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Sewage TreatmentTrends in Malaysia

THE RIVER THE BEACH

Figure 2.1: Rural Sanitation Direct Discharges

Sewage TreatmentTrends in MalaysiaBy Ir. Haniffa Hamid and Dr. Aminuddin Mohd Baki,Indah Water Konsortium Sdn. Bhd.

Malaysia's sewerage industry has evolved over thelast half a century. Prior to the country'sindependence in 1957, there were no proper

sewerage systems and no need for a proper sewagetreatment one due to the low population densities andvery limited urbanised developments.

Sewage treatment was mainly by way of primitivemethods such as pit and bucket latrines, over-hanginglatrines and direct discharge to rivers and seas. The needfor proper sanitation arose when the country developedand moved from agriculture to an industry-basedeconomy.

In the 1960s, sewage treatment systems in the form ofindividual septic tanks (ISTs) and pour flush systems wereintroduced. Small communal systems engaging mainlyprimary treatment such as the communal septic tanks(CSTs) and Imhoff tanks (ITs) started developing.

In the 1970s, the technology engaged expanded tobiological treatment processes in the form of oxidationpond systems using natural means of treatment. In the1980s, mechanised systems were introduced in Malaysiaand oxidation ponds were converted to aerated lagoonsystems.

The late 1980s and the 1990s saw the accelerateddevelopment of fully mechanised systems in the form ofbiological filters and activated sludge systems. The laterpart of the 1990s saw efforts concentrated on the controlof mechanised systems which allowed for processoptimisation of new systems.

This evolution of treatment processes from primitiveto primary and then to secondary systems was mainlydue to technology development in the sewerage industry.

The evolution also saw the move from non-mechanicalsystems to a more mechanical and automated system.New and improved equipment were also continuouslyintroduced due to technological advancements. With timethis increased the expectation on environmental standardsand the skill level in the design, construction andoperations of new sewerage works.

The Evolution of Sewage Treatment Technology

In early days of human civilisation, life was too harshto worry about sewerage systems. As the population wasvery small, nature took care of the sanitation problemsbut as civilisation progressed and the population increased,the need for proper sanitation arose.

In Europe, the development of sewerage systemsfollowed the needs that arose as townships grew andpopulation rose. Its evolution started with direct dischargeto the streets during the Middle Ages where the streetswere the sewage disposal area. Outbreaks of bubonicplague raised the concern for improved sanitation.

In the 19th century, development in sewerage systemsincluded the use of pour flush and sewers discharging tothe river. When the pollution level in the rivers worsen,sewage farms were introduced to treat sewage and laterdeveloped into proper sewage treatment plants.

During Malaysia's pre-independence period, thedevelopment of sanitation facilities was very limited asthe need for sanitation was not critical. Figure 2.1 showedthe sanitation practices in the rural areas while Figure 2.2looked at the sanitation practices in the towns. See theearly technologies used in Figures 2.3.

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Figure 2.2: Town Sanitation Night Soil Systems

Figure 2.3 Technologies in the early days in Malaya

Figure 2.4: Individual Septic Tanks

Figure 2.5: Individual Septic Tank Systems

Pit Latrines

Bucket Latrines

Hanging Latrines

In the 1950s, towns started to develop and populationdensities began to grow. There was increased need forimprovement in the sanitation sector. Technologicaladvancement at that time saw the primary systems usingthe sedimentation processes. ISTs used this treatmentconcept. See Figures 2.4 and 2.5.

Pour Flush

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Figure 2.6: Typical Performance ofIndividual Septic Tanks

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ITs, another improved version of primary treatmentsystem, were later introduced for the community seweragesystems. See Figure 2.8. Here, BOD was reduced from 200-400 mg/l to 50-175 mg/l as shown in Figure 2.9.

This primary system could only provide basic primarytreatment via sedimentation and digestion. The expectedperformance of such systems is shown in Figure 2.6.

In the towns, ISTs started to replace the primitivesystems, thus reducing the direct pollution levels to theenvironment. For example, BOD was reduced from 200-400 mg/l to 150-200 mg/l as shown in Figure 2.6.

After Malaysia's independence in 1957, the need forimproved sanitation expanded to community basedsanitation as more towns were established. CSTs wereintroduced to improve the community sewerage systems.See Figure 2.7. In terms of performance, they were similarto ISTs but the CSTs served a bigger population via aseries of pipes connecting a row of tanks.

Figure 2.7: Communal Septic Tanks

Figure 2.8: Imhoff Tanks

Figure 2.9: Typical Performance of Imhoff Tanks

In the 1970s as Malaysia continued to develop and asits towns grew to become cities, the need to improveenvironmental conditions arose and led to the enactmentof the Environmental Quality Act in 1974. Partialsecondary treatment systems such as oxidation ponds wereintroduced. See Figure 2.10.

Figure 2.10: Oxidation Ponds

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In the 1990s, improvement in pumps technologyallowed for more efficient pumps being introduced intothe sewerage industry. Improvements were made in theimpeller design, the materials used and the compactnessof the whole pump.

Various types of aerators such as aspirators,submersible aerators and various improvements in theirdesign were also introduced over the years to allow formore efficient oxygen transfers.

The technological development also includedimprovement of existing systems such as the use of PLCand SCADA in 1990s. Technological advancement incomputer technology and microelectronics allowed forenhancement and optimisation of sewage treatmentsystems. For example, the use of PLC allowed for bettercontrol of the sequencing batch reactors processes orintermittent decanted extended aeration (IDEA) systems.

Progress in Sludge Management

All existing treatment methods mentioned earlier werecapable of producing massive quantities of sludge. Priorto the privatisation of sewerage services, there were noproper programmes to handle, treat and dispose sludgesafely back to the environment. Sludge management wasneglected in Malaysia. It was assumed that sludgemanagement would be provided by others but it nevermaterialised. See Figure 2.17.

Figure 2.11: Typical Performance of Oxidation Ponds

Figure 2.12: Aerated Lagoons

Oxidation ponds were capable of providing partialsecondary treatment mainly in the form of biologicaltreatment. The treatment performance improved as BODcould be reduced from 200-400 mg/l to 20-100 mg/l asshown in Figure 2.11.

In the late 1970s, aerated lagoons were introduced toserve a larger population within a limited land areareserved for oxidation ponds. This was done by introducingaerators to the systems. This technological advancementallowed for enhancement of oxidation ponds capacitiesup to more than five times the original capacities. SeeFigure 2.12.

The needs for improvement in the sewerage systemsbecame more prevalent in 1980s when the EnvironmentalQuality Regulations in 1979 were enacted. Technologicaladvancements included the introduction of full secondarytreatment via mechanised sewage treatment plants.

There are various types of mechanised sewagetreatment plants ranging from the conventionalactivated sludge, extended aeration, rotating biologicalcontactors and trickling filters. Figure 2.13 showed anexample of an extended aeration activated sludgesystem.

Mechanised sewage treatment plants capable ofproviding full secondary treatment were more superiorthan the other systems discussed earlier. Figure 2.14illustrated typical unit processes of mechanised sewagetreatment plants.

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Figure 2.14: Typical Mechanised Plants Performance

Figure 2.13: MechanisedSewage Treatment Plant

Figure 2.15: Examples of Equipment Used inSewerage Systems

Figure 2.16: IDEA Systems

Figure 2.17 illustrates this assumption that sludge management would be provided by others.

Pump Sump

Grit

GritWAS

RAS

ClarifierTreated

Effluent

Scum

Coarse

Screen

Raw Influent

Grease

Trap

Anoxic

Tank

Aeration

Tank

Screening

Fine

Screen

Sludge Treatment - BY OTHERS

- which never materialised

Disposals

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Figure 2.18: Typical Sewage Treatment Systems with Sludge Neglected

Figure 2.19: Progress Improvements of Sludge Management

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Figure 2.20: Sewage Treatment Trends in Malaysia

Currently, there are about 7,500 public sewagetreatment plants which generate sludge as by-productsof the sewage treatment. There are over one millionISTs which also generate sludge. The nationalsewerage concessionaire is responsible to providedesludging services at a frequency of once every twoyears. Figure 2.18 demonstrated the extent of theexisting sludge treatment, collection and disposalneeds for Malaysia.

Figure 2.19 showed the technological evolution interms of sludge treatment in Malaysia. The progressincluded trenching systems, sludge lagoons and sludgedrying beds. This was followed by changes to themechanised dewatering such as fi lter presses,centrifuges and belt presses to complete centralisedsludge treatment facilities which consist of mechanisedthickening followed by stabilisation by anaerobicdigestions to mechanised dewatering, thermal dryingand incinerations. BEM

An Overview

In Malaysia, the sewerage technology has evolved frompre-independence era of no treatment to the primarytreatment by individual septic tanks in the 1950s. Thisimproved the level of sanitation by providing partialtreatment of sewage. In the 1960s, the introduction ofCSTs and ITs further improved the effluent quality whilethe 1970s saw the introduction of partial secondarysystems such as oxidation ponds which can produce bettereffluent quality.

Fully mechanised systems were introduced in the 1980swhich provided full secondary treatment that can meet theDepartment of Environment's effluent standards consistently.

The above figure demonstrates the technologydevelopments of sewage treatment over the years. Aninteresting fact is that with advancement in treatmenttechnology, the user of mechanical and electricalequipment shows a steep increasing trend.

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