WTO Cheat Sheet 2026

The 30 highest-yield WTO facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What is the role of the Occupational Safety and Health Administration (OSHA) in water treatment? → To enforce workplace safety standards for employees
2. A circular clarifier has a diameter of 80 feet and a water depth of 15 feet. If the plant flow is 4.0 MGD, what is the detention time in hours? → 3.37 hours
3. Which device is installed at a customer service connection to allow the utility to shut off water supply without entering private property? → Curb stop
4. A fluoride concentration of 2.0 mg/L is detected in a community water system. What regulatory action is triggered? → A primary MCL violation requiring public notification
5. During the water treatment process, what is the correct sequence for coagulation and flocculation? → Rapid mixing followed by slow mixing.
6. When evaluating filter performance under the Surface Water Treatment Rule (SWTR), the maximum allowable combined filter effluent (CFE) turbidity is: → 0.3 NTU in 95% of samples per month
7. What unit is used to express chlorine residual in a distribution system? → Milligrams per Liter (mg/L)
8. Which of the following best describes 'hardness' in water? → The concentration of dissolved calcium and magnesium ions
9. What is the significance of the 'dead end' sections in a water distribution system from a water quality standpoint? → They cause stagnation, chlorine residual loss, and increased microbial growth risk
10. Which of the following pathogens is regulated under the Surface Water Treatment Rule (SWTR) and requires 3-log removal/inactivation? → Giardia lamblia
11. What is the primary regulatory purpose of maintaining a chemical feed log in a water treatment plant? → To document doses applied, verify compliance, and support regulatory reporting
12. Which filter media characteristic is described by the uniformity coefficient (UC)? → The ratio of d60 to d10, describing the range of grain sizes
13. When performing a routine inspection of a chemical metering pump, the operator notices the diaphragm is cracked. What is the appropriate immediate action? → Replace the diaphragm before resuming chemical feed
14. Which of the following water quality parameters is a measure of the water's ability to neutralize acids and acts as a buffer against pH changes? → Alkalinity
15. Why are water treatment operators required to have certifications? → To ensure knowledge of water quality regulations and safety procedures
16. Under the Safe Drinking Water Act (SDWA), which agency has primary enforcement authority over public water systems? → EPA
17. What is the maximum contaminant level (MCL) for total trihalomethanes (TTHMs) in drinking water under the EPA Stage 2 D/DBP Rule? → 0.080 mg/L
18. Why are backflow prevention devices important in water distribution systems? → To prevent contamination of the water supply
19. What is the action level for copper under the Lead and Copper Rule that triggers additional treatment requirements? → 1.3 mg/L
20. The term 'hydraulic grade line' (HGL) in a water distribution system represents: → The elevation to which water would rise in a piezometer tube at any point in the system
21. The ratio of bicarbonate, carbonate, and hydroxide ions in source water determines its: → Alkalinity
22. Under the Revised Total Coliform Rule (RTCR), what triggers a Level 2 assessment? → Multiple positive total coliform samples meeting a defined threshold
23. What does a CT value represent in disinfection calculations? → Disinfectant concentration (mg/L) multiplied by contact time (minutes)
24. What type of sedimentation basin uses a rotating rake mechanism to collect settled sludge at a central drain? → Circular clarifier
25. How can water distribution systems reduce energy consumption? → By improving system efficiency and reducing friction losses
26. Fire hydrant flow testing is conducted primarily to: → Determine available flow and residual pressure for fire suppression
27. What is the purpose of a Vulnerability Assessment (VA) required for large public water systems under the Bioterrorism Act of 2002? → Evaluate susceptibility of the system to deliberate attack or sabotage
28. A three-phase motor is running on two phases only due to a blown fuse. What will most likely happen? → The motor will overheat and may burn out
29. What is the most likely cause of a centrifugal pump that runs but delivers no water? → Motor rotating in the wrong direction
30. What is the maximum disinfectant residual level (MRDL) for chlorine in a public water system under the DBPR? → 4.0 mg/L