This method is for the determination of mercury from wastewater treatment plant sewage sludge samples. Time-composite sewage sludge samples are taken from a conveyor belt susequent to de-watering and before incineration or drying. A weighed portion of the sludge is digested in aqua regia, oxidized by KMnO4 and analyzed using cold vapor atomic absorption spectrometry (CVAA).
During sampling, equal volume increments for a total of at least 15L at intervals of 30 minutes over an 8-hour period are taken and combined in a rigid plastic container. These portions are put into a mixer and mixed for 30 minutes at 30rpm. Six 100mL portions of the mixed sample are taken and combined in a 2L blender. Once the samples are blended, four 20mL portions are put in separate, tared 125mL Erlenmyer flasks. The flasks are then reweighed.
One of the 20mL sample portions is dried to determine the percent moisture of the sample. The remaining 20mL portions of the sample are digested with aqua regia. Once the samples are digested, the samples are analyzed following Method 101A procedures. Each sample is analyzed in duplicate by CVAA. Each measurement must be within 3% of the mean value or the samples must be reanalyzed.
Final sample results are an average of all results reported on a dry weight sample basis.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | 28 days from sampling to analysis. |
| Preservatives: | Keep at 4°C +/- 2°C from sampling until analysis. |
| Required Preps: | None specified in method. |
| Collection Method: | Time-composite sampling |
| Analytical Methodology: | CVAA following Method 101A procedures. |
| Documentation: | 
105
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Mercury | Hg |
7439-97-6 |
0.2 |
ppb |
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.