POTABLE WATERWater which is safe for human consumption and use is called potable water. It is mainly drinking water.

1.

Parameters for quality check

PHYSICAL:

1. Temperature: The water should not possess any adverse temperatures (neither too hot nor too cold). Temperature should range between 15° C and 25° C.

2. Turbidity: Turbidity is the light passing factor of water. It depends on the amount of suspended impurities in water. If turbidity is less, the water is clean from suspended particles. Upto 5 units of turbidity is allowed in potable water.

Surface Water Treatment

Stilling Chamber: Water after aeration reaches here, due to its large volume the velocity of water is reduced and air bubbles entrapped in it move up, thus deaerating the water.

Flash Mixer and Flocculator: More or less consist of same mechanism. A Flash Mixer mixes coagulants to the water at very high speed to remove fine suspended colloidal particles. Its retention time is about 1 -2 minutes. A Flocculator mixes clarifying agent to water so that colloidal particles form flocs and are removed. Its retention time is 30 minutes to 1 hour.

Pre Settling Tank: Pre settling tanks cater to the following needs – a) For water in emergency period or breakdown period b) To remove heavier suspended particles

Aeration Chamber

Intake Structure: To draw water safely from the river.

Filtration: In the process of filtration, water is allowed to pass through granular media for better clarity of water. It can also remove about 90 – 95% of virus and bacteria.

Disinfection: Waterborne diseases rise when the distribution system is close to the sewer lines and non potable water gets mixed with potable water due to cross connection or back syphonage. Chlorine is used as a disinfectant – it kills pathogens and e. coli. However excessive chlorine causes cancer.

Clean Water Reservoir

Water is now sent to different households via distribution pipes

Clariflocculator: Consists of a Flocculator and Clarifier. A Clarifier is used for sedimentation, removal of turbidity etc. The outer portion of the clariflocculator is a clarifier and inner part is a flocculator.

Sedimentation

Groundwater Treatment

Groundwater contains the following impurities: • TDS (Total Dissolved Solids)•Fe2+• Hardness• Arsenic or Fluoride• Chloride

Spray AerationCascade Aeration

Natural AerationOxidation occurs in aeration units. Ferrous (Fe2+ ) and manganous (Mn2+ ) present in the water are oxidised to ferric (Fe3+ ) and manganic (Mn3+ ).

Coarse MnO2 lumps are used to fasten aeration. Sometimes even activated silica is used. CO2 is also converted to CO3

-. Aeration units treat dissolved gases, iron and manganese.