During 1960s, sewerage treatment systems in the form of individual septic tanks (ISTs) and pour flush systems were introduced in the town areas. That method helped to reduce the direct discharge of sewage pollution to the environment. As more towns were established, the use of communal septic tanks (CSTs) was introduced to provide for communitybased sanitation. These CSTs gave similar performance to ISTs but by way of a series of pipes connecting to a row of tanks.
CST was quite commonly used and currently made up 53% of all treatment plants in Malaysia. CST is clarified as a primary treatment and consisted of two chambers. The effluent enters into the first chamber where solids settle and partially clarified effluent overflows into the second chamber. The sludge then accumulates in the first chamber and requires regular desludging. Additional settlement occurs in the second chamber before the effluent is discharged to the drain.
Figure 7: Typical plant layout of Communal Septic Tanks
Besides that, another improved version of primary treatment system, that is Imhoff Tanks were later used for treatment as community sewerage systems. Imhoff tanks constitute 24% or 800 numbers of all sewerage treatment plants in Malaysia and are the second most common form of treatment plant.
Imhoff tanks are normally used to service small communities up to a population equivalent of 1,000. They are relatively cheap to install, operate and maintain. However, the Imhoff tanks only partially treat sewage. The effluent from the tank does not meet the environmental requirements of the Department of Environment.
Study on the Current Issues and Needs for Water Supply and Wastewater Management in Malaysia
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