Biological phosphorous removal
Introducing side stream hydrolysis on a part stream of the return sludge, an easily degradable carbon source is obtained for biological nitrogen and phosphorus removal.
- The hydrolysis produces easily degradable organic material (VFA) on a small flow of the return sludge with long retention time (20-40 hours)
- The hydrolysis activates the biological phosphorus removal process
- The hydrolysis tank can be used for pretreatment of reject water containing high ammonia concentrations´, concentrated industrial waste water, external sludge or carbon sources (e.g. molasses)
- The side stream hydrolysis is run with a fixed hydraulic retention time regardless of the return sludge flow to obtain a very stable process condition
- The process has been used in full scale applications in Denmark since 1996 and is in operation on 50 Danish wastewater treatment plants.
- A small amount of return activated sludge is introduced eliminating problems related to high content of nitrate in the return sludge
- Reduction of operational cost as chemicals for precipitation of phosphorous is decreased
- No internal load of phosphorous under storm water conditions
- Less chemical sludge reduces operational costs related to excess sludge handling