The improvement to the pond system was required to increase the organic sewage loading treatment capacity for the city and its waste water customers. AMPI urged the city to make the improvements as they were discharging beyond their recommended limits and paying a surcharge. AMPI and the city developed an 80/20 percent cost share program for the new system.
Construction started on the new pond the fall of 1994 with hopes of having it in operation by the fall of 1995. The new pond is located west of the present lagoon system on 1.5 acres of land. It is 14 feet deep and holds about seven million gallons of waste water. The aerators are expected to run 24 hours per day, 365 days per year. They will never be shut down, Ron Mergen, public works director, said. Water from the aerated pond is gravity fed to the lagoons across Highway 33.
There are five headers with 320 diffusers feeding difused air into the pond. The diffusers lay on the bottom of the pond. The purpose of the diffusers is to keep the waste water in suspension, in a mixing action and to supply air to the bacteria which will decompose the solids.
When it came time to test the new pond, it failed the 30-day water balance test, the pond leaked. A company from San Antonio, Texas, was hired to find the leak. The pond was drained last fall and the company used an electronic probe to find the leak in the liner. "By the time the leak was found, it was too late in the fall to test again and put into use," Mergen said. "The pond was put to the test again this spring and another leak was found, this time in the outlet piping. The leak was repaired and the pond had to go through another 30- day water balance test, this time passing the test.
The pond was put to use on July 19. Mergen said it usually takes the bacteria two to four weeks to start working. A sign the bacteria is working is that the color of the water in the pond will change. When the pond was first put to work the water was clear, but gradually changed colors to a murky gray and it should turn a crisp brown. The sight of algae growth on the rocks indicates to Mergen the bacteria was starting to work in the new pond.
One benefit area residents will notice is the strong oder in the spring should be less when the ice goes off the lagoons. The pre-treatment pond will be in operation year-round and only a thin layer of ice will form on the pre-treatment pond, with many areas open. Stale air won't be trapped under the ice.
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