The average bacteria size is 0.45 micron, what is the reason behind the use of 1.5 or 0.7 microns for VSS analysis in wastewater?
Which pore size you use is dependant both on which fraction of particular matter that you are searching and which country you are in.
One recognised approach is that you use two different pore sizes l. 1.5 um is used to find the particular fraction. And you pass a flocculated sample through 0.45 um. What goes trough is soluble and the difference between what is retained on the 1.5 um and the 0.45 um is the colloid fraction. The fact that the sample is flocculated assure that also small free swimming bacteria is retained.
I think this was discussed before, please see
https://www.researchgate.net/post/What_filter_size_are_you_using_for_Total_Suspended_Solids_analysis
Which pore size you use is dependant both on which fraction of particular matter that you are searching and which country you are in.
One recognised approach is that you use two different pore sizes l. 1.5 um is used to find the particular fraction. And you pass a flocculated sample through 0.45 um. What goes trough is soluble and the difference between what is retained on the 1.5 um and the 0.45 um is the colloid fraction. The fact that the sample is flocculated assure that also small free swimming bacteria is retained.
Specifically for bacteria I wonder how important would that be... Bacterial counts in fresh water are usually rather low (less then 10^6/100 ml) resulting in less then 10 mg/L fresh weight and less then 3mg/L dry weight. What would common TSS values in such water?
Obviously wastewater and water with high load of small slit particles will result in very different results.
Yoram
Because the use of this specific parameter is related to the indirect evaluation of teh amount of microornanisms present in a biological reactor, to control its performance and operation. Since the performance of biological treatment systems relies on the amount of microorganisms present and these microorganims are clumped (flocs with diameters higher than 2 microns), because of specific biological process, the measurement of VSS in an indirect measurement of the biomass contained in the biological reactor.
it will always depend on the fraction you are interested in as indicated by Dr. Kim Helleshoj
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