Agri Kultuur January / January 2018 - Page 12

design to provide additional oxygen to the fish tank .
• Shutter board – To help distribute the weight ( 3.3 tons ) as well as to protect the suspended wooden floor in this case .
• Cement Blocks – To elevate DWC troughs and fish tank enabling gravity flow .
• Plumbing – Various PVC connectors and pipes connecting the various aquaponics components .
Information about the design : Water flow :
In a deep water culture ( DWC ) method , also known as the raft method or floating system , the nutrient rich water is circulated through long canals at a depth of about 25cm – 30cm while rafts ( usually polystyrene ) float on top . Plants are supported within holes in the rafts by net pots . The plant roots hang down in the nutrient-rich , oxygenated water , where they absorb large amounts of oxygen and nutrients which contribute to rapid growth conditions .
In the deep water culture unit described in this technology , water flows by gravity from the fish tank , through the mechanical ( radial ) filter into the combination biofilter / sump . From the biofilter , the water is pumped in two directions through a “ Y ” connector ( T-Junction ) and valves . 80 % of the water is pumped to the fish tank while the remaining water ( 20 %) is pumped into a circulating loop system which distributes the water evenly through the canals . By gravity , the water exiting the canals and returned to the biofilter / sump , where again it is pumped either into the fish tank or canals . The water that enters the fish tank causes the fish tank to overflow through the exit pipe and back into mechanical filters , thus completing the cycle .
However , when a low stocking density of fish ( i . e . 1 – 5 kg of fish per m 3 of fish tank ) is used , the DWC can be designed without using external filtration containers , mechanical or biological . In this system , water is pumped to the fish tank as well as the DWC canals . Water in the fish tanks , biofilter and canals is aerated using an air pump . The fish waste is broken down by nitrifying and mineralizing bacteria living in the biofilter , plant root surface and the canal walls . To avoid waste accumulation of solids at the bottom of the canals and biofilter , a radial filter is positioned where the water exits the fish tank .
Filtration :
Two types of filters need to be constructed for the system : first , a physical trap to catch the solid wastes ( radial filter ), and then a biological filter for nitrification . The designs described in this document use a mechanical swirl or radial filter to trap particulate wastes , with periodic draining of the captured solids . On exiting the radial filter , the water passes through a mesh screen ( Japanese matting ) to trap any remaining solids and then reaches the biofilter . The biofilter is well oxygenated with air stones and contains a biofiltration media , usually Bioballs ®, nylon netting or bottle caps , where the nitrifying bacteria transform the dissolved wastes . With insufficient filtration , the DWC units would clog , become anoxic and exhibit poor growing conditions for plants and fish alike .
The flow rate of the water entering each canal is relatively low . Generally , every canal has 1 – 4 hours of retention time . Retention time is a similar concept to turnover rate , and refers to the amount of time it takes to replace all the water in a container . For example , if the water volume of one trough is 300 litres and the flow rate of water entering the container is 150 litres / h , the retention time would be 2 hours ( 300 litres ÷ 150 litres / h ).
AgriKultuur | AgriCulture
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design to provide additional oxygen to the fish tank. • Shutter board – To help distribute the weight (3.3 tons) as well as to protect the suspended wooden floor in this case. • Cement Blocks – To elevate DWC troughs and fish tank enabling gravity flow. • Plumbing – Various PVC connectors and pipes connecting the various aquaponics components. Information about the design: Water flow: In a deep water culture (DWC) method, also known as the raft method or floating system, the nutrient rich water is circulated through long canals at a depth of about 25cm – 30cm while rafts (usually polystyrene) float on top. Plants are supported within holes in the rafts by net pots. The plant roots hang down in the nutrient-rich, oxygenated water, where they absorb large amounts of oxygen and nutrients which contribute to rapid growth conditions. In the deep water culture unit described in this technology, water flows by gravity from the fish tank, through the mechanical (radial) filter into the combination biofilter/sump. From the biofilter, the water is pumped in two directions through a “Y” connector (T-Junction) and valves. 80% of the water is pumped to the fish tank while the remaining water (20%) is pumped into a circulating loop system which distributes the water evenly through the canals. By gravity, the water exiting the canals and returned to the biofilter/sump, where again it is pumped either into the fish tank or canals. The water that enters the fish tank causes the fish tank to overflow through the exit pipe and back into mechanical filters, thus completing the cycle. However, when a low stocking density of fish (i.e. 1 – 5 kg of fish per m 3 of fish tank) is used, the DWC can be designed without using external filtration containers, mechanical or biological. In this system, water is pumped to the fish tank as well as the DWC canals. Water in the fish tanks, biofilter and canals is aerated using an air pump. The fish waste is broken down by nitrifying and mineralizing bacteria living in the biofilter, plant root surface and the canal walls. To avoid waste accumulation of solids at the bottom of the canals and biofilter, a radial filter is positioned where the water exits the fish tank. Filtration: Two types of filters need to be constructed for the system: first, a physical trap to catch the solid wastes (radial filter), and then a biological filter for nitrification. The designs described in this document use a mechanical swirl or radial filter to trap particulate wastes, with periodic draining of the captured solids. On exiting the radial filter, the water passes through a mesh screen (Japanese matting) to trap any remaining solids and then reaches the biofilter. The biofilter is well oxygenated with air stones and contains a biofiltration media, usually Bioballs®, nylon netting or bottle caps, where the nitrifying bacteria transform the dissolved wastes. With insufficient filtration, the DWC units would clog, become anoxic and exhibit poor growing conditions for plants and fish alike. The flow rate of the water ѕɥ)́ɕѥٕ䁱ܸɅ䰁ٕ䁍̀NJL)́ɕѕѥѥIѕѥѥ́)ͥȁЁѼɹٕȁɅєɕ́Ѽ)ѡչЁѥЁх́Ѽɕѡ)݅ѕȁхȸȁᅵѡ݅ѕ)ٽյɽ՝̀ɕ́ѡ)Ʌє݅ѕȁѕɥѡхȁ̀)ɕ̽ѡɕѕѥѥݽձȁ(ɕ̃܀ɕ̽)ɥ-ձȁɥ ձɔ(