SCADA Only One Tool in Water System Management
SCADA is a tool with a very specific defined set of functions. SCADA can: turn devices on or off, display real time operational data, provide equipment-wide to system-wide views of operation, trend data, and alarms. It is not supposed to be a tool for detailed analysis of past performance.
Grant Van Hemert
In the 1969 sitcom "The Brady Bunch", the character Jan was living in the shadow of her older sister Marsha. Jan would lament "Marsha, Marsha, Marsha". As you peruse through trade journals and magazines, you see article after article on SCADA. Like Jan, you could lament "SCADA, SCADA, SCADA". From this plethora of articles you can get the feeling that SCADA is the "Go-To" tool for water and wastewater control. But is it?
The simple answer is yes, maybe, and no. SCADA is a tool with a very specific defined set of functions. SCADA can: turn devices on or off, display real time operational data, provide equipment-wide to system-wide views of operation, trend data, and alarms. If this is all you want then SCADA is your tool, and the answer to the question above is "Yes".
What is SCADA not intended to do?
SCADA is a real time tool. It is not supposed to be a tool for detailed analysis of past performance. Of course, you may need to know something about past performance to be able to react to current conditions. Thus some form of trending is included. The trending function is as close to analysis as most SCADA softwares get.
Let's say a water treatment operator wants to look at chemical usage in three GAC filters and determine how each filter behaved over the past six weeks. In this case, SCADA is your tool of choice. Some SCADA let you look at these three filters and compare their performance with some time period in the past.
What if you want more analytical capability?
As stated, SCADA, by design, is limited in its data analysis tools. If you want more, then you have a variety of options. One is to install something called a historian. A historian sometimes called an Operational Data Management System (ODMS), bolts onto a SCADA and has expanded analytical tools for trended data. Some people believe a historian is just an expansion of the SCADA trending tools, however a historian can look at any data in a database even if it was not collected via the SCADA system. Use of a historian, or ODMS, is already a mainstream feature in large to extra large facilities, and is quickly being adopted by many small to medium size facilities.
To continue the analogy above, what if you wanted to graphically see how the three basins operated during the period between Thanksgiving and New Year's for each of the past six years? Most SCADA systems are not capable of doing this. So, the answer to whether or not SCADA is your "Go-To" tool is a "Maybe". But, a historian can do this. Of course, the historian is still just reporting data, it is up to the operator to find a way to analyze that data, and remove the unwanted data.
|Water Management Suite (WMS) interconnection map.|
For instance, when the filters mentioned above are backwashed, then the turbidity spikes. This data point might register as the maximum turbidity detected in a historian report, but this is not a relevant piece of operational data. In order to find the true relevant maximum, an operator would have to eliminate all the turbidity spikes associated with backwash to find the true maximum. SCADA is not designed to handle this task so the answer to the "Go To" question in this instance is "No".
Traditionally, obtaining this requires taking raw data and exporting it into a customized database. Does this sound like a lot of work, with some potential problems? Yes it does.
First, the database has to be developed. Some of the larger plants have internal staff that is capable of doing this. Others may rely on external developers. Once facility staff see what this tool can do, they tend to want to add their own items. These homegrown tools tend to evolve overtime as different needs are bolted on, which may cause the tool to become cumbersome to use. Also, if the staff person leaves, or the facility has a falling out with the developer, then the facility can be left with a tool and no resources to modify it.
Another problem is if you want to integrate a distribution systems flow monitoring with an AMR system, or if you want to incorporate online instrumentation with laboratory testing results. This type of information analysis requires sampling from multiple databases and could require complex coding in the database.
This type of integration amongst all the available databases within a facility has significant benefits, including mass balancing, water age, and effectiveness and efficiency of a device or system. Also, this gives you the ability to do some detailed correlated cause and effect between various aspects of your processes.
What is a better way to analyze data?
Although SCADA is still advancing with technology, the concept itself is well defined. Advanced water operations analysis tools, however, are a rapidly evolving area, with multiple active players from suppliers, to systems integrators, to consultants leading the innovation.
While the effort has not fully solidified, it is apparent that different types of analysis can be accomplished at a water or wastewater utility. Some analysis tools may be specific for water, others for wastewater. Some might be suited for large facilities, while others may be better for smaller facilities. Finally, some facilities may elect to use only some tools with the possibility of expansion later. This means the solution must incorporate the flexibility that SCADA was not designed for. A term is emerging to describe this philosophy; it is a Water Management Suite (WMS).
What is the concept of a WMS?
A WMS is commercially available software with a core component and separate modules that can be added for various water and wastewater functions. These modules are the reason why it is called a suite, and not a system. Since a WMS is a commercially available solution, it does not have the associated challenges presented by a homegrown solution. There are a variety of water information management suites available in the US water industry. Schneider Electric has two WMS systems, Citect's Ampla™ and Telvent's WMS. These systems can be used together, or separately.
A WMS works by connecting to the databases of applications within a water district including: Graphical Information Systems (GIS), meter reading systems (AMR/AMI), Maintenance Management System (MMS), Laboratory Information Management (LIM) system, SCADA, power monitoring systems, and others. Once connected, data is examined and correlated together to create reports on different aspects of plant operation.
Part of a WMS' operation is to contextualize the data. This is where data is tested for validity before it can be used in the report. An example was given earlier when we discussed the need to remove high turbidity spikes that correlated with backwash. In this case, the data that remained after the filtering would be contextualized. The report therefore would be only comprised of valid relevant data, which helps lead to solid decisions, and trust in the accuracy of the report.
One common application is in the area of leak detection. In this application, the software gathers data to mass balance the system, and help to determine where imbalances are occurring. A southern California municipality used to take weeks to mass balance. With their WMS, they can do it in a few clicks.
Another way that a WMS can be used is in the realm of effectiveness. In this application, the software studies the performance of the system, its individual processes, and each device. The software then follows the methodology detailed by a group called OEE (www.oee.com), to come up with an effectiveness factor. This factor can be used to understand a best performance spot for each machine, by looking at up time, quality of water produced, and total run rate (including downtime).
As we all know, energy is becoming a greater concern. A WMS can look at how energy is used, and compare it against other parameters to develop total cost. For instance, a new coagulant may be used for cost, but it increased the number of backwashes. By correlating the total cost of energy with the backwashes, it can be determined if the cost of the additional backwashes offset the chemical savings.
A last example is in regards to Demand Forecasting. This function allows operators to balance water production and demand, using weather forecasts and consumption trends, and generate total system send-out for the current and subsequent delivery days.
With the amount of articles written about SCADA it is easy to assume that it is the ultimate "Go To" tool for water and wastewater operation. But SCADA is the first step to a facility reaching its best most efficient operation. The next steps are a historian, followed by a WMS. These tools allow a utility to become hyper accurate in its process, maintenance, and operations. Once installed, a WMS will make you utter another quote from our "Brady Bunch" friend Jan. This time we will say "Lovely, Lovely. Isn't it just absolutely lovely?"
About the Author: Grant Van Hemert, P.E., is a water wastewater applications specialist for the Schneider Electric Water and Wastewater Competency Center. He has 17 years experience in water and wastewater automation, and another five years in automation and control engineering. He is a registered P.E. in the state of North Carolina and is the past chairperson for the AWWA Instrumentation and Control Committee. Van Hemert can be contacted at firstname.lastname@example.org.