High Biological Nutrient Removal from Domestic Wastewater in Combination with Phosphorus Recycling

Pilot plant studies on biological nutrient removal and using settled domestic waste water have been carried out in combination with phosphorus recycling on the basis of crystallisation of calcium phosphate on sand pellets in a fluidized bed-reactor. The bioreactor had been divided into four zones, respectively anaerobic, aerobic, anoxic and aerobic. To eliminate nitrate sludge recirculation for denitrification, a part of the influent was led to the anoxic zone. In the by-pass of the bioreactor a phostripper tank was incorporated followed by a fluidized bed-reactor. The experiments carried out at low F/M ratios and at a constant and variable influent flow resulted in nearly 100% P-removal. P-total effluent was lower than 0.1 mg P/l. The total nitrogen content in the effluent amounted to an average value of approximately 16 mg N/l.