Sampling procedures, chain of custody forms, QA/QC controls, parameter reference table, and lab calculators — everything you need for the lab section of your certification exam.

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Microbiological Sampling (Total Coliform / E. coli)

O. Reg. 170/03 Schedule 10 — sampling frequency and locations

Use sterile, pre-labelled sample bottles with sodium thiosulfate (Na₂S₂O₃) dechlorinating agent
Remove aerator/screen from tap — do not sample through filters or softeners
Flame or disinfect the tap with 70% isopropyl alcohol and allow to dry
Run cold water for 2–3 minutes to flush the service line
Fill bottle without touching the inside of cap or bottle neck — do not overfill
Label immediately: sample ID, location, date, time, collector name
Keep at 4°C during transport — deliver to lab within 24 hours (6 hours preferred)

💡 EXAM TIP Sodium thiosulfate neutralizes residual chlorine to prevent false negatives. Bottles must be pre-dosed by the lab.

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Chlorine Residual (Free & Total)

O. Reg. 170/03 — minimum 0.05 mg/L free chlorine at point of consumption

Measure in the field immediately — chlorine dissipates rapidly after collection
Use DPD colorimetric method (DPD #1 = free chlorine, DPD #3 = total chlorine)
Rinse the sample cell 3× with sample water before filling
Add DPD reagent tablet or powder — do not touch reagent with fingers
Read within 1 minute of adding reagent — colour fades over time
Record result, sample location, time, temperature, and operator name
Calibrate comparator or photometer before each sampling event

💡 EXAM TIP Free chlorine = hypochlorous acid (HOCl) + hypochlorite (OCl⁻). DPD #1 measures free Cl₂ only. DPD #3 measures combined + free (total).

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Turbidity Sampling

O. Reg. 170/03 — treated water turbidity ≤ 1 NTU (target ≤ 0.3 NTU for GUDI sources)

Use a calibrated turbidimeter (NTU or FTU scale)
Rinse the sample cell 3× with sample water
Fill cell completely — avoid air bubbles which cause false high readings
Wipe outside of cell with lint-free cloth before inserting into instrument
Record NTU value, date, time, location, and instrument ID
Calibrate with AMCO-AEPA standards (0.1, 1.0, 10, 100 NTU) per manufacturer schedule
For continuous monitoring, verify against grab sample at least weekly

💡 EXAM TIP Turbidity is measured in NTU (Nephelometric Turbidity Units). High turbidity shields pathogens from disinfection — it must be controlled BEFORE chlorination.

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pH Sampling

O. Reg. 169/03 — aesthetic objective pH 6.5–8.5 for drinking water

Calibrate pH meter with 2-point calibration (pH 4.0 and 7.0 buffers, or 7.0 and 10.0)
Rinse electrode with distilled water and blot dry between calibration and sample
Allow electrode to stabilize in sample — wait for stable reading (±0.01 pH units)
Measure temperature simultaneously — pH is temperature-dependent
Record pH, temperature, date, time, location, and meter ID
Rinse electrode with distilled water after use and store in storage solution
Replace electrode if slope is outside 95–105% range during calibration

💡 EXAM TIP pH affects chlorine effectiveness: at pH 6.5, ~90% of chlorine is HOCl (effective). At pH 8.5, ~10% is HOCl. Lower pH = better disinfection but more corrosive.