Effluent Standards (ES)

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.

Standards have been established for the quality of effluent discharged from treatment plants to receiving waters. These take the form of acceptable upper limits for various effluent contaminants. Effluent from treatment plants are regularly sampled and tested in laboratories to ensure that these standards are met and that treatment plants are operating correctly. 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.

Population Equivalent (PE)

In order to design pipe network, pump stations and sewage treatment plants, estimates need to be made of the volumetric flow rate which will be expected to be carried, pumped and treated.

Such flow rates are measured in cubic metres per second and need to be calculated for both existing land use and for expected future development.

There are many methods for calculating expected flow rates. One method is to calculate a design parameter called the "population equivalent" (PE) of a catchment and convert this to a flow rate.

The PE is an estimate of the usage made of sewerage facilities. It is not a measure of population.

For residential areas the population equivalent is calculated as five per dwelling and is a direct measurement of the population in an area.

However, for commercial areas it is calculated from the floor area, which is considered to be proportional to the number of people using a premise during the day. In this case it does not reflect the population living in an area.