Pertanika 11(2), 273-281 (1988)

Water Quality Profile of Sg. Langat

ANHAR SUKI, MOHD KAMIL YUSOFF and MOK THEAN POEDepartment of Environmental Sciences

Faculty of Science and Environmental StudiesUniversiti Pertanian Malaysia

43400, Serdang, Selangor, Malaysia.

Key words: Water quality; Sg. Langat

ABSTRAK

Kajian ini telah dijalankan pada bulan Ogos hingga Disember 1985 yang bertujuan untuk menilaikesan-kesan pencemaran yang berpunca daripada corak penggunaan tanah yang berlainan atas kualiti airsungai. Sebanyak sembilan lokasi penyempelan telah dipilih sepanjang 60 km bermula dari hulu sungaiBeberapa parameter fizikal dan kimia telah diukur. Ujian statistik dan Indeks Kualiti Air diguna untukmenentukan perubahan kualiti air. Keputusan kajian menunjukkan nilai-nilai BOD, pepejal terampai,pengkonduksian elektrik dan kekeruhan meningkat selepas bandar Hulu Langat. Ujian statistik menunjuk-kan perubahan kualiti air sangat bererti (p < 0.05). Berdasarkan Indeks Kualiti Air, kualiti air sungai yangberhampiran bandar Kajang menurun dengan ketarajika dibandingkan dengan lokasi yang lain.

ABSTRACT

This study was conducted between August and December 1985 in order to assess polluting effectsfrom different landuse patterns. Nine sampling sites were chosen over a distance of 60 km. A numberof physical and chemical parameters were analysed. Statistical tests and Water Quality Index were used toevaluate the water quality variation. The result shows that relatively high BOD, suspended solids, electricalconductivity and turbidity occurred after Hulu Langat town. The statistical test indicated that the waterquality variation is significantly different (p < 0.05); the Water Quality Index shows that the waterquality near Kajang town has deteriorated compared to other stations.

INTRODUCTIONWater serves a multitude of uses. As the varioususes have grown in diversity, constrained by themore or less fixed quantity available, significantinteraction of uses and reuses of water has alsodeveloped. Water quality is a very broad termwhen used by some people and quite specificfor others and is the complementary aspect ofwater quantity (Biggar, 1979).

Chemically pure water rarely occurs innature. Its content varies largely from region toregion, and is a reflection of the local geographyand climate (Hynes, 1970). According to Tanji

(1979), water is often referred to as a universalsolvent and because of this solvent power, it tendsto pick up impurities as it comes into contactwith gases, liquids and solids. Water in the hydro-logic cycle is highly mobile and acts as a conveyorwhich then transports the pollutant downstream(Tanji, 1979). The solvent power and the mobilityof water are the basic reasons why we have waterpollution problems in rivers or any water bodies.

In a developing country like Malaysia, rapidchanges are continually taking place. These includepopulation growth, urbanisation, agricultural,mining and logging activities, and industrialisation.

Key to authors' name: A. Suki; M. Kamil; T.P. Mok

ANHAR SUKI, MOHD KAMIL YUSOFF AND MOK THEAN POE

These changes bring about complex environmentalproblems and the most important natural re-source that is affected is water (Abu Bakar, 1985).The development of land and natural resources,and the discharge of waste products into the waterbody are the main water pollution sources inMalaysia.

In the early days the water quality of Sg.Langat was of little concern as demand for waterwas relatively low. Now, with increased demandfor water by the growing population, industry andagricultural sectors, there is an increased pollutionload in the river, and this affects its uses (Mok,1986). This study was carried out along Sg.Langat, to check on the variation in water qualitywith respect to landuse. Similar studies have alsobeen carried out on other river systems. Law(1980), concentrated more on faecal coliformcounts in Kelang River and Tan and Ng (1980),studied the effect of rubber effluent and domesticwaste discharges into Gombak River and a tribu-tary.

Basin CharacteristicsThe study area was confined to a catchment

area of aproximately 700 sq. km within the Sg.Langat basin (Figure J). The area is drained bySg. Langat with its headwaters rising in the hills inthe north and flowing generally southward to-wards the plains before turning westward towardsthe sea, covering a distance of approximately 120km. The headwaters of the Sg. Langat is made upof forested foothills and rugged mountain ranges.

TABLE 1A description of the sampling sites or stations.

Station

SI

S2

S3

S4

S5

S6

S7

. S8

S9

274

Distance fromEstuaiy (km)

118

109

105

95

92

87

81

74

60

River width(m)

9.9

11.9

14.7

16.7

17.3

17.5

18.0

31.0

31.0

PERTANIKA

Within the study area, there are six townslocated along the river; Kg Kuala Panson, DusunTua, Hulu Langat, Cheras, Kajang and Dengkil(Figure 2). The largest town is Kajang, located'inthe middle section of the catchment area.

The landuse pattern is depicted in Figure LThe basin comprises urban and associated areas,cultivation of rubber, oil palm, mixed horti-culture and coconut, tin mining and forest reserve.Percentage wise, agricultural land and forestoccupy 52 and 40 percent of the total acreagerespectively (Mok, 1986).

Most of the industrial areas are located inKajang and comprise various type of factories;the major factories being rubber, textile andpaper mills (Figure 2).

MATERIALS AND METHODS

On-site surveys were carried out determine thepotential sampling sites. The siting of the samplingsite was based on accesibility and homogeneity irorder to obtain a representative sample. Based orthe above criteria, nine sampling sites were choser(Figure 2). Table 1 shows the distance of th<sampling sites from the estuary (at the riveimouth).

Sampling of water from each site was carriecout at a frequency of once a week from Augusto December 1985 for a duration of 12 weeksFor the purpose of this study, grab samples wencollected for in-situ and laboratory analysis. Iiorder to get a representative sample, the watesample was taken in the middle section of thriver at 0.6 depth from the water surface (v60% of the total depth).

The selected parameters fojr measuremenwere pH, temperature, dissolved oxygen (DO]electrical conductivity (EC), turbidity, suspendssolids and biochemical oxygen demand (BOD'The first three parameters were determined orsite and the rest of the analysis were performerin the laboratory within 24 hours. Nutriermeasurements were not carried out. Table 2 shovthe analytical methods adopted throughout thstudy.

The analysis of variance (one way ANOVAand Duncan Multiple Range tests were used t<detect the significant difference of means betweeisampling sites (Steel and Torrie, 1960). The inteipretation of variation in water quality was evzluated with the Water Quality Index (Norhayat1981).

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WATER QUALITY PROFILE OF SG. LANGAT

N

3* A Forest

Rubber

Scrub forest

Oil palmUrban andass areasHorticultureTin minesnewly clearedLands

Swamps

Pasture

Town

Rivers

Scale 1 cm : 2.5 km

Fig 1. Landuse pattern in the study area.

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ANHAR SUK1, MOHD KAMIL YUSOFF AND MOK THEAN POE

N

101° 47'I

KEY

A Industrial Area

® Rubber Factory

• Sampling station

— - Road

Scale : 1 c m = 2.5 km

Fig 2. Location of sampling sites.

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WATER QUALITY PROFILE OF SG, LANGAT

RESULTS AND DISCUSSION

BOD and DOThe average DO profile for the period of study isgiven in Figure 3. As shown, the dissolved oxygenvalue varies from 8.1 to 6.1 mg/1. Statisticalanalysis shows that the mean DO at each samplingstation is significantly different (p < 0.05). Atthe upstream regions (Sampling station SI-S3),the value is above 7.8 which represents greaterthan 95% saturation. This is expected as the riverin the upper region is mainly shallow and turbu-lent allowing ample reaeration. There is alsolimited organic pollution load in that section ofthe river as the area is mainly covered by rubberplantation and forest. The BOD value is on averageless than 1.0 mg/1. This compares well with dataobtained by the Department of Environment(1980-1984).

Further downstream the DO value reducesto 6.9 mg/1 near Cheras area and to 6.2 mg/1 atKajang Town. The latter represents a reductionof the dissolved oxygen content by as much as23% as compared to the upstream region (SI).The built-up areas from Cheras to Kajang towncontribute to the increase in organic load parti-cularly via the open drains. There is also a rubbermill downstream of Hulu Langat town and a paperand a textile mill at Kajang town. These industries

15.0

85 92 99 106 113 120

Distance from Estuary (km)

Fig 3. BOD and DO values for the various sampling sites.

also contribute to the increase in pollution load(Table 3). Beside these, there are also a numberof other small industries and several saw millsalong the river.

The BOD values were also obtained alongthe river. The statistical analysis shows that themean values between each sampling station werefound to be very significantly different (p <0.01).This is also true for the other parameters discussedbelow. There is a distinct increase in the BODvalue after sampling station S3. (Figure 3) At

TABLE 2Analytical methods adopted

Parameter Method of analysis

PH

TemperatureDissolved oxygenTurbidity

Electrical conductivitySuspended solids*BOD*

Orion digital pH meter model 201 with glass electrode (± 0.1pH unit)Thermistor probe (YSI 58) ( ±03)Dissolved oxygen meter model YSI 58 ( ±0.1 mg/1)Turbidimeter (HACH Model 2100A)( ± 2 % of the full scale :-Ranges:- 0 - 0.1 NTU

0 - 1.0 NTU0 - 1 0 NTU0 - 100 NTU0 - 1000NTU)

Digital conductivity meter model PCM 3 ( ± 0 . 0 1 umhos/cm)Filtration with Whatman glass microfibre filtersAzide modification of the Winkler method and incubation timeof 5 days at 20 C.

* APHA, 1975

PERTANIKA VOL. 11 NO. 2, 1988 277

ANHAR SUKI, MOHD KAMIL YUSOFF AND MOK THEAN POE

the water quality index can be based on a weigh-ted or unweighted arithmetic mean, weighted orunweighted geometric mean of partially weightedarithmetic or geometric mean (Horton, 1965 and;Ball and Church, 1980). The easiest to use isprobably the arithmetic mean which can be givenas(Ott, 1978);

100-4

WQI = I n2 (1)

where — qi is the quality of the i th parameter(subindex quality) and;

— n is the number of parameter to be inclu-ded.

40.0

57 64 71 78 85 92 99 106 113 120Distance from Estuary (km)

Fig <5. pH and temperature values for the differentsampling sites.

The subindex quality (qi) is obtained fromrating curves which range from 0 (worst waterquality condition) to 100 (best water qualitycondition). The rating curves are determined bythe Delphi's method, which is based on a ques-tionaire survey carried out on a panel of expertsin water quality (Ott, 1978). The WQI calculatedfrom the above equation ranges from 0 to 100.A higher value would indicate a better qualityof water. The qi value for Malaysian conditionscan be obtained from Norhayati (1981). Usingthese rating curves and equation (1) the WQIobtained for various points in Sg. Langat is givenin Figure 7. Based on the available data, 5 para-meters namely pH, temperature, dissolved oxygen,

SI S2 S3 S4 S5 S6 S7 S8 S9Sampling Station

Fig 7. WQI values for the various sampling sites.

BOD and suspended solids were used in the com-putation. The highest value of 87 is for stationSI and station S6 at Kajang has the lowest valuei.e. 66. At the last station at Dengkil, the waterquality appears to have recovered slightly. Thewater quality index gives a relative indication ofthe quality of the water along the river. A riverwith a WQI value in the ranges 0 -31 , 32-57,58-78 and 79-100 would be considered grossly,moderately, slightly polluted and clean respective-ly. Using this classification, the river would onlybe termed slightly polluted at Kajang. However,these are only rough indications and the divisionsare rather subjective.

CONCLUSIONThe results show that the changes in water qualityof Sg. Langat can be explained by the landusecharacteristics of the river basin. Similar trendswith respect to distance were obtained for thevarious water quality parameters. The waterquality at the upper catchment is very clean witha BOD less than 1.0 mg/1 and DO at greater than95% saturation. This makes the water a goodsource of potable water. Unfortunately the uptakefor potable water supply is further downstream atCheras (between S3 and S4) and another afterDengkil. The most polluted section of the riveris between S4 and S8. This section includes theKajang town, the worst point in the river. Theorganic loading to the river is mainly from nonpoint sources rather than specific large industries.However, the discharges by the industries aresignificant.

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REFERENCES

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APHA. (1975): Standard Methods for the Examination ofWater and Wastewater. 14ed. Washington. Ameri-can Public Health Association.

BALL, R.O and R.L. CHURCH (1980): Water qualityindexing and scoring. / . of the EnvironmentalEngineering Division. 105(4), 7 5 7 - 7 7 1 .

BIGGAR, J.W. (1-979): Soil and Water Salinity. Depart-ment of Land and Water Resources. University ofCalifornia, Davis.

DEPARTMENT OF ENVIRONMENT. (1980-1984):River water quality data, (unpublished)

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NORHAYATI MUSTAPHA. (1981): Indices for waterquality assessment in a river. Master's Thesis.Environmental Engineering Department. Bangkok.Asian Institute Technology.

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(Received 22 May, 1987)

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