Water accounting as a tool for tracing the industries responsible for the point-source loads into water bodies

Returning flows of water from the economy to the environment, particularly wastewaters, are highly important contributors to the quality of freshwater resources and the health of aquatic ecosystems. While the total loads of various harmful substances received by wastewater treatment facilities are often measured and reported, the origins of these loads are generally not allocated to specific industries. Instead, they pass from treatment facilities to the environment and are thus simply attributed to arising from the sewerage industry. In this study, we introduce a method for employing high-quality water accounting of the phosphorous and nitrogen loads and apply it to the Finnish economy. We also introduce a means for assessing the quality of the resulting accountancies and, for our Finnish case study, we show a close correspondence between independent top-down and bottom-up calculations, indicating the figures are highly reliable. We thus conclude, firstly, that the presented methodology can produce versatile and reliable data on different wastewater-related loads in the water; secondly, that such data can assist in developing appropriate mitigation strategies; and, thirdly, that the data may also be applied in further sustainability analyses, such as in environmentally extended input-output modelling.