Merry Christmas, a Happy New Year, and a safe holiday season to everyone!
This newsletter is to give an insight into one of the impacts of using the Method 5 type filter in the Method 25 train during inlet monitoring.
While this effect has not been seen in a large number of tests, it has been indicated in some and clearly shown in others. The concern has been giving the information on those tests without possibly identifying the source while there are still possible legal issues to be reconciled. I believe I have gathered enough information to show the effect without compromise of any identities.
I have combined the information from a couple of sources which have some similarities and a good record of data. These have multiple inlets and a single outlet from a control device. I have mixed them in such a manner that the effect can be seen without knowing which inlets are connected to which outlets, in order to prevent identification of the sources.
I have taken a ten year series of data, using the last year as a comparison to the previous nine year average concentrations. As the averages indicate, there has been little change over the period until the last year when the filter was changed and the size of the aerosols sampled was limited. The results are not corrected for any flows and are rounded ppmC concentrations.
Nine Year Average
As can be seen in the two outlet and the first two inlet concentrations, there is not a lot of change from the long term average. The change is in the other three inlets which are all similar in nature. The 90% minimum drop in the inlet loading compared to the long term average shows the problem. The destruction efficiency of the control device dropped because of the loss in inlet loading, which was removed from the sample by the filter, but not from the stream to the control device.
All of the reported initial concentrations and all but one of the reported last year concentrations exceed the levels for which Method 25-A would be considered as an option. This would be further compounded by the lack of filtration required in Method 25-A, which should in reality place the concentration much closer to the nine year average. The use of Method 25-A in the projects where the Method 5 type filter in the Method 25 sample console has apparently caused a drop in loading indicated a much higher concentration than reported by those Method 25 analyses. The use of Method 25-A without filtration has a calculated control device efficiency approaching a more realistic and believable range than Method 25 with the new filter. Generally the Method 25 analysis reports a higher concentration due to the lack of the response factor differences between the sample gas and the compound used for calibration in Method 25-A.
Of course, there could always be a modification to the new filter specification used for Method 25, but that would generally be done on a case-by-case basis and after a first attempt had shown the problem affecting compliance. The cost of that first failed test would have to be written off by someone, but hopefully would result in sufficient data to allow for future modifications to be accepted for that source.
One of the issues facing this type of source is the filtration of what appears to be aerosols rather than solid particulate matter. This means at some point during the process the aerosol will become a vapor and will have to be dealt with as such. It could possibly be corrected by sampling at another location closer to the control device, if possible, where this transformation had already occurred. If not, removing the aerosol as a particulate would seem to require some type of additional control device for the organic compounds. Any additional series of controls are to be unnecessary for actual control based on historic data, but might be necessary for the definitions to be used.
I suppose this is why so many people dislike the way the regulations are handled, because it appears it could cause unnecessary costs to be incurred. I am not sure that would actually be the case, but there is the appearance.
I believe when a known problem exists and can be corrected by merely not making a change to the inlet filtration sampling the reasonable course is to do just that. Making a change to the inlet sampling that really has no effect, since the majority of the filters used previously would still be used, and the sampling is still within the process seems counterproductive. I can see where there would be an issue with an emission to the atmosphere, but not within the process itself. Thus, the correction to the outlet requirement is understandable, but not so with the inlet filter given there will be issues created with future testing and will impact the comparison to previous data.
Triangle Environmental Services, Inc.