No abstract

It has been reported that about 10-15% of the fresh water intake in a paper mill is used for feeding and diluting retention aids, so important savings could be achieved replacing fresh water with process water. Water from different sources and qualities: fresh water (FW), the outflow from an internal ultrafiltration placed in the machine circuit of a paper mill (UFW), and water from a membrane bioreactor used to treat the final effluent of this paper mill (MBRW), were used to prepare a dual retention system consisting of a cationic polyacrylamide (cPAM) and bentonite. While the behaviour of bentonite was not significantly affected by the quality of the water used in its preparation, the efficiency of the cationic polyacrylamide was reduced around the 12%, when it was prepared with water with high anionic trash content and conductivity due to a partial neutralization of the charged groups. The effect of non-ionic chemical oxygen demand on the efficiency of the polymer resulted negligible.