The purpose of this document is to provide general information on the testing and analysis methods used by Steward Environmental Solutions. Steward routinely uses the EPA test method 245.7 modified slightly to incorporate some of the EPA method 1631 requirements. Steward is also able to perform EPA test method 1631. These methods prescribe the procedures for using cold vapor atomic fluorescence spectroscopy to determine mercury concentrations. Steward uses the Tekran Series 2600 CVAF spectrometer.

Variation from Method

The Steward methods differ from strict EPA 1631 and EPA 245.7 in these two points:

1. Class 100 clean bench a nonmetal glove box. We operate in an enclosed laboratory with filtered HVAC and inside a chemical hood.
2. EPA 245.7 sample preparation method. We take Tekran’s recommendation, using the more advanced EPA 1631 sample preparation protocol.

Measurement

Quality Control Acceptance Criteria. Table 2 of Method 1631 rev E, page 34 states the limits for Initial Precision and Recovery (IPR), Ongoing Precision and Recovery (OPR), and Matrix Spike/Matrix Spike Duplicate (MS/MSD). Steward has measured each of the requirements of this Table. Steward also periodically tests the known reference samples from different sources and the results show very good agreement. The Tekran 2600 CVAF is capable of measuring mercury concentration as low as 0.5 ppt.

Determination of kinetic response and capacity

1. Kinetics Measurement
   1. Contact solution: the standard contact solution is made with 0.1M NaNO3 solution spiked with 10 ppm of Hg. The contact solution is the customer waste water when conducting treatability study.
   2. Preconditioned thiol-SAMMS® material (preconditioned with 10 – 20 % ethanol water solution).
   3. Mix preconditioned thiol-SAMMS with sufficient volume of contact solution to achieve a solution to solid ratio of 2000 ml/g for standard tests. The solution to solid ratio may vary when conducting treatability study
   4. Equilibrate the mixture, and using 0.22 µm or 0.45 µm syringe filters sample the solution phase periodically as needed.
   5. Analyze Hg concentrations in the contact solution and the filtered samples using CVAF analytical method.
2. Capacity Measurements
   1. Contact solution: 0.1M NaNO3 Solution spiked with 200 ppm of Hg
   2. Preconditioned thiol-SAMMS material (preconditioned with 10 – 20 % ethanol water solution).
   3. Mix preconditioned thiol-SAMMS with sufficient volume of contact solution to achieve a solution to solid ratio of 5000 ml/g
   4. Equilibrate the mixtures for 24 hours using a shaker.
   5. Centrifuge the tubes to settle the solids
   6. Obtain supernatant contact solution samples using 0.22 µm or 0.45 µm syringe filters
   7. Analyze Hg concentrations in the contact solution and the filtered samples using CVAF analytical method.
3. Capacity Isotherm Measurements Using a Static Batch Mode
   1. Contact solution: 0.1M NaNO3 solution spiked with a certain concentration Hg solution
   2. Preconditioned thiol-SAMMS material (preconditioned with 10 – 20 % ethanol water solution).
   3. Mix preconditioned thiol-SAMMS with sufficient volume of contact solution to achieve a solution to solid ratio of 5000 ml/g
   4. Equilibrate the mixtures for 24 hours using a shaker.
   5. Obtain supernatant contact solution samples using 0.22 µm or 0.45 µm syringe filters
   6. Analyze Hg concentrations in the contact solution and the filtered samples using CVAF analytical method.
4. Capacity Isotherm Measurements Using a Dynamic Membrane Mode
   1. Contact solution: 0.1M NaNO3 solution spiked with a certain concentration Hg solution
   2. Preconditioned thiol-SAMMS material (preconditioned with 10 – 20 % ethanol water solution).
   3. Mix preconditioned thiol-SAMMS with sufficient volume of contact solution to achieve a certain solution to solid ratio.
   4. Contact solution is pumped into a contactor, where thiol-SAMMS is present, with a fixed rate similar to the permeate flowrate.
   5. The mercury solution after thiol-SAMMS treatment (out of the contactor) is pumped to a membrane system. The concentrate is fed back to the contactor and the permeate is collected in a separate container.
   6. The mercury concentration in the permeate solution is analyzed using CVAF periodically.
   7. The system continuously runs until a clear breakthrough of mercury concentration is observed.