Investigating phosphorus loads removed by chemical and biological methods in municipal wastewater treatment plants in Poland

The article presents an analysis of the current methods for phosphorus removal applied in municipal wastewater treatment plants in Poland. Within the study, 131 wastewater treatment plants were investigated, constituting 17 630 500 population equivalent, which is about 1/3 of the overall population equivalent (designed) in Poland. The research was based on a detailed technical questionnaire analysis obtained from wastewater treatment plants operators and calculations of pure metal doses in the applied chemical reagents and their type per a treated wastewater volume, population equivalent and phosphorus load removed. The analysis results show that annually a minimum of 1 470 Mg of phosphorus removed by 35 wastewater treatment plants based entirely on biological treatment methods could be used for phosphorus recovery to produce struvite, calcium phosphate or other highly bioavailable alternative fertilizer products. Moreover, 1 490 Mg of phosphorus removed by other 17 wastewater treatment plants with a minimal coagulant dose (< 1 g of metal per m3 of wastewater), increase the base for phosphorus recovery to approx. 2 960 Mg per year using the sewage sludge or its dewatering liquors. These results suggest that the implementation of the means mentioned above would significantly increase the possibilities for obtaining phosphorus from secondary sources, especially in wastewater treatment plants without a direct access to sewage sludge incineration plants.