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High Tech Focus
A unique ammonia/phosphate analyzer designed to take
readings directly in the wastewater, in other words, precisely where the
nutrient concentration needs to be measured, also delivers real-time, online
information about nutrient concentration in the process.
Designed especially for the water and wastewater industry,
the EVITA® INSITU 4100 analytical nutrient analyzer now is available from
Danfoss Water & Wastewater, N.A. Division. It was developed to provide a
system that saves money, improves efficiency and measurement accuracy, and
Monitoring and controlling nutrients with a real-time,
online system can provide these important benefits to a wastewater treatment
cost savings of up to 30 percent, realized by improved plant efficiency resulting from stability and continuity in the treatment process;
control lowers sludge production and has been proven to increase plant capacity
by as much as 25 percent;
and polymer usage throughout the plant is significantly reduced;
quality is improved.
How does INSITU 4100 work? It utilizes a unique
antibacterial, ion-permeable membrane to stop bacteria and sludge from entering
the analyzer. This membrane allows the analyzer to operate using a clean
carrier solution, instead of wastewater as used in a traditional analyzer. This
helps eliminate any measurement errors caused by a fluctuation in sludge
density or color, thereby increasing measurement accuracy and reducing
maintenance frequency. The insitu analyzer measures continuously —
performing a new measurement of the ion concentration every second.
The output signal is only delayed slightly from the
real-time value, making it useful for advanced process control.
The insitu analyzer "sees" the wastewater's
nutrient concentration by allowing only ions to transfer through its
ion-permeable membrane; wastewater does not flow into the analyzer.
A carrier solution (de-ionized water) is pumped through a
channel behind the membrane. Ions in the wastewater migrate through the
membrane, into the carrier solution, until the concentration of ions in the
carrier solution is equal to the concentration of ions in the wastewater.
Reagents are mixed into the carrier solution, resulting in a
color change. The color intensity, which depends on the ammonia or phosphate
concentration, is measured by a photometer (colorimetric technology) and an
electronic signal is sent to the converter for display and control.
After the measurement is complete, the waste solution is
pumped to a sealed retention bag for storage within the transmitter.
The cost of installing a traditional nutrient monitoring
system often can exceed the cost of the system itself. Traditional analyzers
require the installation of a pump to draw a sample from the wastewater basin,
heated piping to bring the sample to the analyzer, a filter to
"clean" the sample, and a protective housing or building to ensure
a stable measurement environment. These external environmental requirements add
to the installation cost, impede real-time measurement, and create the
potential for inaccurate measurement results.
The traditional system pumps a sample from the wastewater to
the analyzer, where it is measured. Using wastewater as the carrier solution
results in a measurement error when the sludge density or color fluctuates. In
order to reduce the effect of this problem, these systems depend on filters to
clean the sludge and bacteria from the wastewater sample before it enters the
The problem with using a filter is that they tend to clog.
If the system has a clogged filter, it will adversely effect the response time,
causing a delay of up to 100 minutes before the sample reaches the analyzer.
Finally, filters can also distort the measurement because the bacteria trapped
in the filter is still active. Consequently, the concentration of nutrients
from the sampling point is altered before the sample ever reaches the analyzer.
Once the sample reaches the analyzer, a periodic measurement is taken only once
every 20 to 30 minutes. This long delay, between taking the sample and
measuring it, makes reliable automatic process control very difficult to
The development of the insitu system was driven by a desire
to provide a system that saves money, improves efficiency and measurement
accuracy, and reduces maintenance. As shown in the photo, the analyzer is
easily mounted directly into the wastewater, significantly reducing the cost of
installation (no pumps, piping, filter, or protective housing). Its unique
design allows the analyzer to float up or down with the surface of the
wastewater, making it ideal for applications with frequent fluctuations in
The INSITU 4100 analyzer comes with a replaceable,
ion-permeable membrane cartridge. All of the reagents necessary for reliable
calibration and measurement are supplied in an easily replaced, sealed
container. This container consistently ensures the correct quantity and
concentration of chemicals and eliminates the need for handling of potentially
dangerous chemicals by the operator.
The insitu analyzer requires only about 15 minutes of
maintenance five to six times per year. Traditional analyzers must be
disassembled for internal cleaning once a week and require cleaning of the
filter, using a strong acid, at least once a week or more (depending on process
conditions). They also have tubes and lamps that must be checked and/or
replaced every two months, and the filter material must be replaced at least
once a year.
The insitu analyzer also features an optional cellular
communication package, which enables the transmission of alarm/error messages
in text format for up to four mobile phones. Using this information a problem
can be diagnosed and corrected from a remote location, further reducing labor