Buoy Marks Performance

Kalamazoo Water Reclamation Plant uses analyzer to meet

Isco, Inc.

The Kalamazoo Water Reclamation Plant has the reputation of
producing some of the best effluent in the state of Michigan.

Flow into the plant is approximately 27 mgd, half of which
comes from significant industrial users such as large manufacturers and hospitals,
the rest comes from residential customers, schools, and other industries. With
this combination, the potential for large, unpredictable phosphorous loading
exists.

In the past, the plant relied on lab results to dictate
appropriate actions with respect to control of chemicals for prosperous removal
and how they impacted effluent quality.

To provide faster and more economical means of controlling
chemical addition for phosphorous removal and monitor effluent quality for the
NPDES permit, the plant wished to have a continuous online monitoring system
installed.

A closer look

In the fall of 2003, the city, after closer examination of
available analyzers on the market, opted to evaluate the Isco/STIP Model Helios
Phosphate Buoy System, manufactured by Isco, Inc., to measure the concentration
of phosphate in their final effluent.

The process buoy measures phosphate in wastewater using
continuous batch analysis, typically in aeration basins, activated sludge, or
final effluent. The measurement cycle, using photo optical detection, occurs in
intervals of 6-8 minutes. Automatic, dual-standard calibration and
automatic self-cleaning allow continuous, maintenance-free operation for
4-6 weeks.

A sample is pulled through an insitsu onboard filtration
device to remove solids. The phosphate reaction is based on the ascorbic acid
method. Within the optical cell, the sample then is analyzed for light
absorption with a dual-diode light source. The full range of phosphate content
is evaluated at a wavelength of 525nm, based on polynomial algorithm. Lower
concentrations also are evaluated at a more sensitive wavelength of 732nm,
based on linear calibration.

The initial objective of the Kalamazoo study was to
investigate the phosphorous concentration patterns achieved over a four-week
period and evaluate the performance of the Isco analyzer. Samples were tested
in the water treatment plant lab using the ascorbic acid method--the same
method used by the Isco buoy system. Samples were taken several times during the
course of the day in duplicate. At the time when the sample was drawn, a log
was kept to record the output of the analyzer. The 4-20mA output also was
interfaced to an in-house SCADA system.

“The comparison of manual samples collected, with
concentrations indicated by the Isco/STIP process buoy were excellent,”
said Ron Jansen, plant supervisor, Kalamazoo Wastewater Treatment Plant.
“The analyzer performed flawlessly over a period of four weeks without
any manual intervention.”

“During the course of the evaluation, a call was
received from a local industrial discharger to alert the plant to an increase
in phosphorous load,” said Jansen. “Ironically, the buoy system has
already detected the increase such that the plant could adjust the chemical
feed to ensure effluent quality guidelines were not exceeded.”

4700 Superior St. * P.O. Box 82531 * Lincoln, NE
68504

Phone: 402/464-0231

www.isco.com

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