Acidification of primary sludge to promote increased biological phosphorus elimination and denitrification

The acidification of primary sludge is an important measure to promote increased biological P elimination and denitrification at wastewater treatment plants. In laboratory experiments and at large-scale plants it has been found that the COD in the influent of biological treatment stages can be increased by 10–15% in the form of easily degradable carbonic acids. However, the operation of acidification thickeners leads to odour problems, as well as to considerable problems in terms of safety, in covered tanks.