Environmental Engineering Reference
In-Depth Information
when simple in-process corrections could save them. Likewise, natural waters testing of
coastal and lake water with these delays slow down authorities' visibility on water-quality
issues and can also lead to conservative behavior such as unnecessary beach closings.
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More rapid tests such as the very common ELISA have poor sensitivity and remain rela-
tively complex. Thus, an unilled need exists for detectors that are very rapid. Depending
on the application, operators may want to be able to identify a speciic type or strain of
bacteria, or may wish to broadly monitor the activity of a broad range of single-celled
organisms:
• Tests must be speciic, broad, and rapid. The ideal test for microbes would speciate
them and determine whether cells were dead or alive, all while having a broad
bandwidth to identify a range of cell species. Few if any of the technologies cur-
rently in the works can achieve this in a rapid test. Most are overly speciic, to the
point of missing important species, or so broad, as in the case of Dutch start-up
Unisensor's cell counting technology, that they lump together living and dead
cells and put huge varieties of similarly shaped cells into broad categories.
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Such
technologies may ind narrow markets, but they fail to meet the industry's key
needs.
• Current technologies fail to deliver. If few prospective technologies it the need,
none of the current technologies do. Cell analysis is slow and cumbersome, and
inevitably requires an expert technician. Water-quality tests generally rely on
a narrow subset of the species that can cause disease. Related tests are also
relative failures. Wastewater's biological oxygen demand (BOD), a measure
of biological activity and, indirectly, the wastewater's organic strength, takes
5 days to deliver a result wastewater operators need immediately. The key tra-
ditional substitute to BOD, chemical oxygen demand, fails to reliably track
BOD's response and contains a generous dollop of mercury that requires special
disposal.
Biosensors based on living cells seem unlikely to be robust enough to replace
current practice.
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Electromechanical biosensors, similarly, face high barriers to
become practical.
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Miniaturized luidic devices, which automate laboratory pro-
cesses, may ultimately prove more promising.
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• Promising technologies remain in the literature. We see recent hints of next-
generation technologies such as Raman scattering and high-sensitivity luorescence,
and promising technologies funded by the EPA that might transform microbe
measurement.
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Even ANDalyze, which we mentioned earlier, believes it could
measure speciic strains of living cells with some more research. It will be some
time before these techniques escape the laboratory.
This is a ield with more opportunity than activity, but some nanotechnology systems
have been deployed for broader purposes, such as fouling.
Neosens' most innovative product is a fouling sensor, based on micro-electromechanical
technology, a classic nano analytic technique. The company, acquired in 2012 by Aqualabo
and now part of Orchidis Laboratoire, directly measures fouling that would otherwise be
inferred indirectly by measuring levels of antifouling chemicals.
An Italian start-up, Alvim, also offers biofouling sensors; however, these measure bio-
fouling only, using an electrical technique to measure biological activity on the sensor.
