The water treatment industry encompasses four core stages: "raw water intake - purified water treatment - sewage treatment - reclaimed water reuse". Level monitoring at each stage directly impacts process stability, effluent water quality, and operational costs. Traditional level measurement devices (such as float-type and submersible-type) often fail in water treatment scenarios due to issues like medium contamination (sediment, suspended solids), environmental interference (foam, corrosion), and frequent maintenance needs. Leveraging non-contact measurement, strong anti-interference capabilities, and low maintenance requirements, ultrasonic level transmitters have become core equipment for full-process level monitoring in water treatment. Their application requires customized design based on the operating characteristics of each stage.
Raw water intake marks the starting point of water treatment, with common scenarios including reservoirs, rivers, and groundwater intake points. The core monitoring requirement is to real-time track raw water storage to avoid process fluctuations caused by insufficient or excessive water intake. Below are the operating pain points of this stage and the adaptation solutions for ultrasonic level transmitters:
- Turbid Medium: Raw water contains large amounts of sediment and algae (e.g., river turbidity exceeds 500 NTU during flood seasons). Probes of traditional submersible level transmitters are prone to fouling, leading to significant measurement drift.
- Extreme Weather Interference: Weather events like heavy rains and typhoons cause sudden rises and drops in raw water levels. Turbulent water flow also generates waves, affecting measurement stability.
- Harsh Outdoor Environment: Intake points are mostly located outdoors, facing temperature variations from -20℃ to 40℃, high humidity, and lightning risks. Equipment must have high protection and lightning resistance capabilities.
- Choose models with an empty-load range 30% higher than the actual water intake depth (e.g., a 15-meter range for a 10-meter intake point) to reserve redundancy for signal attenuation caused by waves and sediment.
- Use probes made of 316L stainless steel (resistant to outdoor corrosion) with an IP68 protection rating. Some models are equipped with lightning protection modules (complying with GB/T 17626.5 standard) to resist lightning interference.
- Adopt a 24V DC wide-voltage power supply design to adapt to voltage fluctuations from outdoor generators or solar power systems.
- Enable the "wave filtering algorithm": Smooth level fluctuations caused by waves by averaging 10 sets of data within 10 seconds, reducing the data fluctuation range from ±10cm to ±2cm.
- Dynamic threshold adjustment: Adjust the echo detection threshold based on raw water turbidity (linked with on-site turbidity meters at the intake point). The threshold automatically increases when turbidity rises to avoid misjudgment caused by sediment-scattered signals.
- Install the probe at a position of the intake point away from water flow impact (e.g., the intake tower platform), and add a wave shield (made of metal or PVC) below to reduce the impact of water flow disturbance on the sound wave beam.
- For deep well intake points, use a "probe + waveguide tube" combination. The waveguide tube has an inner diameter of 100-150mm to avoid well wall reflection and water flow interference, controlling the error within ±1cm for a 10-meter range.
- Operating Conditions: The reservoir intake depth is 8 meters, turbidity reaches 800 NTU during flood seasons, and the minimum temperature in winter is -15℃. Traditional float level transmitters require cleaning twice a month due to sediment entanglement, with a measurement error of ±15cm during heavy rains.
- Solution: Select an ultrasonic level transmitter with a 12-meter range, IP68 protection, and a lightning protection module, combined with a wave shield and wave filtering algorithm.
- Results: The measurement accuracy is stably maintained at ±2cm, with 18 months of maintenance-free operation. No data jumps occur during heavy rains, and the device works normally at low temperatures in winter, reducing maintenance costs by 90%.
Purified water treatment is the core stage of purifying raw water into tap water. Key monitoring scenarios include sedimentation tanks, filter tanks, and clear water tanks. The core requirement is to ensure stable sedimentation efficiency, filtration performance, and clear water storage through accurate level control. Below are the operating pain points and adaptation solutions for this stage:
- Technical Adaptation: Use a 25kHz low-frequency probe (with strong penetration to pass through thin floating slag layers) and enable the "floating slag filtering algorithm" — automatically eliminate floating slag interference by identifying differences between floating slag echoes (weak amplitude, long duration) and liquid surface echoes (strong amplitude, steep rising edge).
- Practical Results: After application in an 8-meter sedimentation tank of a waterworks, the measurement error is still controlled within ±1cm even when the floating slag thickness reaches 10cm. The sedimentation effect is stable, and the effluent turbidity is reduced from 0.5 NTU to 0.3 NTU.
- Technical Adaptation: Adopt the "two-point level triggering" mode — trigger the backwashing process when the filter tank level drops to 1 meter (increased filtration resistance); stop backwashing when the level rises to 3 meters after backwashing is completed. The entire process is real-time fed back by the ultrasonic level transmitter.
- Practical Results: After application in the filter tanks of a water purification plant, the backwashing trigger response time is reduced from 10 seconds to 1 second, backwashing water consumption is decreased by 15%, and the service life of filter media is extended by 2 years.
- Technical Adaptation: Select high-precision models (accuracy ±0.2% FS) that support Modbus-RTU communication for integration into the water supply scheduling system. Real-time level data is transmitted to link with water pumps, enabling automatic control of "water replenishment at low levels and pump shutdown at high levels".
- Practical Results: After application in a 15-meter range clear water tank of a county, the water supply pressure fluctuation is reduced from ±0.2MPa to ±0.05MPa, significantly improving residents' water use experience, and the overflow accident rate is reduced from 3 times per year to zero.
Sewage treatment is a key stage in the water cycle. Core monitoring scenarios include equalization tanks, aeration tanks, secondary sedimentation tanks, and sludge thickening tanks. The operating conditions are complex and harsh, requiring high anti-pollution, anti-corrosion, and anti-interference capabilities of level transmitters.
- Pain Point: A stable foam layer of 20-30cm is formed on the liquid surface during aeration. Traditional level transmitters mistakenly identify the foam surface as the actual liquid surface, resulting in an error of ±15cm.
- Solution:
- Hardware: Use a 15W high-power transmitting probe (to enhance sound wave penetration), with the probe surface coated with polytetrafluoroethylene (PTFE) to prevent foam adhesion.
- Algorithm: Enable the "enhanced foam filtering mode" — extend the echo detection time to 100ms to capture the real liquid surface echo below the foam, and correct the sound speed through temperature compensation (aeration tank temperature fluctuates by 5-10℃).
- Result: After application in a 10-meter aeration tank of a chemical industrial park sewage treatment plant, the measurement error is reduced from ±15cm to ±2cm, fully meeting the process control requirement of ±5cm.
- Pain Point: Industrial wastewater (e.g., electroplating wastewater, pickling wastewater) contains strong acids and alkalis (pH=1-13) and heavy metal ions. Traditional metal probes are corroded within 3-6 months.
- Solution:
- Probe Material: Use fully PTFE-coated probes (including housings and cable interfaces) with corrosion resistance complying with ISO 10289 standard, capable of withstanding extreme conditions of pH=1-14.
- Explosion-Proof Design: For explosion-proof requirements in chemical industrial parks, select ultrasonic level transmitters with Ex d IIC T6 explosion-proof rating to prevent safety accidents caused by oil-gas mixtures.
- Result: After application in a 5-meter pickling wastewater tank of an electroplating factory, the probe operates for 24 months without corrosion damage. Its service life is 4 times longer than that of traditional equipment, and maintenance costs are reduced by 80%.
- Pain Point: Sludge concentration exceeds 10,000mg/L, and suspended solids easily scatter sound waves, resulting in weak echo signals and measurement failure.
- Solution:
- Waveguide Tube Assistance: Install a 316L stainless steel waveguide tube (inner diameter 120mm) below the probe. Sound waves transmit along the waveguide tube to avoid scattering by suspended solids.
- Dynamic Power Adjustment: Automatically increase the transmitting power based on sludge concentration (linked with on-site concentration meters). The higher the concentration, the greater the power (up to 20W) to ensure the strength of echo signals.
- Result: After application in an 8-meter sludge thickening tank of a municipal sewage treatment plant, the effective measurement rate is increased from 60% to 99.8%, the error is controlled within ±3cm, and the sludge dewatering efficiency is improved by 10%.
- Covered Scenarios: 5-meter equalization tank, 10-meter aeration tank, 8-meter secondary sedimentation tank, 6-meter sludge thickening tank.
- Unified Solution: Use ultrasonic level transmitters of the same brand, integrated into the park's SCADA system via Modbus-RTU protocol to achieve full-process level data visualization and linked control.
- Comprehensive Results:
- The measurement accuracy of each stage is ≤±2cm, and process stability is improved by 30%.
- The average mean time between failures (MTBF) of the equipment reaches 18 months, and maintenance costs are reduced by 92%.
- By linking with water inflow, aeration, and drainage systems, sewage treatment capacity is increased by 20%, and the effluent compliance rate is raised from 95% to 100%.
Reclaimed water reuse is an important measure for water conservation and emission reduction. Core monitoring scenarios include reclaimed water tanks and reuse water supply tanks. The requirement is to ensure sufficient reclaimed water storage and on-demand supply through accurate level monitoring, avoiding waste or insufficient water supply.
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