Exceptional ‘sieve’ goes into service at Dutch sewage treatment plant

Innovative project gives used toilet paper a new role

A fine sieve was put into service at the Ulrum sewage treatment plant in the Netherlands on Friday 19 September 2014. It was a special milestone in a project called CADoS (Cellulose Assisted Dewatering of Sludge) in which the public sector, the private sector and research institutions are cooperating with each other. From the sewage the fine sieve extracts cellulose that comes mainly from domestic toilet paper. The cellulose fibres are then used to dewater the treated sludge still further. This process requires fewer chemicals and saves money. Biogas is made from the residual product. It is good for the environment and good for the wallet.

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Over the coming three years there will be an examination of how well this innovative application works in practice and how it impacts on operations at the treatment plant. Various studies will be conducted into the effects of adding cellulose to sludge. The leftover waste – i.e. the sieved matter containing cellulose – will also be scrutinised. A key question is by how many percent this method will increase the biogas yield. Another question concerns the possibilities for using the sieved matter as raw material for such purposes as bio-plastics, filler for asphalting or insulation.

Laboratories and trial site
Experiments will be conducted in several laboratories and at the trial site in Ulrum. The sewage treatment plant of the Noorderzijlvest Water Authority was specially modified for this project. An extra building was recently erected to accommodate the fine sieve. On Friday morning the fine sieve system was put into service in the presence of project partners, regional officials and other interested parties. Bob van Zanten, a member of the executive board of Noorderzijlvest Water Authority, said: “Every year 200,000 tons of paper are used in the Netherlands and flushed down the toilet. But we can do more with toilet paper than you ever imagined. Instead of being waste it’s now a raw material. Sustainability is the objective. For the water authority it opens up the prospect of lower treatment costs. A unique project definitely got underway today.”

Strong cooperation
Research institutions are working in the project alongside private companies and government authorities. The six project partners (Noorderzijlvest Water Authority, Brightwork B.V., Attero, Groningen University, the Water Technology Center of Expertise and the Friesland Water Authority) came together to form a powerful collaborative venture. CADoS is also being subsidised by the three northern provinces of the Netherlands and by a collaborative platform called SNN (North Netherlands, Heading North). Eise van der Sluis, Director of SNN, said: “Innovating is great. Each year we receive numerous good proposals for projects. It’s always difficult to check them against compliance with the conditions for a subsidy. But it was impossible to find fault with CADoS. In fact, CADoS excellently meets the new subsidy conditions of the Northern Innovation Agenda.”

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