Discussion of methods to monitor chlorine in landfill gases (LFG).
Recently there have been some questions concerning the analytical methods for total chlorine landfill gas, specifically starting with the ATSM methods E776, D6721, or D4208. The modifications required to convert these to gas sampling and analysis would be as much or more than the initial method development since both the sampling and analysis would be changed.
ASTM D6735-01 could be considered as a possible option given it analyses for Cl and F ions using ion chromatography, but the sampling requires a heated filter, which poses a clear safety risk for a flammable gas source such as LFG. The effect on the method by such a change is unknown
One of the methods of which I am aware that reports total chlorine is Method 25-D. This is a wastewater method so the sampling aspect would have to be modified, but the analysis utilizing an ELCD would not have to be changed. The VOC aspect of the analysis using an FID should probably be ignored for any purpose given there is no provision for the response factor differences. We had at one time started to set up this process but stopped with the FID because of problems we encountered keeping the glassware together with the specified back pressure and the lower level of interest in the analysis. Thus, I have no direct information on the chlorine analysis other than the information surrounding the method.
The other EPA methods mentioned were 26/26-A, which are both designed for the gas sampling aspect but would also require a similar modification of the filter temperature as the ASTM D6735-01. The impact of such a change could be significant, so there would need to be some type of study performed to develop an adequate sampling protocol for any of these methods for LFG. The filter portion seems to be discarded, so if there was sufficient confidence in the lack of particulates containing Cl this sampling method could be used. That would open up most of the analytical methods for use, depending on the other concerns.
For example, there are indications that the presence of both HBr and Cl2 will cause them both to be under reported and the HCl and Br2 to be over reported. Given that LFG can and often does contain the most varied mixture of compounds sampled this is a valid concern.
This, of course, deals only with the methods as they are written and without modification other than the aforementioned filter temperature. There can be many variations of the analysis of the different fractions which may improve or even expand on the potential problems modifying any method to be used for LFG monitoring.
I found references to OSHA and NIOSH methods for Cl, but for exposure monitoring more than a concentration or emission level. This is not to say that some of these methods could not be modified for use, but again there would probably be more method development involved.
Some web references I have found on the subjest
Triangle Environmental Services, Inc.
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