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Conventional wastewater treatment lagoons encounter numerous problems that must be solved constantly. Prime among these problems are the sludges that eventually settle to the bottom of a pond; under traditional circumstances, these must be removed regularly so that the sludge layer will not accumulate more quickly than it can be biodegraded.
Slow degradation means odorous septic conditions that produce sulfuric acid, methane gas and other gases that create low pH conditions, making pond water more difficult to treat. Such ponds often must hold incoming sewage for six months or longer to achieve acceptable levels of pollution removal.
There is a fundamental reason that these conditions occur: the lack of an ample oxygen supply to allow bacteria to do its proper job. The beneficial bacteria is aerobic—meaning it requires oxygen—and in the presence of sufficient oxygen, the material that settles to the bottom of a pond is eventually biodegraded into carbon dioxide and inert materials. Because a large portion of municipal wastewater consists of biodegradable organic carbon matter, the remaining active bacteria can quickly decompose much of the settled sludge.
Plentiful oxygen can be supplied by a few different methods, but the most cost-effective and cleanest method available today is that of windmills. Compressors are turned by wind, and oxygen is then pumped into the pond, aerating the water.
The benefits of such aeration were recently realized by the city of Muldrow, Okla. The town has a wastewater pond that is located about 500 yd from a high school and directly adjacent to a baseball field; the lack of oxygen in its water was causing problems.
“When the weather started changing, the water would start getting septic,” said Muldrow City Manager David Taylor. “The smell would get pretty bad.”
Driving down the highway one day, Taylor noticed a windmill on a pond. He observed that the pond water was very clean and inquired about it. His inquiry led to the city being provided two 20-ft windmills on a trial basis by Koenders Windmills, Inc. The problem appears to have completely abated.
“The oxygen level is well up in the pond,” Taylor said. “The smell has gone way down.”
A prime indication of the health of the pond is nature itself. “We have lots of turtles out there,” Taylor added. “When you’ve got a lot of turtles in a holding pond, that indicates your water is in pretty good shape. We’ve got a lot of ducks and geese landing on it too.”
The health of Muldrow’s wastewater pond has attracted the attention of other municipalities interested in cost-effective and environmentally safe methods of treating wastewater lagoons. The Oklahoma Department of Environmental Quality also recently paid the city a visit.
The windmills installed were 20-ft double-diaphragm models, as the company has found through research that one such windmill per acre of wastewater lagoon has produced the best results. The double-diaphragm compressor allows the pumping of double the air of a single-diaphragm model. The windmill can provide oxygen with as little as 3- to 5-mph winds.
Using Nature to Restore Nature
Adequate aeration is also important for keeping lagoon water mixed and in suspension. Insufficient mixing causes the creation of thick solids that fall to the bottom of the lagoon before proper treatment has occurred. Septic conditions then occur that pull available oxygen from the upper layers of the pond and reduce the overall effectiveness of treatment.
When water is in an ideal mixed condition, incoming pollutants and wastewater are more evenly distributed, resulting in uniform and efficient treatment. The action also causes settled solids to be resuspended and brought back into contact with the microbial population floating throughout the pond.
Another method of providing oxygen to wastewater ponds is powered aerators operating with motors. While these may be effective at pond aeration, they are expensive in terms of power consumption. A windmill obtains its power directly from the wind and consumes no electrical power; hence, it contributes to the environment not only by aerating the pond but by conserving vital energy as well.
These windmills are being successfully used in farm ponds, golf courses, stocked fishing ponds, residential ponds and lakes. They restore water quality and reduce algae and mosquito problems.
They are a case of using nature to restore nature. Proper treatment of wastewater lagoon systems with windmills is another step in safely reclaiming our environment.