Which instrument is used to measure dissolved oxygen in an activated sludge process?

• A. DO meter
• B. Settleometer
• C. Sludge blanket finder
• D. Flow meter

Answer: (A)

Dissolved oxygen in the activated sludge process is what you monitor to ensure the aerobic microbes have enough oxygen to treat the waste. The instrument used to measure this is a DO meter, which uses an oxygen-sensitive sensor to determine the concentration of oxygen in the mixed liquor (typically in mg/L). This direct measurement lets you maintain DO at the proper level for efficient biological treatment and energy efficiency.

The other instruments serve different purposes: a settleometer evaluates how well solids settle, a sludge blanket finder estimates the depth of the sludge blanket in the clarifier, and a flow meter measures the rate of liquid flow. None of these provide the dissolved oxygen concentration, so they aren’t suitable for monitoring oxygen availability in the process.