Environmental Engineering Reference
In-Depth Information
Toxicity Monitoring and Toxicity Meters
Tox ic it y measurement devices measure general toxicity to biological organ-
isms, and detection of toxicity in any water/wastewater asset can indicate a
potential threat to the treatment process (in the case of influent toxicity), to
human health (in the case of drinking water toxicity), or to the environment
(in the case of effluent toxicity). Currently, whole effluent toxicity (WET) tests,
in which effluent samples are tested against test organisms, are required of
many National Pollutant Discharge Elimination System (NPDES) discharge
permits. The WET tests are used as a complement to the effluent limits on
physical and chemical parameters to assess the overall effects of the dis-
charge on living organisms or aquatic biota. Toxicity tests may also be used
to monitor wastewater influent streams for potential hazardous contamina-
tion, such as organic heavy metals (arsenic, mercury, lead, chromium, and
copper) that might upset the treatment process.
The ability to get feedback on sample toxicity from short-term toxicity
tests or toxicity meters can be valuable in estimating the overall toxicity of
a sample. Online real-time toxicity monitoring is still under active research
and development; however, several portable toxicity measurement devices
are commercially available. They can generally be divided into categories
based on the way they measure toxicity:
• Meters measuring direct biological activity (e.g., luminescent bacte-
ria) and correlating decreases in this direct biological activity with
increased toxicity
• Meters measuring oxygen consumption and correlating decrease in
oxygen consumption with increased toxicity
Communication and integration
This section discusses those devices necessary for communication and the
integration of water and wastewater system operations, such as electronic
controllers, two-way radios, and wireless data communications. Electronic
controllers are used to automatically activate security equipment (such as
lights, surveillance cameras, audible alarms, or locks) when they are trig-
gered. Triggering could be the result of the tripping of an alarm or a motion
sensor, a window or glass door breaking, variation in vibration sensor read-
ings, or simply input from a timer. Two-way wireless radios allow two or
more users who have their radios tuned to the same frequency to commu-
nicate instantaneously with each other without the radios being physically
connected with wires or cables. Wireless data communications devices are
used to enable transmission of data between computer systems or between
a SCADA server (see Section 3.4) and its sensing devices, without individual
components being physically linked together via wires or cables. In water
