Effects of water chemistry on flocculant makedown and subsequent retention & drainage performance

In paper mills that already recycle a significant portion of process water, retention and drainage aid make down systems remain one of the largest users of fresh water. To further increase water reuse, mills are now channeling recycled process waters for polymer makedown. The recycled water contains higher levels of inorganic ions (sodium, calcium, sulfate, chloride), organic materials and fines. Retention and drainage aids will need to maintain good performance when made down with these more contaminated waters. The objective of this study was to evaluate the use of recycled process waters for the makedown of several different flocculant types. After makedown with recycled water of poor quality (conductivity 5,000 to 10,000 mu S/cm and cationic demand 100 to 3,000 mu eq/l), the retention and drainage activities of these flocculants were then determined on furnishes used in the production of alkaline fine paper and board of different grades. Performance was compared to the same polymer made down in a relatively clean tap water containing low dissolved solids. Evaluations were conducted both in the laboratory and in the field. The results showed that the retention and drainage performances of the flocculants studied were not significantly altered upon makedown in recycled waters.