Case Study

Water Clarification Project Using AOS 7368

AOS was approached by an engineering firm working with a development company on a project where they were attempting to dewater a five-acre lake enough to install features needed to convert the lake into a retention pond. For the construction to take place, roughly 360 million gallons of water had to be removed prior to installing the necessary features.

Once treated, the water would be discharged into the adjacent river. To comply with the river authority and the state’s requirements, the lake required surface water treatment to improve its clarity. At the beginning of the raw water clarification project, the clarity of the water in the lake was khaki in color with zero clarity. The average NTU of the river was 30 NTU. The goal was to match or beat the quality of the water in the river.

AOS recommended treating the water with AOS 7368 to improve the water’s clarity. AOS 7368 is a biodegradable polymer used to enhance settling, reduce TSS and Turbidity, and remove sand and silt. The product would be introduced into the lake by injecting the product into the suction side of 12” pumps positioned around the lake, recirculating the water while being dosed with the product.

Phase One

The project was performed in two phases. The initial phase consisted of treating a small portion of the lake, in order to showcase the product’s abilities. A floating boom with a ten-foot curtain was stretched from one bank to another, creating a smaller area of water to treat. AOS 7368 was injected at 30 ppm into this portion of the lake using a chemical metering pump injecting into the suction side of a 6” trash pump. As the pump circulated the water, the clarity improved from a 278 NTU down to 47.2 NTU within ten days. The transformation would have been much quicker if the boom installed completely isolated the small area from the entire lake. Since the treatment was not isolated in the sectioned off area, the NTU results were slightly throughout the entire lake.

Phase Two

Once the product proved its ability on the small scale, four 12” trash pumps, each having a tote of AOS 7368 and metering pump, were positioned around the banks of the entire body of water treating with 30 ppm of AOS 7368. After three days of treatment, the clarity improved to 2.0 NTU, far exceeding the requirement of 30 NTU to match the river. The progress was much quicker due to the entire body of water being treated simultaneously.

When the clarity of the water was desirable, a sample was submitted to a laboratory for analysis to determine it was safe to discharge into the river. Once the laboratory results were available and showing the water to be no threat to aquatic life and of the environment, the contractor was able to position multiple 12” pumps in order to discharge the treated water into the river without concern of any environmental hazards.

 Turbidity Results
Phase One: Treating SW Corner Finger with two 6″ Pumps
8/3/20 Day #1
339 – North side of Lake
319 – 20 yards outside of boom
278 – Inside Boom
330 – North side of Lake
332 – 20 yards outside of boom
299 – Inside Boom
330 – North side of Lake
332 – 20 yards outside of boom
297 – Inside Boom
323 – North side of Lake
309 – 20 Yards outside boom
261 – Inside Boom
314 – North side of Lake
293 – 20 Yards outside boom
117 – Inside Boom
294 – North side of Lake
283 – 20 Yards outside boom
98 – Inside Boom
281 – North side of Lake Approximately 550 Gallons of Product Used on Phase #1
274 – 20 Yards outside boom
47.2 – Inside Boom 65.5 8″ Below Surface
Phase Two: Treating Entire Lake with Four 12″ Pumps (Treatment began on 8/25/2020
8/27/20 Day Three of Phase Two
Pump 1 (North Side): 85.2
Pump 2 (Northwest Side): 39.3
Pump 3 (Southwest Side): 24.4
Center of Lake: 39.3 12″ down 40.1 6″ down 38.6 12 feet down 72.0
Pump 1 (North Side): 3.12 Approximately 1900 Gallons of Product Used on Phase #2
Pump 2 (Northwest Side): 2.51
Pump 3 (Southwest Side): 4.75
Pump #4 (Southeast Side): 2.6 Total Chemical Usage: Approximately 2500 Gallons to Date
Center: Surface 2.4 12′ Down 3.01

Photo Galleries

Before Treatment

During Treatment

After Treatment

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