What are PLC-Based Water Treatment Plants?

Most of the water treatment plants in the previous decade were manually operated. However, they were automated to a certain degree using relays or electrical control panels but the system was not reliable and required a lot of space. 

In this modern era, water treatment facilities are automatically operated using PLC or Programmable Logic Controllers along with other electrical circuits which can be programmed to operate the plant without human intervention. The programming language used for PLC is based on Ladder logic (operation of relays) or C language. 

If you are familiar with automation in industries then you must have heard about PLC. These electro-mechanical controllers are used to control various industrial processes based on input from the users or sensors in the field. If you have studied the working of AND, NOT, OR, XOR, etc. gates in your electrical subjects then it is easier to program this industrial minicomputer. 

For example, if you want that your pump should stop after a certain level of water is reached and should start if the water level is low then you can program PLC to do that. The sensors in the field will provide the input regarding water levels and based on that PLC will generate output to run or stop the pump. This is just a simple scenario but in the actual world, they are programmed to handle complex industrial automation processes with precision. For example we have a manufacturing facility that designs automated water treatment plants in Dubai, UAE. 

In this blog, we will dig deep into the various electrical components that are needed to automate water treatment plants. 

PLC

As we talked about before, PLC is a mini industrial computer that receives an input from outside devices such as push buttons or sensors and based on the program installed into it, generates the output. Moreover, PLC supports communication over Ethernet or other modes depending upon the model and this enables them to connect with other systems such as SCADA, AC drives, etc. 

Electrical Control Panel 

An electrical panel is a metallic cabinet or closed box that houses all the electrical circuits. All the AC drives, wiring, circuit breakers, transformers, terminal blocks, PLC, relays, contactors, HMI, and other components that are essential for monitoring and controlling an electrical system are mounted in the panel. 

All the electrical panels are provided with the drawing and by reading them one can understand and troubleshoot the faults. 

HMI 

HMI or Human Machine Interface is a screen on which a user can interact with the electrical control system. They are connected with PLC and display all the necessary inputs, and outputs, monitoring which pump is running or which one is at fault. Furthermore, you can start and stop, increase speed and check the history of faults of any device from the HMI. However, the HMI needs to be programmed to get those parameters displayed on the screen. 

SCADA 

SCADA or Supervisory Control and Data Acquisition system allows you to monitor and gather data from remote locations on your personal computer. In addition to this, you can also perform operations such as starting or stopping a pump or machine, increasing or decreasing the speed or temperature of the device, monitoring the error log files, the present status of field sensors, etc. from your computer. 

Field Sensors 

Field sensors play an important role when it comes to water treatment systems. There are various types of sensors used in the water treatment system. 

• Conductivity Sensor – To measure the conductivity of water 
• pH sensor – To monitor the pH of flowing water 
• ORP sensors – To measure oxygen reduction potential 
• Turbidity sensors – To measure the turbidity of water 
• DO sensors – To monitor levels of oxygen in the water 
• Level sensors – To check levels of the tank

AC Drives 

An AC drive or Variable Frequency Drive (VFD) is used to control the speed of the motor enhance process control, reduce energy requirements, increase efficiency, decrease mechanical stress, etc. The need for energy conservation is the main motive behind the usage of AC drives in water treatment plants. These drives can directly communicate with PLCs on Ethernet or Modbus and can be operated automatically or manually from HMIs or SCADA. In case of any fault, these drives trip automatically and save the motor from burning. 

Conclusion 

The PLC-based electrical control systems are helpful in the automation of water treatment plants and also reduce the energy consumption of the whole system. This is a one-time investment which ensure smooth running of your water treatment plant for longer duration