Innovation makes it easier and cheaper to recover raw materials from sewage.
AFTER AN EXTENSIVE TEST PERIOD ON A LARGE SCALE, THE DUTCH COMPANY CIRTEC IS LAUNCHING CELLCAP, A NEW OPTIMISED TECHNOLOGY WITH WHICH CELLULOSE, SEPARATED FROM THE RESIDUE, CAN BE EXTRACTED DIRECTLY FROM SEWAGE, WITHOUT THE NEED FOR ADDITIONAL PUMPING STEPS (I.E. WITH LIMITED HYDRAULIC FALL). AN IMPORTANT AND INTENDED EFFECT OF CELLCAP IS THAT THE REMOVAL OF CELLULOSE FROM SEWAGE WATER LEADS TO A SIGNIFICANT REDUCTION OF CO2 EMISSIONS.
The Purmerend company CirTec B.V. has been a frontrunner for many years in the development of innovative sieving technology and the recovery of raw materials from sewage. The knowledge gained from a large number of long-term research projects and experiences from realisation of installations and their maintenance have been translated into an optimised technology with which cellulose, separated from other undissolved components such as fats, hairs and seeds can be extracted from sewage without additional pumping. The new CellCap technology is a major step forward in cellulose recovery from sewage.
For more than 10 years, CirTec conducted research into the application of rotating belt fine sieves on sewage treatment plants (STP’s) and the extraction of cellulose from sieved material. On small and medium-sized treatment plants (up to a scale of 300, 0000 PE) the impact of rotating belt finesieves on downstream processes was monitored long-term. Next to the impact on the STP, extensive research was carried out, in collaboration with Cellvation BV and Recell Group, into upgrading and use of recovered cellulose (Recell®) as a high-quality raw material.
Sieved material from rotating belt fine sieves contains a significant proportion of cellulose, but must be post-processed to allow high-quality marketing. The separation of undesirable components is best done at the STP itself, partly because this stream can be digested in site for biogas production and no waste is released during the further processing of cellulose.
In 2017 CirTec realized a proof-of-concept for in-line separation of cellulose at the STP Geestmerambacht of the Hoogheemraadschap Hollands Noorderkwartier (HHNK). This proof-of-concept has been the basis of the new CellCap installation that is officially launched this week and that can extract cellulose and residuals separately from influent. CellCap has been tested long term and have proven to extract cellulose that is pure enough to be used as a high-quality raw material after hygienisation and post-treatment.
The product, Recell®, is a product that is used as a green raw material for, eg. In asphalt, construction materials, street furniture, and green chemistry. It is therefore an excellent alternative to cellulose sources for which trees are felled. Previous projects have shown that the demand for recovered cellulose (from the point of view of circularity and sustainable use of raw materials) is already there.
In addition to the sustainability aspects and the creation of sales value by valorizing cellulose, the CellCap concept has significant added value for the sewage treatment facilities. The main advantages are:
- Increase in biological capacity; Due to the removal of COD, additional space is created to increase the biological capacity. Since cellulose is only partially degraded in the aeration tank (AT) and inert material is removed, the proportion of active biomass in the AT increases.
- Lower operational costs; By removing carbon and nutrients from influent based on particle size, the energy consumption for the downstream aeration is significantly reduced. As a result, sludge production is reduced, resulting in lower energy costs for sludge dewatering, lower use of chemicals (polyelectrolyte) and a reduction in costs for the discharge of dewatered sludge. Finally, hair and fibers are almost completely removed, so maintenance costs on process equipment will go down, while extending the technical life span.
- Limited space requirements; If the biological capacity of a STP must be expanded, the space required for a CellCap plant (part of the Cellvation process) is smaller than most alternatives.
The removal of cellulose in the biological process at the STP’s requires a lot of energy due to the energy-intensive steps required. In particular for aerating, thickening, dewatering, drying and transporting the sludge are the biggest energy consumers. In addition, based on the current sewage treatment process, the cellulose is lost because it is either bio-degraded or burned in the process.
The cellulose that is present in the sewage can be made suitable for reuse in for example construction materials, as an additive in asphalt or raw material for biocomposite. It is therefore an excellent alternative to recycled paper or virgin cellulose for which trees are felled.
Previous studies and projects have shown that the demand for recovered cellulose from sewage (from the point of view of circularity and sustainable use of raw materials) is already there. The challenge, however, is to recover high-quality and reusable cellulose from sewage on a large scale. The new energy-efficient CellCap technology is an important step in large-scale cellulose recovery.
CellCap is developed with an EFRO contribution from the program “Kansen voor West II” program and with co-financing from the Province of North-Holland.
For more information, please contact:
Coos Wessels, Managing Director CirTec BV
Telephone +31 (0)299 – 79 20 80