An average paper mill consists of several sites where waterborne and biofilm microorganisms can survive and grow. Different kind of populations can be found in different environments, e.g. wet mineral and starch slurries, coating pasts, white waters, pulps and brokes as well as all wet surfaces inside the paper production systems. The effective prevention of these sub-populations is depending of the biocide alternatives (storing, fast-acting or even sporicidic compounds) available. Their use should be combined with other measures, however: the prevention of their growth by process technology, production strategies, cleaning of the processes etc. - This combined activity, if clever planned, can the be called "Integrated Prevention of Microbial Growth".
The most beneficial tool for the planning of IPMG is the HACCP procedure which evaluates the potential microbiological hazards in every site and gives hints to choose the Critical Control Points in the total process.
But - what does the stimulation of microbial growth in a paper mill mean?
It shall be kept in mind when biological waste water treatment plant is the last step of the process water route from water source to recipient lake, river or sea. The growth conditions, in oppotie to those of manufacturing processes, should be as beneficial as possible to keep the growth rates of activated sludge or anaerobic treatment just on optimal level.
We have to understand the microbes and their needs when preventing or stimulating their growth activities. The count of microbes is only one variable - their responses to temperature, pH, redox potential and other growth factors, their metabolic features (e.g. sporulation-germination cycles), their tendencies to grow in water or surfaces) and other important factors should be taken into account when planning the programs for microbe prevention (inside the mill) or stimulation (biological waste water treatment).
- More about these issues in next posts...stay on the line.
(Schematic picture: MENTU, J.V. 2001)