Water Quality at Bakun HEP Reservoir, Belaga, Sarawak
WiUieKoh
(44620)
Bachelor of Science with Honours (Aquatic Resource Science and Management) 2016 Pusat 1\ UNM
1111111111111111111111111 1000272665 Water Quality at Bakun HEP Reservoir, Belaga, Sarawak
Willie Koh (44620)
This dissertation is submitted in partial fulfilment of the requirements for the degree of Bachelor of Science with Honours in Aquatic Resource Science and Management
Faculty of Resource Science and Technology
Universiti Malaysia Sarawak
2016 DECLARATION OF AUTHORSHIP
I, Willie Koh, declare that the final year project report entitled:
Water Quality at Bakun HEP Reservoir, Belaga, Sarawak and the work presented in the report are both my own, and have been generated by me as the result of my own original research. I confirm that:
• this work was done wholly or mainly while in candidature for a research degree at
• this University;
• where I have made corrections based on suggestion by supervisor and examiners,
• this has been clearly stated;
• where I have consulted the published work of others, this IS always clearly
attributed;
• where I have quoted from the work ofothers, the source is always given. With the
• exception of such quotations, this report is entirely my own work;
• I have acknowledged all main sources of help;
• where the thesis is based on work done by myself jointly with others, I have made
• clear exactly what was done by others and what I have contributed myself;
• none of this work has been published before submission
Signed:
Aquatic Resource Science and Management Department of Aquatic Science Faculty of Resource Science and Technology Universiti Malaysia Sarawak (UNIMAS)
I ACKNOWLEDGMENT
My utmost gratitude and thanks to my supervisor, Professor Dr. Lee Nyanti @ Janti ak Chukong for his valuable advice, suggestions, guidance, constructive criticisms and commitment, from the start of this research until the final submission of this thesis.
Besides that, a special thanks to my co-supervisor, Associate Professor Dr. Ling Teck Vee on the guidance and support.
I would also like to express my appreciation to the staff of the Department of
Aquatic Science, Mr. Benedict ak Samling, and Mr. Richard Toh for their friendly help and facilitation during the field work and laboratory work. Not forgetting my fellow peers who helped me and for their valuable support. Also, special thanks to my seniors, Angie
Sapis and Ahmad Aklunal Atan for the precious advice. Without their kind support and technical assistance, it would not be an easy task to complete this study. Also, warmest regards and thanks to Mr. Laing and his family for providing us a comfortable accommodation during our field work in Bakun.
Special thanks also goes to Sarawak Energy Berhand for the financial assistance in this study through the research grant no GL (F07)/SEB/4A12013 (24).
Finally, my family members are highly acknowledged for their understanding and never ending support. To those who indirectly contribute to this research, your kindness is greatly appreciated. All praises to God for the strength and opportunity for completing this thesis. Without his mercy, I may not be able to go through the tough times in the course of this study.
II
i Water Quality at Bakun HEP Reservoir, Belaga, Sarawak
Abstract
Since the water supply at Bakun Hydroelectric Dam reached its full supply level, only one previous study has been done during the filling phase of the dam which was 3 years and 10 months earlier than this study. As water in the reservoir is very important for the aquatic organisms in the reservoir and downstream of the dam, a study was conducted at 3 stations to determine the selected water quality parameters 5 years 6 months after impoundment started. At each station, water in triplicate samples were collected at 6 levels, which is the subsurface, at 10m, 20m, 30m, 40m and 50m depth. Results showed that thermocline occurred at 3m to 10m depth at all stations. DO at the subsurface (4.99 - 6.10 mg/L) dropped drastically to anoxic level starting from 2m to 10m depth at all stations. Water conductivity and turbidity increases while pH decreased as depth increased. The highest chlorophyll-a (11.68 J-lg/L) was recorded at 10m depth with positive correlation with turbidity. Increasing levels of ammonia-nitrogen (0.0533 - 0.6400 mg/L), total suspended solids (3.30 - 63.06 mg/L), and five-day biochemical oxygen demand (1.86 - 4.30 mg/L) were observed while depth increases. Nitrate (0.01 - 0.22 mg/L), nitrite (0.0020 - 0.1170 mg/L), silica (0.39 - 1.54 mg/L) and orthophosphate (0.0900 - 1.7067 mg/L) showed different variations with depth. This present study showed that the water quality at Bakun Hydroelectric Dam was improving and still changing compared to the previous study during the filling phase and has not stabilize even after 5 years 6 months after impoundment started.
Keywords: hydroelectric dam, turbidity, water quality, nutrients.
Abstrak
Sejak bekalan air di Empangan Hidroelektrik Bakun mencapai tahap penuh, hanya satu kajian telah dijalankan semasa fasa pengisian, iaitu 3 tahun dan 10 bulan lebih awal daripada kajian ini. Disebabkan air di dalam empangan adalah sangat penting untuk organisma akuatik di dalam empangan dan bawah empangan, satu kajian telah dijalankan di 3 stesen untuk mengenalpasti parameter kualiti air 5 tahun selepas penakungan bermula. Di setiap stesen, air telah diambil sebanyak tiga kali daripada 6 tahap iaitu, subpermukaan, 10m, 20m, 30m, 40m dan 50m. Hasil kajian menunjuk perbentukan termoklin pada kedalaman dari 3m ke 10m di semua stesen. DO di subpermukaan (4.99 6.10 mglL) menurun dengan drastik kepada tahap anoksik bermula pada kedalaman 2m ke 10m di semua stesen. Konduktiviti air dan kekeruhan meningkat dan pH menurun dengan kedalaman. Klorofil-a paling tinggi (11.68 p.gIL) adalah pada kedalaman 10m dan berkorelasi positijdengan kekeruhan air. Peningkatan tahap ammonia-nitrogen (0.0533 0.6400 mgIL), jumlah pepejal terampai (3.30 - 63.06 mgIL), dan keperluan oksigen biokimia selepas lima hari (1.86 - 4.30 mglL) meningkat apabila kedalaman meningkat. Nitrat (0.01 - 0.22 mgIL), nitrit (0.0020 - 0.1170 mgIL), silika (0.39 - 1.54 mglL) dan ortofosfat (0.0900 - 1.7067 mglL) menunjukkan variasi yang berbeza dengan kedalaman. Kajian ini menunjukkan bahawa kualiti air di Empangan Hidroelektrik Bakun bertambah baik dan masih berubah berbanding dengan kajian semasa fasa pengisian dan belum lagi staNI selepas 5 tahun dan 6 bulan sejak penakungan bermula.
Kata kunci: empangan hidroelektrik, kekeruhan air, kualiti air, nutrien
III Pusat Khidmat Maklumal Akadt'mi' UNIVEftSm MALAYSIA SAKAWA}.
TABLE OF CONTENTS Page Declaration of Authorship I Acknowledgement II Abstract III Abstrak III Table of Contents IV List of Figures VI List ofTables VII List ofAbbreviations VIII 1.0 Introduction 2.0 Literature Review 3 2.1 Reservoir 3 2.2 Water Quality 3 2.2.1 Temperature 4 2.2.2 Dissolved Oxygen (DO) 5 2.2.3 pH 5 2.2.4 Nutrients 6 2.3 Impact ofHydroelectric Dams on Water Quality 7 3.0 Materials and Methods 9 3.1 Study Site 9 3.2 Water Samples 11 3.3 Water Quality Parameters Measured In-situ 11 3.4 Water Quality Parameters Analysed Ex-situ 11 3.4.1 Biological Oxygen Demand (BODs) 11 3.4.2 Total Suspended Solids (TSS) 12 3.4.3 Chlorophyll-a 13 3.4.4 Ammonia-Nitrogen (NH3-N) 14 3.4.5 Nitrate (N03-) 14 3.4.6 Nitrite (N02-) 15 3.4.7 Orthophosphate (P043-) 16 3.4.8 Silica (Si04) 16 3.5 Statistical Analyses 17
IV 4.0 Results 18 4.1 Water Quality Parameters Measured In-situ 18 4.1.1 Water Depth and Transparency 18 4.1.2 Temperature 18 4.1.3 Ph 23 4.1.4 Water Turbidity 26 4.1.5 Water Conductivity 28 4.1.6 Dissolved Oxygen (DO) 31 4.2 Water Quality Parameters Measured Ex-situ 35 4.2.1 Chlorophyll-a 35 4.2.2 Biochemical Oxygen Demand in Five Days (BOD5) 37 4.2.3 Nitrate (NOf) 39 4.2.4 Nitrite (N02-) 42 4.2.5 Ammonia-Nitrogen (NH3-N) 44 4.2.6 Silica (Si04) 46 4.2.7 Orthophosphate (P043-) 48 4.2.8 Total Suspended Solids (TSS) 50 5.0 Discussion 52 5.1 Water Parameters Measured In-situ 52 5.2 Water Parameters Measured Ex-situ 57 6.0 Summary 63 7.0 Conclusion 65 8.0 References 66 9.0 Appendices 71
v ,..... -
I'
LIST OF FIGURES Figure Title Page Figure 1 The location ofsampling stations at Bakun Dam, Sarawak. 10 Figure 2 Temperature values in August 2015. 19 Figure 3 Temperature values in November 2015. 21 Figure 4 Temperature profile in August 2015. 22 Figure 5 Temperature profile in November 2015. 23 Figure 6 PH values in August 2015. 24 Figure 7 PH values in November 2015. 25 Figure 8 Turbidity values in August 2015. 27 Figure 9 Turbidity values in November 2015. 28 Figure 10 Water conductivity values in August 2015. 29 Figure 11 Water conductivity values in November 2015. 30 Figure 12 Dissolved oxygen (DO) values in August 2015. 32 Figure 13 Dissolved oxygen (DO) values in November 2015. 33 Figure 14 Dissolved oxygen (DO) profile in August 2015. 34 Figure 15 Dissolved oxygen (DO) profile in November 2015. 34 Figure 16 Chlorophyll-a values in August 2015. 36 Figure 17 Chlorophyll-a values in November 2015. 37 Figure 18 BODs values in August 2015. 38 Figure 19 BODs values in November 2015. 39 Figure 20 Nitrate-N values in August 2015. 41 Figure 21 Nitrate-N values in November 2015. 41 Figure 22 Nitrite-N values in August 2015. 43 Figure 23 Nitrite-N values in November 2015. 43 Figure 24 Ammonia-N values in August 2015. 45 Figure 25 Ammonia-N values in November 2015. 45 Figure 26 Silica values in August 2015. 47 Figure 27 Silica values in November 2015. 47 Figure 28 Orthophosphate values in August 2015. 49 Figure 29 Orthophosphate values in November 2015. 49 Figure 30 TSS values in August 2015. 51 Figure 31 TSS values in November 2015. 51
VI LIST OF TABLES
Table Title Page
Table 1 Coordinates and locations ofsampling stations. 10
Table 2 Water depth and transparency values in August 2015. 18 Table 3 Classification ofwater quality parameters according to NWQS 64
VII LIST OF ABBREVIATIONS
°C Degree Celsius
/lm Micrometre
BOD Biological Oxygen Demand
DO Dissolved Oxygen km2 Kilometre Square m3 Cubic Metre mg/L Milligram per litre . mL Millilitre
L Litre nm Nanometre mm Millimetre pH Potential of Hydrogen
N Nitrogen
N02- Nitrite
N03- Nitrate
P04 3- Orthophosphate
Si04 Silica
NH3-N Ammonia-Nitrogen
TSS Total Suspended Solids
TDS Total Dissolved Solids
GPS Global Positioning System
VIII 1.0 Introduction
Hydroelectric dams have been constructed worldwide to provide an alternative energy source as petroleum in the world is depleting and is not renewable. Hence, impoundment started around the world to collect water bodies to act as a reservoir.
Reservoirs formed by impoundment, they will undergo great changes in water quality (Chapman, 1996). This was observed in tropical reservoirs such as Feitsui
Reservoir in Taiwan (Chang and Wen, 1997) and Lake Brokopondo in Surinam (Van der
Heide, 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium
(Lourantou et. aI., 2007) and Bureye Reservoir in Russia (Shesterkin, 2008). This happens because of the impact of inundated soil and vegetation including the standing forest on the water quality such as pH level and dissolved oxygen concentration (Van der Heide, 1978;
Shesterkin, 2008), which is essential for aquatic life.
In Malaysia, hydroelectric dams have been constructed to meet the energy needs and security. Among the hydroelectric dams that have been built in Sarawak is the Bakun
Hydroelectric Dam. Construction of the dam started in 2002. It is located about sixty kilometers from the town of Belaga and is situated on the Balui River. Bakun
Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to
2,400 MW of electricity (http://www.sarawakenergy.com.rny).Itis the second highest concrete faced rockfill dam in the world with an area of 695 square kilometers and a height of 207 meters (http://www.sarawakenergy.com.rny). Research on the characteristics of physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012).
However, it was conducted during the filling phase of the hydroelectric dam, which is fifteen months after impoundment has started. Since then, there has been no publishing literature on the characteristics of the water quality.
1 Hence, the goal of this study is to obtain detailed information on the physico
chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it
has reached its full supply level. Therefore, the objectives ofthis study were:
(i) To determine the water quality at six depths at three stations in the
reservOIr,
(ii) Compare the characteristics of the water quality among the depths and
stations, and
(iii) Determine the changes in water quality characteristics 5 years 6 months
after the dam was impounded.
2
l .-- . j I 2.0 Literature Review
2.1 Reservoir
According to Pawar & Shembekar (2012), water is important and it is the most abundant resource in the world which man has used for decades. Water covers about 70% of the earth's surface, but only 2.7% of the total amount is freshwater, of which 1% is ice free water in the rivers, lakes and atmosphere as biological water. It is believed that only
0.001 92% of the total water on earth is available for human use (Pawar & Shembekar,
2012). Hence, reservoirs are created in order to provide domestic water supply, generation of electricity and aquaculture. In Malaysia, 63 large reservoirs with a total storage of 25 billion m3 have been constructed (Makhlough, 2008).
Water quality in reservoirs is greatly affected by the composition of plant materials that were submerged during the inundation process. In a study done by Ling (2012), water in the Batang Ai reservoir contains high sulfide concentrations especially at inundated areas. Besides that, Nyanti (2012) also reported that the anoxic condition and the acidic condition in Bakun Dam is due to the decomposition of submerged carbonaceous materials.
Additionally, human activities in and around reservoirs and the physical and chemical properties of water will be affected (Mustapha, 2008). Precipitation, evaporation, and ground movement can also affect water quality. In Batang Ai reservoir, the dissolved oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by microorganisms in the decomposition of organic matter (Ling, 2012).
2.2 Water quality
Water quality in a reservoir is the physical and chemical limnology of a reservoir
(Sidnei, 1992) and includes all physical, chemical and biological aspects of water that
3 influence the beneficial usage of water (Mustapha, 2008). In reservoirs, water quality
deterioration usually comes from excessive nutrient inputs, eutrophication, acidification,
heavy metal contamination, organic pollution and obnoxious fishing practices (Mustapha,
2008).
Therefore, water quality is an important indicator of the ecological status of a
reservoir. It is reported that the significant lower dissolved oxygen is recorded due to
higher turbidity and increased suspended solids which affect the dissolution of oxygen
which is brought in by the flood that occurred in Oyun Reservoir (Mustapha, 2008).
Additionally in a study done at Bakun Dam, turbidity is affected by the suspended solids
from eroded soils from the logging activities in the watershed upstream from the north of
the reservoir (Nyanti, 2012).
2.2.1 Temperature
Temperature is very important to a reservoir as it affects chemical and biological
activities of aquatic organisms (Sangpal, 2011). In a reservoir, when the upper layer and
the lower layer have great variation in temperature, thermocline will occur. Thermal
stratification in deep reservoir is an important natural process which gives significant
effects on water quality. The production of ammonia, sulphide, and algal nutrients are
dependent on the changes in water temperature which subsequently affects the water
quality (Baharim, 2011). Besides that, vertical distribution and change in water
temperature can affect productivity of the natural organisms in the reservoirs. However,
the effect varies from reservoir to reservoir. According to Li & Xu (1995), thermocline is
common in reservoirs and usually occurs at the depth of 8m to 23m. In a study done by
Nyanti (2012), water temperature in Bakun reservoir was reported to undergo thermocline
as depth increased from subsurface to 18m.
4
l I Pusat Khidmat Maldumat Akadfmil: UN .nsmMALAYSIA SARAWAI'~
2.2.2 Dissolved Oxygen (DO)
DO is a very essential environmental factor that affects the entire production of a reservoir and it is also an important indicator of water quality, health of reservoir and also ecological status as it is used for respiration and in biological and chemical reactions
(Mustapha, 2008).
DO fluctuate from reservOIr to reservOIr and it is usually affected by photosynthesis, respiration and diel fluctuation. In a study done by Ling (2012), it was reported that the DO is higher at 0.5m depth at a11 stations in Batang Ai reservoir ranging from 4.7 to 8.7 mg/L due to the high phytoplankton photosynthesis rate. An example of diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry season than the rainy season (Ibrahim, 2009). This shows that the fluctuation also depends on temperature, depth, wind and amount of biological activities such as decomposition. In
Bakon Dam, DO is high at the subsurface but dropped drastically until anoxic level at depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of organic matter (Nyanti, 2012).
2.2.3 pH
pH that is suitable for optimal production for inland waters should be about 6.5 to
8.5 (Ibrahim, 2009). However, changes in pH can affect the transfer of nutrients and affect the condition ofwater quality (Li & Xu, 1995).
Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons as was reported in Batang Ai reservoir where all pH value was above 7 (Ling, 2012).
Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic acid will be formed when carbon dioxide reacts with water (Sangpal, 2011).
5 Acidic effects in reservoirs can be caused by the transfer of cooler water from other tributaries where the water is denser and lower in pH. Nyanti (2012) reported the pH value at Bakundam were all acidic ranging from 5.17-5.92, and the overall trend of pH in Bakun dam decreases from upstream towards the dam (Nyanti et. aI., 2012).
2.2.4 Nutrients
Reservoirs are often have higher chances of getting higher element loading compared to natural lakes as they have greater catchment area and high inflow rates
(Pawar & Shembekar, 2012). The concentration of nutrients varies from reservoir to reservoir due to the differences in soil and vegetation in the catchment area (Li & Xu,
1995). Nutrients such as nitrates, phosphates, silicates, and iron are important nutrients required for aquatic growth but may also cause eutrophication and water quality problems
(Li & Xu, 1995). Eutrophication can occur easily in reservoir due to high input of nutrients into the water and water quality of reservoir will be affected, giving rise to unpleasant taste and odour, and affects the dissolution of other gases, especially dissolved oxygen
(Mustapha, 2008). According to Nyanti (2012), strong rotten egg smell discovered in
Bakun dam indicates high volume of hydrogen sulfide. This observation is also supported by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium.
Nutrients input can also be affected by weather and season where nitrate was recorded at higher values in Ujjani reservoir during post-monsoon season. This may be caused by the oxidation of nitrifying bacteria and biological nitrification. Sulphate concentrations in the dam were very high in both pre and post-monsoon which were probably caused by the mineral rocks anthropogenically added and also by rain (Sangpal, 2011). The phosphate levels were found to be lower during the pre-monsoon and higher during the post
6 monsoon. Phosphate leads to eutrophication that can cause unpleasant taste and odour to the water (Sangpal, 2011).
2.3 Impacts of hydroelectric dams on water quality
Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of a water course to produce electricity. The building of hydroelectric dams has direct impact towards the chemical, thermal and physical parameters of the water body (Bunea, 2012).
According to a study done by Bunea (2012), hydroelectric dams have relatively low DO concentration, mostly lower than 5.0 mglL because of the organic sediments that are left at the bottom of the reservoir bottom during the initial filing. Organic substances left at the bottom of the reservoir bottom floor will absorb oxygen from the water in order to decompose, producing hydrogen sulphide, carbon dioxide and methane (Bunea, 2012).
Due to damming for hydroelectric generation, water in a reservoir will undergo stagnation which will lead to thermal stratification (Bunea, 2012). According to a study done by Elci (2008), thermal stratification of the reservoir involves the higher temperature at the surface and lower temperatures at the bottom which suggests that thermal energy is very slowly transferred to the bottom layers of the water body. Thermal stratification act as a barrier to re train mixing of the water column. This causes an uneven concentration of nutrients, lack of light for photosynthesis at the hypolimnion and the water column may become anoxic (Elci, 2008)
Hydroelectric dams also greatly reduces the water self-purification capacity.
According to Wei et al. (2009), water self-purification mechanisms are affected by the physical, chemical and biotic processes in a reservoir. However, dam construction affects all of the processes as the flow regime, water quality and biotic community in the river. In other words, dams slow down the river flow capacity, block the river continuum, and raise
7 water temperature, which decreases the water self-purification capacity (Wei et aI., 2009).
In a study done in China by Wei et al. (2009), it is recorded that the Manwan-Dachaosan dam has higher ammonia-nitrogen concentration due to the decreased water self purification capacity as compared to the pre-dam period. This suggests that damming has severely decreased the water self-purification capacity as it blocked the river continuum.
8 3.0 Materials and Methods
3.1 Study Site
Bakun Hydroelectric Reservoir is a man-made reservoir, which is located 60 km west of Belaga, Sarawak, Malaysia (Figure 1). The dam was formed after the impoundment of Balui River. The reservoir has a catchment area of 14,750 km2 and a total
3 2 capacity 43,800000 m with a surface area of 695 km . The dam is the second tallest concrete-faced rockfill dam in the world.
Three sampling stations, namely stations 1, 2 and 3 was selected in the reservoir.
Station 1 is at the inundated estuary of the Linau River, Station 2 is at the inundated Balui
River and Station 3 is located in the inundated Balui River as well but nearer to the dam.
At each station, sampling was conducted at 6 levels namely, the subsurface, 10m, 20m,
30m, 4Om, and 50m depths. The coordinates of Bakun dam is at longitude 02°45'23"N and latitude 114°03'47"E. The coordinates of every sampling station were recorded by the
Global Positioning System (GARMIN, GPSMAP 62S) (Table 1). Sampling was carried out twice, the first sampling was from 21 SI August to 27th August 2015 and the second sampling was 5th November to 11 th November 2015.
9
"-I River I "-I Flooded Area
Station
* Dam o ; 0 I kill I
Figure 1: Location of the three sampling stations at Bakun Reservoir.
Table 1: Coordinates and locations of sampling stations.
Station Coordinates Location N 02° 39' 32.2" E 114° 03' 29.5" Estuary of Linau River 2 N 02° 43' 34.4" E 114° 01' 44.2" Balui River 3 N 02° 43' 41.35" E 114° 03' 34.0" Further downstream of Balui River
10 3.2 Water samples
The water samples were taken using Van Dorn water sampler at all three stations
and were taken at 6 different depths which are the subsurface (0.2m), 10m, 20m, 30m, 40m
and 5Om. At each station, three replicates of water samples were taken back for laboratory
analysis. Water samples were kept in 2 L polyethylene water bottles that has been acid washed and were stored in cooler box filled with ice. All samples were taken to the
laboratory for further analysis.
3.3 Water quality parameters measured in-situ
Temperature, dissolved oxygen (DO), pH, electrical conductivity, total dissolved solids (TDS), and turbidity were taken using YSI Multiparameter Water Quality 6920 V2.
The depths of each station were measured using depth finder. Water transparency was also measured using secchi disc at each station.
3.4 Water quality parameters analysed ex-situ
3.4.1 Biochemical oxygen demand in five days (BODs)
BODs were determined by filling water samples into 300 ml BOD bottles. DO readings of the water samples were measured from the bottles. All BOD bottles were wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for
5 days. The initial DO value was recorded as DJ and on the 5th day, the DO reading was
recorded as Ds. The formula that was used for measuring BODs follows the protocol
outlined by APHA (1998):
11 BOD5 (mglL) = DJ - D5
Where, DJ = Initial DO of sample immediately after preparation (mglL)
D5 = DO value after 5 days incubation at 25°C (mglL)
3.4.2 Total suspended solids (TSS)
Total suspended solids were analyzed using standard method APHA (1998). For
TSS analysis, there was pre-fieldtrip sampling method and post-fieldtrip method. For pre
fieldtrip method, glass fibre filter paper (GFIC, 47 nun diameter, 0.45 Ilm membrane) were soaked in distilled water. Each filter paper is placed on a piece of aluminum foil and was dried in the oven at 103°C - 105°C overnight. Filter paper then was allowed to cool for 10 minutes before weighing it using an analytical balance (ACCULAB, ALC - 210). The initial weight was recorded. For post-fieldtrip method, the glass fibre paper was placed on the inter-plate of the filter funnel using a pair of forceps. A known volume of water samples was filtered using a vacuum pump. After that, filter paper was removed from the filtration funnel and was placed back into the aluminum foil. Filter paper was dried in the oven at 103°C - 105°C overnight (APHA, 1998). Filter paper was then taken out of the oven and allowed to cool until room temperature before weighing. The final reading of the filtered glass fibre paper was recorded and TSS was calculated using the formula: w -w TSS (mglL) = J I V
Where, W; = Initial weight of filter paper
WJ = Final weight offilter paper
V = Volume of water samples filtered (L)
12 .4 Chlorophyll-a
The concentration of chlorophyll-a In the water samples were analyzed using staDdard method APHA (1998). For chlorophyll-a analysis, water samples were filtered using vacuum pump. Filter paper containing chlorophyll-a was taken from the vacuum pump for analysis. The samples were grinded by using a grinder and 5 - 6 mL of 90% acetone was added into the mortar. Samples were grinded for about 5 minutes and all materials in the mortar were placed into a capped test tube. Ninety percent acetone was added into the test tube to make up the volume to 10mL. Test tube was folded with aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete extraction of the pigments. The liquid extracted was transferred into the centrifuge tube.
The samples were placed into a centrifuge for about 10 minutes under 3000 rpm. Optical density was determined using spectrophotometer at wavelength of 750 nm, 664 run, 647 am, and 630 nm. Each extinctions for small turbidity blank was corrected by subtracting
750 nm from 664 nm and 630 run absorptions.
The concentration of chlorophyll-a in the extract of the pigment after correction was calculated using:
Where, E = the absorption in the respective wavelength
After determining the concentration of the chlorophyll-a in the extract, the amount of cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows:
13 Ca(v) Chlorophyll-a (J!g IL) = - v
Where, Co = Chlorophyll-a pigment concentration in J!g/mL
v = Volume ofacetone in mL
v = Volume of samples in L
3.4.4 Ammonia-nitrogen (NH3-N)
For ammonia-nitrogen (NH3-N), the concentration was determined using standard method 8038, Nessler Method (HACH, 2000). A 25 mL prepared sample and 25 mL of deionized water were filled into a separate 25 mL mixing graduated cylinder. Three drops of Mineral Stabilizer were added to both of the cylinders. The cylinders were inverted several times to mix the content. After that, 1 mL of Nessler reagent was pipetted into both of the cylinders and the cylinders were inverted several times to mix the content. A one- minute reaction was started. Both the solutions were poured into a square sample cell. A yellow colour formation will indicate the presence of ammonia. When the timer expired, the blank was inserted into the square sample cell with the fill line facing the right. The reading at 425 run was zeroed. The prepared sample was inserted into the cell holder of
Spectrophotometer DR 2800 (HACH, 2000) with the fill line facing right and the reading displayed was recorded.
3.4.5 Nitrate (NO)-)
For nitrate analysis, the concentration was determined using standard method 8192,
Cadmium Reduction Method (HACH, 2000). The sample was filled until the 15 mL mark of a 25 mL graduated measuring cylinder. The content of one Nitra Ver6 Nitrate Reagent
Pillow Powder was added into the cylinder and capped with a stopper. The cylinder was 14