LAUSR

ABSTRACT The study evaluates the wastewater treatment plant reconstruction via the Grey Water Footprint methodology. The application was tested on a medium-size wastewater treatment plant discharging water into a small watercourse. The 6-year monitoring was assessed. The assessment included a period before and after the reconstruction when a capacity was increased and the treatment technology had been equipped with a membrane sludge separation. Ammonium nitrogen is causing the Grey Water Footprint the most often; both, before and after the reconstruction. The assessment has shown that the current setting of legal discharge limits may not cover all environmental risks even if the wastewater treatment plant meets all requirements. For environmental sustainability, it is necessary if the recipient watercourse was at least 1.4 times more watery for assimilation of total nitrogen pollution, and 3.9 times more watery for assimilation of total phosphorus pollution.