With frequent heavy rainfall, the SCM530 Streaming current detector demonstrates its effectiveness in monitoring sudden turbidity fluctuations in water quality.

Streaming current detector is one of the core online equipment for coagulant dosage control in water plants. Especially in the case of sudden change of water turbidity during the rainstorm season, its ability to directly detect colloidal charge characteristics can effectively deal with the limitations of traditional turbidity detection methods under rapid change conditions, and improve the treatment efficiency and the stability of effluent water quality.

The streaming current detector working principle

The streaming current detector indirectly evaluates coagulation efficiency by measuring the Zeta potential (electrostatic charge) of colloidal particles in water.

The sampled water is subjected to a reciprocating flow by the piston.

The charged colloidal particles carry counter ions in the flow to form a current (flowing current).

The current signal is converted into an SCD value and compared with the preset reference value.

Output the signal to adjust the metering pump or dosing valve opening for automatic dosing control.

Advantages of turbidity mutation in streaming current detector

1. Overcome the lag of traditional turbidity detection

Question: Turbidity meter measures the light scattering degree of suspended particles in water. When the turbidity of raw water changes suddenly (such as heavy rain leading to a sharp increase in the turbidity of surface water), the traditional control system based on the feedback of effluent turbidity has significant lag:

Sampling and measurement takes time (especially for samples that need to settle).

The whole process of coagulation, flocculation, precipitation/filtration takes a long time.

The dosage at the front end is adjusted according to the final effluent turbidity, but the reaction is too slow to respond to sudden changes in time.

Streaming current detector Solution: The flow cytometer directly and in real-time measures the colloidal charge state (flow current value) in water samples before flocculation and after coagulation. Positioned at the very front end of the treatment process (typically after rapid mixing), it can detect changes in raw water quality (particularly colloidal charge characteristics) almost instantaneously (within seconds to minutes), including variations in colloidal load caused by turbidity fluctuations.

1. Fast response and accurate drug delivery control

When turbidity changes abruptly, the Streaming current detector detects the change in flow current (deviation from the set point). The control system (usually a PID controller) adjusts the dosage of coagulant (such as aluminum salt, iron salt, or cationic polymer) in real time based on this deviation to neutralize the colloidal charge.

Advantages: This direct and rapid feedback control based on charge state is much faster than waiting for the final turbidity result to adjust, and can significantly reduce the deterioration of effluent water quality (running alum) caused by insufficient dosage or waste and subsequent problems caused by excessive dosage during turbidity mutation.

The streaming current detector application scenarios

Surface water treatment during heavy rainfall: The turbidity of river and reservoir water rises sharply (from a few NTU to hundreds or even thousands NTU) due to rainwater scouring. The Streaming current detector responds quickly to ensure the dosage of chemicals is promptly adjusted, preventing the filter bed from being penetrated.

For example, when heavy rainfall caused a sudden increase in raw water turbidity (20NTU to 200NTU) at a water treatment plant in Nan Shui, the flow meter automatically adjusted the chemical dosage from 13kg/kt to 24kg/kt, maintaining the sediment water turbidity at approximately 0.8NTU.

Key points in the practical application of streaming current detector

Installation location: It is usually installed after the rapid mixing tank to ensure that the agent is fully mixed with water and can represent the water quality before entering the flocculation tank. The sampling point must be representative and the flow rate is stable.

Integration with control system: The Streaming current detector needs to be closely integrated with the coagulant dosing control system (usually variable frequency metering pump) to achieve closed-loop control.

Sum up

In applications involving sudden changes in water turbidity, the core value of the Streaming current detector lies in its real-time capabilities and direct sensitivity to colloidal charge states. It can detect abrupt changes in raw water's colloidal load and characteristics before traditional turbidity detection methods can sense them, allowing immediate adjustment of coagulant dosage. 

This enables water treatment plants to:

The response time to sudden turbidity increase is significantly shortened.

Effectively prevent the effluent water quality from exceeding the standard (increasing turbidity) due to insufficient drug input.

It greatly reduces the waste of drugs, the increase of operating costs and the subsequent process problems (residual metals, DBPs, filter blockage) caused by excessive drug dosage.

Improve the stability and toughness of the whole treatment process in response to shock load.

Therefore, in the areas where the turbidity of raw water fluctuates frequently due to the influence of rainstorm, seasonal change or emergency, the Streaming current detector is one of the key tools to realize the efficient, stable and economic coagulation dosage control.