The Shrimp aquaculture industry is rapidly expanding and accounts for 15% of the internationally traded seafood products. For several decades, the increase in world shrimp production relied mostly on traditional extensive farming practices, but more recently, industry expansion has focused on intensification. The rapid expansion of this industry has stimulated the intensification of production systems.
However intensive farms were confronted with a number of barriers that prevented further development. They relied on relatively high rates of water exchange to flush out wastes, maintain water quality, regulate plankton density, and introduce supplemental food organisms. But then, water exchange imposed potentially catastrophic disease risks as well as pumping costs and environmental impacts due to eutrophication of the receiving water body and entrainment of organism form the source water.
Further, shrimp waste water management is an international problem form nook of the nook of the world. In view of this, the concept of recycle and reuse arise everywhere. Apart from that, it is reported that effluent released from the aqua farms contain more nutrients than the other industries. The organic load present in the waters can be used for production of horticultural plants. This aqua effluent contains biologically available forms of Nitrate Nitrogen, ionic form of Ammonia and organic nitrogen which are made available through conversion of Ammonia which are important for various fruit plants cultivation.
In aqua farming especially shrimp farming, waste water reutilization or reuse is an important pollution and quality production of Shrimps. The solids discharged from the aqua farm effluents can be reutilized through modern technology like Recirculatory Aquaculture Systems (RAS). Besides, another advanced aqua system is Closed Race Way Systems (CRWS) where water consumption is reduced and release of effluent is also reduced. Various fishes like tilapia and shrimps can be cultured in these systems effectively by utilizing the wastes again and again for their culture and hence only partial sludge only is released to the environment.
The modern Aqua systems like RAS, CRWS effluent are mainly constituted with feces, unconsumed feed, inorganic nitrogen and phosphorus, which are serving as potential organic fertilizers supporting the plants’ production through aquaponics systems. Owing to these, a system called as bio-floc was developed which actually treats the waste water of the intensive systems. It encourages the solid discharge reduction into the environment by maintaining the organic solids in suspension which helps in control the ammonia in the aqua system. However, the total solid also should be maintained in control limit. The excess solid wastes to be removed periodically to maintain the required C: N ratio in the CRWS system. The excess solid wastes can also be discharged into hydroponics plants. The biofloc influences positive growth and production of shrimp juveniles, in addition providing more favorable water quality conditions irrespective of higher stocking densities. Intensive nursery rearing of Litopenaeus vannamei in Aerobic Microbial Floc (AMF) driven raceways offers the tremendous production potential in the low saline raceway system(Felix et al,.2015b).
Reduction of water exchange or zero water exchange is also considered as a bio-security measure since it prevents entry of disease from outside source. The bio-floc systems itself persuaded the association of solid wastes and bacteria in the system and they are kept in suspension in aerobic environment through intensive aeration.
What is Bio-Floc?
Bio-Floc is a congregation of animal feces, waste feeds, phyto and zoo planktons, bacterial community. The flocs are micro and macro in sizes having light weight. The floc has good nutritional value having protein range of 20-45% and 1-5% fat in dried condition( Hargreaves,2013). Besides, it contains various minerals and vitamins and serves as natural probiotic instead of inoculating externally. It can also be used as aqua feed ingredients in dried form. The flocs can settle easily in bottom of the tank when there is no aeration which facilitates to remove the excess sludge from the system.
Source : Aqua Tech