**FGD Wastewater Sample Selection Criteria for Methods Development Study** 
To the extent possible, selection of FGD wastewater samples for use in an EPA CRC

ICP
- MS methods development study should satisfy

the following criteria: **Criterion #1**

**– Analytical**  **Interferences** Several characteristics of FGD wastewater make them anal yticall y challenging using the “standard” implementation of plasma methods in most commercial laboratories. To insure that the samples selected are representative of the anal ytical dif ficulties ty

pically encountered, the following criteria should be met by any s ample selected. Sample characteristics (criteria) are listed more or less in the order of priority but the samples selected should meet as many of the criteria as possible: 1. Tot al dissolved solids (TDS) ranging from 15,000 mg/L up to a maximum, which should be in the 40,000 to 6 0,000 mg/L range. It is important to select samples representative of the range of TDS that can be expected in FGD wastewaters. 2. Calcium (Ca) concentrati ons ranging from 1,000 up to an expected maximum of 6,000 mg/L or more. 3. Sulfate (SO4) concentrations ranging from 1,000 up to an expected maximum of 4,000 mg/L or more. 4. Chloride (Cl) concentrations ranging from 2,000 up to an expected maximum of 20,000 m g/ L or more. 5. Magnesium (Mg) concentrations ranging from 1,000 up to an expected maximum of 5,000 mg/L or more. 6. Sodium (Na) concentrations ranging from 300 up to an expected maximum of 2,000 mg/L or more. **Criterion #2**

**– Elemental Concentrations**  All crit eria #1 characteristics being equal, the samples selected should exhibit low concentrations of the elements of interest to provide the most realistic information regarding actual method detection limits (MDL) and reporting limits (RL) achievable using CRC

- IC P
- MS for FGD wastewater analy ses. For example, selenium concentrations should be low in the range of < 100

- 3 00 μg/L (ppb). This criterion is more easil y satisfied for many other elements (e.g., Ag, As, Cd, Cr, Cu, Ni, Pb, Sb, Tl, V, Zn) whose typical c oncentrations in FGD wastewaters are low (i.e., < 50 ppb).**Criterion #3**

**– Addressing FGD Wastewater Variability** 

To the extent possible, the major sources of variability in trace metals concentrations in FGD wastewaters should be addressed during sample s election to allow an evaluation of the range of possible interferences during this methods development study
. Two important factors to be considered are as follows: 1. Coal source being used at a given facility. The most important coal sources used by the steam electric industry in the U.S. are eastern bituminous , western bituminous, and subbituminous coals (e.g., Powder River Basin). The characteristics of these coal ty pes are very

different and will impact the characteristics of FGD wastewater. 2. Additi ves to enhance air pollution controls . Various additives can be used in a coal

- fired power plant to enhance the removal of air pollut ants , such as SO 2 an d mercury . These additives include, but are not limited to, DBA, formic acid, and bromi n e. Other fac tors being equal, FGD wastewater samples should be selected that involve the use of as many additives as possible. This approach will increase the number of potential interferences that can be evaluated during the study. It is recommended that as many of the criterion #1 parameters be determined in all candidate samples to facilitate an informed decision on sample selection. Depending on the number of samples to be used in the study , it may not be possible to address all criteria. In this case, samples with the highest concentrations of criteria #1 parameters, lowest metals levels (criteria #2) and most additives should be selected. **Other Potential Issues to Consider** UWAG would be happ y to review and comment on a proposed Statement of Work ( SOW ) for E PA ’s CRC
- ICP
- MS methods development study . UWAG has specific experience in dealing with anal yt ical issues related to FGD wastewaters and could share lessons learned and approaches that could help the EPA conduct a successful methods development study
. UWAG would appreciate the opportunity to participate in EPA ’s methods development study . For example, if agreeable with the members hip , UWAG would be willing to provide an independent analy s i s, such as HR

- ICP
- MS and H GAFS (for arsenic and selenium), on spli ts of all the study samples. These additional anal ys es would provide confirming anal ys es that would assist EPA in evaluating the protocols developed for CRC
- IC P
- MS. EPA should also consider conducting a methods development study using EPA Method 200.7. Experience gained with the anal ys is of split samples collected during the EPA sampling events has shown that a robust implementation of Method 200.7 optimized for FGD wastewater analy sis can produce accurate, quantified data for many potential elements o f interest. It is likely that a majority of compliance monitoring of FGDeffluent wastew aters could be effectivel y handled by Method 200.7 using an optimized method. The sampling study also demonstrated that the standard implementation of Method 200.7 b y many commercial laboratories did not perform well for the anal ys is of FGD wastewaters. If a version of Method 200.7, optimized for FGD wastewaters could be developed, the number of commercial and in

- house laboratories able to generate acceptabl y accurat e data would be significantly increased.