Click here to enlarge imageWhen selecting a partner to implement this kind of a water quality monitoring system, utilities must understand that no one solution will fit every plant, and they should be wary of vendors that sell only one pre-packaged solution. Each plant has its own individual points of vulnerability it must protect and its own needs in terms of cost, training and maintenance, so the solution should be flexible enough to be customized as much or as little as the plant requires.
In addition, it's important the utility selects instrumentation that's been proven to be reliable and have a long-life even in the harshest environments. Sensors that have proven they can stand up to harsh applications, such as those in chemical or pulp and paper processing, will need to be replaced less often than sensors that are normally used in more benign applications, such as lab environments.
Another cost factor that plants must consider during the selection process is total cost of ownership, such as installation, training and maintenance requirements. Some instruments available in water quality monitoring systems are easy to use and minimize training and start-up time. Using smart instruments allows analyzer and sensor diagnostic information to be accessed by the operator to eliminate false positive alarms caused by instrument or sensor failures.
In addition, many long-life sensors require so little maintenance that operators do not need to interact with the analysis system on a day-to-day basis. In terms of installation, there are a couple of options utilities can choose from depending on their needs. They can choose a system that comes pre-integrated with a complete process control system and, in that case, installation is greatly simplified. A utility may also select a plug-and-plumb system that is compatible with an existing SCADA system.
A complete solution for water quality protection should incorporate the continuous measurement of the following parameters:
• pH – to detect changes that impact the potential corrosion of the distribution network
• ORP – to determine the level of chemical reactivity
• Conductivity – to provide an indication of total dissolved solids
• Free Chlorine – to maintain optimum residual disinfection levels
• Monochloramine – to monitor effective disinfection levels
• Ammonium – to determine if enough ammonia is present to complete monochloramine reaction
• Dissolved Oxygen – to indicate if a healthy environment exists
• Turbidity – to indicate biological growth and suspended matter
The days of using only grab sample analysis are coming to an end. The key to a safe and secure water quality system in today's environment is to use established parameters to measure change over time by continuously monitoring at various locations throughout the water distribution network. By monitoring patterns and detecting changes in these patterns, utilities can be better prepared to detect problems in the water before those problems affect the communities they serve.
About the Author:
Richard Baril, Product Marketing Manager, Emerson Process Management, Rosemount Analytical, Liquid Division has been active in the drinking water, wastewater and process industries for over 17 years. He is a current board member for the International Ozone Association, has spoken at several industry conferences and has authored numerous articles in a variety of publications.