primarily by pollutants disposed into rivers and streams Water quality in Thailand varies throughout the country In Chiang Mai city, which located in northern Thailand, a city famous for its rich culture heritage but water degradation here has been a serious concern for both resident and local authority in many years, one of the prominent polluted water bodies

is Mae Kha canal Many projects and researches had been carried out to solve that problem, but until now, resident live along the water source still find Mae Kha canal is

in poor conditions and gradually turn their back on the canal (Sunantana , 2016) The current situation is shown in Figure 1.1 below People have complained that the wastewater from local houses especially slums was the main cause of pollution, besides, resident littering also add to the problem (Sunantana, 2016; Harmony, 2006; Unchulee, 2014) This is worsened by environmental policies, which are concerned

with city aesthetics rather than environmental rehabilitation or protection (Ribeiro & Srisuwan, 2005)

Figure 1.1: Mae Kha canal in city moat

Among all of current methods, there is a method which can both achieve high pollutant removal rate and aesthetic appearance that is Constructed wetlands (CWs) Conventional wastewater treatment plants involve large capital investments and operating costs not mention to a large area to build the whole systems In contrast, Constructed wetlands offer low cost operation and maintenance since no mechanical components or external energy is required (Sohair, 2013) Therefore, in this study, four

small duplicates of Constructed wetland planted with Hedychium coronarium were

created in greenhouse conditions of Department of Biology, Faculty of Science, Chiang Mai University and treated by domestic wastewater collected from municipal pipe systems along the canal

1.2 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

1.3 Research questions and hypotheses

1.3.1 Research questions

❖ 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?

- 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

PART II LITERATURE REVIEW

As one of largest cities in Thailand, Chiang Mai has been through the same development process as Bangkok and other big city after 1950’s, during the urbanization period Chiang Mai city was found in 1296 under King Mengrai’s rule as the capital of old Lanna Kingdom At present, it is the center of culture, economics and education of northern Thailand According to Sangawongse, 2005, the urban area of Chiang Mai increased from 15 km2 in 1952 to 339 km2 in 2000, with a tendency to increase over time Besides, the number of tourists arrivals in the year 2002, which reached 3,460,886 according to Tourism Authority of Thailand; together cause a dense population in Chiang Mai city, particularly, in 2015 there was 5,000 people per square kilometer bases on a report of The World Bank This rapid population increase has become a burden to many environmental sources such as water, land, and air Today, according to the Air Visual app, which monitors air quality around the world, Chiang Mai ranked sixth worst in the world in terms of air pollution, according by US Air Quality Index, not to mention the serious water degradation here which has degraded Chiang Mai image in foreign friends and disturb residents’ lives (The Nation, 2018)

2.1 Water pollution in Mae Kha canal

Mae Kha canal defines the historical outer borders of Chiang Mai, and today still accompanies parts of the outer wall as historical monuments The canal is presently about 16 km long, its width fluctuates seasonally and locally between 1 and

10 m and has an average depth of 2.5 m, which also varies by season and location (Ribeiro & Srisuwan, 2005) Before 1950’s, Mae Kha Canal was an exuberant, beautiful, clean canal that could be used for drinking, fishing, and other functions of daily life At that time most of land was used for rice paddy and forest, Mae Kha was a

major water resource for agriculture, irrigation, and drinking (Sunantana, 2016) However, a 1978 report indicates that the Mae Kha canal was already heavily polluted

at that time, with the water quality being classified as standard type 5, that indicated water source was unsuitable for drinking or bathing based on the surface water classification in “Water Quality Standard” Pollution Control Department, Ministry of Natural Resources and Environment (Gustavo, 2005) Water quality became poorer as the result of general drainage discharges from the city as well as the presence of informal settlements located right on the banks of the canal In 2006, a research from

Buffalo State University of New York cooperated with Chiang Mai University

examined the impact of Chiang Mai on water quality in the Mae Kha canal that runs through the city, according to them water quality became degraded as it passed through the city, as compared to upstream control sites Seasonal differences have also impacted pollution rate in Mae Kha canal that the pollution rate in dry season is higher than those in rainy season, due to low water input In contrast, during rainy season, more water flushes pollution substances down the drain In the late rainy season, pollution rate tends to raise back again (Christie, 2014)

A Why water in the city center could be that serious degraded?

Since urbanization, Chiang Mai attracted poor rural migrants who settled in informal settlements seeking for jobs in inner city, some of which were located on the banks of the Mae Kha canal, lead to the canal getting narrower after a period of time and this caused flooding during the rainy season (Gustavo, 2005) Besides, the way they discharge wastewater directly to the canal adds together with commercial and industrial factories, and urban run-off have worsen the problem, it was visualized 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

Typically, domestic wastewater is often considered to contain a higher ratio of biodegradable organic matter than that in many of industrial wastewater (Norio, 2011) Industrial factories have their own facilities for treating industrial wastewater and then discharge the treated water into the sewer system (Yun-Young et al., 2013) On the other hand, domestic wastewater is the water that has been used by a community and which contains all the materials added to the water during its use It is thus composed

of human body wastes (faeces and urine) together with the water used for flushing toilets, and sullage, which is the wastewater resulting from personal washing, laundry, food preparation and the cleaning of kitchen utensils , thus contributes a wide variety

of chemicals into sewage (Duncan, 2003) To alter water degradation in Mae Kha canal, the consensus of local authority and community is needed to reduce the amount

of domestic wastewater as well as commercial and industrial wastewater

2.2 How about solutions?

2.2.1 Previous solutions

Conventional systems require significant inputs of chemicals and energy, and need to be operated by specially-trained personnel Furthermore, the useful life of such systems is limited (25–40 years) and replacement/retrofitting costs to make outdated facilities operational again are significant (Vassiolios, 2017) Therefore, this method is not suitable to apply in tropical countries since most of the developing and the least developed countries are located in tropical and subtropical regions of the world In these countries, public and private wastewater treatments and disposal systems are often very deficient or even entirely missing (Norio, 2011)

Moreover, that is an inadequacy of water treatment plant in Chiang Mai, pointed out by Sunantana in 2016, where the drainage system is a combined system of wastewater and runoff In rainy season, there is an overload of water in the treatment plant that directly affects a purifying process With only one treatment plant available, the system to clean water for the entire city before releasing to the natural river is not sufficient Futhermore, in 1990’s, with support from OECF, Overseas Economic Cooperation Fund organization, Mae Kha was constructed with concrete lining in the urban area, expanded the canal to 2-2.5 meter in depth and 4-5 meter in width in order

to improve water flow and reduce erosion However; this project was not quite successful in long-term management and maintenance program

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

be encouraged in developing countries in general and tropical developing countries in particular

2.2.2 Constructed Wetland

Today more than ever, with an increase in environmental awareness and corporate social responsibility, biological treatment methods are considering effective alternatives to deal with environmental degradation One of those methods that has been used worldwide is Constructed Wetlands

A What is Constructed Wetland?

The first constructed wetland was built in Australia in 1904 Such systems are designed to mimic the function and processes of natural ecosystems, such as lakes and wetlands, in treating pollutants, and are called “natural wastewater treatment systems” (Vassiolios, 2017) Another definition of Constructed Wetland by Dr Kadlec and Mr

designed to emphasize specific characteristics of wetland ecosystems for improved treatment capacity Treatment wetlands can be constructed in a variety of hydrologic modes”

According to Torczon, the basis Constructed wetland structure includes:

1 A basin containing water

2 A substrate

3 Plant life

In particular, a basin can be constructed by using the topography of the land and various grading operations Substrates used in a constructed wetland are depend on the site location and function of the CW Various soil, gravel, sand, rock, and organic

material are typically used as substrates The type of substrate is very important in determining the type of plant life that will predominant a CW (Carl et al., 2006) Some

common wetland plants are: Canna, Heliconia, Spartina alterniflora, Elodea canadensis, Azolla caroliniana…(Department of Environment, Health and Natural

Resources, North Carolina, 1997)

In Thailand, the use of CW systems is not widespread but it is expected to be recognized more due to the fact that they are sustainable and energy saving (Suwasa, 2013) since CWs have showed better performances in tropical areas as the warm climate is more conductive to year-round macrophyte growth and microbiological activity (Karin & Hristina, 2007) Some prominent constructed wetlands in Thailand can be name are Ban Pru Teau at Ban Pru Teau, Phang-nga Province; Koh Phi Phi Integrated Wastewater Management System which famous for its special design - the flower and the butterfly park, attracts tourists returning to the island after the tsunami

in 2004 (Brix, 2011)

B How wetlands improve water quality?

The potential applications of wetlands include the secondary treatment of municipal and certain industrial wastewaters and the polishing of secondary effluent and runoff that would have carried pollution from diffused sources (Norio, 2011) There are four stages in wastewater treatment: Primary treatment (Removes solid matter); Secondary treatment (Uses tiny living organisms knows as micro-organisms

to break down and remove remaining dissolved wastes and fine particles); Nutrient removal (Removes nitrogen and phosphorus nutrients that could cause algal blooms in our waterways and threaten aquatic life); Disinfection (Removes disease-causing micro-organisms) based on an article on website of Queensland Government in 2017

CWs can treat various types of wastewater, including, among others: domestic/municipal, industrial, azo-dye and textile, dairy, mine drainage, landfill leachate, agricultural, i.e., animal farms, etc (Vassilios, 2017) The performance of CWs depends on many factors including its type and design, organic loading rate and hydraulic retention time (Karpiscak, 1999) The pollutants in such systems are removed through a combination of physical, chemical and biological processes including sedimentation, precipitation, and absorption to soil particles, assimilation by the plant tissue, and microbial transformations (Davis, 2006) The most effective treatment wetlands are those that foster the above mechanisms

C Types of Constructed Wetland

Constructed wetlands are categorized into two types as:

• Subsurface flow (SSF)

• Free water surface (FWS)

The subsurface flow CWs could be distinguished further into two types according to the flow direction and level and duration of saturation of the substrate: horizontal subsurface flow (HSF); and vertical flow (VF) and latter, more types had been found name: tidal flow, upflow, downflow and integrated according to Vassilios

in 2017 Depend on the targets, different type of constructed wetland could be used For example, according to EPA in 2000, the main advantages of this subsurface water level (SSF) are prevention of mosquitoes and odors, and elimination of the risk of public contact with the partially treated wastewater; whereas the water surface in free water surface (FWS) constructed wetlands is exposed to the atmosphere with the attendant risk of mosquitoes and public access

Researches indicated that both HSF and VF constructed wetlands produced a high quality effluent Based on a research of Sohair in 2013, VF was highly recommended more for wastewater treatment because of its smaller size, high quality

of treated effluent and less evapo-transpiration rate Moreover, VF was proved to be promising technique for wastewater treatment not only for COD, BOD and TSS reductions, but also for nitrification removal In his study, all removal rates of COD, BOD and TSS reached more than 90 percent; these results were almost the same as other studies (Haritash et al., 2015; Konnerup, 2008)

From all reasons above, in this study, VF constructed wetland models were selected

D Roles of Wetland plants

Plants in CWs are not only an aesthetic factor but the most important functions

of plants are related to their physical effects in the wetlands The effects were clarified

in a research poster of USDA Natural Resources Conservation Service in 2013: “The principal function of vegetation in constructed wetland systems is to create additional environments for microbial population The stems and leaves in the water column obstruct flow and facilitate sedimentation, and provide substantial quantities of surface area for attachment of microbes, and constitute thin-film reactive surfaces Plants increase the amount of aerobic microbial environment in the substrate The wetland plants will prevent erosion, retard the entry of pollutants, and prevent the degradation of water quality in our natural waterways and will function as an attractive environmental study area” Therefore, plant species that are common to the

wettest environment often exhibit the greatest degree and the most effective

adaptations to wetland conditions (Norio, 2011) as the active reaction zone of wetlands

is the root zone or rhizosphere This is where physiochemical and biological processes included by the macrophytes, microorganisms, soil, and pollutant interactions take place

E Constructed wetlands’ shortcomings

The tropical condition can play a major role in mitigating some of the shortcomings in climate-influenced performance (Norio, 2011) Even though CWs have been considered as a multi-benefit alternative but no method has no shortcomings In the case of CWs, the main operation problem of CWs is clogging which is a result of gradual accumulation of organic and inorganic solids in the substrate, biomass production, dense plant root development, among others (Stefanakis

et al., 2014) Besides, application of constructed treatment wetlands in the tropics is not without environmental issue and a significant one concerns the breeding of insects, which may be disease vectors An example is the mosquito The latter require standing water to lay their eggs that can hatch into larvae within a week The constructed treatment wetland would need to be appropriately designed and operated to reduce breeding of such insect vectors and hence limit the incidence of diseases such as

malaria (Norio et al., 2011)

2.3 Hedychium coronarium (White Ginger)

In this study, Hedychium coronarium J Koenig, a non-common wetland plant,

was selected This is because this type of plant has satisfied the examiners’ criteria by its geographical distribution, morphology and how it could help in reducing mosquito larvicidal This is because of two reasons below:

Firstly, H coronarium (syn H flavescens Carly; H flavum Roscoe; H

sulphureum Wall) is a rhizomatos flowering plant popularly called white ginger lily

It belongs to Zingiberaceae family and origin from China, Taiwan, Myanmar and the Indian Sub-continent (India and Nepal) H coronarium can be found in shaded or

semi-shaded areas subjected to waterlogging It is found along river banks and in shallow water but not in areas where it may become totally submerged It can also occur on the edges of shaded secondary forests (BioNET-EAFRINET, n.d) In addition, its rhizomes is recognised fleshy, branched and knotty, with many nodes and grows up to 2.5-5 cm in diameter, spreading horizontally under the soil surface (Pooja

& Dixit, 2017) Therefore, it could adapt to the substrate of CWs

Figure 2.2: Hedychium coronarium

Secondly, the essential oil, methanolic and aqueous extracts of the leaves and

rhizomes of H coronarium were assayed for their antimicrobial, mosquito larvicidal

and antioxidant properties There are forty six compounds were identified in the

rhizome oil of H coronarium (Ho, 2011) The main components identified were

linalool, limonene, trans-metamentha, 2,8 diene, γ-terpinene and 10-epi-γ- eudismol Essential oil from the flowers were investigated and a total of 29 components were

identified and the main constituents included β-transocimenone, linalool, 1,8- cineole, α-terpineol, 10-epi-γ-eudesmol, sabinene and terpinen-4-ol (Chaithra, 2017) It is reported that α-pinene, β-pinene and 1,8- cineole present larvicidal effects (LC50 values

15.4, 12.1 and 57.2 ppm, respectively) on A.aegypti larvae (Lucia, 2007) In fact, H coronarium also functions in various forms in daily life such as a source of paper pulp,

high grade perfumes, medicine (Duke et al., 1985; Chopra et al., 1986 and Uphof,

1959) Therefore, H coronarium was expected to reduce significantly mosquito larvicidal in CW models

PART III MATERIALS AND METHODS

This study includes 2 parts: Surveying and Treating domestic wastewater using

CW models with Hedychium coronarium

3.1 Surveying

To have a deeper understanding of what stands behind the contamination of Mae Kha canal especially from residents’ perspective, a survey was conducted as the background of this study In three consecutive days from 18 to 20 March, the questionnaires were distributed to resident who are living alongside the canal in three study plots correspond to upstream, middle and downstream of Mae Kha canal Respondents were asked about their aknowledgement of water pollution in Mae Kha canal and how it affects their daily lives Besides, the researcher also described an alternative solution – creating constructed wetlands, which are distinguished into two scales: household and community, to address the issue Full detail of the questionnaire

is shown in 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 starts from a 12-lane super-highway, the area that indicates the edge

of urban boundaries, pass through dense residential and vibrant tourist-business area and down to the south of city center where Mae Kha Canal merges with Lumkuwai Creek from the West in local community area”

In this study, three selected plots were visualized in Figure 3.1

Figure 3.1: Study sites

- Gravel (fine and medium side)

- Plant: Hedychium Coronarium (White Ginger)

All of the materials were carefully washed before the experiments were set up

3.2.2 Experimental set up

CW replicates were set up at Department of Biology, Faculty of Science, Chiang Mai University under greenhouse conditions from 20 April to 05 June 2018

The experiments included of four tanks covered by Hedychium Coronarium and four

control tanks The water sample was collected from municipal sewer then separated into two different buckets in which it was treated with and without oxygen addition throughout six weeks The tanks were 54.7 cm high and 27 cm diameter They were equally 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

Water sample was seperated and treated with and without oxygen addition was a

trial to examine how nitrogen transformation could affect on H.Coronarium pollutant

uptake ability Initially, wastewater samples from household were highly contaminated In particular, the safety standard for total suspended solids (TSS), total phosphorus and total nitrogen have not over 30 mg/l, at most 2 mg – P/l and not more than 20 mg – N/l in respectively base on a notification of the Thailand Ministry of Natural Resources and Environment for housing estate standard updated in 2010 Table 3.1 below shows how domestic wastewater parameters changed after being

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

(mg/l)

No oxygen added (control)

After oxygen added

by microbes); nitrification (i.e., conversion of ammonia to nitrite first and then nitrate

by microbes); denitrification (i.e., conversion of nitrate to N₂ gas); plant uptake (i.e., use of nitrogen by plants, mostly nitrates and ammonia, as nutrients for their growth); adsorption (mostly ammonia on the porous media material) By adding oxygen into wastewater, the oxygen increase would stimulate the conversion of ammonia to nitrate and generation of more nitrate Once the nitrate is present in the sewage, it will serve

as the electron acceptor of the heterotrophs under low DO condition Then the nitrogen is converted to nitrogen gas by these denitrifying bacteria when DO depletes (Pai et al., 2013)

nitrate-3.2.3 Water Sampling and analysis

At week zero, all tanks were filled by clean water in order to allow the systems

to acclimatize in one week Started from week 1, with and without oxygen addition wastewater were applied to the tanks every day three and day seven (after drained out water to do analysis every week) The water samples were collected at inlet and outlet points of the CWs duplicates on day zero and every seven days in terms of percentage removal of COD, DO, TSS, NH4-N, NO3-N, PO4-P Each CW replicate was extracted

800 ml of water sample into two sample bottles to evaluate the effluent parameters On the other hand, the influent parameters were measured by collecting four sample bottles from bucket with oxygen addition and three bottles from bucket without oxygen addition equal to 1,600 ml and 1,200 ml of wastewater respectively In total, there were 23 sample bottles were collected and analysed

Table 3.2 below presents analysis methods in this study which followed APHA stadard methods for the Examination of Water and Wastewater (23nd 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