Is the energy-independency already state-of-art at NW-European wastewater treatment plants

In the literature of the recent past has been reported from time to time by the so-called energy-autarchic wastewater treatment plant (WWTP) in several countries. On a closer look, this statement refers almost always only on the electricity consumption,
the heat demand mostly was ignored.
A survey concerning energy efficiency on wastewater treatment plants in North-West-
Europe shows, that the so-called energy self-sufficient sewage treatment plant is still
an issue for the next years. The more detailed analysis of already conducted energy
audits and evaluated data from operational diaries shows that in many cases,
especially for plants with anaerobic digestion, the own power production is regarded
as the single criterion for energy self-sufficiency. In this study, therefore, further criteria
such as heat demand/heat production and degradation rates were used for a
comparison at a national level.