Water treatment in Aquaculture

Water treatment

All treatment of water leads to a change in the water quality, and it is improvement that is wanted. Regardless of the incoming water quality, it will always be possible to obtain a quality good enough for growing aquaculture products. The problem is, however, the cost; all water treatment operations involve expenditure. A major advantage for a good farming site is therefore to have good quality incoming water with low treatment requirements.

Several processes may be needed to adjust the water quality. The inlet water to land-based farms is aerated; pH adjustment and particle removal are also required. Heating and chilling are normally used to create optimal growth conditions. In some cases disinfection is needed to reduce the burden of micro-organisms, especially in fry production (Fig. 3.4).

The outlet water from the fish farm may also be treated to avoid affecting the water quality of therecipient water body. If the recipient water body is highly eutrophicated the outlet water must be treated, and this is also the case if there are valuable wild stocks in the receiving water. Treatment of outlet water will, however, increase production costs, and is done only when necessary. Often government regulations will dictate the level of treatment required. Sites that require less water treatment are therefore favoured.

Treatment of the outlet water is normally restricted to removal of part of the suspended solids. From a cost perspective, is it normally impos-sible to remove dissolved substances such as nutri-ents and small micro-organisms in a flow-through farm with relatively high fish densities, because of the size of the water flow; if re-use systems are employed, such treatments may be included. However, re-use systems have much higher invest-ment costs than flow-through farms.

Treatment of outlet water will, however, increase production costs, and is done only when necessary. Often government regulations will dictate the level of treatment required. Sites that require less water treatment are therefore favoured.

Treatment of the outlet water is normally restricted to removal of part of the suspended solids. From a cost perspective, is it normally impos-sible to remove dissolved substances such as nutrients and small micro-organisms in a flow-through farm with relatively high fish densities, because of the size of the water flow; if re-use systems are employed, such treatments may be included. However, re-use systems have much higher invest-ment costs than flow-through farms.