Page 7 - Building services book

screening Was placed at the water entrance of inlet gate to prevent floating impurities such as
rubbish, twigs, plastic, textile, animal carcases and aquatic life from entering

pumping chamber which can damage the pumping equipment

aeration • to increase dissolved oxygen content in water

• to enhance freshness of water
• to reduce hydrogen sulphide odour in water

• to oxidize soluble iron and manganese into insoluble iron and manganese oxide.
Flocculated oxide produced settles through sedimentation process

Chemical diffusion Chemicals are added into raw water immediately after aeration process.

Coagulation and • Alum acts as thickening agent that allows small particles such as clay, colloid, gel and

flocculation emulsion to combine and form flocculants which then traps with small particles,
forming bigger and heavier which settled to the base of basin.

• coagulation is a process where fine flocculants combined to form larger and heavier
flocculants so as it settle easily during settling process.

Sedimentation To remove suspended solid from water which settles through gravity.

Filtering The filtering process is carried out by passing the water through porous medium such

as sand or other materials, that can trap suspended sediment.

Fluoridation Fluoride is added to water to reduce dental problems among consumers, especially in
children.

Sterilization Chlorine agent or chlorine compound in the form of solid, liquid or gas is added into
water at specific dosage to sterilise the water