Aquaculture Engineering

Infrastructural facilities - Water supply system

Unit 9 - Hatcheries

Fresh water prawn hatchery

Infrastructural facilities

Water supply system

The water supply system consists of seawater intake, filtration units, storage tanks for sea water, freshwater and brackish water (mixed water) and their distribution to various sections of the hatchery.

• Sea Water: If the seawater is to be drawn from inter tidal zone sea water should be drawn through a sub-soil filter arranged 5-6 feet below the sand, in order to make the water free from suspended particles and turbidity. If sea water is to be drawn from surface, the water should be passed through a shore sand filter before storing into the reservoir.
• Fresh water: The source of fresh water may be from a tube well or from a perennial canal. If water contains any suspended particles or turbidity, it should be passed through a sand filter before storing into the reservoir. The hardness of the fresh water should be below 50 ppm.
• Brackish water (mixed water): Supernatant water from the fresh water and seawater storage tanks are pumped into the mixing tanks so as to get the desired salinity (14 ± 2 ppt) with thorough aeration or with an agitator. The mixed water is treated with bleaching power to get 10 to 15 ppm chlorine to kill the micro flora and fauna. After 10 to 12 hours of chlorination (contact period) the water should be de-chlorinated with sodium thiosulphate (1 ppm residual chlorine needs 7 ppm of sodium thiosulphate).The de-chlorinated water is treated with 10 ppm of EDTA to eliminate the dissolved heavy metals if any.