Application of SCM520 Streaming current meter in water treatment plants

The Streaming Current Detector (SCD) is a device that detects the charge of ions and colloids in water (similar to Zeta potential) through the streaming current principle, enabling automatic adjustment and control of coagulant dosage. In water treatment, it primarily optimizes coagulant dosage by real-time monitoring of colloidal particle charge states, thereby improving water quality and reducing treatment costs. This article focuses on the application of the SCM520 SCD in water treatment plants.

Core Apps

Optimize coagulant dosage

Mechanism: In tap water treatment, coagulants (such as polyaluminum chloride and aluminum sulfate) are used to neutralize the negative charge of colloidal particles in water, so that they are destabilized and form flocs. The flow current meter detects the change of colloidal charge in water and directly reflects the coagulation effect.

Real-time control: Traditional methods rely on manual experience or laboratory testing, which is delayed. The flow current meter can monitor the charge change in real time, automatically feedback to the drug addition system, and dynamically adjust the drug addition amount to avoid excessive or insufficient.

Benefits: reduce chemical waste (save 10%-30%), reduce sludge production, improve flocculation effect, reduce the burden of subsequent filtration.

Optimize sedimentation and filtration processes

By optimizing the coagulation process, colloidal particles in water can be more effectively aggregated and flocculated into larger flocs. This reduces the load on subsequent sedimentation tanks and minimizes clogging risks in filter beds, thereby indirectly enhancing overall process efficiency. The optimized procedure decreases sludge accumulation in sedimentation tanks, extends backwashing cycles in filters, and conserves water and electricity consumption during backwashing operations, ultimately lowering operational costs.

Water quality fluctuations response

When raw water experiences sudden quality changes due to rainfall, seasonal variations, or pollution incidents, the flow current meter can rapidly detect fluctuations in colloidal charges and trigger the chemical dosing system to make corresponding adjustments. For instance, during heavy rainfall when turbidity spikes, traditional manual adjustments may be delayed, whereas the flow current meter responds in real-time, enabling water treatment plants to take prompt measures and ensure minimal impact on treated water quality.

Process automation upgrade

Closed-loop control system: The flow meter is integrated with PLC and DCS systems to enable fully automated dosing, minimizing manual intervention and enhancing the water plant's intelligent capabilities.

operational principle

A flow current meter consists of a flow current meter sensor and controller. The piston of the sensor moves reciprocally up and down within the annular electrode. When water samples containing coagulants pass through the sensor, the water in the electrode's annular space undergoes corresponding motion. This disturbance disrupts the double electric layer of colloidal particles, causing the water flow to carry counterions from the colloidal diffusion layer, thereby generating a flow current. This current is collected by electrodes at both ends, amplified by a signal amplifier, and rectified into a DC output signal. When the concentration of colloidal particles in water changes, the detection values recorded by the flow current meter also vary accordingly. This method provides real-time, reliable monitoring data for assessing coagulation effectiveness in raw water treatment.

Upon detecting the flow current value from the sensor, the flow meter controller converts and visually displays the measurement. Equipped with PID control functionality, the controller compares the detected current with preset reference values, then outputs a 4-20mA signal to regulate the metering pump or dosing valve opening.

The SCV response value of raw water is detected by the flow current meter to determine the dosage of coagulant, so as to reduce the dosage consumption and cost on the basis of ensuring and improving the water supply quality, and then improve the economic and social benefits of the enterprise.

Advantages and limitations

superiority

Real-time: response in seconds, much faster than laboratory testing (beaker test).

Precise control: directly reflects the state of colloid instability, more sensitive than turbidity.

Economic and environmental protection: reduce the cost of medicine, reduce the secondary pollution of chemical sludge.

Boundedness

Highly contaminated water samples may block the flow channel and need to be cleaned regularly. Some organic matter or ions interfere with charge detection.

Real cases

Case 1: The water source of a waterworks is river water with high turbidity. The daily treatment capacity is 200,000 tons. After using SCM520 flow current meter to control the dosage of chemicals, the dosage of polyaluminum chloride is reduced from 35.3kg/kt to 25.6kg/kt, and the annual cost of chemicals is saved by hundreds of thousands.

Case 2: A water treatment plant with reservoir water source, high pH fluctuation and algae content, and daily treatment capacity of 150,000 tons, adopted SCM520 flow current meter to control chemical dosage, which reduced the probability of alum leakage in sedimentation tank, extended the backwash cycle of filter tank, and greatly saved the electricity and water consumption of backwash cycle.

Case 3: When the raw water turbidity at a water treatment plant spiked from 20NTU to 200 NTU, the SCM520 flow meter automatically adjusted the chemical dosage from 13 kg/kt to 24 kg/kt, keeping the treated water turbidity around 0.8 NTU.

SCM520 Current Meter

Sample flow rate: 1-19 L/min

Measurement parameter: flow current

Measurement range: -1000 to 1000

Sample pool type: external receiver, high flow

Piston type: Quick-change

Water sample inlet: 3/4"(19mm)O.D

Water sample outlet: 3/4"(19mm)O.D

Materials for sample contact: PVDF, POM, PVC, PE, EPDM, or stainless steel

Wiring connection: 4-core shielded cable

Self-diagnosis: motor speed

hull ：PC

Power supply: 220 VAC, 50HZ

Working temperature: 0-50℃

Heat dissipation module: Yes

Dimensions: 310mm (W), 388mm (H), 165mm (D)

Weight: 5kg

Optional accessories:

Self-cleaning: sensors automatically clean

Other measurement parameters: pH measurement

The Bebur streaming current meter, by precisely monitoring colloidal charge states, has become a core tool for water treatment plants to optimize coagulation processes, particularly suitable for scenarios with significant water quality fluctuations and high treatment challenges.