In fact, to comply with environment regulations on re use, Canada is the largest importer of waste paper in the Western World. A few years ago mill whitewater circuits were virtually wide open, and a single paper machine could discharge 20 million gallons of water per day to a nearby waterway. Also, the trend has been to convert to alkaline or neutral papermaking, which greatly enhances conditions for bacteria regrowth. Due to the increased cost of furnish, and also to reduce solids discharge to the sewer or river, recycle waste and recycled fiber is being used to a much higher degree, The immediate effect of these changes was an increase in the rate of bacterial growth within the whitewater system, in some cases so acute as to render the paper machines virtually inoperable. White water systems operate at about 110 F, which makes them a breeding ground for several types of bacterium.
Bacteria grow in colonies, surrounding themselves with a polysaccaride slime.
The colonies grow preferentially in moist partially wetted areas such as the head box, wire pit, broke chest and Saveall. When the colonies break off, and attach to the sheet, a speck, spot, or even a hole appears in the sheet, as the fibers will not settle and consolidate on the slime, if it attaches to a roller, could ruin a whole run of production. The holes, apart from spoiling the product, weaken the sheet, and breakages are more frequent. This requires that the machine be shut down and cleaned, usually called a boilout. Conventional biocides were tested, and some proved effective.