Science Technology News - NAVETCO
Pollution in Aquaculture & Some Water Treatments in Shrimp and Fish Farms
In the end of 2010, Vietnam exported 1.353 million tons of aquatic products, earned more than $ 5 billion, an increase of 11.3% in volume and 18.4% in value compared to 2009, while Delta Mekong is the area with a strategic location in the farming and fisheries exports.
Mekong Delta is a vast wetland as part of the downstream of the Mekong River to the South East Sea and the Gulf of Thailand should have a huge potential for Aquaculture in freshwater and saltwater. However, the Mekong Delta are suffering from the decline of water quality due to the outbreak of aquaculture during the past two decades, both in the area of feeding and stocking density on shrimp or fish per meter square of water surface. An approximate calculation, to get 1 kg of catfish, farmers had to use from 3-5 kg of food.
In fact, only about 17% - 20% of fish food is absorbed by fish and the rest (about 80%) sink to the bottom and become decomposition organic matter, for industrial ponds, the waste in pond can contain 45% nitrogen and 22% other organic matter, other sources of organic waste are from remaining debris by phytoplankton or fibrous algae, soluble deposits are from intake water bringing along. Monitoring data in the ponds, showed the amount of pollutants such as biochemical oxygen (BOD5), chemical oxygen (COD), total suspended solids (TSS), total nitrogen (TKN), H2S, NH3, total coliform, ... beyond the level allowed by Vietnam standards, and on every 1 hectare of shrimp ponds after harvesting will be released to 133 kg nitrogen, 43 kg phosphorus .... Water pollution has also led to an increase in resources for the main diseases and fisheries. Therefore, the water treatment during aquaculture process has very important significance.
Water treatment in fish farming:
- Polymer treatment method (Purolite high speed method) pollutants suspended or dissolved in water after the treatment will settle to the bottom and be sort out.
- In areas has ground, wastewater purification through wetland tectonic undercurrents could be applied
- Another advice method in fish farming water treatment with high efficiency is using probiotics as Navet – Biozym
Treating water in shrimp farming:
- After pumping water, sanitary treatment ponds, liming, farmers need to treat water first before releasing shrimp.
- Choose the best water current( in no epidemic period, no scum…) then watering into settle pond via filtrated nets to remove the mud, alluvial, crustaceans or any other harmful microorganism
- Keep that water within 3-5 days, for harmful species eggs hatching purpose
- Then using disinfectant like Benkocid,, BKA… to kill crustaceans and pathogens
- Water coloring (NPK fertilizer, Urea, DAP,…) – microbial culturing (used probiotics as Navet- Biozim..)
Using probiotics in aquaculture:
Using probiotics in aquaculture is considered a technical and scientific progress, creating environmental safety, as well as in food for consumers. This is a very important step to improve the water environment quality because when probiotics are introduced into the ponds, beneficial microorganisms will proliferate, grow quickly, it will work as follows:
- Decomposition of organic matter in water.
- Reducing toxins in water (NH3, H2S ...) reduce odors in water, helping shrimps and fish growth.
- Enhance immunity for shrimp, fish.
- Inhibit the growth of harmful microorganisms.
- Help to stabilize water pH, water color stability, increase dissolved oxygen in water.
The use of probiotics brings lots of meaning in many aspects in improving the economic efficiency of aquaculture such as:
- Increase the efficiency in using feeds
- Shrimp, fish grow quickly, shorten feeding time
- Increase survival rates, increased productivity of shrimp, fish
- Decrease the cost of water changes
- Decrease the cost of using antibiotics and chemicals
Therefore the use of probiotics to improve water quality and prevent disease for shrimp and fish is a necessary work should be applied regularly to help the fishery products reached safety standards, food hygiene when releasing product to consumers.
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