Determination of Particulate and Gaseous Mercury Emissions from Sewage Sludge Incinerators
This method is for the determination of mercury emissions from sewage sludge incinerators and other applicable sources. Particulate and gaseous mercury emissions are withdrawn isokinetically from the source and are collected in an acidic potassium permanganate (KMnO4 ) solution. The mercury collected (in the mercuric form) is reduced to elemental mercury, which is then aerated from the solution and measured by cold vapor atomic absorption (CVAA).
Samples are collected using a modified Method 5 sampling train consisting of a heated probe and glass fiber filter containing no organic binders and a series of impingers. The first impinger contains 50mL of the potassium permanganate (KMnO4) absorbing solution. The 2nd and 3rd impingers contain 100mL of the KMnO4 solution. The 4th impinger contains 200-300g of silica gel.
It is important that no metal be used in the probe, probe liner, filter support, or in the collection brushes used in sample recovery. Metal parts could serve as a source of contamination of the sample. The method also calls for the solution of KMnO4 to be prepped daily. It is also important to note safety precautions to be used when shipping the KMnO4. There must be a way for the glass container to vent as KMnO4 reacts with acid present in the solution to form a gas and there must be a way for the container to vent, otherwise, it becomes an explosion hazard.
After collection, the contents of all impingers are measured to later assist with the determination of stack moisture. The filter is folded such that the particulate is on the inside on the filter and placed in glass bottle containing 20-40mL of KMnO4 absorbing solution. The probe, liner, and filter holder is rinsed with KMnO4 and collected in a separate container. The contents of the impingers and associated rinses can be combined into one container or multiple containers if needed for volume. The impingers are then washed with 100mL of water. which is combined with the impinger and rinse contents If brown deposits remain on the impingers, they are rinsed with 25mL of 8N HCl and put into a separate container holding 200mL of water.
The filter and impinger contents/rinses are digested separately with HNO3 and then combined for analysis by CVAA. Each sample is analyzed in duplicate. The value of each duplicate must be within 3% of the mean value or the sample must be reanalyzed.
(EPA 40CFR Part 61 Appendix B)