Water treatment for Aquaculture
DynaSand
Dynasand continuous filter
DynaSand is widely used worldwide to clean and produce water for drinking, wastewater treatment and industrial processes.
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DynaSand by Nordic Water is a sand filter with an integrated washing process that cleans the sand continuously, or if desired intermittently. DynaSand has been in the market for more than 30 years.
A freestanding DynaSand consists of a cylindrical tank with conical bottom and filter internals. It has flanged connections for feed, filtrate, and wash water. A filter plant may consist of a single filter or several filters working in parallel.
An up-flow, moving bed filter suitable for various media
Raw water enters near the top (Feed) and is led to the bottom of the tank by means of a water distributor. Suspended solids are filtered out as the raw water flows up through the media bed. As the water reaches the top of the filter, it passes over the effluent weir as filtrate and is discharged. A small portion of the filtrate is diverted through the sand washer and used for cleaning and transferring the waste solids.
The filter employs a backwash rinse that is performed continually while the tank is processing water. An air lift pump, located at the centre of the media, pumps sand from the bottom of the filter up into the wash box. As the media is released into the wash box, it falls into the sand washer where the filtered solids are separated from the sand. From there, the filtrate carries the solids out as waste (Backwash). The washed sand falls onto the media bed for continued use. In most applications the filter media is natural, graded quartz sand. Normally the sand in the filter does not need replacing, but a small amount of refill may be needed on a yearly basis (abt. 0.3% of the volume).
Each air lift pump is adjusted and regulated by the pneumatic cabinet supplied with the installation. Unlike conventional sand filters that must be shut down when backwashing, the cleaning of the sand will not affect the operation of the in DynaSand filter, neither in terms of capacity nor performance.
Ideal for aquaculture
More recently DynaSand has been applied in aquaculture. It has proven highly effective for removal of both fine particles and for nitrification and may be used for inlet water filtration as well as for biofiltration in recirculated aquaculture systems. Low head loss and power consumption makes these filters ideal for use in aquaculture in several applications:
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Microparticle and suspended solids removal
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BOD reduction and nitrification (aerobic)
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Denitrification and biological phosphorus removal (anaerobic)
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Treatment of influent, effluent, and RAS water
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Large plants
Large plants are generally built with filter modules in concrete basins. The filter cells (each consisting of multiple filter modules) consist of a stainless steel or FRP bottom cone and filter internals and share a common sand bed.
This brings around several benefits:
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Low head loss and energy consumption
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No downtime or reduction in filter capacity and performance during washing
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Automatic control over the washing process
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High hydraulic capacity (with up to 25 m hour water velocity through sand beds).
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Assurance that all sand is cleaned
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Low reject water production
