CHEMICAL PRECIPITATION IN PONDS FOR WASTEWATER TREATMENT Influence of Detention Time on the Separation of Phosphorus and Organic Matter
The use of pond systems for wastewater treatment is reviewed, especially with respect to the use of chemical precipitation. A field study was conducted at the pond system of Funäsdalen where lime is added to the wastewater. The removal of organic matter (CODCr) and phosphorus was investigated during a range of well-controlled wastewater detention times. The water was sampled after having passed a pre-settlement pond. After subsequent lime addition, the water was again sampled, at different detention times. COD removal was about 50 % due to lime precipitation, giving an effluent average concentration of 100 mg O2/1. The detention time had no significant influence on COD removal. The removal of phosphorus by lime precipitation was about 90 %. An increased detention time up to about 10 days seemed to improve phosphorus removal.