New technologies or innovative treatment lines for reliable water treatment for P&P and minimization of waste production
The project for sustainable water use in chemical, paper, textile and food industries
This report is a result of the project AquaFit4Use, a large-scale European research project cofinanced by the 7th framework program of the European Union on water treatment technologies and processes. In the Pulp&Paper industry a lot of effort is put into to water saving and closing water circuits, also reducing substantially the environmental impact, both by process modelling and Kidney technologies as internal process water treatment. However a number of problems around the removal of substances are not solved yet and further closing of the water cycle causes other problems. Challenges for water re-use in the Pulp&Paper industry are the following: - The elimination of residual (soluble) COD and BOD which can both affect the production process and the paper quality; - The removal of sticky solids and suspended solids, which can induce plugging of pipes and showers, deposit formation, abrasion, loss of tensile strength; - The treatment of concentrate streams containing calcium, sulphate, chloride and organics which can lead to salt accumulation in case of water loop closure, corrosion, scaling of pipes and showers in the paper production process. The removal of calcium carbonate is crucial in the last case. Therefore there is a need to find new and reliable (combinations of) technologies to solve this challenges to achieve the water quality target for water re-use and which are tailored to suit product demands and standards. The work described in this report concerned the laboratory and preliminary work for the implementation of pilot trials on two industrial paper mills. The emphasis was on different technologies as part of a global treatment line to solve the above challenges. On the basis of waste water characterization and the defined water quality requirements for paper mills, new treatment lines were defined to reach the water quality target including effectiveness, reliability and minimization in waste and concentrate production. These new treatment lines are focused on internal recycling. The emphasis was on different key steps of the global treatment train: - Biological treatment: anaerobic processes and MBR; - Filtration processes: 3FM high speed technology and nanofiltration; - Tertiary treatments to reduce hard COD: AOPs, coagulation/precipitation; - Integration of processes (evapoconcentration, electrodialysis and softening) in the treatment line: o To treat the concentrate streams containing calcium, sulphate, chloride, organics; o To minimize the waste production and enhance internal recycling. Technologies were tested at lab scale on the waste waters from 3 different paper mills: • Paper mill 1 (PM1), producing corrugated board and board; • Paper mill 2 (PM2), producing high quality coated and uncoated board from recycled paper; • Paper mill 3 (PM3), producing standard newsprint, improved newsprint (higher brightness) and light weight coated paper (for magazines). On basis of the obtained results, the best treatment combinations to be implemented and tested at pilot scale within WP5.1.4 were selected and summarized for each type of paper mill.