WTO Chemical Feed Systems & Dosing

Question 1

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?

Accepted Answer

8.34

Answer

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).

Question 2

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

Accepted Answer

300.24 lbs/day

Answer

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

Question 3

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

Accepted Answer

Dry chemical feeder

Answer

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

Question 4

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

Accepted Answer

To dilute concentrated chemicals and provide a measured daily supply

Answer

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

Question 5

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

Accepted Answer

0.7 mg/L

Answer

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

(WTO) Water Treatment Operator Certification Practice Test