A new Dissolved Oxygen (DO) monitor and ORP monitor with automatic sensor cleaning from Process Instruments, via its North American municipal water and waste water partner (Chemtrac Inc.), has recently been installed by Shupe and Associates out of North Little Rock AR.
The DO and ORP readings are used to help control The Lakeside oxidation ditch and the waste sludge holding tank. The Lakeside control panel uses the DO reading to control the speed of the brush aerators to maintain the plant operator’s entered DO value. The ORP sensor is used to keep the waste sludge slightly aerobic. The ORP value is sent to the Primex in-plant SCADA panel that turns on/off a blower feeding air to a fine bubble grid in the tank based on the operator entered start/stop ORP readings.

Chemtrac HA2 and AirFlush Compressor
Pi’s AirFlush Automatic Sensor Cleaning and Verification
The analyzer was equipped with both a DO sensor and an ORP (Redox) sensor along with an AirFlush compressor to automatically clean the DO and ORP sensor. The DO sensor and AirFlush combination is designed to not only keep the DO sensor clean, but also to verify the sensor readings every time the sensor is cleaned. It does this by the force of the AirFlush excluding the water from the face of the sensor (even though it is still submerged). The sensor then sees the change in oxygen levels and if the sensor is operating correctly, the reading changes in a predictable way thereby verifying that the sensor is operating correctly.
Bull Shoals, AR Wastewater Treatment Plant





