WTO Chemical Feed Systems & Dosing 2

Question 1

What type of pump is most commonly used for metering chemicals in water treatment plants?

Accepted Answer

Diaphragm metering pump

Answer

Diaphragm metering pumps deliver accurate, adjustable flow rates at high pressures, making them ideal for precise chemical dosing.

Question 2

Which chemical is typically added to water to raise pH for corrosion control in the distribution system?

Accepted Answer

Lime (calcium hydroxide)

Answer

Lime increases water pH, which reduces corrosion of distribution system pipes and limits lead and copper leaching into drinking water.

Question 3

When a 150-lb chlorine cylinder is being connected and there is risk of chlorine gas release, which personal protective equipment is required?

Accepted Answer

SCBA or supplied-air respirator with full-face protection

Answer

Chlorine gas is immediately dangerous to life and health (IDLH) at 10 ppm; SCBA or supplied-air respirators with full-face protection are required.

Question 4

A gas chlorinator feeds at 8 lbs/day and plant flow is 2 MGD. What is the applied chlorine dose in mg/L?

Accepted Answer

0.48 mg/L

Answer

Dose (mg/L) = Feed rate ÷ (Flow × 8.34): 8 lbs/day ÷ (2 MGD × 8.34) = 8 ÷ 16.68 = 0.48 mg/L.

Question 5

What does 'flow-paced' chemical feeding mean?

Accepted Answer

Automatically adjusting chemical feed rate proportional to plant flow

Answer

Flow-paced feeders automatically vary the chemical feed rate in direct proportion to water flow, maintaining a consistent dose as flow changes.

(WTO) Water Treatment Operator Certification Practice Test