Continuous sand filtration system with air addition to facilitate removal of ammonia from wastewater.
DynaSand® Oxy delivers ammonia, TSS and BOD removal in a single stage for tertiary treatment of final effluent discharge from sewage and industrial wastewater treatment plants.
DynaSand® Oxy is a continuous sand filtration system with air addition to facilitate removal of ammonia from wastewater.
Primarily designed for ammonia removal, for which it delivers removals down to 2 mg/l, the DynaSand® Oxy can also provide removals of effluent phosphorus down to 0.2 mg/l as well as effluent BOD and TSS down to 10 mg/l. Read about the year-long optimisation trial at Watton Water Recycling Centre.
As the water flows upwards through the filter bed, ammonia is converted into nitrate by bacteria - Nitrosomonas and Nitrobacter - which form a layer on the surfaces of the filter grains. The bacteria, which are autotrophic and thus live only on inorganic materials, produce new biomass out of carbon dioxide.
The water to be treated is admitted through the inlet distributor in the lower section of the unit and is cleaned as it flows upwards through the media bed, prior to discharge through the filtrate outlet at the top.
To ensure that the autotrophic nitrifying bacteria have sufficient oxygen and carbon dioxide to convert ammonia to nitrates, aeration hoods fed by process air are sited within the upper layer of media to provide sufficient aeration. The resultant nitrates remain dissolved in the water. The media containing the entrapped solids is conveyed from the tapered bottom section of the unit, by means of an airlift pump, to the media washer 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 are discharged through the wash water outlet, while the grains of clean media (which are heavier) are returned to the media bed. 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