IA Water Operator cheat sheet

Conventional treatment sequence: coagulation → flocculation → sedimentation → filtration → disinfection.

CT = disinfectant residual concentration (mg/L) × contact time (minutes); required CT depends on disinfectant, temperature, pH, and log inactivation target.

Log inactivation: 1-log = 90% removal, 2-log = 99%, 3-log = 99.9%, 4-log = 99.99%.

Filter loading rate = flow (gpm) ÷ filter area (ft²); rapid sand filters typically 2–5 gpm/ft².

Backwash rate must expand filter media 15–25%; typical rate 15–20 gpm/ft² for sand, 20–25 gpm/ft² for anthracite.

Jar test determines optimal coagulant dose and pH by simulating coagulation/flocculation/sedimentation on a bench scale.

Turbidity limits: conventional filtration must produce ≤0.3 NTU in 95% of monthly samples and never exceed 1 NTU.

Chlorine demand = applied dose − residual after contact time; demand must be satisfied before free residual persists.

Minimum residual disinfectant in distribution: 0.2 mg/L free chlorine (or 0.5 mg/L chloramine) at all points.

Distribution system pressure must be maintained at ≥20 psi under normal conditions; never allow negative pressure.

Water hammer prevention: slow valve closure, surge tanks, air valves, and proper pump startup/shutdown sequencing.

Pipe flow: Q = A × V; for a full circular pipe, A = π × (D/2)², so Q (cfs) = 0.7854 × D² (ft) × V (ft/s).

Hazen-Williams head loss: hf = 4.52 × Q^1.852 × C^-1.852 × d^-4.87 (Q in cfs, d in ft, C = roughness coefficient).

Cross-connection control: air gap is the only absolute backflow prevention; RPZ and PVB are testable mechanical devices.

Storage tank turnover: maintain minimum 3–5 day turnover to prevent stagnation and disinfectant decay.

Leak detection: acoustic listening, correlators, and step testing; unaccounted-for water above 10–15% warrants investigation.

Groundwater under direct influence (GWUDI) of surface water: must be treated as surface water under the Surface Water Treatment Rule.

Well drawdown = static water level − pumping water level; specific capacity = pumping rate ÷ drawdown (gpm/ft).

Cone of depression: drawdown shape around a pumping well; radius depends on pumping rate, transmissivity, and storativity.

Aquifer types: unconfined (water table) vs confined (artesian); confined aquifers are protected by a confining layer and less vulnerable to surface contamination.

Source water assessment: delineate protection area, inventory potential contaminants, determine susceptibility.

Surface water turbidity and pathogen spikes follow rainfall events; monitor raw water turbidity and adjust coagulant dose accordingly.

Saltwater intrusion: occurs when pumping lowers freshwater head below seawater interface; managed by reducing pumping or recharge barriers.

Total maximum daily load (TMDL): maximum pollutant load a waterbody can receive and still meet standards; affects source water protection planning.

Safe Drinking Water Act (SDWA) authorizes EPA to set national primary drinking water regulations (NPDWRs).

Maximum contaminant level (MCL) is an enforceable limit; maximum contaminant level goal (MCLG) is a non-enforceable health goal.

Total coliform rule: no more than 5% of monthly samples positive for total coliform (systems >40 samples/month); any E. coli positive is a violation.

Stage 2 Disinfectants and Disinfection Byproducts Rule: TTHM MCL = 80 µg/L, HAA5 MCL = 60 µg/L, based on locational running annual average (LRAA).

Lead and Copper Rule: action level Pb = 0.015 mg/L, Cu = 1.3 mg/L; 90th percentile calculation determines compliance.

Consumer Confidence Report (CCR) must be delivered to customers by July 1 each year and include source water, detected contaminants, and health effects.

Public notification: Tier 1 (immediate, 24 hours) for acute violations; Tier 2 (30 days) and Tier 3 (annual) for less urgent violations.

Operator certification: state primacy agencies set certification requirements, training hours, and renewal cycles under SDWA.

Confined space entry: test atmosphere for oxygen (19.5–23.5%), flammables (<10% LEL), and toxics before entry; permit required.

Chlorine gas: IDLH = 10 ppm; use supplied-air respirator, not air-purifying, for chlorine response; evacuate upwind.

Hazardous energy control (lockout/tagout): isolate, lock, tag, and verify zero energy before maintenance on pumps or electrical equipment.

Ladder safety: 4:1 ratio (1 ft horizontal for every 4 ft vertical); extend 3 ft above landing.

Excavation: spoil pile at least 2 ft from edge; trench deeper than 5 ft requires protective system (shoring, sloping, or shielding).

Chemical splash: eyewash and safety shower within 10 seconds travel distance; flush eyes for at least 15 minutes.

Electrical safety: GFCI protection required for portable tools in wet locations; maintain 10 ft clearance from overhead power lines.

Bloodborne pathogens: use universal precautions, PPE, and proper disposal for potentially infectious materials.

Turbidity measured by nephelometry in NTU; calibrate with primary standards (formazin or approved alternatives) and verify with secondary standards.

pH: measure with calibrated electrode; buffers at pH 4, 7, and 10; calibrate daily or before each use.

Free chlorine: DPD colorimetric method (4500-Cl G); read absorbance at 515 nm; monochloramine interferes unless differentiated.

Total coliform: membrane filtration (0.45 µm) or enzyme substrate method; incubate at 35°C for 24 hours.

Heterotrophic plate count (HPC): pour plate method, incubate at 35°C for 48 hours; report as CFU/mL.

Jar test procedure: rapid mix 1–2 min at 200–300 rpm, flocculate 15–20 min at 20–40 rpm, settle 15–30 min, then sample.

Quality control: run method blank, duplicate, and matrix spike with each batch; acceptable duplicate RPD typically ≤20%.

Chain of custody: record sample ID, date/time, collector, preservation, and analysis requested; maintain from collection through reporting.