MS Water Operator cheat sheet

CT (contact time × residual) determines disinfection credit; CT required rises as pH, temperature, and turbidity increase, so colder water demands more chlorine contact time.

Free chlorine residual target in distribution: detectable at all points, typically ≥0.2 mg/L; 4-log virus inactivation is a common CT-based goal under the Surface Water Treatment Rule.

Conventional treatment sequence: coagulation → flocculation → sedimentation → filtration → disinfection; jar tests set coagulant dose and optimal pH.

Turbidity limits: combined filter effluent ≤0.3 NTU in 95% of monthly samples and never >1 NTU for conventional filtration; individual filter effluent action at 1.0 NTU.

Filter backwash triggers: headloss limit, turbidity breakthrough, or run-time cap (commonly 30-100 hours); backwash rate must expand media bed about 20-30%.

Alkalinity and pH govern coagulation: alum consumes about 0.45 mg/L alkalinity per mg/L dose; add lime or caustic if alkalinity is insufficient.

Fluoride optimum is temperature-dependent (roughly 0.7-1.2 mg/L); the MCL is 4.0 mg/L and the secondary standard is 2.0 mg/L.

Disinfectant residual measurement: DPD colorimetric method for free/total chlorine; amperometric titration is an approved alternative for interference-prone samples.

Minimum residual pressure under normal conditions is commonly 20 psi; during main breaks or fire flow it must not drop below 20 psi at any point.

Hydrant flow test formula: Q = 29.83 × C × d² × √P, where d is nozzle diameter (in) and P is pitot pressure (psi); C is the discharge coefficient.

Storage tank turnover: tank volume divided by average daily demand gives detention time in days; long detention degrades residual and raises DBPs.

Water main disinfection after installation: chlorinate to 25 mg/L for 24 hours (or 50 mg/L for 24 hours), flush, and confirm two consecutive negative bacteriological samples 24 hours apart.

Dead-end flushing frequency is set by residual and bacteriological history; flushing velocity should exceed 2.5 ft/s to scour biofilm and sediment.

Pressure test for new mains: 1.5 times working pressure or 150 psi, whichever is greater, held for at least 2 hours with allowable leakage per AWWA formula.

Backflow prevention: air gap is the highest protection; reduced-pressure zone assemblies protect against both backpressure and backsiphonage; test annually.

Groundwater under direct influence (GWUDI) of surface water must meet surface water treatment rules; determined by site-specific hydrogeologic and microbial study.

Wellhead protection: sanitary seal, grout to required depth, and a casing extending above grade; the wellhead protection area is delineated by time-of-travel (commonly 1-year and 5-year zones).

Specific capacity = pumping rate ÷ drawdown (gpm/ft); declining specific capacity indicates well screen or aquifer clogging.

Darcy's law: Q = K × i × A; hydraulic conductivity K, gradient i, cross-sectional area A.

Static water level is measured before pumping; pumping water level is measured during pumping; drawdown is the difference.

Confined aquifers are bounded by low-permeability layers and are under pressure (artesian); unconfined aquifers have a water table open to the atmosphere.

Source water assessment: inventory potential contaminant sources, assess susceptibility, and make results public; source water protection plans follow state programs.

Total coliform rule: routine samples per month scale with population; any total coliform-positive routine sample triggers repeat samples within 24 hours (three repeats for a single-sample site).

E. coli-positive repeat triggers public notice within 24 hours; total coliform MCL is exceeded when >5% of samples (or ≥2 for systems with <40 samples/month) are positive.

Stage 2 Disinfectants and Disinfection Byproducts Rule: LRAA TTHM MCL 80 µg/L, HAA5 MCL 60 µg/L; monitoring at each location is based on the highest TTHM/HAA5 LRAA.

Lead and Copper Rule: action level 0.015 mg/L lead and 1.3 mg/L copper at the 90th percentile; corrosion control treatment optimization and public education required on exceedance.

Consumer Confidence Report (CCR) must be delivered by July 1 each year covering the prior calendar year; includes source water, detected contaminants, and health effects language.

Public notification tiers: Tier 1 within 24 hours (acute health risk), Tier 2 within 30 days, Tier 3 within one year (annual CCR can satisfy Tier 3).

Operator certification: each state sets certification requirements and continuing education; AWWA and state primacy agencies administer exams and renewals.

Confined space entry requires permit, atmospheric testing (oxygen 19.5-23.5%, LEL <10%, H2S <10 ppm, CO <35 ppm), ventilation, attendant, and rescue plan.

Chlorine gas is heavier than air; use SCBA and upwind approach; never use ammonia or acid to detect leaks.

Lockout/tagout: isolate all energy sources, apply locks and tags by each worker, verify zero energy before work.

Excavation protection required at 5 ft depth or greater: sloping, shoring, or trench box; spoil pile at least 2 ft from edge; ladder within 25 ft of workers.

Hazard communication: Safety Data Sheets for each chemical, container labeling, and employee training on hazards and PPE.

Electrical safety: ground-fault protection, maintain 10 ft clearance from energized lines, and use nonconductive ladders near electrical hazards.

Ladder and fall protection: fall protection at 4 ft in general industry, 6 ft in construction; inspect ladders before each use.

Duty to warn and public notice: Tier 1 notices within 24 hours, Tier 2 within 30 days, Tier 3 within one year; maintain documentation of delivery methods.

Recordkeeping: bacteriological and chemical sample results, CT calculations, and operation records retained per state rule (commonly at least 3-5 years; some records longer).

Budgeting: separate operating and capital budgets; rate structure should cover O&M, debt service, and reserves.

Asset management: inventory, condition assessment, criticality, and renewal planning; prioritize by risk = probability × consequence.

Emergency response plan: identify hazards, roles, communication, and alternate water sources; test annually and update after changes.

Cross-connection control program administration: maintain device inventory, require annual testing, and track test reports.

Operator certification and staffing: confirm certification level required by system classification and ensure adequate staffing for coverage and emergencies.