Application of SCM530 Streaming current meter in a water treatment plant in Heze, Shandong Province

Coagulation and chemical addition is the core step of raw water treatment in water plant, and its effect directly affects the success of subsequent sedimentation, filtration and disinfection.

Traditional chemical dosing relies on manual experience adjustment, which is difficult to deal with water quality fluctuations. However, the single-factor coagulation dosing control equipment SCD Streaming current  current meter can achieve accurate regulation by real-time monitoring of colloidal charge changes, which is a key technology for the automation upgrade of modern water plants.

This article introduces the application of the SCM530 current meter in a water treatment plant in Heze, Shandong.

Application Background

A water treatment plant in Heze, Shandong Province primarily draws its water from the Yellow River. Key parameters such as turbidity, organic matter content, algae levels, and colloidal charge fluctuate significantly due to seasonal variations (flood/low-water periods), rainfall, and upstream activities. This instability in raw water quality poses substantial challenges for traditional coagulant dosing methods based on empirical or fixed ratios, often resulting in either insufficient dosing (exceeding effluent turbidity/particle count limits) or excessive dosing (wasting chemicals, increasing sludge volume, disrupting downstream processes, and generating disinfection byproduct precursors).

Purpose of application

Precise dosing: Dynamically adjust the coagulant dosage based on real-time changes in the surface charge (ζ-potential) of colloidal particles in the raw water to ensure optimal coagulation.

Stable water quality: Reduce the fluctuation of effluent quality in sedimentation tank/filter caused by water quality fluctuation, and ensure that the final effluent turbidity is stable and meets the standard.

Reduce chemical consumption: Avoid excessive dosing to significantly lower coagulant (e.g., PAC) costs.

Optimize operation: reduce the labor intensity of workers, improve the automation level and operation management level of water plant.

Installation site

Core location: Install before the coagulation reaction tank and after the rapid mixing section. The key is to test the position where the flocculant is fully mixed with the water body and the flocculation is not yet large.

Sampling point: The water sample is usually drawn from the well-mixed position and returned or discharged after passing through the SCM530 detection unit.

Core Features

Real-time monitoring: Continuous online measurement of the Streaming current  current of colloidal particles in water samples after coagulant treatment. This value serves as an indirect and sensitive indicator of the colloidal charge (ζ-potential) in water.

Control signal output: The SCM530 Streaming current  current meter transmits the measured Streaming current  current signal (typically 4-20mA or Modbus) to the water plant's chemical dosing PLC or DCS system.

Closed-loop control principle: The SCM530 Streaming current  current meter compares its actual signal with a preset reference value, which represents the expected Streaming current  current when optimal coagulation is achieved.

Actuator control: The SCM530 Streaming current  current meter transmits PID signals to the PLC/DCS system via PID control algorithms, which then output control signals to the coagulant dosing pump (metering pump) or regulating valve. This enables real-time adjustment of coagulant dosage, maintaining the measured Streaming current  current value near the set point.

App effect

Significantly reduced chemical consumption: This is the most direct economic benefit. By avoiding excessive dosage, coagulant savings of 10% to 30% are usually achieved.

Stable effluent quality: The turbidity fluctuation of the sedimentation tank and filter tank is reduced, the stability is improved, the risk of water quality exceeding the standard is reduced, and the water supply safety is guaranteed.

Improve automation level: Reduce manual intervention, realize continuous and automatic optimization control of coagulation process.

 The reduction of chemical consumption directly leads to the reduction of chemical 

Reduce sludge production:sludge production, reducing sludge treatment and disposal costs and environmental burden.

Improve the subsequent process: reduce the excessive coagulant into the filter, which helps to prolong the filter operation cycle and reduce the frequency of backwashing; reduce the disinfection byproduct precursor.

Quick response to water quality changes: More timely and accurate response to rapid fluctuations in water quality of the Yellow River (such as high turbidity after rain and algal outbreak).

Improve management level: Provide continuous process data to facilitate analysis of operation status, optimization of process, and accumulation of operation experience.

Challenges and solutions

Effect of high turbidity: When the turbidity is extremely high, the probe may be easily blocked or worn.

Solution: Strengthen the maintenance frequency; install a pre-filter device; select a more wear-resistant probe.

High organic/water with high algae: Dissolved organic matter or algal metabolites may interfere with charge or attach to the probe.

Solution: Enhance cleaning; integrate other parameters (e.g., UV254) to assist in judgment or adjust settings; optimize coagulant type.

Setpoint drift: Long-term changes in water composition may cause the original setpoint to become undesirable.

Solution: Perform periodic (e.g., quarterly) beaker tests to verify and adjust the baseline value.

Equipment failure/maintenance: Probe failure or improper maintenance may cause control failure.

Solution: Maintain adequate spare parts inventory; enhance staff training; implement redundant configurations for critical water plants; ensure the system can seamlessly transition to a Streaming current and turbidity-based backup control mode when SCD fails.

Sum up

The application of SCM530 Streaming current meter in a water plant in Heze, Shandong province is the core technical means to realize intelligent, accurate and efficient coagulant dosage. It directly responds to the change of colloidal charge in water, and is one of the essential equipment for controlling coagulant dosage.