This sampling protocol applies only to samples collected for use in measurement of COD when demonstrating compliance with the regulations set forth in this part. Collect a representative sample of the effluent from the airport deicing treatment system, based on the discharge permit requirements (e.g., a grab sample or a composite sample). Because only the COD sample is filtered, do not use in-line filters if collecting a sample with a compositing device.

A. Grab Samples

1. Cap the container and shake the grab sample vigorously to mix it. Remove the plunger from a 10-milliliter (mL) or larger Luer-lock plastic syringe equipped with an Acrodisc Luer-lock filter containing a 1.5-μm glass fiber filter (Whatman 934-AH, or equivalent), and fill the syringe body with sample.

2. Replace the plunger and filter the sample into a clean 50-mL screw-cap glass, plastic, or fluoropolymer bottle.

3. Additional 10-mL volumes of sample may be filtered and the filtrate added to the same sample bottle. This additional volume may be used to repeat sample analyses or to prepare Quality Control (QC) samples, as needed.

4. Unless the filtered sample will be analyzed within 15 minutes, preserve the filtered sample with H2SO4 to pH <2. Cap the bottle and label with the sample number. Place in a cooler on ice prior to shipping.

5. Once at the analytical laboratory, the sample must be stored at ≤6 degrees Celsius and analyzed within 28 days of collection (see the requirements for COD in Table II at 40 CFR part 136).

6. Analyze the sample using a method approved for COD in Table IB at 40 CFR part 136.

7. Report the sample results as Soluble COD in units of milligrams per liter (mg/L). There is no Chemical Abstracts Service (CAS) Registry Number for soluble COD.

B. Composite Samples

1. If the sample will be analyzed in a fixed laboratory (as opposed to field testing), transfer at least 50 mL of well-mixed sample from the compositing device into a clean 50-mL screw-cap glass, plastic, or fluoropolymer bottle. Preserve the sample with H2SO4 to pH <2. Cap the bottle and label with the sample number. Place in a cooler on ice prior to shipping.

2. Once at the analytical laboratory, the sample must be stored at ≤6 degrees Celsius and analyzed within 28 days of collection (see the requirements for COD in Table II at 40 CFR part 136).

3. Prior to analysis, remove the sample from cold storage and allow it to warm to room temperature. Shake the sample vigorously to mix it.

4. Remove the plunger from a 10-mL or larger Luer-lock plastic syringe equipped with an Acrodisc Luer-lock filter containing a 1.5-μm glass fiber filter (Whatman 934-AH, or equivalent), and fill the syringe body with sample.

5. Replace the plunger and filter the sample into a clean COD vial or other suitable container.

6. Additional 10-mL volumes of sample may be filtered and the filtrate added to separate containers, as needed, to provide samples for repeat analyses or to prepare QC samples.

7. Analyze the sample using a method approved for COD in Table 1B at 40 CFR part 136.

8. Report the sample results as Soluble COD in units of mg/L. There is no CAS Registry Number for soluble COD.