Role of wastewater treatment plants in pollution reduction – evaluated by Grey Water Footprint indicator

The study assesses the pollution discharged from 251 wastewater treatment plants (WWTPs) throughout the Odra river basin in the Czech Republic. The development of pollution production over a period of 15 years (2004–2018) together with a number of WWTPs in the Odra river basin were analyzed. The Grey Water Footprint (GWF) of discharged pollution was determined both in terms of individual size categories of WWTPs and in terms of the parameter that most affects the level of pollution. The share of the small WWTPs size categories (up to 2,000 PE) on the total GWF value of discharged pollution is only 8%, although these are the most numerous. The share of the WWTPs of the size category > 10,000 PE on the total GWF value of discharged pollution is 82%. Total phosphorus (at large WWTPs) and ammonium nitrogen (at small WWTPs) were identified as the key pollutants that most determine the value of the Grey water footprint of discharged pollution.