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Keeping the water in our lakes, rivers, and streams clean
requires monitoring of water quality at many points as it gradually makes its
way from its source to our oceans. Over the years ever increasing environmental
concerns and regulations have heightened the need for increased diligence and
tighter restrictions on wastewater quality. Control of water pollution was once
concerned mainly with treating wastewater before it was discharged from a
manufacturing facility into the nation's waterways. Today, in many cases, there
are restrictions on wastewater that is discharged to city sewer systems or to
other publicly owned treatment facilities. Many jurisdictions even restrict or
regulate the runoff of stormwater — affecting not only industrial and commercial
land, but also residential properties as well.
In its simplest form, water pollution management requires
impoundment of stormwater runoff for a specified period of time before being
discharged. Normally, a few simple tests such as pH and suspended solids must be
checked to verify compliance before release. If water is used in any way prior
to discharge, then the monitoring requirements can expand significantly. For
example, if the water is used for once-through cooling, testing may include
temperature, pH, total dissolved solids (TDS), chemical oxygen demand (COD), and
biochemical oxygen demand (BOD), to name a few.
Once water is used in a process, some form of treatment is
often required before it can be discharged to a public waterway. If wastewater
is discharged to a city sewer or publicly owned facility, and treatment is
required, the quality is often measured and the cost is based not only on the
quantity discharged, but also the amount of treatment required. As a minimum
requirement suspended solids must be removed. Such removal is often accomplished
by filtering or using clarifiers. Monitoring consists of measuring total
suspended solids (TSS) or turbidity.
If inorganic materials have been introduced into the
water, their concentration must be reduced to an acceptable level. Inorganics,
such as heavy metals, typically are removed by raising the pH to form insoluble
metal oxides or metal hydroxides. The precipitated contaminants are filtered or
settled out. Afterward, the pH must be adjusted back into a “normal” range,
which often requires continuous monitoring of pH.
Organic materials by far require the most extensive
treatment. Many different methods have been devised to convert soluble organic
compounds into insoluble inorganic matter. Most of these involve some form of
biological oxidation treatment. Bacteria are used to metabolize the organic
materials into carbon dioxide and solids, which can be easily removed. To insure
that these processes work smoothly and efficiently requires regular monitoring
of the health of the biological organisms. The level of food (organic material),
nutrients (nitrogen and phosphorous), dissolved oxygen, and pH are some of the
parameters that must be controlled. After bio-oxidation the wastewater is
filtered or clarified. Often the final effluent is treated with an oxidizing
compound such as chlorine to kill any remaining bacterial agents, but any excess
oxidant normally must be removed prior to discharge. Oxidation Reduction
Potential (ORP)/Redox is ideal for monitoring the level of oxidants before and
after removal. The final effluent stream must be monitored to make sure it meets
all regulatory requirements.
The monitoring of wastewater pollution does not end there.
Scientists are continuously testing water in streams, ground water, lakes,
lagoons, and other bodies of water to determine if and what effects any
remaining contamination is having on the receiving waters and its associated
aquatic life. Measurements may include pH, conductivity, TDS, temperature,
dissolved oxygen, TSS and organic levels (COD and BOD).
Environmental testing is not limited to monitoring of
wastewater systems. Control of air emissions often includes gas-cleaning systems
that involve the use of water. Wet scrubbers and wet electrostatic precipitators
are included in this group. A flue gas desulfurization (FGD) system is one type
of wet scrubber that uses a slurry of lime, limestone, or other caustic material
to react with sulfur compounds in the flue gas. The key to reliable operation of
these units is proper monitoring of solids levels and pH. After use, the water
in these systems must be treated or added to other wastewater from the plant,
where it is treated by one of the methods previously discussed.
With proper monitoring, systems that maintain cleaner air
and water can be operated efficiently and effectively. Such operation will go a
long way toward maintaining a cleaner environment for us and future generations.
The Myron
L Company offers a full line of handheld instruments and in-line
monitor/controllers that can be used to measure or monitor many of the
parameters previously mentioned. The following table lists some of the
model numbers for measuring, monitoring, or controlling pH,
conductivity, TDS and ORP. For additional information, contact your
local distributor, refer to Myron L data sheets,
or Contact us by phone, fax or email (sales@myronl.com)
Note: When using a monitor/controller to measure pH
in streams that contain heavy metals, sulfides, or other materials that react
with silver, Myron L recommends using a double junction pH sensor with a
potassium nitrate (KNO3) reference gel to avoid fouling the silver electrode.
See the Myron L
720II
Sensor Selection Guide
for pH and ORP Monitor/controllers for more information.
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