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The process that the City of Ocoee uses to treat wastewater that comes from residential and commercial sources is called Bio-Denitro process. This process was designed in Denmark and used successfully throughout Europe and eventually introduced into the United States. The City of Ocoee spent a great deal of time researching various systems and the Bio-Denitro was determined to be the best.
The incoming (influent) wastewater contains biodegradable and nonbiodegradable materials, including some chemical compounds. The larger non-biodegradable materials are removed from the wastewater by mechanical bar screens. Grit, sand and other small materials are disposed of at a Class I landfill site.
The cleaned influent water goes into 2 oxidation ditches. Each ditch holds one million gallons of wastewater but is capable of treating 3 million gallons of wastewater per day. The ditches provide a controlled environment where microscopic organisms can live, grow and reproduce. This environment must have oxygen present in the water for respiration; 99% of the incoming wastewater is simply water.
The other 1% is waste material. This material is food for the bacterial organisms. By providing a suitable environment for the bacteria to live and grow, and by bringing the material in contact with the bacteria we have the beginnings of the wastewater treatment process.
After treatment in the ditches, we need to separate the solids from the liquids and this process is done in the clarifiers. A clarifier provides a turbulent-free environment where the solids settle to the bottom and the water flows from the top. The clarifier begins with 2 flow paths. One is the path that the settled solids take and the other is the path the water takes. Solids are sent back to the ditches if necessary, to balance the available food supply. If it is not necessary, the solids are sent to a digester as waste solids.
The function of the digester is to reduce the solids from the liquid to its most stable condition. There are no food sources introduced at this stage of processing. The bacteria that are present consume any food that may have escaped earlier treatment, and without any additional food they begin to consume each other.
From the digester, the waste solids are sent to the dewatering process. The press separates as much water as possible from the mixed liquid and the remaining solids are pressed into cake. This cake is eventually disposed of through land application by dumping it into an approved landfill site.
The clear water that leaves the clarifier is passed through a sand filtering process where any materials that may have escaped from the clarifier are removed. From the filters, the flow is sent into the chlorine contact chambers. In these chambers, chlorine is added to disinfect the water. Once the water has been disinfected, it is useable for irrigation and is then sent to the above ground reuse storage tanks.
By the time the water reaches the reuse tanks, it is clear and clean and in such good condition that it can be safely put back into the ground through irrigation. The City of Ocoee is continuing to install infrastructure to carry reuse water to residential homes and commercial businesses.