Delivering the highest quality water has always been top priority for water utilities. But now, more than ever before, water supply safety is a US national priority and the Department of Homeland Security has charged the Environmental Protection Agency (EPA) with ensuring this safety.
Increasingly, municipalities are finding that integrated monitoring and control systems provide a valuable, central repository of information necessary to ensure the safe, reliable and cost-effective control over local and remote processes and operations.
The EPA requires plants to submit a plan on how they secure their distribution networks. Utilities must set effective security policies and procedures to ensure water quality and safety. This job is complex because ageing infrastructures and limited resources create vulnerabilities throughout the water distribution system. Utilities must be equipped to identify these security vulnerabilities and take reasonable steps to protect the water distribution system.
Physical security, including fences and perimeter security, guards, procedures and other similar measures, is one important focus and the most visible to the average person. An equally important security focus involves cyber security pertaining to system hacking, data integrity and verification.
However, a third focus of security efforts - contaminant detection and abatement - has probably the most directly relevant focus on public health and safety, especially now that new technologies, such as an online multiparameter measurement, are available to address the challenges associated with this type of security monitoring.
Multiparameters: forewarned is forearmed
The most significant challenge to contaminant detection and abatement is the sheer magnitude of the task. It is simply not feasible for plants to run tests that attempt to detect the presence of every conceivable contaminant and agent. Besides, the vulnerabilities in any distribution system can be very large.
The only way utilities can detect a problem is to identify changes in the water composition and understand what the various changes might indicate.
To do this, it is necessary for them to utilise an online, multiparameter electrochemical or optical water quality system (WQS). Such a system continuously monitors the raw and processed water online to develop a baseline for the normal water composition in order to detect any change.
A new online multiparameter WQS has been introduced by Emerson Process Management that incorporates a Foundation Fieldbus-based single panel of integrated instrumentation. The fieldbus enables this online WQS to continuously measure a variety of critical water quality variables at strategic points in the treatment and distribution systems, such as remote pumping stations.
A number of major US cities have begun to utilise online multiparameter water quality systems as part of their overall water monitoring and control programme. Incorporating an online multiparameter water quality system into such a district-wide automation and information system gives operators the realtime information they can use to quickly take action in protecting the water supply and helps ensure that acceptable water quality parameters are maintained throughout the distribution system.
This kind of monitoring makes up a crucial early warning system that enables plant personnel to quickly take action, thereby safeguarding the well-being of the public and the environment.
A complete multiparameter 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.
It is best to have baseline data for at least a year to understand, monitor and detect patterns. Once the baseline is determined, informed decisions can be made when changes beyond the normal patterns emerge.
Selecting a system
The first question many utilities ask when determining how to go about installing continuous online monitoring systems is: "How many early warning monitors does my plant and distribution system need?"
It is important to do a security vulnerability assessment to determine the weaknesses in the water distribution system. Utilities will most often find several vulnerabilities throughout the distribution, and it is best to install a WQS in each of these weak areas.
When selecting a partner to implement this kind of water quality monitoring system, utilities must understand that no one solution will fit every municipality. Each operation has its own individual vulnerabilities it must protect, so the solution should be flexible enough to be customised as much, or as little, as required. The most effective water quality systems combine specified instruments and sensors to create a customised system for monitoring water quality.
It is also important to select instrumentation that has been proven reliable and has a long life, even in the harshest environments. Another factor that plants should consider during the selection process is total cost of ownership, which includes installation, training and maintenance.
Using smart instruments allows analyser and sensor diagnostic information to be accessed by the operator to eliminate false positive alarms caused by instrument or sensor failures.
The days of using only 'grab sample' analysis are ending. 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.
Given the current environment of competing resources, priorities and pressures, multiparameter water quality systems are poised to play an increasingly important role in helping water utilities safeguard the health and safety of their communities.
For more information contact Luculle Stols, Alpret Control Specialists, +27 (0)11 249 6700, [email protected], www.alpret.co.za
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