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3.18 Reuse of Cooling Water For Fish Farming

Technical Description

This technology is based upon the use in fish hatchery and farming operations thermally-polluted cooling water discharged from an electric power plant. The farming operation in which this technology is used deals primarily with European fish, but the technology is particularly suited to raising Asian fish as the farm is supplied with warm water.

In Hungary, this technology is used at TEHAG Ltd. The water in this hatchery's ponds does not cool to below 20oC during May and June, as other Hungarian waters are frequently wont to do, and hence fishes which are highly sensitive to cool (16o to 18oC) water mortality during the first weeks of their lives can be reared safely. This facility rears about 300 to 400 million larvae annually in a propagating house with a floor area of 1 500 m². The farm also has 131 ha of fish ponds, with more than 80 compartments ranging in area from 100 000 to 300 000 m². Because fish farm production is very intensive, the rearing ponds are treated annually with several hundred kilograms of inorganic fertilizer (N and P) and 3 to 5 Mg of organic fertilizer. Oxygen is supplied by aeration. All stages of work are highly mechanized. Production is facilitated by modern, automated, heated hatchery and nursing halls, fry storage tanks, self feeders, fish sorting conveyors, and vehicles equipped with an oxygen supply for transporting fish. A unique characteristic of this type of technology is the simultaneous propagation of breeding fishes having different spawning times and temperature requirements. The annual water demand of 1.6 million m³ is supplied through an gravity-fed, underground pipeline system which carries cooling water effluent from a power plant on the Danube River. The temperature of this water is 10o to 12oC higher than that of the river water, which not only makes warmwater fish propagation possible, but also prolongs the propagation season for coldwater fishes. After use in the fish farm, the water, now cooled to ambient temperatures, is discharged through Benta Creek into the Danube without causing any heat pollution. Fish yields in the farm are among the highest in Hungary with an average of 1.8 to 2.6 Mg/ha, ranging upwards to 3.5 to 4.5 Mg/ha in some ponds.

Extent of Use

This reuse technology is only known to be employed at one site in Hungary.

Operation and Maintenance

Operation and maintenance requirements of this technology are the same as employed at conventional fish farming operations, and require the same level of water quantity and quality control measures.

Level of Involvement

This technology was implemented at the company and local administration level, with financial backup and support from relevant governmental organizations.

Costs

The farm was constructed between 1970 and 1974 by the Food and Agriculture Organization of the United Nations (FAO) and the Hungarian government at a cost of $2 million. Maintenance costs are difficult to identify. Beside fish breeding, the farm doubles as a development and training centre, and the costs of lecture rooms and guest houses for the purpose of training persons in the operation of fish farming enterprises mask the net cost of the reuse technology.

Effectiveness of the Technology

The technology is fully effective in preventing the thermal pollution of natural water ecosystems and the resultant water quality deterioration.

Suitability

This technology is suitable for use in localities with appropriate soil conditions and relief, situated near power plants.

Advantages This technology has the advantage of preventing the thermal pollution of natural waters while producing marketable goods.

Disadvantages

This is a land intensive technology.

Cultural Acceptability

This technology is a well-accepted, efficient wastewater treatment technology.

Further Development of the Technology

The technology is complete in itself.

Information Sources

Petèr Kovac and Dr Kornèlia H. Kocsis, Felsö - Tisza - Vidèki Környezetvèdelmi Felügyelösèg, 4400 Nyiregyhàza, Szèchenyi u.19, Hungary, Tel. (36-42) 310 155, fax: (36-42) 310 713.

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