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Water Quality Status of Petani River Basin Based on Water Quality Index and Physico Chemical Properties

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THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
(ECOMOD 2007), PENANG, MALAYSIA
Water Quality Status of Petani River Basin Based on Water
Quality Index and Physico-Chemical Properties
Hazzeman Haris* and Wan Maznah Wan Omar
School of Biological Sciences, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia.
(*Corresponding author: Tel: 013-5019425, Email: [email protected])
ABSTRACT
Water samples were collected from 6 sampling stations along the Petani River Basin.
Water Quality Index (WQI) was used to classify the river basin according to the
pollution level where 100 represent the highest water quality. The subindex for each
parameter used in the WQI equation was calculated. These parameters are dissolved
oxygen, biological oxygen demand, chemical oxygen demand, pH and ammonia.
Other parameters such as alkalinity, nitrite, nitrate, orthophosphate, salinity and TDS
were also determined. During the 12 months sampling period, the highest WQI was
recorded at the Petani River-Jetty (74.21) in February 2006 and the lowest was
recorded at Bakar Arang River (38.54) in August 2006. Generally it can be said that
the sampling stations that were located near the town centre and tributaries that flows
through industrial area showed lower WQI value compared to other sampling stations
that were located further downstream or tributaries that flow through residential areas.
Gelugor River recorded a higher concentration of nitrite and nitrate compared to other
sampling stations. Petani River-Jetty on the other hand recorded a higher level of total
suspended solids (TSS). One-way ANOVA (p< 0.05) showed no significant
differences in the amount of orthophosphate and ammonia between all the sites but
there were significant differences between sampling intervals.
Keywords: Water Quality Index, physico-chemical properties, nutrients
I#TRODUCTIO#
Malaysia has an annual rainfall of 3000 mm or 990 billion m3 of which 566
billion m3 appears as surface run-off, 64 billion m3 becomes groundwater recharge
and 360 billion m3 return to the atmosphere through evapo-transpiration (Azhar,
2000). Being the nation with the highest water consumption, freshwater resources
such as streams and rivers are of paramount importance to the development of the
country since they contributed up to 98% of the total water used in Malaysia and the
rest are from groundwater (Abdullah and Jusoh, 1997).
As the nation develops and increases in population, a serious water crisis such
as pollution due to poor planning can cause environmental degradation and a decline
in beneficial use of river (Madsen et al, 2002). Therefore regardless of the abundance
of water, there is simply a shortage to support the consumption of the population
(Madsen et al., 2002).
The major aim of this study was to evaluate the river surface water using the
Water Quality Index and the classification used by the Malaysian Department of
Environment (DOE). Other physico-chemical analyses were also carried out to
determine the level of pollution in the river.
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
(ECOMOD 2007), PENANG, MALAYSIA
Petani River Basin. Petani River is the main river that flows through the centre of the
town of Sungai Petani. The commercial centre of the town is situated on both sides of
the riverbanks between 4500 m to 6000 m from the confluence. The total length of
Petani River is 12.5 km with a 3500 ha of catchments area (including the catchments
areas of its tributaries). Petani River is tidal in nature from the confluence until more
than 6 km upstream (Perunding Bakti, 1997a). There are three main tributaries that
contribute to the overall water quality of Petani River. These tributaries are the
Gelugor River, Bakar Arang River and Air Mendidih River.
MATERIALS A#D METHODS
Water samples ware collected monthly from September 2005 to February
2006 using a water sampler and kept in polyethylene bottle which were later
preserved at 4ºC. All the water quality analysis which comprised of nitrite, nitrate,
ammonia, orthophosphate, alkalinity, biological oxygen demand (BOD), chemical
oxygen demand (COD) and suspended solids (SS) were carried out according to
APHA (1992). Total dissolved solids (TDS), conductivity, salinity and temperature
were measured in-situ using ‘sensION5 conductivity meter’. Dissolved oxygen (DO)
was measured using YSI Model 57 oxygen meter, while the pH value was determined
using a CyberScan 500 pH meter.
Water Quality Index (WQI) was calculated using the mean values of DO,
BOD, COD, pH, ammonia-N (AN) and SS. The values were converted to sub indices
(SIs) using the best-fit equation and aggregated to compute the WQI according to the
following equation (Wan Maznah & Mansor, 2002):
WQI = 0.22 × SI DO + 0.19 × SI BOD + 0.16 × SI COD + 0.15 × SI AN + 0.16 ×
SI SS + 0.12 × SI pH,
where SI is the sub index of each parameter. The descriptions of the water quality
status related to the WQI are stated in Table 1 which is according to the values
referred by the Malaysian Department of Environment (DOE, 2001).
Table 1. Water quality index by the DOE (DOE, 2001)
Parameter
Class
Unit I
II
III
mg/L < 0.1
0.1 – 0.3
0.3 – 0.9
Ammoniacal
#itrogen
mg/L < 1
1-3
3-6
BOD
mg/L < 10
10 - 25
25 - 50
COD
mg/L > 7
5-7
3-5
DO
mg/L
>
7.0
6.0
–
7.0
5.0 – 6.0
pH
25 - 50
50 - 150
Total Suspend mg/L < 25
Solids
> 92.7 76.5 – 92.7 51.9 – 76.5
Water Quality
Index
IV
0.9 – 2.7
V
> 2.7
6 - 12
50 - 100
1-3
< 5.0
150 - 300
> 12
> 100
<1
> 5.0
> 300
31.0 – 51.9
< 31.0
Statistical analysis for ANOVA and Tukey HSD were done using SPSS
software version 13. Multivariate Statistical Package (MVSP) was used to do the
cluster analysis.
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
(ECOMOD 2007), PENANG, MALAYSIA
RESULTS A#D DISCUSSIO#
The water classification for selected physico-chemical parameters and Water Quality
Index (WQI) at each sampling station is shown in Table 3. Air Mendidih River
recorded the highest WQI of 60.49 followed by Petani River-Jetty with WQI 59.56.
The lowest WQI was recorded at Pasir Kecil (55.07). This showed that there was
improvement in the water quality at some of the sampling sites compared to the first
six months of sampling data. During the six months period, the average water quality
at Gelugor, Bakar Arang and Petani-Bus was in class 4 while Petani-Jetty recorded
the best WQI with 54.35 (class 3) while the lowest WQI was recorded at Gelugor
(51.18).
Even though the water quality at most of the site had improved, it still can be
seen that the WQI was getting lower at the sampling site located further downstream
except for Petani River-Jetty. This is in agreement with the report by the DOE (2000)
that the rivers in Malaysia were slightly polluted or polluted at the downstream
(Jørgensen, 2002; Azrina et al, 2005). Arienzo et al., (2001) studied the impact of
land use and urban runoff on the Sarño River Basin in southern Italy, and reported the
degradation of the river water quality especially near the river mouth. This can be
attributed to several man induced activities such as urban runoff to the river surface
water due to direct or unregulated sewage discharge into the river or its tributaries
(Ka┼łok, 1997; Absalon et al., 1997, 2007). The development and landuse activities in
the catchment area can cause a high pollutant load to be discharges into the river and
wetland through the V-drains and gross pollutant traps (Sim et al., 2007). The slightly
better WQI recorded in Petani River-Jetty can be caused by the dilution of nutrients
by the seawater from the confluence where Petani River joins the Merbok River. As
for Pasir Kecil River, the low WQI can be attributed to rapid development at the site
and its surrounding area. Since it is a small flowing water body, the nature of this
river makes it more vulnerable even to the minor changes in the weather or its
surrounding compared to other sampling stations.
Table 3. Classification of each sampling stations along Sungai Petani River Basin
based on various water quality parameters (ammonia, BOD, COD, DO, pH, TSS) and
Water Quality Index (WQI).
Classification of individual parameters
Stations
Ammonia BOD COD DO pH TSS WQI
Pasir Kecil
IV
IV
IV
IV II
V
III (55.07)
Air Mendidih
IV
IV
IV
IV II
III III (60.49)
Gelugor
IV
IV
IV
IV II
IV III (57.13)
Bakar Arang
IV
IV
IV
IV II
IV III (56.92)
Petani (Bus)
IV
IV
V
IV II
V
III (55.20)
Petani (Jetty)
III
IV
V
III
I
V
III (59.56)
Individual parameters such as ammonia, BOD, COD, DO, pH and TSS were
classified using classification by the DOE. The level of ammonia and DO at all of the
sites were in class IV except for Petani-Jetty where both parameters were in class III.
BOD at all sites were in class IV. COD at all sites was in class IV except for PetaniBus and Petani-Jetty which were in class V, while pH value at all sites were in class II
except for Petani-Jetty which was in class I.
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
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From these results, it can be seen that Petani-Jetty recorded the best water
quality based on the parameters used for the classification except for COD and TSS.
The high level of COD in Petani-Jetty is shown in Figure 3 where it recorded the
highest COD value in September 2005 (896 mg/L) throughout the sampling period.
The high COD recorded at this site might be caused by the high level of organic
matter in the water which is contributed by litterfall (leaves, twigs, and other plant
material) from the mangrove area, as reported by Mitsch and Gosselink (2000) which
refers the riverine mangrove wetlands as a significant exporter of organic matter due
to its high productivity. Litterfall in the scrub, basin, fringe and riverine system can
range from approximately 200g m-2 yr-1 to 1200g m-2 yr-1 (Mitch and Gosselink, 2000),
and the litter production increased with the hydrological turnover. Clough et al. (2000)
reported that mangrove area in the Cha Mau Province in Southern Vietnam recorded
up to 1879g dwt m-2 yr-1 of litterfall, while in the US it has been reported that forested
wetlands both tidal and non-tidal can produce litterfall of up to 2000g dwt m-2 yr-1
(Conner, 1994; Ozalp et al., 2007). Since mangrove leaves in rapidly flush
environment decay more rapidly (Mitch and Gosselink, 2000) it may lead to a greater
export of dissolved organic material (Cintrón et al., 1985) by increasing the litterfall.
Apart from that, the high nutrient loading from the upstream area especially from
Gelugor, Bakar Arang and Petani River-Bus increases the productivity of the
mangrove area (Day et al., 1987). The Petani River-Jetty is affected by tides which
increase the productivity of the mangrove area as mentioned by Lugo and Snedaker
(1974) and Mitsch and Gosselink (2000) that “environment flushed adequately and
frequently by seawater and exposed to he high nutrient concentration are more
favorable for mangrove ecosystem development, where forest in these areas exhibit
higher rate of net primary productivity”. Tukey HSD test for COD reveals 2 group of
subset, where Air Mendidih River, Pasir Kecil River, Bakar Arang River, Gelugor
River and Petani River-Bus were in the first group (except for Petani River-Bus which
exist in both group of subsets), while Petani River-Jetty was in the second group.
High level of organic matter increases the TSS. Apart from that, human
activities at the Petani-Jetty and the surrounding area caused sediment disturbance and
thus increases the amount of suspended solids in the water. The high TSS
concentration was also contributed by suspended solids from the Merbok River during
high tide. This condition is similar to the flooding of the Mississippi River which
supplies a pulse of suspended sediments, inorganic nutrients and organic materials
that stimulate primary and secondary production (Lane et al., 2007). At Pasir Kecil
River, the rapid land conversion from plantation area to housing estate contributed
higher TSS through surface runoff from the roads and exposed soil at the sampling
site especially during wet season. Ellis et al. (1987) reported that road represent 20%
of urban catchment area, but their drainage water can contribute 50% of the TSS
discharged directly to receiving streams. The runoff loads include sediment with
associated metals, hydrocarbon and ionic concentration (Luker and Montague, 1994;
Pontier et al., 2004). Air Mendidih was the only site that recorded a class III in TSS
level. The Air Mendidih has sandy and rocky substrate making it less prone to wave
disturbance that release sediments to the water column as recorded at sampling sites
that have silt as substrate on their riverbed. The amount of TSS was generally stable at
all sites throughout the sampling period, but in January 2006 there was a sudden
increase where Petani River-Jetty recorded the highest amount of TSS with 170 mg/L
as can be seen in Figure 5. The lowest was recorded in February and July 2006 (4
mg/L) at Air Mendidih River. The high amount of TSS at Petani River-Jetty can be
due to the high rainfall which caused heavy silt load being washed to the river (Sim et
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
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al., 2007). The Tukey HSD test for TSS shows 3 different subset group with the first
group consists of Air Mendidih River, Bakar Arang River, Gelugor River and Petani
River-Bus. The second group consists of Bakar Arang River, Gelugor River, Petani
River-Bus and Pasir Kecil River, while the third group consist of Petani River-Bus,
Pasir Kecil River and Petani River-Jetty site.
The mean concentration of ammonia in Petani River-Jetty was in class III
while the rest of the sampling stations recorded a class IV. The slightly better
classification for these parameters at Petani-Jetty can be explained by the dilution
effects caused by the intrusion of sea water into the Petani River. Apart from that, the
low level recorded there can be due to the removal of nitrogen through plant uptake,
microbial assimilation and denitrification process (Kadlec and Knight, 1996; Ingersoll
and Baker, 1998; Mitch and Gosselink, 2000; Yang et al., 2001; Iamchaturapatr et al.,
2007). This is consistence with the findings from studies on wetland which stated that
nutrient storage in wetland plants and sedimentation is an important process in
removing nutrient from wastewater (Breen, 1990; Wetzel, 1993). This emphasises its
vital role in the treatment and purification of wastewater (Mugisha et al., 2007).
Throughout the sampling period, it can be seen that there is a distinct pattern in the
concentration of ammonia at all of the sites (Figure 7). The level of ammonia was
generally high from September 2005 to January 2006, but from February onward the
concentration of ammonia had dipped to below 0.5 mg/L. Then in August 2006, the
level of ammonia suddenly increases back to the level before February 2006. The
highest concentration recorded was 3.968 mg/L in August 2006 at Pasir Kecil River,
while the lowest concentration recorded was 0.004 mg/L at Petani River-Jetty in May
2006. The high concentration of ammonia at Pasir Kecil River can be caused by the
surface runoff of urea fertilizer from the farms located near the river. Since it is a
small flowing water body it is more susceptible to weather changes compared to other
sampling stations. With no rain to dilute the water and low concentration of DO, the
water inhibits the aerobic bacteria from processing the organic compound into
substances less hazardous, stable and less putrid such as nitrite and nitrate (Wan
Maznah, 2002). ANOVA (p<0.05) test for ammonia shows significant differences
between sampling interval. Tukey HSD test for ammonia reveals three groups of
subsets. Group 1 consists of May, July, June, March, February, April and September.
Group 2 were made of September, October, January, November and December, while
members of group 3 were January, November and December 2005 and August 2006.
Most of the sites have an average pH that falls into class 2 except for PetaniJetty which falls under class 1. The range of pH recorded at Petani-Jetty can be caused
by several reasons such as dilution of the river water through the intrusion of sea
water during high tide, the presence of limestone along the riverbank which increased
the pH (Figure 4) and thus improved the level of WQI. Generally the level of pH was
stable throughout the sampling period (Figure 4). The highest pH recorded was in
August at Petani River-Jetty (7.91) while the lowest was recorded at Petani River-Bus
(5.54) in February. The low pH at Petani River-Bus can be due to the formation of
dissolved carbon dioxide (CO2) and carbonic acid (H2CO3) in water by the
degradation of organic compounds (residual organic matters in media beds and
planted materials) or aerobic organisms which results in pH reduction (Kadlec and
Knight, 1996; Coleman et al., 2001; Kyambadde et al., 2004; Iamchaturapatr et al.,
2007). Analysis of pH data through ANOVA (p<0.05) and Tukey HSD test shows
significant differences between sampling months. Through Tukey test, four groups of
subsets were established. The first group consist of September, December February
and November, while group 2 consist of November, January, August, May, June, and
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
(ECOMOD 2007), PENANG, MALAYSIA
October. The members of group 3 was similar to the second group, but with the
addition of July and without November. Group 4 only consist of June, October, July,
March, and April. As for conductivity, the Tukey HSD test shows that only
September and January were significantly different from the other sites.
BOD at all sites recorded a class IV. Decomposition of organic matter by
microorganisms reduces the DO (Bellos and Sawidis, 2005) and contributes to the
low water quality classification for BOD. The impact of microorganism activity on
DO can be very severe where dissolved oxygen may drop to a very low level and
causing organism that depend on oxygen to die (Bellos and Sawadis, 2005). The high
level of BOD at all sampling sites reflects the high amount of organic substances in
the water which fuels the microorganism activity, thus reducing the amount of oxygen
in the water.
The concentration of DO remained stable and did not vary except at PetaniJetty which fluctuated throughout the sampling period (Figure 2). The lowest DO
recorded at Petani-Jetty was 1.65 mg/L in October, while the highest was 12.6 mg/L
in August which makes it the highest DO concentration recorded throughout the
sampling period. Bakar Arang recorded the lowest DO of 0.5 mg/L in August with
Petani-Bus recording the same concentration in June. The high DO in Petani-Jetty can
be contributed by the high boating activity at the Petani-Jetty which created water
movement and thus facilitate in the aeration of the water and increases the DO level.
The movement of water due to the tidal effect also play a role in the high DO level
obtained at Petani-Jetty. The low level of DO at Bakar Arang and Petani-Bus can be
contributed by the low flow rate (Sriyaraj and Shutes, 2001) at these sites and the lack
of activities that can help to increase water movement. Another factor that may
explain the low DO level was the high amount of organic material decomposing at
these sites. The high organic material supplies the resources for microorganism
activity which uses oxygen and thus reducing the DO in the water (Iamchaturapatr et
al., 2007). Apart from that, plant shading along the Bakar Arang River can inhibit the
growth of suspended photosynthesis organism such as phytoplankton resulting in
almost nil or reduced oxygen (O2) production in the water (Iamchaturapatr et al.,
2007). As for DO, there were two groups of subsets where group 1 consist of Air
Mendidih River, Bakar Arang River, Gelugor River, Pasir Kecil River and Petani
River-Bus. Group 2 only consist of Petani River-Jetty.
Figure 6 which depict the amount of TDS at each site, clearly shows that
Petani River-Jetty always recorded a higher level of TDS compared to the other site
followed by Petani River-Bus and Gelugor River. The highest level of TDS at 17000
mg/L was recorded at Petani River-Jetty in September 2005. In January 2006, it was
observed that four of the six sites recorded a sudden surge in the concentration of
TDS (Figure 6); and the differences between the sampling months were not
significant. There were significant differences in the concentration of TDS between
sites from the (Tukey HSD, p<0.05). The first group consists of Pasir Kecil River, Air
Mendidih River, Bakar Arang and Gelugor. The second group was made of Petani
River-Bus and the third group consists of Petani River-Jetty.
Figure 8 and 9 shows the concentration of nitrite and nitrate at each site during
the 12 months sampling period. Gelugor River recorded a higher level of nitrite and
nitrate throughout the sampling duration. This can be due to the discharges of
wastewater from the housing area along the Gelugor riverbank and the Bakar Arang
Industrial Area from which the source of Gelugor River is located. Shamshad et al.
(2006) reported that the main sources of nitrogen compound in urban area can be from
the usage of lawn fertilizer, decomposing organic matter, urban street refuse and
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
(ECOMOD 2007), PENANG, MALAYSIA
atmospheric deposition. The amount of nitrite and nitrate at each site in December
2006 increased compared to other sampling months, although this increase was not
significant statistically. The highest concentration of nitrate was observed in April
2006 at Gelugor River (8.76 mg/L) while the lowest was recorded in December 2005
at Pasir Kecil (0.004 mg/L). As for nitrite, Gelugor River recorded the highest
concentration in September 2005 (0.768 mg/L) while Pasir Kecil River recorded the
lowest concentration also in September 2005 (0.005 mg/L). Tukey HSD test for nitrite
and nitrate between sites shows that Gelugor River was significantly different
between sites (ANOVA, p<0.05).
Orthophosphate concentration was generally stable during the sampling period
except for a few occasions where the reading fluctuated at Gelugor River, Pasir Kecil
River, Petani River-Bus and Bakar Arang River. Most of the sites recorded a higher
concentration of orthophosphate from February to April 2006, and recorded their
highest level in April (Figure 10). The highest level of orthophosphate was recorded
in March 2006 at Pasir Kecil River while the lowest was in February (Petani RiverJetty) and May (Gelugor River). The low level of orthophosphate at the Petani RiverJetty can be attributed to the soil in the wetland which act as a major sink for
phosphorus (Kadlec and Knight, 1996; Sim et al., 2007). The high concentration
recorded at Pasir Kecil River can be due to runoff from agriculture sites. This in
agreement with the results reported by Coulter et al. (2004) from his study in the Inner
Bluegrass Region of Kentucky, which recorded a higher orthophosphates in the
agricultural watershed than in the urban watershed. Rainfall can cause certain amounts
of phosphates to wash from farm soils into nearby waterways and thus increasing the
phosphate content in the water (Shamshad et al., 2006). The area along Pasir Kecil
River was being developed during the sampling period and the clearance of land has
made it more susceptible to soil erosion. The trees and shrubs cleared from this land
were dumped near the river and this contributed to the enrichment of orthophosphate
when it decomposed. Meanwhile the high orthophosphate concentration recorded at
Bakar Arang River and Gelugor River and Petani River-Bus can be due to untreated
domestic sewage that contains high amount of phosphorus from detergent, toothpaste
and etc. As for orthophosphate, it also has 2 groups of subset. The Tukey HSD test
shows that the results in September, July and November 2005 were significantly
different from the results in April 2006.
The clearing activities along the riverbanks of Petani River and its tributaries
increased leaching of chemical and soluble that pollutes the river. This situation is
similar to the findings made by Abdul Rahim and Zulkifli (1999) which reported the
removal of forest cover especially the undergrowth and litter layer induced erosion
and enhanced leaching of chemical and other solutes. The additional source of organic
matters in the form of shrubs and trees that had been cut down to clear the land,
coupled with greater sunlight exposure enhanced microbiological activities leading to
higher rates of decomposition, mineralization and nitrification (Abdul Rahim and
Zulkifli, 1999).
The level of alkalinity was at its highest in September 2005 at Petani RiverJetty (108.07 mg/L) while Gelugor River recorded the lowest alkalinity level in
August (20.0 mg/L) (Figure 11). There was no significant difference in alkalinity
throughout the sampling period, especially at Air Mendidih, where the concentration
of alkalinity remained between 40 to 70 mg/L. The greatest range in the concentration
of alkalinity was recorded at Pasir Kecil River where the lowest level recorded was
19.26 mg/L in October and the highest was above 100 mg/L in April 2006. The Tukey
HSD test of alkalinity also shows 3 different groups of sites where group 1 consist of
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Pasir Kecil River, Air Mendidih River, Bakar Arang River and Gelugor River. Group
2 were made of Bakar Arang River, Gelugor River and Petani River-Bus, while group
3 consists of Petani River-Bus and Petani River-Jetty. Tukey HSD test for alkalinity
according to sampling months revealed 2 groups of subsets. From these subsets,
alkalinity in December 2005 was significantly different from the result obtained in
April 2006, while there were no significant differences between the other sampling
months.
The temperatures at sampling sites did not vary much as most of the sites
recorded temperature between 27°C to 31.1°C (Figure 12). WQI of the sampling sites
also did not differ throughout the sampling period. Almost all of the sites have a WQI
ranging from 40 to 70. The biggest differences of WQI in one particular site was
recorded in Bakar Arang River where the highest WQI was 72.56 in June, while the
lowest was 38.54 in August 2006 (Figure 1).
The highest conductivity was recorded in January at Petani River-Jetty and the
lowest was recorded in October at Pasir Kecil River. Three sites which were Gelugor
River, Petani River-Bus and Petani River-Jetty recorded conductivity level higher
than 20000µs/cm (Figure 13). The level of conductivity increases at the sampling
stations located nearer to the confluence. This can be explained by the higher salinity
due to the intrusion of seawater from the Merbok River which increase the amount of
free ions and enable the water to conduct electricity. The high concentration of
nutrient and TDS from anthropogenic contaminants such as point discharges in urban
and agricultural runoff also affects the level of water conductivity which increase the
level of free ions (Bellos and Sawidis, 2005). This effect can especially be seen at
Gelugor River where the high level of conductivity increases as the level of nutrient
also increases. Turkey HSD test for conductivity reveals three groups of homogenous
subset where Pasir Kecil River, Air Mendidih River, Bakar Arang River and Gelugor
River were in the first group (Bakar Arang River and Gelugor River exist in both
group 1 and 2 of the subsets, which means that they were not significantly different
from other sites in group 1 and 2 but is significantly different from sites in group 3),
followed by Petani River-Bus in the second group and Petani River-Jetty in Group 3.
Conclusion
It can be concluded that the water quality in the Petani River basin is moderately
polluted with all sites recorded an average of class III according to the WQI by the
DOE. Natural and anthropological factors such as agriculture, industries, urbanization,
and natural land uses play an important role in determining rivers water quality.
Petani River Basin also plays an important role in determining the river water quality
of the watershed by acting as a nutrient sinks and improving the overall water quality.
Acknowledgement
The principal author would like to thank all the staffs, friends and family members for
their ideas and assistance in the field and data analysis. This study was partly
sponsored by grant number 304/PBIO650248/E104.
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Water Quality Index
80
Pasir
Kecil
Air
Mendidih
Gelugor
Index Value
70
60
50
40
30
20
10
Au
gu
st
Ju
ly
Ju
ne
M
ay
Ap
ril
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
M
ar
ch
0
Bakar
Arang
PetaniBus
Petani
Jetty
Month
Figure 1. Water Quality Index at the sampling sites from September 2005 to August
2006.
Dissolved Oxygen
Dissolved Oxygen mg/L
14
Pasir Kecil
12
Air
Mendidih
Gelugor
10
8
6
Bakar
Arang
Petani-Bus
4
2
PetaniJetty
Au
gu
st
Ju
ly
Ju
ne
M
ay
Ap
ril
M
ac
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
0
Month
Figure 2. Dissolved oxygen (DO) at the sampling sites from September 2005 to
August 2006.
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(ECOMOD 2007), PENANG, MALAYSIA
Chemical Oxygen Demand
Pasir Kecil
900
800
Air
Mendidih
Gelugor
700
600
500
Bakar
Arang
Petani-Bus
400
300
200
Petani-Jetty
100
us
t
ly
Au
g
Month
Ju
Ju
ne
M
ay
Ap
ri l
0
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
M
ar
ch
Chemical Oxygen Demand
(mg/L)
1000
Figure 3. Chemical oxygen demand (COD) at the sampling sites from September
2005 to August 2006.
pH Level
9
Pasir Kecil
8
Air
Mendidih
Gelugor
7
pH
6
5
Bakar
Arang
PetaniBus
PetaniJetty
4
3
2
1
Ju
ly
Au
gu
st
Ju
ne
M
ay
Ap
ril
M
ac
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
0
Month
Figure 4. The pH level at the sampling sites from September 2005 to August 2006.
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
(ECOMOD 2007), PENANG, MALAYSIA
180
160
140
Pasir Kecil
Air
Mendidih
Gelugor
120
100
80
60
Bakar
Arang
Petani-Bus
40
20
0
Ju
ly
Au
gu
st
Ju
ne
M
ay
Ap
ri l
M
ac
PetaniJetty
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
a
Fe r y
br
ua
ry
Suspended Solids mg/L
Total Suspended Solids
Month
Figure 5. Amount of TSS at the sampling sites from September 2005 to August 2006.
Total Dissolved Solids (TDS)
18000
Pasir
Kecil
Air
Mendidih
Gelugor
16000
TDS mg/L
14000
12000
10000
8000
6000
4000
2000
Au
gu
st
Ju
ly
Ju
ne
M
ay
Ap
ril
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
M
ar
ch
0
Bakar
Arang
PetaniBus
PetaniJetty
Month
Figure 6. Amount of TDS at the sampling sites from September 2005 to August 2006.
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(ECOMOD 2007), PENANG, MALAYSIA
Ammonia
Ammonia (NH3-N) mg/L
4.5
Pasir
Kecil
4
3.5
Air
Mendidih
3
Gelugor
2.5
2
Bakar
Arang
1.5
1
PetaniBus
0.5
Ju
ly
Au
gu
st
Ju
ne
M
ay
Ap
ril
M
ac
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
0
PetaniJetty
Month
Figure 7. The concentration of ammonia from September 2005 to August 2006 at all
sites.
Nitrite
0.9
Pasir
Kecil
Air
Mendidih
Gelugor
Nitrite (NO2-N) mg/L
0.8
0.7
0.6
0.5
Bakar
Arang
PetaniBus
PetaniJetty
0.4
0.3
0.2
0.1
Ju
ne
M
ay
Ap
ri l
M
ac
Ju
ly
Au
gu
st
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
0
Month
Figure 8. The concentration of nitrite from September 2005 to August 2006 at all sites.
THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007
(ECOMOD 2007), PENANG, MALAYSIA
Nitrate
10
Pasir
Kecil
Air
Mendidih
Gelugor
Nitrate (NO3-N) mg/L
9
8
7
6
Bakar
Arang
PetaniBus
PetaniJetty
5
4
3
2
1
Ju
ly
Au
gu
st
Ju
ne
M
ay
Ap
ri l
M
ac
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
0
Month
Figure 9. The concentration of nitrate from September 2005 to August 2006 at all
sites.
Ortho-Phosphate
Orthophosphate mg/L
1.2
Pasir
Kecil
Air
Mendidih
Gelugor
1
0.8
0.6
Bakar
Arang
PetaniBus
PetaniJetty
0.4
0.2
Au
gu
st
Ju
ly
Ju
ne
M
ay
Ap
ril
M
ac
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
0
Month
Figure 10. The concentration of ortho-phosphate from September 2005 to August
2006 at all sites.
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(ECOMOD 2007), PENANG, MALAYSIA
Alkalinity
Alkalinity (HCO3) mg/L
120
Pasir
Kecil
Air
Mendidih
Gelugor
100
80
Bakar
Arang
PetaniBus
PetaniJetty
60
40
20
Ju
ne
M
ay
Ap
ri l
M
ac
Ju
ly
Au
gu
st
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
0
Month
Figure 11. The alkalinity at each site from September 2005 to August 2006
Temperature
Temperature in Celsius
32
Pasir
Kecil
Air
Mendidih
Gelugor
31
30
29
28
Bakar
Arang
PetaniBus
PetaniJetty
27
26
25
Au
gu
st
Ju
ly
Ju
ne
M
ay
Ap
ril
M
ac
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
ar
y
Fe
br
ua
ry
24
Month
Figure 12. The average temperature at all sites from September 2005 to August 2006.
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Conductivity
Conductivity us/cm
40000
Pasir
Kecil
Air
Mendidih
Gelugor
35000
30000
25000
20000
Bakar
Arang
PetaniBus
PetaniJetty
15000
10000
5000
Au
gu
st
Ju
ly
Ju
ne
M
ay
Ap
ril
M
ac
Se
pt
em
be
r
O
ct
ob
er
N
ov
em
be
D
r
ec
em
be
r
Ja
nu
a
Fe r y
br
ua
ry
0
Month
Figure 13. Conductivity level from September 2005 to August 2006.
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