Sampling, Laboratory Tasks, and Regulatory Recordkeeping

Why Sampling, Lab Work, and Recordkeeping Matter

Every permit limit, treatment decision, and regulatory report rests on two things: a sample that truly represents what is in the water, and a record that honestly captures what happened. A flawed sample or a careless entry can cause a facility to miss a violation, report false data to regulators, or make the wrong treatment adjustment. State licensing boards and the EPA treat falsified or negligent records as serious violations. As a licensed operator, your signature on a report is a legal declaration that the information is accurate.

Collecting Representative Samples

Grab samples capture conditions at one moment in one place. Use them when you need a snapshot—for example, chlorine residual at the distribution system tap or influent pH before a treatment step.

Composite samples blend multiple grab sub-samples collected over time (or at multiple locations) to average out short-term swings. They are common for daily BOD and TSS monitoring at wastewater facilities.

Before you collect any sample, confirm three things with your supervisor and the lab's standard operating procedure (SOP):

1. Container type – Some analytes require glass; others require plastic. Containers may be pre-preserved by the lab.

2. Preservation method – Temperature (ice to ≤6 °C is common), chemical addition (such as sulfuric acid for BOD or ammonia samples), or keeping samples in the dark may all be required.

3. Holding time – The maximum time from collection to analysis. Exceeding the holding time invalidates the sample. Write the collection time on the label immediately.

Collect samples away from foam, dead spots, and the very surface or bottom unless the method specifically requires otherwise. Rinse the container twice with sample water unless it is pre-preserved or sterile (never rinse a coliform container). Label every container before you fill it: sample location, date, time, your name, and preservative added.

Chain-of-Custody (COC) Documentation

A chain-of-custody form is the legal record of who handled the sample from the moment of collection to the moment of analysis. Fill in every field: sample ID, location, collection date and time, preservative, required analyses, collector's name, and temperature at collection. Each person who receives the sample signs and dates the form. Seal sample containers with custody seals if required. Do not let samples leave the site without a completed, signed COC. Your supervisor must review the form before release.

On-Site Laboratory Tests

Many critical measurements are made in the field or in the plant lab because results are needed immediately for process control. Common tests include:

• pH – Use a calibrated pH meter. Calibrate with at least two buffer solutions that bracket the expected range before each use. Rinse the probe with deionized water between samples.
• Turbidity – Calibrate the turbidimeter with standards traceable to Formazin or AMCO-AEPA standards. Read in nephelometric turbidity units (NTU).
• Chlorine residual – DPD colorimetric method is most common. Follow the reagent manufacturer's instructions exactly; timing affects the result.
• Dissolved oxygen (DO) – Membrane electrode or optical probe. Calibrate according to manufacturer instructions; record water temperature alongside DO.
• BOD setup and incubation – Dilute sample, measure initial DO, incubate at 20 °C for five days, measure final DO.

Record every result on the bench sheet immediately—never from memory later. Note the instrument ID and calibration date. Compare results to permit limits or process targets and note any value that requires follow-up. If a result seems out of range, re-check calibration, re-run the test if holding time allows, and notify your supervisor.

Safety in the Lab and at Sampling Points

• Wear the PPE required for each task: safety glasses, nitrile gloves, and a lab coat or coveralls for chemical handling; steel-toed boots and a hard hat at outdoor sampling points.
• Acids and bases used for preservation are corrosive. Keep the SDS accessible. Never add water to concentrated acid—add acid to water.
• Biological samples (coliform, wastewater) are potential biohazards. Wash hands thoroughly after handling.
• Follow lockout/tagout (LOTO) procedures if accessing any sampling point that requires isolating energy—never reach into a confined space or near rotating equipment without following facility confined-space and LOTO protocols.
• Dispose of chemical waste from lab tests according to the facility's waste disposal SOP; never pour reagents down a drain without authorization.

Regulatory Operating Reports

Daily and monthly operating reports (also called discharge monitoring reports or DMRs at wastewater facilities) are official regulatory documents submitted to the state agency. Key rules:

• Copy directly from source data. Transcribe instrument readings, bench sheets, and lab reports—do not estimate or round beyond the number of significant figures your method supports.
• Fill every required field. A blank field is a critical error. If a measurement was not taken, note why (equipment down, no flow, etc.).
• Units must match the permit. mg/L is not the same as µg/L; MGD is not the same as gpd.
• Math must be correct. Check averages, totals, and unit conversions before signing.
• Supervisor review before filing. Your supervisor will provide written feedback; correct every noted error before the final version is filed.

Falsifying any entry on a regulatory report is a criminal offense under federal and most state laws. If you make an honest mistake, correct it promptly and transparently, following the facility's error-correction procedure.