Control Narrative: How Do Water Treatment Plant SCADA & RO Membrane Treatment Systems Communicate?

When multiple Reverse Osmosis trains are offered then we will supply identical control systems for each RO train. Normally, each of these control plans will utilize an Allen-Bradley PLC for R/O train control, and communication with the water treatment plant SCADA. Each R/O control board will also have a color touch screen operator interface (HMI). This will provide the operator complete access to monitor and manage all elements of each particular Reverse Osmosis train. Each of the PLCs will communicate over an Allen-Bradley based Ethernet network with the water treatment plant SCADA. The plant SCADA will then have the ability to interact with all pre and post ancillary equipment in addition to each RO train individually or collectively using message block transfers of data. Many water treatment plant SCADA systems monitor the finished water level, control the well(s), the well flush valve, the plant inlet valve, the scale inhibitor, the feed pH tracking, and other pretreatment devices or chemicals that might be required.

As soon as once again, without full understanding of the scope of work at a particular center, we make no declaration that this will be all of the devices at the "front end" of the plant. Assuming these fundamental components and requirements, the RO Membrane control would continue according to the following series of events. Membrane Treatment Systems - HarnWhen either of the Reverse Osmosis trains is in automatic mode and consist of no alarms they will send out a "all set" status bit to the main PLC over the network. The water treatment plant SCADA will then monitor the completed water level or another RO production starting point. When RO production is needed, the main water plant PLC will open the well flush valve and validate that the plant inlet valve is closed. The plant SCADA will then start several wells as required by hydraulic considerations and preferred level of water production based on readily available RO trains. The well water will be diverted to squander up until the turbidity reaches an appropriate level for the RO train.

At this point, the primary plant PLC will inform the RO train(s) that the well flush is total via a command over the network. The RO train(s) will open their particular inlet valve(s) and begin to accept the well water as the plant SCADA starts to open the plant inlet valve and close the well flush valve. At this time the scale inhibitor will begin at a predetermined rate and that rate will be confirmed by the scale inhibitor circulation meter at the plant SCADA. The level in the scale inhibitor day tank and the scale inhibitor circulation will be monitored anytime scale inhibitor is being injected. If at any time the day tank shows a low level or there is a loss of circulation, the water treatment plant SCADA system will alert the RO PLCs which will begin a regular shutdown with an RO train flush. This series will be described later on. The RO train(s) will then go through a pre-flush sequence followed by getting in run mode.

When the RO train(s) go into run mode the RO PLC will direct the water plant SCADA PLC to call on the RO HPP in addition to the RO interstage pump by means of the Ethernet connection in between the plant SCADA PLC and the MCC based VFD's. We will read the running and or fault status from both of these VFD's over the Ethernet connection from the plant PLC.  The wanted speed of each VFD will be sent out to the water plant PLC constantly throughout the run sequence for VFD control. The RO train(s) mode will be shown the water treatment plant SCADA. Each RO train can be off, in pre-flush, running, or in post-flush due to an alarm or level. The RO train will now be producing water and will continue until an alarm takes place or the system is directed to end water production by the main water treatment plant SCADA based on finished water level or other events. While the RO train is running all status and monitoring points will be shown the plant SCADA. This will include all pressures and flows in addition to valve statuses. The water treatment plant SCADA will have control over all post treatment systems typical to the RO trains also. This might consist of chemical additions, degasifiers, transfer pumps and/or high service pumps. Again, we are not totally knowledgeable about the balance of plant operations outside the RO trains and therefore can not advise regarding manage plans or supply any type of detailed I/O lists. Nevertheless, normally we would see the water treatment plant SCADA start any post treatment chemicals and/or degasifiers based upon a running feedback verification gotten from any of the RO Membrane Housing trains by method of the communication network.

The circulation system controls are normally totally independent based on system needs and in no chance affect the Reverse Osmosis water production. As the RO Antiscalant trains remain in production they will be constantly monitoring various alarm specifications. Some of these include however are not limited to low RO pump suction pressure, high pump discharge pressure, low concentrate flow rate, high differential pressure throughout the cartridge filter, high or low feed pH, and high pressure pump VFD fault. The water treatment plant SCADA will keep an eye on for scale inhibitor low day tank level as well as loss of scale inhibitor circulation. , if the water plant SCADA senses any of these conditions for a time they will communicate the alarm to both of the RO trains .