IDNR Laboratory Certification


IDNR Laboratory Certification

Basic Analytes For Wastewater

The certification process involves an evaluation of a number of facets of each laboratory seeking certification. In addition to specific criteria and/or general guidelines given in the laboratory certification manual and analytical procedures the following quality assurance checks are required or recommended. A detailed written explanation or authorized substitution may be required for recommendations which are not followed.


DO meters require calibration each day of use. (Required)

When "air calibrating" the DO meter use the true barometric pressure at the time of calibration instead of the average barometric pressure based on altitude. (Recommended)

Dilution water blanks are necessary with each set of BOD (CBOD) analysis. (Required) If nitrification inhibitor is used in samples it must also be added to at least one distilled water blank. (Recommended)

Periodic check of dilution water quality, seed effectiveness, and analytical technique are required by making a BOD measurement on pure organic compounds (normally a glucose/glutamic acid mixture). (Required) How often this is done depends upon the sample load of the laboratory, but in general if a laboratory analyzes samples once a week or less frequently, it should be done at least quarterly. If the sample load is such that the laboratory analyzes samples daily, the glucose/glutamic acid check should be done at least weekly. (Recommended)

Duplicate analysis should be run on at least one sample each time BODs are analyzed. If more than ten samples are being analyzed one of each ten samples should be set up with a duplicate set of dilutions. (Recommended)

Ammonia (NH3-N) as N

EPA requires samples be distilled prior to analysis unless comparative data for each sample source is on file at the laboratory demonstrating comparable analytic results between distilled and non-distilled portions of the sample. (Required) Comparative data should be based on a sufficient number (generally 30 required, but may be less in some circumstances) analytical comparisons performed over a sufficient time period to validate NH3 levels as they change with seasons. After initial comparison is completed periodic comparisons should be performed to insure comparability has not changed. (Recommended)

A reagent blank, a check (reference) standard, duplicate and spiked quality control samples should be run each time samples are analyzed. (Recommended)

Total Suspended Solids (TSS)

If using EPA or SM-18 method, filters weight must be shown to be at constant weight both after washing and after filtration and drying of sample. Constant weight is defined as weight change of 4% or 0.5 mg (0.0005g) whichever is LESS. (Required)

Quality control should consist of duplicate analysis of 10 % of samples analyzed and quarterly analysis of a known concentration reference sample. (Recommended)