10.6 Laboratory Equipment, Calibration and Verification, QA/QC Program & Certified Laboratory Requirements

The laboratory is a regulated instrument

WPI's Laboratory Analysis content area opens with ensure proper operation of laboratory equipment (calibration, verification, maintenance) and, in the wastewater outline, follow laboratory SOPs and operate and maintain laboratory instrumentation. Analytical data is the evidence behind every compliance report and every process decision, and it is only as good as the quality system behind it.

Certified laboratories and what operators may run

Colorado, like every primacy state, requires that compliance analyses for drinking water be performed by a laboratory certified for that method and analyte, either the state laboratory or a certified commercial laboratory. There is one important exception category: certain field measurements may be performed by the operator, including free and total chlorine residual, pH, temperature, turbidity, and dissolved oxygen, provided the operator uses an approved method, an instrument maintained and calibrated per the manufacturer, and documented procedures. Wastewater compliance analyses are likewise performed by laboratories meeting the permit's method requirements.

Everything else an operator runs at the plant bench is process control data. It is enormously valuable — settleometer tests, jar tests, sludge judge readings, MLSS by filtration, alkalinity titrations — but it is not compliance data unless the laboratory and method qualify.

Standard operating procedures

Every test the plant performs needs a written SOP identifying the method reference, the equipment, reagents and their preparation, the step-by-step procedure, the calculation, the quality control checks and acceptance criteria, and the corrective action when QC fails. SOPs are dated, approved, and revised under control, and a copy is at the bench. WPI lists "follow laboratory SOPs" and "establish and/or update SOPs" as job tasks in the wastewater outline.

Calibration versus verification

The distinction is tested and is worth stating precisely:

• Calibration establishes the relationship between the instrument's response and known standards. A turbidimeter is calibrated against formazin or an approved equivalent across its range. A pH meter is calibrated with at least two buffers that bracket the expected sample pH, commonly 7.00 and 4.00 or 7.00 and 10.00, and the meter reports a slope that should fall near 95 to 105 percent of theoretical.
• Verification confirms, between calibrations, that the instrument still reads a known value correctly. A turbidimeter is verified daily with sealed secondary standards; a pH meter is verified with a check buffer; a balance is verified with a check weight.

If verification fails, the instrument is recalibrated, and the operator must consider whether data generated since the last acceptable verification is defensible.

The quality control set

Precision is repeatability; accuracy is closeness to the true value. A method can be precise and wrong. Duplicates measure precision, and spikes and control samples measure accuracy.

Control charts plot QC results over time with warning limits at two standard deviations and control limits at three. A single point outside control limits, or a run of points trending in one direction, signals a problem before the data become unusable.

Equipment care

• Analytical balance. Level, on a stable surface away from drafts and vibration, verified with check weights, and calibrated on a schedule.
• Drying oven and muffle furnace. Thermometers verified against a NIST-traceable reference; temperatures recorded.
• Incubators. Recorded twice daily; total coliform incubation at 35 plus or minus 0.5 degrees Celsius, and thermometers NIST-traceable.
• BOD incubator at 20 plus or minus 1 degree Celsius, and dark to prevent algal photosynthesis.
• Refrigerator for sample storage at 6 degrees Celsius or below, recorded daily.
• Turbidimeter. Cells matched, scratch-free, clean, oiled with silicone, and indexed; sample degassed of bubbles.
• pH electrode. Stored in the manufacturer's storage solution — never in distilled water, which leaches the reference junction and destroys the electrode.
• Glassware. Class A volumetric glassware for compliance work, washed and rinsed by the SOP, and never dried with a towel inside.
• Reagents. Labeled with contents, concentration, preparation date, expiration, and preparer. Expired reagents are discarded.
• Thermometers. Each working thermometer verified annually against a NIST-traceable reference, with the correction factor recorded and applied.

Data handling and integrity

Bench sheets record the raw observation — the buret reading, the balance weight, the meter display — not just the calculated answer, along with date, time, analyst, method, instrument ID, and QC results. Errors are corrected with a single line, the correct value, initials, and date. Data are never selectively discarded: if a result is rejected, the reason is documented on the bench sheet.

This matters beyond good practice. Falsifying laboratory data supporting a compliance report is a criminal act and, under Regulation 100 section 100.13, grounds for suspension or revocation of a Colorado operator certificate.