Sewage fed fish culture

how to use the sewage fed fish culture and its advantages

1. SEWAGE FED FISH CULTURE nithyavenkatesan

2. SEWAGE FED FISH CULTURE: Sewage is a water carried waste. That is rich nutrient resource,cheaply available around big towns and cities. The use of sewage for aquaculture results in high yields and economices on fertilizer and fed costs, resulting in higher profits. The sewage water has to be treated before it is used in aquaculture .

3. COMPONENTS OF SEWAGE:

4. The sewage water in order to be used for aquaculture has to undergo series of process, which can be divided into 3 steps 1)SEDIMENTATION: Sedimentation helps to remove suspended solid from the sewage to the maximum possible extent. The sewage is allowed to flow at high velocity in a channel. This process is completed in two tanks where 1 is build at high level then second one. In first tank sewage is kept for 10 days. So that organic matter is decomposed aerobically into nitrates, sulphur etc.

5. Then after sewage is passed in second tank where sewage is allowed to stay for 15-20 days so that it looses its foul odour and becomes green due to development of algae. 2)DILUTION: Stabilized and odorless sewage which flows out of second tank is diluted with freshwater in the ratio of 1.5 (one part sewage and 5 parts freshwater) which helps in bringing down the concentration of toxicant like CO2 NH3 to sub sewage quality.

6. 3)STORAGE: In this step treated sewage water is kept in pond in which duckweeds, such as Azolla , Lemna are grown. Duckweeds serve as nutrient pumps which reduce the eutrophication effect and provide oxygen from their photosynthetic activity.

7. MAJOR PRCEDURE OF CUTURING FISH IN POND WITH TREATED SEWAGE WATER Firstly the pond should undergo liming which help in fertility status of sewage fed ponds and also act as disinfectant against harmful parasite. Ponds are also sundried before stocking . The treated sewage water from the duckweed ponds is then taken into another set of pond of culturing fish. Treated sewage water is maintained at a depth of 1meter and diluted with fresh water.

8. Considering the high carrying capacity and high productivity of sewage fed ponds, stocking is done with higher density. The stocked fish are checked at monthly interval for their health and growth by means of sample netting. Rotational cropping system is followed to maintain regular supply to the marked, ie after completion of one phase fishes are restocked at 1 kg fingerlings per 5 kg harvested fish. Another harvesting phase start after 15 days of restocking.

9. Advantages of sewage-fed fish culture No manuring and supplementary feeding is required due to high content of nutrients in sewage. Input cost is very low and production is very good. It reduces the pollution load of river and in the aquatic ecosystem. There is opportunity.…to produce fish….and avoid environmental damage being caused by the discharge of untreated sewage.

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