Temperature Transmitter for Water Treatment: Corrosion-Resistant Wastewater and Aeration Basin Monitoring

Temperature Transmitter for Water Treatment and Wastewater Plants

Water and wastewater plants run outdoors, in humidity and around chlorinated or brackish media. This application case covers the temperature measurement points that keep biological treatment, disinfection and heat exchange stable: raw-water intake, aeration basins, UV disinfection inlet, and sludge and return-water lines.

Real Working Condition

• Aeration basins: process water held near ambient to 35 °C, splashed and constantly humid.
• Chlorinated / brackish water: aggressive media that attack ordinary carbon-steel housings.
• Wet wells and pump stations: submerged or high-humidity installation with condensation risk.
• Heat exchangers and sludge lines: 40–60 °C with abrasive solids.

Customer Pain Points

• Galvanic corrosion: brass and low-grade stainless fittings pitted within a season in chlorinated water.
• Humidity ingress: moisture reached the electronics in wet wells, causing erratic readings.
• Signal degradation: millivolt sensor signals faded over the long cable runs to the central SCADA panel.
• Surge damage: nearby pumps and lightning transients damaged transmitter circuits.

Engineering Selection

The site used the QW-SLS65 integrated temperature transmitter (selectable 4–20 mA / 0–20 mA / 0–5 V output) for its flexible interfacing to existing PLC cards. For corrosive duties the QW-SLS60 anticorrosive thermal resistor was chosen, and the QW-SLS66 split temperature transmitter handled points where the head and electronics had to be separated.

Installation Logic

• Thermowell of sufficient immersion length keeps the element below the splash zone and in the representative flow.
• An on-site 4–20 mA conversion at the transmitter head carries a strong signal that resists electrical noise over long runs.
• Inline surge-protection modules are fitted at the field end of each loop.
• Cable glands and IP68 sealing protect the wet-well junction boxes; heads are shaded from direct sun.

Results

Because the signal is converted at the point of measurement, readings stay stable over long runs. Corrosion-resistant wetted parts tolerate chlorinated and brackish water, and the sealed housing resists condensation, keeping the biological and disinfection loops within control limits.

Procurement Decision

Specify the correct IP rating for submerged or high-humidity points, confirm wetted-material compatibility with chlorine and solids, check surge-protection options, and match the output type to the existing control card. Value buyers should compare total installed cost rather than unit price alone, since corrosion failures drive repeat labour and downtime.