Sac and Fox (Meskwaki) Permit Renewal Application Site Visit Report July 12, 2022 By Alex Owutaka Wastewater Treatment Plant Summary: Plant receives wastewater from casino, hotel, school, trading post, and tribal community of approximately 300 homes and 17 tribal buildings. The plant receives 50% of raw wastewater from the nearby casino lift station and 50% from the Spring Road Lift Station. These two lift stations were recently repaired and rehabilitated. Excess wastewater during high precipitation events is diverted to a 3-cell lagoon system, which was the original WWTF. A flow diversion valve in the main headworks opens when influent flows exceed 1100 GPM (1.58 MGD) and closes when they fall below 600 GPM (0.86 MGD). Flow is diverted to the 3-cell lagoons constructed in a series alignment (Cell 1 is 8.0 acres; Cells 2and 3 are 4 acres each; Total volume is 25.23 MG). The three lagoon cells have synthetic liners. A return flow pumping station is used to pump wastewater from the lagoon back to the wastewater treatment plant. The wastewater treatment train is as follows: • Headworks with stair screen and backup bar screen (installed in 2008) • Grit chamber and grit washer/classifier • Influent parshall flume with ultrasonic and flow totalizer • Storm flow diversion valve to lagoons and return flow pump station • 3-cell lagoon holding basin in series • 3 parallel treatment trains (Aeromod Sequox nutrient reduction) each with: o Selector tank o 1st stage aeration tank (continuously aerated) o 2nd stage aeration tank (intermittently aerated) o 2 clarifier tanks o Aerated sludge digestion tank o Sludge holding tank (only on first two trains) o 4 blowers with variable frequency drives o 0.8 meter sludge belt filter press and polymer feed system (installed in 2008) o Ultraviolet disinfection Unit (4 banks with 8 lamps each) o Emergency backup generator The effluent disinfection system is operated year-round and the bulbs are changed out every other year. Outfall 001 discharges treated effluent from the activated sludge plant to the receiving stream (unnamed tributary, locally known as Onion Creek), which flows one mile to the Iowa River. Outfall 002 is constructed to discharge from the 3-cell lagoon system to the receiving stream, but has not discharged in 10 years. Biosolids generated at the wastewater treatment facility are dewatered by using a belt filter press two or three times per year and ------- hauled to the Tama County Landfill. The sludge management plan developed in 2010 is still current. Water treatment Summary: Seven raw water wells along the Iowa River watershed. Wells 1-4 are oldest and treated with separate dual media (anthracite/green sand) filters and separate RO system. Wells 5-7 are newest and are treated with dual media filters (anthracite/gravel) and separate RO system. All filtered and RO water then blended for final treatment in radon removal chambers before discharging into clear well. Chlorine is added for disinfection and fluoride is added for dental treatment. The water treatment plant treats groundwater to remove iron, manganese, total dissolved solids and radon with a treatment chain that includes: a) single and dual media filters, b) reverse osmosis unit, c) radon aerator, and d) chlorination equipment. Effluent discharges from the filter backwash and reverse osmosis units are sent to the receiving stream via Outfall 003. Planned changes to the drinking water plant: a) Increased capacity of finished water with new storage, possibly 450,000 gallons, b) Install raw water bulk storage tank inside the treatment plant, c) Add permanganate removal system to precipitate out manganese, d) Change dual media filters for wells 5-7 from anthracite/gravel to green sand for better removal of manganese in order to lengthen life of the RO membranes from 2-3 yrs. To 5-6 years, e) Will drill new wells in 2023 to replace two well casings that collapsed and were taken offline. In essence, the entire drinking water plant will be repaired and rehabilitated in 2023, in addition to the pressure relieve station that has been replaced. Wastewater Treatment Planned Improvements: During high flows, excess wastewater is diverted from the headworks into the lagoon through a manhole and gravity main. The wastewater from the sludge press also flows into the lagoon cell through the same manhole and gravity main. The sludge press wastewater contains a polymer that binds the solids in the wastewater and has caused the manhole/lift station to backup nearly full of solids. Sludge has also built up at the end of the gravity sewer main, where it discharges to the lagoon. This has caused occasional overflows at the manhole because gravity flow does not have enough pressure to overcome the sludge pile in the lagoon. The plant also experiences issues with its control system because is outdated and valves are operated pneumatically. During the winter months, condensation in the airlines freezes preventing the controls from operating and results in valves being stuck open or closed. When the valves do not operate, the return activated sludge (RAS) and sequencing batch reactor (SBR) processes are bypassed resulting in poor effluent quality. The controls issues also affect the high flow equalization process. When the high flow diversion valve fails the wastewater simply goes out the overflow at the headworks and flows straight into the nearby creek untreated. As a consequence, total repair and rehabilitation of the wastewater treatment plant is planned in 2023. ------- |