CellCap, simple and energy-efficient recovery of cellulose from sewage water
4 June 2021
Innovation makes it easier and cheaper to recover raw materials from sewage.
AFTER AN EXTENSIVE LARGE-SCALE TESTING PERIOD, CIRTEC LAUNCHES CELLCAP®, AN OPTIMIZED TECHNOLOGY THAT ALLOWS CELLULOSE TO BE EXTRACTED FROM SEWAGE WATER SEPARATELY FROM OTHER UNDISSOLVED CONSTITUENTS WITHOUT INTERMEDIATE PUMPING STEPS (WITH LIMITED HYDRAULIC DECAY). A KEY INTENDED EFFECT OF CELLCAP® IS THAT THE REMOVAL OF CELLULOSE (MAIN COMPONENT OF TOILET PAPER) LEADS TO ENERGY SAVINGS AND REDUCTION OF CO2 EMISSIONS.
For years, the Purmerend company CirTec B.V. has been at the forefront of the development of innovative screening technology and the recovery of raw materials from sewage water. The knowledge gained from a large number of long-term research projects and experience with realization and maintenance of installations have been translated into a new optimized technology with which cellulose, separated from other undissolved components such as fats, hairs and seeds, can be extracted from sewage water without additional pumping. The new CellCap technology is a major step forward in the recovery of cellulose from sewage.
For more than 10 years, CirTec has been conducting research on the application of rotary belt finescreens at sewage treatment plants (WWTPs) and the specialization of cellulose from screenings. At small and medium-sized treatment plants (up to a scale of 300,0000 PE), the long-term impact of rotary belt finescreens on downstream processes has been monitored. In addition to the impact on the WWTP, extensive research has been conducted in cooperation with Cellvation BV and Recell Group on upgrading and applying recovered cellulose (Recell®) as a high-value raw material.
Screenings, the product of rotary belt fine screening contain a significant proportion of cellulose, but must be post-processed to enable marketing as a high-quality raw material. Separation of unwanted components would preferably be done at the WWTP itself, partly because this stream can be fermented on site for the sake of biogas production and no waste is released in further processing of cellulose.
In 2017, CirTec realized a proof-of-concept for in-line separation of cellulose at the Geestmerambacht WWTP of Hoogheemraadschap Hollands Noorderkwartier (HHNK). That proof-of-concept has been the basis of the new CellCap installation that is being officially launched this week, which can extract cellulose and residues separately from influent. CellCap has been long-term tested and has proven that separated cellulose is pure enough to be used as a high-quality raw material after hygienization and post-treatment.
The product, Recell®, is a product used as a green raw material for bicycle paths, street furniture, cladding and green chemistry, among others. This makes it an excellent alternative to cellulose sources for which trees are cut down. 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.
Besides the sustainability aspects and the creation of added value by extracting marketable cellulose, the CellCap technology has important added value for the purification process. The main benefits are:
- Increasing biological capacity; Removing COD (carbon) increases the biological capacity of a treatment plant. Since cellulose is only partially decomposed in the aeration tank (AT) and inert material is removed, the application of screening technology increases the proportion of active biomass in the AT.
- Lower operating costs; The removal of suspended solids significantly reduces energy consumption for downstream aeration. Less sludge is produced, resulting in lower energy costs for sludge dewatering, lower use of chemicals (polyelectrolyte) and lower costs for depositing dewatered sludge. Also, bristles and fibres are almost completely removed, reducing maintenance costs of process equipment, while extending technical life.
- Space savings; If the biological capacity of a rwzi needs to be expanded, the space required for a CellCap plant (part of the Cellvation process) is smaller than for almost all alternatives.
About CellCap
Removing cellulose at a WWTP costs a lot of energy because of the energy-intensive steps required to do so. In particular, aerating, thickening, dewatering, drying and transporting the sludge are the biggest energy consumers. Moreover, in the current sewage treatment process, cellulose is lost because it is either biodegraded or incinerated with sludge at the end of the process.
The cellulose present in sewage can be made perfectly suitable for use in building materials, for example, as an additive in asphalt or raw material for biocomposite. This makes it an excellent alternative to recycled paper or new cellulose for which trees are cut down.
Previous studies and projects have shown that the demand for recovered cellulose from sewage (from the perspective of circularity and sustainable use of resources) already exists. However, the challenge 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 was developed with an ERDF contribution from the Opportunities for West II program and with co-financing from the Province of North Holland.
For more information, contact:
Coos Wessels, Director CirTec BV
c.wessels@CirTec.nl
Phone: +31 (0)299 – 79 20 80
www.CirTec.nl
