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The pollutants in sewage are measured in order to better
understand and thus facilitate the treatment of sewage as
well as to examine the effects of effluent or treated sewage
on the environment.
Effluent from all public sewage treatment plants is sampled
at regular intervals and tested in modern laboratories to
ensure that it meets the required standards. Tests are carried
out as part of a monitoring programme in keeping with Indah
Water's operational license conditions and to ensure the efficient
operation of treatment processes.
This provides for a cleaner and safer environment that improves
the living conditions of Malaysians. The two most important
parameters measured are Biochemical Oxygen Demand (BOD)
and Suspended Solids (SS).
BOD is a measure of the amount of oxygen that sewage consumes
over a given time. High BOD is significant because it means
that sewage will rapidly consume all the naturally-dissolved
oxygen in streams, rivers and lakes, thus killing off all
aquatic life, and rendering the water septic and foul-smelling.
SS is a measure of the undissolved material in sewage. High
SS leads to sludge deposits in the waterways, thus causing
significant environmental deterioration.
Effluent that is discharged upstream of a water supply intake
should meet Standard A, while effluent that is discharged
downstream has to meet Standard B. These standards are set
by the Environmental Quality Act 1974.
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Domestic sewage treatment is mainly designed
to produce an effluent low in solids and organic. However,
other treatments, which remove the nutrients alter the pH
or disinfect the effluent may be added depending on the receiving
environment for the effluent.