| GENERAL
DESIGN CONSIDERATION |
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| 2.1 |
In order to ascertain the effluent quality requirements,
a designer is encouraged to liaise with EPD by submitting
the following information, prior to the design of STP:
- block
and location plans of site;
- maximum
number of persons (resident and non-resident) to be
served;
- presence
of shops, restaurants or other service trades;
- possibility
of the need for future extensions to the plant;
- proposed
location of discharge.
Based
on such information, EPD will then formulate the required
effluent quality standards.
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| 2.2 |
All elements of the STP should be open to view as far
as possible for easy operation and maintenance. |
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| 2.3 |
Mechanical equipment which is critical to the functioning
of the STP should be provided with on-line standby units.
For example, an on-line standby pump at the equalization
tank and an on-line standby chlorine dosing pump at the
chlorination tank should be provided. |
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| 2.4 |
Entrance to the STP should be by a proper door without
the use of steps or ladders and accessible by a vehicle.
A second pedestrian entrance/exit should be provided as
far as possible for emergency purposes at the opposite
end of the plant room. |
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| 2.5 |
Due consideration should be given to the possible initial
low flow condition before full population is achieved.
A multiple of smaller units (with gate or other shut-off
arrangements) should be provided as far as possible in
lieu of a single large unit. |
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| 2.6 |
Excessive quantities of grease and oil may cause malfunction
of an STP. In such cases, arrangements should be made
where practicable for grease and oil to be removed at
source. A properly designed grease trap should be provided
where restaurants or garages are to be served by the STP.
In general, a grease trap should be designed to provide
a minimum water retention time of 20 minutes for all wastewater
discharged from restaurant kitchens during peak flow periods. |
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| 2.7 |
Swimming pool filter backwash, if any, should be discharged
to the STP for treatment. Design of the STP should take
into account the flow and loadings of such wastewater.
Pool water itself should however be drained to the stormwater
system. |
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| 2.8 |
Under special circumstances, an autostart standby power
generator may be required if it is considered that discharge
of untreated wastewater to a specific water course is
unacceptable even for a brief period during power failure. |
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| 2.9
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An
STP design submission should include, but is not limited
to:
- key
plan showing location of development and effluent
discharge location;
- plan
and section showing the location of STP within the
development in relation to residential units and surrounding
facilities;
- process
and instrumentation diagrams;
- hydraulic
profile together with supporting calculations;
- detailed
process design calculation;
- detailed
drawings with plan and elevation showing plant room
layout, including pipework and equipment;
- route
of access to the plant room and access within the
STP;
- ventilation
and lighting details;
- equipment
schedule showing number of duty and standby units,
make, model number, capacity etc. The schedule should
be shown on the drawing;
- equipment
catalogues and operation/maintenance manual.
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