Public Water Supply
Public Water Supply
This domain tests how Oklahoma public water systems protect drinking water from source to tap: system classification, treatment and disinfection, distribution pressure and cross-connection control, monitoring and reporting, and operator certification. Oklahoma DEQ administers the federal Safe Drinking Water Act in the state; OWRB manages water rights and planning. Know the definition of a public water system: it provides water for human consumption through pipes to at least 15 service connections or regularly serves at least 25 people for at least 60 days per year.
Core rules and concepts
- Community, nontransient noncommunity, and transient noncommunity systems have different monitoring and operator requirements.
- Treatment must provide adequate disinfection. Free chlorine residual and contact time produce CT; required CT depends on pathogen, pH, temperature, and log inactivation.
- Distribution systems must maintain pressure and residual, prevent backflow, and collect bacteriological samples at approved sites.
- Chemical dose calculations use pounds = mg/L × MGD × 8.34. Detention time = volume ÷ flow, with matching units.
- Consumer Confidence Reports summarize detected contaminants; failures and monitoring violations have reporting deadlines.
Worked example
A 1,000-foot section of 12-inch main is full of water. What is the contact time at 100 gpm? Area = πr² = π(0.5 ft)² = 0.785 ft²; volume = 0.785 ft² × 1,000 ft = 785 ft³. Convert: 785 ft³ × 7.48 gal/ft³ = 5,872 gal. At 100 gpm, detention = 5,872 ÷ 100 = 58.7 min. If free chlorine is 0.5 mg/L, CT = 0.5 × 58.7 = 29.4 mg·min/L. Compare that CT to the required value for the actual pH, temperature, and target inactivation; do not assume it is adequate.
Traps
Using total chlorine instead of free chlorine; ignoring short-circuiting in tanks; mixing gpm with million gallons; reporting a bacteriological positive late; and treating a maximum contaminant level as a maximum residual disinfectant level.