Streaming Current Detection for Coagulation Control in WWT

Once coagulants are injected and dispersed through flash mixing, suspended particles begin to destabilize as their electrical charge is neutralized. However, without direct measurement, the effectiveness of this reaction remains uncertain.

The SCD continuously analyzes a water sample taken immediately downstream of the flash mixing stage. It measures the net electrical charge of the remaining suspended particles, providing a direct indication of coagulation performance.

This allows operators to immediately understand whether the system is operating under optimal conditions—or if adjustments are required—transforming coagulation from an estimated process into a visible, measurable parameter.

Rather than predicting how much coagulant should be added, Streaming Current Detection evaluates what remains after the reaction has occurred. It measures the residual electrical charge of particles, often described as the “work not done” by the coagulant.  

A target value, or setpoint, is established to represent ideal coagulation conditions. The system continuously compares real-time measurements to this setpoint and automatically adjusts metering pump output to maintain balance.

This creates a closed-loop control system, where the process continuously self-corrects to maintain optimal performance.

Traditional tools such as jar testing provide valuable insights but are inherently limited. Because they are performed offline, they cannot respond quickly to changing process conditions.

In contrast, SCD operates continuously and adapts in real time to variations in turbidity, organic load, and flow conditions. This is particularly critical during sudden events such as stormwater influx or seasonal algae blooms, where rapid changes in water quality can significantly impact treatment performance.

By continuously adjusting dosing in response to actual conditions, SCD ensures stable coagulation regardless of variability.

Coagulation is the foundation of the treatment train. When it is unstable, its effects propagate downstream, leading to inconsistent floc formation, inefficient sedimentation, and increased filtration challenges.

With SCD maintaining optimal charge balance, flocs form more consistently and settle more efficiently. This reduces the load on filtration systems, extends filter run times, and minimizes operational disruptions.

By stabilizing coagulation, SCD enhances the performance of every subsequent treatment step.

Implementing Streaming Current Detection leads to significant improvements in both performance and cost efficiency. By ensuring that coagulant dosing is always aligned with actual needs, plants can reduce chemical consumption while maintaining consistent water quality.

Optimized coagulation also improves the removal of fine particles and microorganisms, including resilient pathogens such as giardia and cryptosporidium.  

At the same time, operational stability is improved. Sludge production is reduced, filtration becomes more efficient, and operators benefit from early detection of process deviations before they impact finished water quality.  

Streaming Current Detection operates as part of a fully integrated system within the coagulation stage.

It works in direct coordination with metering pumps, which adjust dosing based on SCD feedback, and with flash mixing systems, which ensure proper dispersion before measurement. This creates a unified process in which dosing, mixing, and control are fully synchronized.

The result is a treatment system that operates continuously at optimal performance without relying on manual intervention.

Milton Roy’s SCD technology has been successfully implemented in hundreds of installations worldwide and is widely recognized as a reliable solution for coagulation control.  

Designed for real plant conditions, the system is capable of handling variable water quality and high solids content. It also offers features such as continuous operation and automated cleaning options to ensure long-term measurement accuracy.  

By introducing Streaming Current Detection into their process, water treatment plants move from static dosing strategies to adaptive, intelligent control.

Instead of relying on assumptions or periodic testing, operators gain the ability to continuously measure, evaluate, and optimize coagulation performance in real time. This results in a process that is more efficient, more stable, and better equipped to meet the increasing demands of modern water treatment.