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 (Kaňok, 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 (ECOMOD 2007), PENANG, MALAYSIA 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 (ECOMOD 2007), PENANG, MALAYSIA 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 THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007 (ECOMOD 2007), PENANG, MALAYSIA 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. THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007 (ECOMOD 2007), PENANG, MALAYSIA 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. THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007 (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. THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007 (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. THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007 (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. THE 2ND REGIONAL CONFERENCE ON ECOLOGICAL AND ENVIRONMENTAL MODELLING 2007 (ECOMOD 2007), PENANG, MALAYSIA 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. References: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Abdullah, H. K., Jusoh, J., 1997. 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