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

Water Quality Profile of Sg. Langat

ANHAR SUKI, MORD KAMIL YUSOFF and MOK TREAN POEDepartment ofEnvironmental Sciences

Faculty ofScience and Environmental StudiesUniversiti Pertanian Malaysia

43400 , Serdang, Seiangor, 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 sungai.Beberapa 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 menunjuk­kan perubahan kualiti air sangat bererti (p < 0.05). Berdasarkan Indeks Kualiti Air, kualiti air sungai yangberhampiran bandar Kajang menurun dengan ketara jika 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

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

(l979), 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 hydro­logic 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.

ANHAR SUKI, MOHO KAMIL YUSOFF AND MOK THEAN POE

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 1.The basin comprises urban and associated areas,cultivation of rubber, oil palm, mixed horti­culture 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

9.9

31.0

31.0

18.0

17.5

16.7

17.3

14.7

11.9

River width(m)

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

Sampling of water from each site was carriedout at a frequency of once a week from Augustto December 1985 for a duration of 12 weeks.For the purpose of this study, grab samples werecollected for in-situ and laboratory analysis. Inorder to get a representative sample, the watersample was taken in the middle section of theriver at 0.6 depth from the water surface (i.e60% of the total depth).

The selected parameters fqr measurementwere pH, temperature, dissolved oxygen (DO),electrical conductivity (EC), turbidity, suspendedsolids and biochemical oxygen demand (BOD).The first three parameters were determined on­site and the rest of the analysis were performedin the laboratory within 24 hours. Nutrientmeasurements were not carried out. Table 2 showsthe analytical methods adopted throughout thestudy.

The analysis of variance (one way ANOYA)and Duncan Multiple Range tests were used todetect the significant difference of means betweensampling sites (Steel and Torrie, 1960). The inter­pretation of variation in water quality was eva­luated with the Water Quality Index (Norhayati,1981).

PERTANlKA VOL. 11 NO.2, 1988

TABLE 1A description of the sampling sites or stations.

Station Distance fromEstuary (km)

Sl 118

S2 109

53 105

54 95

55 92

56 87

57 81

58 74

59 60

274

Basin CharacteristicsThe study area was confmed to a catchment

area of aproximately 700 sq. km within the Sg.Langat basin (Figure 1). The area is drained bySg. Langat with its headwaters rising in the hills inthe north and flowing generally southward to­wards 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.

These changes bring about complex environmentalproblems and the most important natural re­source 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 tribu­tary.

N

WATER QUALITY PROFILE OF SG. LANGAT

101 047 '

KEY

Forest

Rubber

Scrub forest

Oil palmUrban andass areasHorticulture

[ill] Tin minesnewly cleared

0 Lands

till Swamps. -

~ Pasture

• Town

..".c.. Rivers

Scale I em : 2.5 km

Fig 1. LDnduse pattern in the study area.

PERTANIKA VOL. II NO.2, 1988 275

ANHAR SUKI, MOHO KAMIL YUSOFF AND MOK THEAN POE

101 0 47 .

Scale: I em = 2.5 km

N

(g)

•

KEY

Industrial Area. - "-Rubber Factory

Sampling station

·Road

276

Fig 2. Location of sampling sites.

PERTANIKA VOL. II NO.2, 1988

WATER QUALITY PROFILE OF SG. LANGAT

RESULTS AND DISCUSSION

5'

• -DO• - 100,

78 85 92 99 106 113 120Distance 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

15.0

13.5

12.0

10.5

~ 9.0

S8 7.5

~ 6.0Cl

~ 4.5

3.0

1.5

050 57 64 71

BOD and DOThe average DO profJJ.e for the period of study isgiven in Figure 3. As shown, the dissolved oxygenvalue varies from 8.1 to 6.1 mg/I. Statisticalanalysis shows that the mean DO at each samplingstation is significantly different (p < 0.05). Atthe upstream regions (Sampling station Sl-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 turbu­lent 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/I. This compares well with dataobtained by the Department of Environment(l980-l984).

Further downstream the DO value reducesto 6.9 mg/l near Cheras area and to 6.2 mg/l atKajang Town. The latter represents a reductionof the dissolved oxygen content by as much as23% as compared to the upstream region (Sl).The built-up areas from Cheras to Kajang towncontribute to the increase in organic load parti­cularly 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

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) ( ±O.))Dissolved oxygen meter model YSI 58 ( ±O.I mg/!)Turbidimeter (HACH Mode12100A)(±2% of the full scale:-Ranges:- 0 0.1 NTU

o 1.0 NTUo 10 NTUo 100 NTUo 1000NTU)

Digital conductivity meter model PCM 3 ( ± 0.01 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. II NO.2, 1988 277

ANHAR SUKI, MOHO KAMIL YUSOFF AND MOK THEAN POE

station- S4, the BOD had increased 10 fold com­pared to the value upstream. This is partially dueto developed areas after Hulu Langat town andthe rubber mill. The discharge from the mill andits BOD value is given in Table 3. The BOD valueactually peaks at Kajang town with an averagevalue of 9.0 mg/I. A BOD value of 9 mg/1 wouldbe considered a moderately polluted river accor­ding to a classification by Mok (1985). Here theopen drains from the town normally dischargeinto the river and there are also industries likethe paper and textile mills which discharges theirwastes. The 1985 data on these discharges are alsogiven in Table 3.

After Kajang town, the mean BOD valuesdecreases and at sampling station S9 the valuehas dropped to an average of 3.2 mg/I. This isdue to the reduction in urban activity down­stream and the absence of other major pollutionsources. The DO as expected did not increaseimmediately and has a minimum value at stationS7. This is due to the time taken for biologicalactivity to reduce the oxygen content of thewater. The Streeter-Phelps equation which cal­culates oxygen deficit in rivers due to organicpollution also predicts a similar prof11e (Metcalfand Eddy Inc. (I 979)).

It is interesting to note that a BOD of 9.0mg/l at Kajang represents an organic mass trans­port of about 68 kg/h (assuming lowest stream­flow for the period of study (Table 4) and theinput from the two major mills (paper and tex­tile) at Kajang is about 4 kg/h (using data fromTable 3). This rough calculation shows that themajor organic input to Sg. Langat comes fromother non point sources. It is suspected that thedrain serving the developed areas are the maincontributers.

Turbidity and Suspended SolidsThe suspended solids and' turbidity results areshown in Figure 4. The trend obtained withrespect to distance is similar to that obtainedfor BOD and DO. Stations SI, S2 and S3 huelower suspended solids as the area is mainlycovered by forest. As such there is little erosionoccuring. This result is also reflected in the lowturbidity values. The suspended solids value ofless than 26 mg/1 is in the class of good qualitywater which- requires little or no treatment forpotable ust:.

The suspended solids and turbidity areexpected to rise as the river flows past deve­loped and developing areas from Cheras andKajang town. The mean suspended solids valueat station S8 is a high 377 mg/I. This representsmore than a 10 fold increase compared to the

455 100

410 Turbidity 91

Suspended Solid360 82

320 73

~215s.

64:;

"0 ~'g 230 55 ~VI"0 >-

~ 185 • 46~<=It~140 37 ~

95 28

50 19

$.

50 57 64 71 78 85 92 99 120Distance from Estuary (km)

Fig 4. Suspended solids and turbidity values for thedifferent sampling sites.

TABLE 3Characteristics of industrial effluents in the study area

Type of Discharge Average Monthly Concentration

Factory (m3/day) Suspended solid BOD(mg/!) (mg/I)

Rubber 256 34 189

Textile 360 236 55

Papermill 246 20 265

Source: Department of Environment (1985)

278 PERTANlKA VOL. II NO.2, IS88

WATER QUALITY PROFILE OF SG. LANGAT

TABLE 4Weekly river discharge at Kajang (S6) and Dengkil (S9)

Month

August

September

October

November

Source: Mok (1986)

StationKajang (S6)

(cumecs)

3.02.13.73.07.72.72.63.47.54.43.54.3

18.821.4.17.315.8

Dengkil (S9)(cumecs)

10.17.45.54.95.75.76.0

15.536.518.534.235.463.371.863.457.8

value at Sl to S3. Between S6 and S8, develop­mental projects are underway. These includeland clearing and housing development. As suchthe suspended solids and turbidity continue torise.

At .station S9, the suspended solids decreasein concentration. This last station is about 14 kmfrom S8, and the area is mostly palm oil plan­tation, forest and swamps. Therefore there islittle additional input of solids and sedimentationwould reduce the settleable component. Two tri­butaries namely Sg. Chua and Sg. Semenyih jointhe Sg Langat 4 km and 9 km upstream of stationS9. These two factors partially explain the reduc­tion in the suspended solids values.

Electrical Conductivity (EC)The results are given in Figure 5. The electricalconductivity range from 33 to 88 uS/em. This isconsidered low and does not affect the waterquality, as river water has an EC value of between50 to 150 uS/em. The EC trend downstream issimilar to the other parameters as given above.

pH and TemperatureThe mean pH for the various sampling stationsrange from 6.3 to 6.8 (Figure 6). This is a relative­ly narrow range and well within the pH of naturalwaters. Even though the range is small, the mean

at each station was found to be significantlydifferent (p < 0.01). The temperature of thesampling points are apprOXimately constant,ranging from 26 to 28oC. The variation is mainlydue to the time of sampling rather than any realdifference between the sampling stations. Thesampling was carried out from morning to evening.

Water Quality Index (WQI)The water quality index can be computed usingthe various mathematical equations. For example

100

91

~ 82

~ 73§;64:Eg 55"0

"846-;;

'S 37.l!UJ

28

9\

50 57 64 71 78 85 92 99 106 113 120Distance from Estuary (km)

Fig 5. Electrical conductivity values for the differentsampling rite,.

PERTANIKA VOL. 11 NO.2, 1988 279

ANHAR SUKI, MOHD KAMIL YUSOFF AND MOK THEAN POE

the water quality index can be based on a weigh­ted 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);

\00 r----------------.,

80

60

o~

40

WQI-= 1.n

n

~

i = 1qi (1)

20

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

- n is the number of parameter to be inclu-

51 52 53 54 5S 56 57 58 59Sampling Station

Fig 7. WQI values for the various sampling sites.

ded.

Fig 6. pH and temperature values for the differentsampling sites.

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/l 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.

BOD and suspended solids were used in the com·putation. The highest value of 87 is for stationS1 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 respective­ly. Using this classification, the river would onlybe termed slightly polluted at Kajang. However,these are only rough indications and the divisionsare rather subjective.

12.0

33.0

29.S

40.0

26.0_~

22.5i

"19.0~

5IS.Sf-

..1! S2 ---1'.....

• _ Temperature 36.5

• - pH

..

2.3

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 ques­tionaire 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 (l) the WQ1obtained for various points in Sg. Langat is givenin Figure 7. Based on the available data, 5 para­meters namely pH, temperature, dissolved oxygen,

8.5

1.0 l--~_~__---.._~_.-------.._........__~ S.OSO S7 64 71 78 8S 92 99 106 113 120

Distance from Estuary (km)

7.5

3.6

6.2

49

8.8

10.1

11.4

12.7·

14.0

280 PERTANlKA VOL. II NO.2, 1988

WATER QUALITY PROFILE OF SG. LANGAT

REFERENCES

ABU BAKAR JAAFAR. (1985): The state of the environ­ment in Malaysia: Public sector perspective. Paperpresented at the Seminar on the State of Environ­ment Quality in Malaysia. Kuala Lumpur. Ministryof Science, Technology and Environment. 8-11July 1985.

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

BALL, R.O and R.L. CHURCH (1980): Water qualityindexing and scoring. J. of the EnvironmentalEngineering Divi9ion. 105(4), 757-771.

BIGGAR, J.W. (1979): Soil and Water Salinity. Depart­ment of Land and Water Resources. University ofCalifornia, Davis.

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

DEPARTMENT OF ENVIRONMENT (1985): Factorydischarged data (unpublished).

HORTON, R.K. (1965): An index - Number system forrating water quality. J. Water Poll. Control. 37(3),300-306.

HYNES, H.B.N. (1970): The Ecology of Running Waters.Toronto. University of Toronto Press.

LAW, A.T. (1980): Sewage pollution in Kelang River anditsestuary.Pertanika. 30U, 13-19.

METCALF AND EDDY INC. (1979): WasterwaterEngineering: Treatment Disposal and Reuse.Second edition. New York. McGraw-Hill BookCo.

MOK, T.P. (1986): Water quality changes in Sg. Langat.B.Sc.(Env.). Project Report 1985/86. UnivenitiPertanian Malaysia. 108 p.

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

OTT. W.R. (1978): Environmental Indices - Theoryand Practice, Michigan. Ann Arbor Science, AnnArbor.

STEEL, R.G.D. and J.H. Torrie (1960): Principles andProcedures of Statististics. New York. McGraw­Hill Book Company.

TAN, W.T. and B.S. NG, (1980): A chemical survey ofthe Batang Belungkung River and the GombakRiver. Pertanika. 3(1),40-46.

TANJI, K. (1979): Water quality and pollution. InIntroduction to Water Science by Silk, W. et a1. ,.Department of Land and Water Resources. Univer­sity of California, Davis.

(Received 22 May, 1987)

PERTANIKA VOL. 11 NO.2, 1988 Z81