PMEU method is based on the rapid cultivations of several samples. The old idea to apply it in MPN (Most Probable Number) analyses has now proven to be correct: referring the Finnish Standard Book "SFS-KÄSIKIRJA 94: Mikrobiologiset vesitutkimusmenetelmät" (Methods for Microbiological Water Analysis) and discussions with specialists, PMEU can be used as an alternative, rapid method instead of the traditional technique, tube series in water bath or in an incubator. PMEU itself works as an incubator with a temperature deviation of < 0.1 oC.
A combination of 4 (levels of dilutions) * 5 (repeats) allows to follow the Finnish standard SFS 4447 (The Tube Method in Microbiological Water Analysis) as well as standards derived of it like SFS-EN ISO 9308-3 (for and coliforms) and SFS-EN ISO 7899-1 (for enterococci). Standards usually give MPN tables in the framework of 3*5 tubes (eg. for dilutions from 0 to 0.01) but PMEU gives an extra level (eg. 0 to 0.001) which covers a wider range of microbial counts. Samples with unknown levels of microbial densities are therefore easier to analyse correctly.
It seems that the leading status of membrane filtration has revised today. There are types of samples which are difficult or impossible to analyse with them (too much suspended solids etc.) and tube tests like MPN should be chosen. PMEU Tube Tests should be preferred also in situations where fast results (in hours, compared with days with colony count analyses) are needed.
The microbiological control of certain paper industry samples (pulp slurries,starches, minerals) are better to perform with tube methods. An example of the priority of the tube methods can be seen when samples with polymers should be analyzed: polymers tend to stuck membranes immiadely but do not prevent any analyses performed with tube methods. Rapid detection of harmful or hazardous bacteria can also be done faster with selective broths than in/on selective agars.
Showing posts with label starch. Show all posts
Showing posts with label starch. Show all posts
Friday, August 28, 2009
Sunday, June 7, 2009
"Top Three" microbiological problems of paper machines
Certain types of microbiological problems in paper mills seem to be acute all the time. Looking back to last months, this may be "Top Three" among them:
* Microbiological spoilage of raw materials. This is an everlasting hazard for mineral and starch slurries, and the reasons are very easy to understand: both raw materials mentioned may contain high densities of bacteria (mainly aerobic sporeformers and actinobacteria), slurries containing starch are very nutritive growth media for different microbial species and the very challenging biocidic treatments of slurries (especially mineral ones), when inaccurate, can lead to the total spoilage of them.
* Growth of biofilm and production of slime. This problem seems to be connected to poor washing and boil-out programs which leave rests of biofilm inside the machine and give growth time for it because too long running periods. The chose of ineffective biocide and/or its insufficient dosing can also stimulate the activity of these trouble-makers.
* Microbial growth in the broke system. Especially big machines with large broke towers suffer of this problem. If the basic biocide program is insufficient and the retention times inside the towers are too long, aerobic population tend to increase the number of its cells to the level of 10 000 000 cfu/g or even higher. Consumption of oxygen by respirating bacteria leads to anaerobic conditions, redox potential will be dropped and the growth conditions for both fermentative and anaerobic bacteria turns to be excellent. Drop of pH, slime and spore formation, smells and odours - even the production of H2S and H2 - will be found in such situations.
There are some measures to prevent these hazards. Growth period of microbial population shall be kept as short as possible, the control of waterborne and bioflim bacteria shall be as rapid and frequent as possible and the bioside programs, intended in killing of raw material, process water and biofilm bacteria shall be evaluated more frequently.
A realistic and accurate way to control both process water and biofilm growth, as well as to evaluate biocide programs, is now available. The Finnish company SAMPLION Ltd is manufacturing and selling "Portable Microbiological Enrichment Unit", a "mini-fermentor" for 10 simultaneous tests in controlled conditions, to detect the failures of biocide programs in only hours (watesr) or days (biofilms). Some results of PMEU's paper industry applications will be published in next Spring - coming back to refer them later.
Some wrong ideas about the overdosing of biocides will also rise up frequently among publicity. Basically it is not a question of only the cubic meters of biocides consumed, however, The chose of most effective biocides for different areas of processes towards different problems, the dosing of these compounds, their type of action and some other factors play a major role when building an effective biocide program for paper machine. Overdosing of biocides is a problem only in cases, when the program does not work, and leads to the loss of money and the rise of biocide concentration in paper machine effluents.
* Microbiological spoilage of raw materials. This is an everlasting hazard for mineral and starch slurries, and the reasons are very easy to understand: both raw materials mentioned may contain high densities of bacteria (mainly aerobic sporeformers and actinobacteria), slurries containing starch are very nutritive growth media for different microbial species and the very challenging biocidic treatments of slurries (especially mineral ones), when inaccurate, can lead to the total spoilage of them.
* Growth of biofilm and production of slime. This problem seems to be connected to poor washing and boil-out programs which leave rests of biofilm inside the machine and give growth time for it because too long running periods. The chose of ineffective biocide and/or its insufficient dosing can also stimulate the activity of these trouble-makers.
* Microbial growth in the broke system. Especially big machines with large broke towers suffer of this problem. If the basic biocide program is insufficient and the retention times inside the towers are too long, aerobic population tend to increase the number of its cells to the level of 10 000 000 cfu/g or even higher. Consumption of oxygen by respirating bacteria leads to anaerobic conditions, redox potential will be dropped and the growth conditions for both fermentative and anaerobic bacteria turns to be excellent. Drop of pH, slime and spore formation, smells and odours - even the production of H2S and H2 - will be found in such situations.
There are some measures to prevent these hazards. Growth period of microbial population shall be kept as short as possible, the control of waterborne and bioflim bacteria shall be as rapid and frequent as possible and the bioside programs, intended in killing of raw material, process water and biofilm bacteria shall be evaluated more frequently.
A realistic and accurate way to control both process water and biofilm growth, as well as to evaluate biocide programs, is now available. The Finnish company SAMPLION Ltd is manufacturing and selling "Portable Microbiological Enrichment Unit", a "mini-fermentor" for 10 simultaneous tests in controlled conditions, to detect the failures of biocide programs in only hours (watesr) or days (biofilms). Some results of PMEU's paper industry applications will be published in next Spring - coming back to refer them later.
Some wrong ideas about the overdosing of biocides will also rise up frequently among publicity. Basically it is not a question of only the cubic meters of biocides consumed, however, The chose of most effective biocides for different areas of processes towards different problems, the dosing of these compounds, their type of action and some other factors play a major role when building an effective biocide program for paper machine. Overdosing of biocides is a problem only in cases, when the program does not work, and leads to the loss of money and the rise of biocide concentration in paper machine effluents.
Wednesday, January 28, 2009
The need of paper machine biocides?
IM is wondering: are there any other sector of process industry, where microbes are allowed to grow like in paper industry?
Biotechnological processes, of course. But their populations are carefully selected and controlled. And they are employers of the company, not criminals trying to cause harm to the company.
Some significant changes in paper industry processes have taken place after the rise of active environmental care. Both the closure of water circulation and the cancelling of biocides having mercury as an active incredient are favorable for the environment, of course. But the microbial growth inside the paper machines has activated at the same time.
The beginning of neutral paper production led to an "ecocatastrophe" inside paper machines. The rise of pH value (as well as the rise of temperature, caused by the extended recirculation of water) was fatal for slow, acid-loving fungal growth. New mineral additives are an important source of certain types of bacteria, causing severe problems like production of slime, spoiling of the process compounds and hygiene faults of the products.
IM has published an article "Paper Machine: an Ecosystem and a Bioreactor" (INOCULA 1/2007. Helsinki, Finland). Many readers agree: paper machines offer ecological niches for bacteria, and the controlled environments of wet end circulations are very much similar with those of biotechnical processes, based on chemostatic fermentors.
A lot could be do to make paper machines more unfavorable growth environment for microbial contaminants. Very good results have been achieved in some projects where ecological aspects have been taken into account. These issues will be discussed later in this blog.
But the main question is: how much biocides we still need to control the microbial growth in all regions of a paper machine?
Incoming raw materials, sorry to say, may be very contaminated: the highest value of total count during IM's career has been over 100 000 000 cfu/g in a mineral slurry (which was fortunately replaced by a fresh lot by the supplier!). It is therefore obvious that a continuous control - both analytical and practical - is needed for starches, mineral pigments and other contaminated raw materials. This does not mean that all lots are spoiled: there are suppliers which know their response to deliver pure products to the mills but all kind of errors in biocidic pre-treatment, transport and storage of these products may happen.
Certain sites of paper machines also need biocidic treatments all the time. Chosing proper solutions for biocide programs (type of biocide, active compound, dosing sites, timing etc.) of a paper machine is a challenging tasks. In best cases, both the paper mill and biocide personnel are sitting down and discussing of the individual problems of the paper process hygiene.
When specified laboratory services, having tools like PMEU and biofilm microscopy, are included, the final result can be optimal one. Paper industry microbiologists can also help significantly by declaring the effects of process parameters on the growth of planktonic and biofilm bacteria.
The more competence is included, the better solution will be find.
Biotechnological processes, of course. But their populations are carefully selected and controlled. And they are employers of the company, not criminals trying to cause harm to the company.
Some significant changes in paper industry processes have taken place after the rise of active environmental care. Both the closure of water circulation and the cancelling of biocides having mercury as an active incredient are favorable for the environment, of course. But the microbial growth inside the paper machines has activated at the same time.
The beginning of neutral paper production led to an "ecocatastrophe" inside paper machines. The rise of pH value (as well as the rise of temperature, caused by the extended recirculation of water) was fatal for slow, acid-loving fungal growth. New mineral additives are an important source of certain types of bacteria, causing severe problems like production of slime, spoiling of the process compounds and hygiene faults of the products.
IM has published an article "Paper Machine: an Ecosystem and a Bioreactor" (INOCULA 1/2007. Helsinki, Finland). Many readers agree: paper machines offer ecological niches for bacteria, and the controlled environments of wet end circulations are very much similar with those of biotechnical processes, based on chemostatic fermentors.
A lot could be do to make paper machines more unfavorable growth environment for microbial contaminants. Very good results have been achieved in some projects where ecological aspects have been taken into account. These issues will be discussed later in this blog.
But the main question is: how much biocides we still need to control the microbial growth in all regions of a paper machine?
Incoming raw materials, sorry to say, may be very contaminated: the highest value of total count during IM's career has been over 100 000 000 cfu/g in a mineral slurry (which was fortunately replaced by a fresh lot by the supplier!). It is therefore obvious that a continuous control - both analytical and practical - is needed for starches, mineral pigments and other contaminated raw materials. This does not mean that all lots are spoiled: there are suppliers which know their response to deliver pure products to the mills but all kind of errors in biocidic pre-treatment, transport and storage of these products may happen.
Certain sites of paper machines also need biocidic treatments all the time. Chosing proper solutions for biocide programs (type of biocide, active compound, dosing sites, timing etc.) of a paper machine is a challenging tasks. In best cases, both the paper mill and biocide personnel are sitting down and discussing of the individual problems of the paper process hygiene.
When specified laboratory services, having tools like PMEU and biofilm microscopy, are included, the final result can be optimal one. Paper industry microbiologists can also help significantly by declaring the effects of process parameters on the growth of planktonic and biofilm bacteria.
The more competence is included, the better solution will be find.
Wednesday, August 13, 2008
Shared responsibility for paper machine hygiene.
Current situation of process hygiene control in paper industry is relatively complicated.
No matter very effective control methods are already available (epifluorescence microscopy, ATP Assay, PCR, PMEU incubations) the roles of paper mills, biocide suppliers and raw material producers are not very clear.
Based on the experiences by Industrial Microbiologist since beginning of 80', it seems that paper mills prefer external services and this tendency is evergrowing today. Biocide suppliers have developed novel analyse methods which can be applied even at the mills, and many raw material suppliers know their response to deliver minerals, starches etc. with good hygienic quality for paper and board mills.
What should still be developed is the active role of paper mills themselves to control their machines. There is no more any need for expensive microbiological laboratories - in opposite, many methods could either be applied by wet end laboratories of the mills or be bought from external companies (ref. BIOTOUCH Service).
Wet end chemistry has already been controlled with ON LINE analyse units by certain institutes in Finland over years. ON LINE microbiological control is also coming soon, referring several current project proposals.
A combination of all parties - paper mills, biocide suppliers and raw material producers - would spare remarkable amount of money by optimizing biocide programs, by planning washing programs, by responsing immediately to hazardous situations and avoiding costs of returned products.
No matter very effective control methods are already available (epifluorescence microscopy, ATP Assay, PCR, PMEU incubations) the roles of paper mills, biocide suppliers and raw material producers are not very clear.
Based on the experiences by Industrial Microbiologist since beginning of 80', it seems that paper mills prefer external services and this tendency is evergrowing today. Biocide suppliers have developed novel analyse methods which can be applied even at the mills, and many raw material suppliers know their response to deliver minerals, starches etc. with good hygienic quality for paper and board mills.
What should still be developed is the active role of paper mills themselves to control their machines. There is no more any need for expensive microbiological laboratories - in opposite, many methods could either be applied by wet end laboratories of the mills or be bought from external companies (ref. BIOTOUCH Service).
Wet end chemistry has already been controlled with ON LINE analyse units by certain institutes in Finland over years. ON LINE microbiological control is also coming soon, referring several current project proposals.
A combination of all parties - paper mills, biocide suppliers and raw material producers - would spare remarkable amount of money by optimizing biocide programs, by planning washing programs, by responsing immediately to hazardous situations and avoiding costs of returned products.
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