Recognising that sludge imports will place considerable pressure on the waste water treatment plant at Tollebeek in the future, the client – Waterschap Zuiderzeeland – needed a sustainable solution that would be able to treat larger volumes of sludge with energy- and resource-recovery facilities, to generate (green) energy, reduce the plants’ carbon footprint and reduce sludge volumes.
The existing system, a conventional mesophilic anaerobic digestion with a single tank, was only capable of treating the sludge from WWTP Tollebeek. Danny Traksel, Director Business Development at Royal HaskoningDHV, says that Waterschap Zuiderzeeland acted as a professional and enthusiastic launching customer for the Ephyra® technology.
Royal HaskoningDHV, together with partners Stichting Toegepast Onderzoek Waterbeheer (STOWA), TUDelft, Logisticon, HHSchieland & Krimpenerwaard, applied for the LIVE EU funding to develop the Ephyra® innovation from lab to pilot and from pilot to full scale at Tollebeek. Royal HaskoningDHV’s major strengths include our expertise and innovation in this sector, proactive approach to business development, ability to create partnerships, and our in-depth knowledge of anaerobic digestion.
Separating Key Processes
The Ephyra® concept is based upon a plug flow digestion in which the hydraulic retention time (HRT) and solids retention time (SRT) are separated. The Ephyra® plug flow digester consists of three or four compartments, either separated as individual tanks or integrated as compartments in a single tank. Separating the different processes in the anaerobic degradation of organic matter allows Ephyra® to operate at much shorter retention times, as short as six to eight days.
Ben Roelfzema, senior engineer at Waterschap Zuiderzeeland, comments, “We can now treat more sludge quicker using smaller digestion tanks. And we now have an excess of biogas, which we use to provide 120 households with green energy.”
The system has provided additional cost benefits for the water authority as higher sludge degradations and better dewatering are produced with less chemical usage, resulting in lower sludge disposal costs. And the ability to process additional sludge from Lelystad has reduced the cost per volume treated (economies of scale).