Continuous sand filtration with carbon addition to facilitate removal of nitrates from wastewater.
DynaSand® Deni is a low-energy, low-maintenance vertical sand filtration plant for nitrogen removal from final discharge.
DynaSand® Deni is a low-energy, low-maintenance vertical sand filtration plant for nitrogen removal from the final discharge using the extensively proven DynaSand® Deni process.
DynaSand® Deni denitrification helps reduce the adverse environmental impact of excess nitrogen compounds from treatment works into receiving watercourses.
Primarily designed for nitrate removal, with the addition of metal salts the DynaSand® Deni can also provide removals of effluent phosphorus down to 0.2 mg/l and effluent BOD and TSS down to 10 mg. Read about how six DynaSand® Deni filters remove phosphorus in Ratzeburg, Germany.
Incoming water flows upwards through the DynaSand® Deni filter bed, where nitrite (NO2) and nitrate (NO3) are converted into gaseous nitrogen (N2) by microbial action. Nitrogen is discharged to the atmosphere by the airlift pump as a continuous stream. The vertical configuration of the DynaSand® Deni means a 90% smaller footprint than the equivalent horizontal sand filtration beds.
Like the DynaSand® filter, the DynaSand® Deni filter is based on the counter flow principle.
To provide optimum conditions for the denitrifying bacteria, a carbon source such as methanol is added to the wastewater stream prior to the filter. The water to be treated (red arrow) is admitted through the inlet distributor (1) in the lower section of the unit and is cleaned as it flows upwards through the media bed, prior to discharge (blue arrow) through the filtrate outlet (2) at the top. The carbon source encourages the growth of heterophic denitrifying bacteria within the filter media bed.
The media containing the entrapped solids is conveyed from the tapered bottom section of the unit (3), by means of an airlift pump (4), to the media washer (5) at the top.
Cleaning of the media commences in the pump itself where impurities are separated from the media grains by the turbulent mixing action. The contaminated media spills from the pump outlet into the washer labyrinth (6) in which it is washed by a small counter current flow of clean water. The separated solids and sloughed biomass (brown arrow) are discharged through the wash water outlet (7), while the grains of clean media (which are heavier) are returned to the media bed (8). As a result, the bed is in slow, constant downward motion through the unit. Compressed air for the air lift pump is provided via the air distribution panel.
Water purification and media washing both take place continuously enabling the filter to remain in service without interruption.
* effluent standards quoted to 95%ile
** annual average