LOW RESIDUAL TOXICITY MICROBIOLOGICAL CONTROL FOR 'INNOVATIONS IN BIOLOGICAL CONTROL' SESSION

摘要

To meet ever more stringent discharge levels and future changes preventing the use of environmentally harmful biocides, UK Paper trialled a new concept in deposit control from Nalco. There was a wish in the mill to reduce reliance on conventional organic biocides, which break down slowly into relatively toxic products. A more environmentally friendly programme that would not jeopardise the runnability of the paper machine - PM6 -was required to give the mill a competitive edge.Extensive evaluation was carried out both on site and at one of Nalco's customer service laboratories, to determine the effectiveness of peroxyacetic acid / hydrogen peroxide technology prior to the first trial. Initial results showed a major improvement in the programme effectiveness in terms of control of microbiological populations, with the added benefits of a significant reduction in levels of residual toxicity. One of the components of the programme can be demonstrated to break down completely to totally non-toxic end products, namely carbon dioxide and water.An on-line deposit monitor had been developed for use with this programme and was used on PM6 backwater system to gather background information, prior to and during the trial. This showed reductions in the rate of microbial slime build-up on-machine, gained through the use of this technology. Paper machine microbial populations reduced from tens of millions to less than 1000 during the dosing period. Noticeable improvements in cleanliness were seen on machine.The use of this technology - new chemistry, new monitoring tools - has now been expanded throughout Europe and is in use in several countries as well as the US.