TORWASH® technology successfully tested on pilot scale at wastewater treatment plant in The Netherlands


TORWASH® is a high temperature treatment of wet biomass streams. This treatment: (1) enables efficient mechanical dewatering of the biomass, (2) enables efficient removal of salts, (3) allows for sufficient biogas production from the effluent because of the mild conditions used, (4) facilitates the recovery of phosphorus and (5) makes the use of additives redundant.

ECN part of TNO has developed the patented TORWASH® technology. This year, a 50-L/h pilot plant has been commissioned and is operational at the wastewater treatment plant of Almere, The Netherlands. The goal is to reduce the volume of the sewage sludge waste stream, produce biogas from the liquid effluent and recover phosphorus. This project is realized together with partners: The Netherlands Enterprise Agency, ECN, TNO, STOWA, Waterboard Zuiderzeeland and PAQUES.



In 2018, a mobile pilot plant for the thermal processing of sewage sludge was built at a scale of 50 L/h. The whole route from basic engineering to construction and functional testing took place in Petten at ECN’s facilities. This pilot was transported to the wastewater treatment plant of Almere, The Netherlands in July 2018. There we aim to prove that by thermally treating sewage sludge with our TORWASH® technology we can reduce this waste stream by a factor 10, produce biogas and recover phosphorus. This means that the treatment of wastewater can become cheaper for citizens, and that wastewater treatment plants can become more sustainable by generating their own bio-based energy and materials.


Tests were realized with sewage sludge, containing 3-6 wt.% dry matter. The produced slurry was dewatered on pilot scale using a filter press and the treated sludge could be pressed into a solid cake containing 50 wt.% dry matter.
The produced effluent is treated in a BIOPAQ®ICX installation of PAQUES where biogas is produced (COD conversion of 70-80%) and phosphorus is recovered. All testing occurs on site at the wastewater treatment facility of Almere and the first pilot results are in agreement with previously obtained results in the lab.