Advanced sludge digestion optimisation – introducing innovative Ephyra® technology
Visser, A., Koornneef, E., Traksel, D., Royal HaskoningDHV, Netherlands
(free)
Abstract
Since 2005 Dutch water authorities aim at energy-neutral sewage treatment plants with maximal
recovery of natural resources. This led to a new focus on sludge digestion, initiating a development of
new, innovative technologies, such the following innovations developed by Royal HaskoningDHV:
• Ephyra®, a high rate plug flow digestion technology;
• Themista®, a pre-treatment technology for sludge;
• Aquasuite® MINE, a smart software application to optimise sludge handling processes;
• Crystalactor®, a crystallization process to recover phosphorus.
This paper focus on Ephyra® technology, a high rate plug flow digester type, consisting of two, three
or four reactors in series. A specific feature of Ephyra® is that it allows for short retention times as low
as 6 to 8 days. This paper describes the Ephyra® development, including the first full scale Ephyra®
digester at Tollebeek, The Netherlands. Results of various lab experiments, a pilot plant study and the
full-scale plant data are shown. Currently, the Ephyra® digester at Tollebeek is operated at a retention
time of about 6 to 7 days. The digester treats a mixture of primary- and waste activated sludge from
the treatment plants of Tollebeek and Lelystad. The organic dry solids removal is 50 to 55%. Since
the introduction of Ephyra®, the energy balance of the treatment plant improved in such a way that all
electricity required by the treatment plant is produced on site via biogas conversion in a CHP unit.
