The problem of over fishing in public waters has led to aquaculture increasingly gaining importancw for global fis supply. Currently aquaculture continue to be the fastest growing animal food producing sector, already generating 50% of global fishsupply FAO-Food and Agriculture Organization of the United Nations. Conventional fish farming methods are rarely sustainable. They produce large amount of nutrient rich waste water, partially loaded with chemical use for fish treatment, which has harmful effect on the receiving aquatic environtment.. In 2009, Europen Commission proposed a strategy for the future of europen aquaculture for sustanable development of this sector. Aquaponic, which is combines the aquaculture of fish with the hydroponic cultivation of plants in a closed water cycle, can contribute to solving the problems outlined by European Commission on the way toward sustainable aquaculture by:
- Saving water; Aquaponics uses small amounts of fresh waters
- Guaranteeing product safety; Aquaponic uses no antibiotics and/or pesticides
- Protecting the environtment; Aquaponics effecientlyreduces nutrient emissions and is thus a hogh level strategy in the fight against eutrophication
A monitored pilot operation of aquaponics under field conditions, a small scale land based cyprinid fish farm with a diversion of arecirculating water into closed loop system with a treatment chain consisting lamellar settler, a rougfing filter, a vertical constructed wetland planted with tomatoes (lycopersion esculentum Mill) and ultrasoun device. The most significant advantages of constructed wetland are the utilisation of natural processes and their cost effectiveness . By planting crop plants in vertical constructed wetland, the aquaculture effuent is recirculated over tricling filters or ather suitable substarates in which crop plants are grown. This special type of vertical constructed wetland provide the necessary nitrification rates for a recirculating aquaculture.
A possible solution for a chemical free aquaculture could be the use of ultra sound devices to reduce pathogenic bacteria in fish ponds and to counteract algae growth. Thus, high pH values during day, oxygen drops at night, and large quantities of organic matter in fish ponds can be avoided.
In contrast to the investigated aquaponic system, other recirculating aquaculture systems (RAS) ussualy apply a biological wastewater treatment mainly as biofil reactor, biofilters, moving beds, and activated sludge processes. However, due to relatively high cost and unstable operation, RAS are not yet widespread. The presented multi-fuctional integrated technology has all the benefits of physical water treatment without the use of any chemicals, since ultrasound device acts as algae inhibitor, while water circulation can contribute to nutrient retension and usage by plants as well as to water savings in accordance with European water policy.