Sand filtration is a classic and proven separation process that has been around for two centuries. In addition to the physical separation of suspended solids, a number of chemical and biological processes such as nitrification, catalytic oxidation of iron and manganese take place on the sand bed. Sand filters are used in the treatment of drinking and process water, as a tertiary stage in wastewater treatment and in the energy sector. Sand filters are most commonly used as a second separation stage after clarification and sedimentation. If the raw water does not contain high levels of contamination, coagulation filtration can be used as the only separation stage, where the coagulant is dosed before the filter itself. In some cases, simple filtration is sufficient. During filter operation, the filter bed gradually becomes clogged and the pressure drop of the filter increases. The filtration cycle is terminated when the maximum pressure drop is reached, or the suspension penetrates into the filtrate, which is manifested by an increase in turbidity behind the filter or an exceedance of selected water quality parameters. It is then necessary to backwash the filter, whereby the trapped contaminants from the filter bed are rejected to waste. Washing is normally done with water, air, or their combination.
Benefits
- Classic proven technology
- High durability of the filter sand
- Catalytic oxidation of iron and manganese, nitrification under suitable conditions
- Filtration possible even at high temperatures (condensate filters)
Resources
| Filtraflo_TGV_Brochure.pdf |
| Filtraflo_Pack_brochure.pdf |