Buoy Marks Performance

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