Phosphorus Balance at Tartu WWTP, Estonia

Abstract

Sewage sludge is usually considered as treatment residue that needs expensive treatment for removal. The treatment and handling of sludge can form 20 to 50 % from a wastewater treatment facility's costs. Sludge volumes will continue to grow worldwide with increasing population and country wealth. In a sustainable society, sludge should rather be seen as a source of energy, phosphorus and other products. Water treatment facilities are exploring technologies to utilise these values worldwide. Technologies on extracting minerals from sludge would either help offset treatment facility’s costs or even turn a profit. First step in turning sludge from a costly waste material into a profitable revenue stream should be a material balance. In Tartu wastewater treatment plant (120 000 pe, 28 000 m³ d^-1) waste water is treated by activated sludge process with an integrated biological nitrogen and phosphorous removal. Sludge is dewatered and stabilized by windrow composting. In the treatment plant, phosphorus balance in various treatment steps was studied and potential technologies for extracting phosphorus were reviewed.