Successful application of the first EXELYS™ continuous thermal hydrolysis system in an operational WWTP in Denmark

The first full scale EXELYS™ continuous thermal hydrolysis system has been in operation since October 2010. The EXELYS™ is part of a Digestion-Lysis-Digestion (DLD) enhanced digestion system implemented at Hillerød WWTP, Denmark. This is the first implementation of the DLD configuration on a full scale, and a number of challenges were met and overcome while implementing this on an operational plant. Results from the 12 month demonstration period indicate that the EXELYS™-DLD has led to an average total VS destruction of 59% over the reactors. This remained stable throughout the period despite a deteriorating quality in the incoming raw sludge. It appears that the double digestion with the EXELYS™ between leads to a rather stable process despite upsets. The results indicate that the application of the EXELYS™ after a first digestion is advantageous and significantly improves the energy balance for the digestion process. The results obtained in Hillerød fit well with modelled simulations, and therefore it is expected that the results can be transferred to other sites.