Biologically Active Filtration for Taste and Odor Control at the Lake Manatee Water Treatment Plant

Mike Nixon, E.I.1; Phillip Locke, P.E.1, Katherine Gilmore2 1McKim & Creed, Inc., 2Manatee County

Lake Manatee Water Treatment Plant (WTP) is switching to the use of biologically active filtration as the primary treatment of taste and odor compounds present in the source water. By-products of blue-green algae (methylisoborneol and geosmin) commonly found in surface waters have an earthy or musty taste and odor. Manatee County currently uses powered activated carbon (PAC) at the WTP for taste and odor control, which has been an effective treatment method. However, the cost of PAC has been as high as $1 million dollars per year at the WTP. The WTP has a rated capacity of 84 MGD with 54 MGD from the surface water source of Lake Manatee and 30 MGD from groundwater sources.

Lake Manatee WTP will be the first to use biologically active filtration at the head of the plant. Through extensive lab scale testing, the staff at the WTP determined that biologically active filtration of the raw lake water prior to the existing treatment trains was effective treating the taste and odor compounds. Pilot testing of biologically active filtration was used to evaluate different types of filter media and design parameters such as various empty bed contact time. The new process design includes a new structure for the biologically active filters, named biological treatment unit (BTU), as well as other improvements at the plant. The new BTU structure will contain six biologically active filters with exhausted granular activated carbon for the filter media.

Some of the design considerations for the BTU project included maintenance of plant operations during construction, coordination with the design of the future ultrafiltration project, proprietary underdrain system, large diameter yard piping and tie-ins at the existing congested facility, incorporating a separate backwash equalization and return system, replacing the existing septic systems, and connecting the plant with the County’s collection system. Completion of construction and commissioning of the BTU are scheduled for early 2018. This presentation will discuss the new treatment process as it integrates into the existing facility, project background, and design and construction challenges and solutions.