Why is it important to use Nitrification Inhibitors in BOD testing?

Document ID

Document ID TE3202

Published Date

Published Date 10/09/2019
Why is it important to use Nitrification Inhibitors in BOD testing?
Nitrification Inhibitors
Formula 2533 inhibits nitrification:

BOD determinations may be inadequate for evaluating efficiency of wastewater treatment processes if nitrifying bacteria are present. When nitrification interference exists, test results may overestimate the BOD of secondary effluents, resulting in an underestimation of the actual plant removal efficiency.

Hach's Formula 2533 (TM) Nitrification Inhibitor eliminates the nitrifying interference when testing samples such as biologically treated effluents (effluents from secondary treatment processes), samples seeded with biologically treated effluents, and river waters.** Nitrification Inhibitor can be used with either the USEPA-accepted BOD dilution method or with the BODTrak Apparatus. Results of BOD tests completed without Nitrification Inhibitor are referred to as total BOD, while tests with inhibitor are referred to as carbonaceous BOD (CBOD). Subtracting the CBOD from total BOD yields the nitrogenous BOD.

Formula 2533 Nitrification Inhibitor, 2-chloro-6-(trichloromethyl) pyridine [TCMP (Standard Methods for the Examination of Water and Wastewater, 18th edition. Hach offers bulk TCMP (Product # 257924), which is USEPA accepted. However, for ease of use, we recommend using Formula 2533 Nitrification Inhibitor, which dissolves quickly and completely. Formula 2533 Nitrification Inhibitor is cited in the 18th edition of Standard Methods 5210B 3.G)], is plated on an inert salt, which allows inhibitor to dissolve quickly in samples. An optional dispenser cap makes measurement of the inhibitor easy. Install the dispenser cap on the 35-gram reagent bottle. Using the dispenser cap, add two "shots" (0.08 grams/shot) of inhibitor to each BOD bottle, or add sufficient amounts to the dilution water to make a final concentration of 10 mg/L TCMP. If 60-mL BOD bottles are used, add approximately 0.03 grams to each bottle. All other steps in the BOD procedure remain the same. Note the use of Formula 2533 Nitrification Inhibitor when reporting test results.

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