Chemical Feed Systems & Dosing Flashcards

What is the primary purpose of a backpressure check valve installed on a chemical injection line?

Answer: To prevent process water from siphoning back into the chemical feed system

A check valve prevents backflow of process water into chemical feed lines, protecting the feeder equipment and preventing cross-contamination.

Which chemical is appropriate for neutralizing an acid spill in a water treatment plant chemical storage area?

Answer: Soda ash (sodium carbonate)

Soda ash is an alkaline chemical that safely neutralizes acid spills by reacting with acids to form neutral salts and water.

A plant must achieve a fluoride dose of 0.7 mg/L at a flow of 4 MGD. How many pounds of fluoride compound must be fed per day?

Answer: 23.35 lbs/day

Using Dose × Flow × 8.34: 0.7 mg/L × 4 MGD × 8.34 = 23.35 lbs/day.

Calcium hypochlorite (Ca(OCl)2) is best described as which type of chemical?

Answer: A granular or tablet oxidizing disinfectant

Calcium hypochlorite is a solid (granular or tablet) form of chlorine used as a disinfectant with approximately 65–70% available chlorine.

What is the OSHA permissible exposure limit (PEL) for chlorine gas in the workplace?

Answer: 1.0 ppm (ceiling)

OSHA sets a ceiling PEL of 1.0 ppm for chlorine gas, meaning workers must never be exposed to concentrations above this level.

Which factor most directly affects the required chemical dose for coagulation in a water treatment plant?

Answer: Source water turbidity and temperature

Raw water turbidity and temperature directly affect coagulant demand — high turbidity and cold water typically require higher doses to achieve effective coagulation.

What is the primary regulatory purpose of maintaining a chemical feed log in a water treatment plant?

Answer: To document doses applied, verify compliance, and support regulatory reporting

Chemical feed logs document dosing history for process control, troubleshooting, and compliance with state and federal regulatory reporting requirements.