Coagulation Controller – CoagSense
What’s the best way to control coagulation on a water treatment plant? The answer is that it depends on the water, the type of plant and the coagulant used. Pi’s CoagSense automatic coagulation controller is an integrated controller that accepts multiple inputs from appropriate parameters including pH, flow, temperature, UV254, turbidity and streaming current. From these measured parameters, the CoagSense outputs a flow proportional coagulation control signal that can go to a site SCADA or direct to control a coagulant dosing pump.
Coagulation is affected by lots of different variables like:
- Raw water pH and alkalinity, turbidity, organic loading, and temp.
- The type of coagulant used
- Post coagulant pH, temperature
- Physical aspects of the plant including mixing etc.
In the past most coagulant control has been dosed automatically with the setpoint determined manually by looking at the variables and sometimes by using lab methods such as jar testing. There are two main problems with this approach. The first is that when the main goal of coagulation was to remove turbidity, operators eyeballing the water and changing the dose was a good method of determining the dose of coagulant required. Now that the focus is on enhanced coagulation and the removal of organics that are often not visible to the naked eye.
This method of manually determining the coagulant dose is no longer providing operators with the outcomes that they need. In addition the consequence of under dosing coagulant is often more severe than the consequence of overdosing coagulant. For this reason the tendency is for operators to add more coagulant than is required leading to shorter filter run times and more sludge to dispose of. This overdosing of coagulant is typically approximately 30%. The implementation of automatic coagulation control will typically save money (often giving a ROI of months rather than years) while improving water quality and plant outcomes.
- Configured and optimized for each site
- Stable and reliable
- Excellent process control
- Can interpret UV254, streaming current, pH, turbidity and flow
- Profibus, Modbus and TCP comms to SCADA
- Help and consulting available
The CoagSense coagulation controller is used exclusively on municipal water treatment plants. The automatic coagulation controller from Pi is suitable for all forms of water treatment plant where the principle of coagulation is charge neutralization. These can be DAF plants, packaged water plants or more traditional coagulation flocculation plants. Water sources are typically surface water but can be any water source. The technology used in CoagSense is currently being used in many thousands of water treatment plants all over North America.
Remote Access over LAN – Provides remote controller access over local area networks such as those belonging to a certain organization or location.
Remote Access over GPRS – Provides remote controller access over mobile networks.
Modbus over LAN – Provides Modbus communication and remote controller access over LAN.
Modbus over RS-485 – Provides Modbus communication and remote controller access over RS-485 networks.
Site sensor inputs – The CoagSense is able to take in outputs from other site instruments potentially saving money.
Data logging – Provides data logging for investigation and troubleshooting purposes.
Onboard PID controls – Offers the ability to manipulate process variables such as pressure, speed, temperature, flow and others.
Direct coagulant pump control – The CoagSense allows for the direct control of the dosing pumps for pH correction and coagulant addition.
Coagulant pump control via SCADA – Allows you to gather and analyze real-time data via the use of SCADA systems.
The CoagSense uses a range of sensors (including existing site sensors) that can be added to a central controller (analyzer). The controller takes the signals and manipulates them, producing a signal that controls the dosing of a coagulant. These are:
Flow – Used to increase or decrease the coagulant dose proportionally to the flow.
Raw Water pH – For information and troubleshooting.
Coagulant Water pH – Used to control pH adjustment chemicals to maintain the correct pH for coagulation.
UV254 – On the raw water to enable the coagulant to be dosed according to the organics load of the water.
Raw Water Turbidity – On the raw water to enable the coagulant to be dosed according to the organics load of the water.
Streaming Current – On the coagulated water to enable feedback control of the coagulation process.
Focus Ons are a series of short articles distributed by email providing technical information regarding instrumentation, process measurement in potable, waste, process and pool waters. If you would like to join the mailing list, please contact us.
>> Coagulation Control During Periods When Plants Are Unmanned
>> Analyzer to Pump – how controllers can interact with and control pumps
>> PID Auto-Tune – why it might not work for water processes
>> Saving Time and Money with PID
Document | Type | Size |
---|---|---|
CoagSense | Brochure | 618kB |
CoagSense Application Questionnaire | Technical Note | 553kB |
Coagulation Control Using Streaming Current Monitoring | Technical Note | 842kB |
PID Control | Technical Note | 710kB |
FAQs
What is coagulation?
Coagulation is the process by which suspended and dissolved solids clump together which is necessary to remove them.
What is flocculation?
Flocculation is the process of the coagulated solids clumping togetehr to make large aggregations or “flocc”.
What is a coagulant?
A coagulant is a chemical, added to water that enables coagulation. Typically a charged metal salt such as Ferric or Alum or PACl.
What is a flocculant?
A flocculant is a chemical added to water to enable flocculation, typically a charged organic chemical.
What is charge neutralization?
Charge neutralization is when solids are held in suspension in water by the negative surface charges. Charge neutralization happens when a positively charged coagulant is added to neutralize the negative charges thereby enabling coagulation.
What affects coagulation?
Many things affect coagulation but the most important ones are;
- pH
- Coagulant charge
- Temperature
- Suspended solids
- Dissolved organics
- Mixing of the coagulant
What coagulants are there?
The most common coagulants are;
- Ferric – Iron Chloride
- Alum – Aluminum Sulphate
- PACl – Polyaluminum Chloride
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