Environmental Engineering Reference
In-Depth Information
10.3 Water Quality Sensors: A Mature Industry, or One in Its Infancy?
At $1.5 billion, the sensor market is barely worth wresting from major players who rely
on Edwardian chemistries and high-margin consumables for their business. The sensor
market, however, is more than it seems. Every thousand dollar instrument can be a major
differentiator in a power plant worth millions. Companies that would never consider play-
ing in the traditional, commoditized market for pH and turbidity meters can ind value in
unique instruments, such as specialized instruments to measure antifoulants deployed in
power plant cooling water.
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What appears to be a mature and rather unattractive industry is in fact in its infancy.
Revolutionary techniques just now inching out of the laboratory and onto the market, and
many more that have yet to make the leap, are making far more useful monitoring possible
for both industry and municipal water.
Miniaturization and entirely new, molecular-level sensors are making this revolution pos-
sible. Growing in many cases out of the very active medical and biological research commu-
nities, next-generation sensors beneit from great progress made in, for instance, the Human
Genome Project and in miniaturization of components for the telecommunications industry.
Water is a less predictable medium than medical samples, containing numerous poten-
tial interferences, and water commonly requires measurement at far lower concentrations
than needed by medical devices. The water industry generally is less deep-pocketed than
medicine, meaning that these higher performance systems must sell for far less than simi-
lar systems targeted to medicine. Nevertheless, technologies are making the leap.
10.4 Limits of Traditional Water Testing
To understand the nature of the revolution, it is necessary to understand the nature of
existing water testing. It falls generally into three categories: laboratory tests, ield tests,
and online instruments.
Traditional laboratory testing requires highly trained technicians and, increasingly, very
expensive and delicate equipment. Operators can choose whether they want to do tests in-
house in a laboratory at great ongoing expense, or outsourced to a contract laboratory, also
at great expense. Laboratory tests at this time can be arbitrarily sensitive, and this explo-
sion in sensitivity has given rise to concerns about so-called emerging contaminants such
as trace carcinogens and endocrine disruptors.
In most cases, getting results from a laboratory takes hours or days. By that time a munici-
pality has already sent its water to the distribution system, where it has been consumed by
the public, or sent their wastewater out of the plant into the environment. Most industrial
processes, likewise, are well along or inished before a laboratory can return relevant results.
Many tests can be done with simple ield tests. A simple pH meter requires little train-
ing, for instance, and there are simple tests for such analytes as chlorine and luoride,
which require a simple spectrometer or other analyzer costing as little as a few hundred
dollars. Field tests work well in relatively clean water and for analytes in the parts-per-
million (ppm) range, where extreme sensitivity is not required.
Field tests, however, have their limitations. They require an operator to be present wher-
ever a test will be performed, or at least someone to collect and prepare a sample for testing
later. Thus, at best, they are near real-time, but cannot be performed in a continuous fashion.
