The goal of this project was to expand Okeechobee Utility Authority’s (OUA) Surface Water Treatment Plant while meeting the challenges of limited space, raw water quality, available capital, and new EPA regulations. The preliminary engineering, consisting of site visits, pilot studies, and research, resulted in an innovative design for surface water treatment. This design combines several processes to compensate for the limited amount of space and remove contaminates associated with surface water. These processes include: rotary screening, Actiflo clarification, chemical addition, peroxone disinfection, and filtration. This combination of Actiflo clarification and peroxone disinfection is a first in the treatment of surface water in Florida.
The goal of this project was to expand Okeechobee Utility Authority’s (OUA) Surface Water Treatment Plant while meeting the challenges of limited space, raw water quality, available capital, and new EPA regulations.
The Okeechobee Utility Authority (OUA) Water Treatment Plant was originally constructed in 1926. The plant was last expanded in 1992 and the treatment process included aeration, coagulation, flocculation, sedimentation, pH adjustment, filtration, and chloramime disinfection. Prior to the current expansion, the plant had a permitted capacity of 3.2 MGD. In 2000, the plant reached 80% of its permitted capacity and thus needed to be expanded. The recent plant expansion and modification expanded the plant capacity to 5.0 MGD. The age of the plant and the surrounding facilities restricted the amount of space available for expansion and the new design utilized a limited footprint. Figure 1 shows the plant site and the new treatment processes (outlined in red) which was constructed on the existing property while still keeping the existing plant online.
OUA had the option of meeting future demand by utilizing either ground water from the surficial or Floridan aquifers, or surface water from Lake Okeechobee. The three important factors to consider when choosing a potable water source are availability, quality, and cost. Lake Okeechobee provides a reliable and adequate quantity of source water and is a Class I water, meaning it is suitable as a potable water source. The small amount of head loss associated with pumping from the lake makes surface water cheaper to pump than ground water. However, surface water is typically more contaminated than ground water. Major contaminants include microbes such as blue-green algae and bacteria, turbidity, and various minerals. Turbidity, total hardness, odor, and color create the greatest concern in Lake Okeechobee. Harmful algal blooms and the varying water quality also make the lake water difficult to treat.
In Okeechobee, ground water is not as readily available as surface water and it can have high concentrations of iron, manganese, and hydrogen sulfide. It is also more expensive to pump due to the high head pressure it must overcome. However, ground water is typically cleaner with a lower bacteria count and has a more uniform quality than surface water. Based on the comparison of the two alternatives for source water for the expansion, surface water from Lake
Okeechobee was chosen as the most viable option.
Several different options were investigated for primary clarification including the Actiflo® and MIOX® systems. Actiflo® is a microsand ballasted coagulation/flocculation, settling water treatment process that was evaluated because of its small footprint and ability to remove turbidity, algae, cryptosporidium, and other undesirable water contaminants. MIOX® is a disinfection system based on a membraneless electrolytic cell that produces a liquefied stream of aggressive mixed oxidants that disinfect water.