Chemical Feed Systems & Dosing Flashcards

What is the standard conversion factor used to calculate chemical feed rates in pounds per day from a dosage in mg/L and flow in MGD?

Answer: 8.34

The factor 8.34 lb/gal is the weight of one gallon of water, used in the formula: Dose (mg/L) × Flow (MGD) × 8.34 = Feed rate (lbs/day).

A treatment plant processes 3 MGD and must apply 12 mg/L of alum. How many pounds of alum are required per day?

Answer: 300.24 lbs/day

Using the formula Dose × Flow × 8.34: 12 mg/L × 3 MGD × 8.34 = 300.24 lbs/day.

Which type of chemical feeder is most appropriate for feeding powdered activated carbon (PAC)?

Answer: Dry chemical feeder

Dry chemical feeders are designed to accurately meter powdered or granular chemicals such as PAC into the treatment stream.

What is the primary purpose of a day tank in a chemical feed system?

Answer: To dilute concentrated chemicals and provide a measured daily supply

Day tanks hold a diluted chemical solution prepared for approximately one day's use, ensuring consistent and safe dosing to the process.

What is the EPA-recommended target concentration for fluoride in drinking water, updated in 2015?

Answer: 0.7 mg/L

The EPA updated the recommended fluoride level to 0.7 mg/L in 2015 to prevent dental fluorosis while still providing cavity protection.

A solution feeder pumps 60 gallons per day of a 5% sodium hypochlorite solution. What is the daily feed rate in pounds of hypochlorite solution?

Answer: 25.02 lbs/day

Multiply volume by the weight of water and the solution concentration: 60 gal/day × 8.34 lb/gal × 0.05 = 25.02 lbs/day.

Which chemical is commonly used as a primary coagulant in water treatment?

Answer: Ferric sulfate

Ferric sulfate is a primary coagulant that destabilizes negatively charged suspended particles, allowing them to aggregate for removal.