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Extensive, meticulous and laborious but no less rewarding process of auditing the energy efficiency and sludge management performance of the IWAMA WWTPs is entering its final stages now. The plant operators and WP leaders from Technical University of Berlin and University of Tartu have gathered last week in Berlin to discuss the results, receive feedback and agree on contents of the Audit Reports that are part of the upcoming smart audit concept outputs

Each partner WWTP received detailed analysis of its energy consumption of various processes, sludge treatment (most commonly applied methods) and sludge quality based on the Key Figure Data from 2016 collected for the energy and sludge benchmarks, as well as the data collected by the audit team of students during the visits in 2017.  

Some of the common findings showed that IWAMA plants are reaching good levels of energy efficiency related to P and N removal and heat balance, having in general minor optimization potentials and needs to cover data gaps. Sludge treatment results though varied greatly based on size and country of the WWTPs location. Several plants were given recommendations on increasing biogas yield, as well as to consider ways of P-recovery due to high content of this nutrient in their treated sludge. General sludge quality also showed very low levels of heavy metals (with exception of Cd being the most commonly problematic one) and low but traceable presence of pharmaceuticals (with significant elimination through the treatment processes such as digestion and humification). Several smaller plants could not be fully audited due to lack of certain measurement practices or because of either not applying or outsourcing sludge treatment after dewatering/thickening.

The updated structure of the Audit Tools and used calculations have been presented and discussed too. Partners learned how to apply the beta tools themselves and agreed to repeat the audits with the new treatment and energy data from 2018 in order to further test the tools’ usability and since most of the partner WWTPs are in the process of piloting and other technological upgrades. It is expected that the audit tools are ready in the beginning of the next year and WWTPs of the Baltic Sea Region can use them for self-evaluation of the energy efficiency and sludge treatment performances.