Yexsensor YEX-MLSS-408-S online sludge concentration sensor is an integrated online monitoring device specially designed for system integrators, IoT solution providers and water treatment engineering companies. The sensor is based on the scattered light method and can achieve continuous and stable measurement of activated sludge concentration. It is widely used in municipal wastewater treatment plants, industrial wastewater biological treatment systems and sludge return control scenarios.

In the activated sludge wastewater treatment process, the mixed liquor suspended solids concentration (MLSS) is a key process parameter that directly affects aeration volume, sludge return flow and sedimentation effect. Traditional manual sampling analysis has long cycles and lagged data, while YEX-MLSS-408-S provides high-frequency and reliable data for PLC, DCS or SCADA systems through real-time online monitoring, supporting process automatic optimization, reducing energy consumption and improving effluent stability.

YEX-MLSS-408-S Online Sludge Concentration Sensor Working Principle

YEX-MLSS-408-S adopts the scattered light measurement method. When a beam of infrared light irradiates the water sample, suspended particles (activated sludge) will produce backscattering. By measuring the intensity of the scattered light and comparing it with the internal calibration curve, the sludge concentration value is output after linearization processing.

The sensor integrates a pure quartz optical path, effectively suppressing external light interference; it uses an infrared LED light source with high stability and small drift; it has a built-in Pt1000 temperature sensor to achieve automatic temperature compensation, ensuring consistent measurement results under different temperature conditions. The built-in cleaning brush design further reduces maintenance frequency and is suitable for long-term continuous operation.

YEX-MLSS-408-S Online Sludge Concentration Sensor Product Features

YEX-MLSS-408-S has the following significant advantages in engineering applications:

• Scattered light method principle, measurement is not affected by color interference, suitable for various activated sludge systems

• Pure quartz optical path design, strong resistance to external light interference

• Infrared LED light source, high stability and long service life

• Built-in cleaning brush, effectively reducing dirt adhesion on the measurement window

• 316L stainless steel shell, IP68 protection level, supports immersion within 20 meters water depth

• Supports RS-485 Modbus/RTU protocol and optional 4-20 mA current output, convenient for system integration

• Fast response time (T90 < 30 s), minimum detection limit as low as 1 mg/L

• Low power consumption design (0.2 W @ 12 V), suitable for on-site distributed power supply

• Integrated structure, easy installation and low maintenance requirements

These features make YEX-MLSS-408-S a reliable and economical online monitoring unit in wastewater treatment process control.

YEX-MLSS-408-S Online Sludge Concentration Sensor Technical Parameters

Mechanical Interface: The sensor connector is M16-5 core waterproof male connector.

Installation and Electrical Connection

Installation Guide

YEX-MLSS-408-S adopts submersible installation. It is recommended to fix it at a suitable position in the aeration tank, secondary sedimentation tank or sludge return pipeline through the 3/4 NPT interface. During installation, ensure that the measuring end face fully contacts the water body and avoid installing in areas with strong bubbles or dead corners. The sensor should be placed vertically or close to vertical to ensure measurement consistency.

Electrical Connection

The sensor uses a 5-core shielded cable with the following wire sequence definition:

• Red wire: Power positive pole (12～24 V DC)

• Black wire: Ground wire (GND)

• Blue wire: RS-485 A

• White wire: RS-485 B

• Yellow wire: Current output (optional; if not used, it can be left floating)

Please carefully check the wiring sequence before powering on. All wiring points must be waterproofed, and the cable should have certain anti-corrosion ability to adapt to long-term immersion in sewage or exposure to humid environments.

YEX-MLSS-408-S Online Sludge Concentration Sensor Maintenance and Care

YEX-MLSS-408-S is designed with low maintenance characteristics, with the focus on keeping the measurement window clean.

Maintenance Schedule Recommendations

• Calibration: Perform two-point calibration according to the requirements of the competent department or actual process fluctuations

• Daily Inspection: Regularly confirm that the self-cleaning brush is working normally and the cleanliness of the measurement window

Maintenance Methods

1. Outer surface cleaning: Rinse with tap water. For stubborn dirt, add a small amount of neutral detergent and wipe with a soft cloth.

2. Cable inspection: Ensure that the cable is not overly tightened or pulled to prevent internal wire breakage.

3. Measurement window and cleaning brush: Regularly check whether there are attachments on the window and whether the cleaning brush is working normally.

There are no user-serviceable parts inside the sensor. Avoid violent mechanical impact.

Calibration Method

• Zero point calibration: Use 0～2.000 g/L sludge concentration standard solution, immerse the sensor vertically in a large beaker, with the measuring end face at least 10 cm away from the bottom. After the value stabilizes for 3～5 minutes, execute the zero point calibration command.

• Slope calibration: Use 2.000～20.000 g/L sludge concentration standard solution, keep the measuring end face at least 10 cm away from the bottom, and execute the slope calibration command after stabilization.

YEX-MLSS-408-S Online Sludge Concentration Sensor Application Scenarios

Yexsensor YEX-MLSS-408-S is widely used in activated sludge wastewater treatment projects.

1. Municipal Wastewater Treatment Plants
          Deployed at the inlet/outlet of aeration tanks, anoxic tanks and secondary sedimentation tanks to monitor MLSS concentration in real time, providing accurate data support for dissolved oxygen control, sludge return ratio adjustment and excess sludge discharge, and optimizing process operating parameters.

2. Industrial Wastewater Biological Treatment Systems
          Suitable for organic wastewater treatment projects in chemical, pharmaceutical, food, printing and dyeing industries. Through continuous MLSS monitoring, precise control of aeration volume is achieved, reducing energy consumption and stabilizing treatment effects.

3. Sludge Thickening and Dewatering Processes
          Monitor the incoming sludge concentration before the sludge thickening tank or dewatering machine to guide chemical dosing control, improve dewatering efficiency and reduce cake moisture content.

4. MBR Membrane Bioreactor Systems
          Monitor the sludge concentration in the membrane tank to prevent excessive sludge concentration from causing membrane fouling and extend the service life of membrane modules.

5. Small and Medium-sized Integrated Wastewater Treatment Equipment
          The integrated structure and low power consumption characteristics are particularly suitable for small wastewater treatment stations or distributed smart water projects, enabling remote monitoring and unattended operation.

In these scenarios, YEX-MLSS-408-S effectively reduces on-site maintenance workload and improves overall system reliability with its self-cleaning function, standard communication protocol and high protection level.

Frequently Asked Questions (FAQ)

Q1. What measurement principle does the YEX-MLSS-408-S use?

The sensor adopts the scattered light method, calculates the sludge concentration by measuring the intensity of backscattered light, and is less affected by color interference.

Q2. What is the range and resolution of the sensor?

Range 0～20.000 g/L, resolution 0.001 g/L, minimum detection limit 1 mg/L, covering the conventional activated sludge concentration range.

Q3. Does it support analog output?

The standard configuration is RS-485 Modbus/RTU protocol, with optional 4-20 mA current output, which is convenient for integration with different control systems.

Q4. What is the function of the built-in cleaning brush?

The built-in cleaning brush can effectively reduce dirt adhesion on the measurement window, extend the maintenance cycle and maintain measurement stability.

Q5. What are the requirements for the standard solution concentration during calibration?

Zero point calibration uses 0～2.000 g/L standard solution, slope calibration uses 2.000～20.000 g/L standard solution, and sludge homogeneity must be ensured.

Q6. What is the protection level and pressure resistance of the sensor?

IP68 protection level, supports immersion within 20 meters water depth, working pressure ≤0.2 MPa, suitable for most wastewater treatment tank bodies.

Q7. Is the daily maintenance workload large?

The maintenance requirement is low, mainly regular cleaning of the outer surface and checking the cleaning brush. Internal optical components do not require user disassembly.

Q8. What about product warranty and after-sales service?

The product has undergone 72-hour aging and stability testing before leaving the factory. One-year whole machine warranty is provided from the date of sale (excluding improper use). The manufacturer provides technical support, spare parts and factory repair services for system integrators.

Summary

Yexsensor YEX-MLSS-408-S online sludge concentration sensor takes the scattered light method as the core technology, integrates a self-cleaning brush, pure quartz optical path and 316L stainless steel structure, providing a stable and reliable solution for online monitoring of activated sludge concentration. Its fast response, low maintenance characteristics and Modbus/RTU compatibility fully meet the needs of wastewater treatment plant process control and intelligent upgrading.

Through real-time and accurate MLSS data, the sensor helps engineering projects optimize aeration and sludge return control, reduce operating energy consumption and improve effluent quality. It has become a practical choice for many water treatment system integrators in the biological treatment link.

For detailed product quotations, technical specification sheets, selection guidance, output configuration customization or project application cases, please contact the Yexsensor professional team. We will provide targeted technical support and complete solutions according to your specific process conditions and control system requirements to help your project be implemented efficiently and operate stably for a long time.