Lake Meade Municipal Authority
The Lake Meade Municipal Authority expanded their existing 0.20 MGD Schrieber process facility by constructing a 0.35 MGD ITT/ABJ Intermittent Cycle Extended Aeration System (ICEAS) continuous fill SBR process facility. The new facility will allow the Authority to meet their future capacity needs and positions them to meet the Department of Environmental Protection’s Chesapeake Bay Strategy nutrient loading limits.
The existing Schrieber process facility was experiencing periodic organic overloading. The community’s collection system, comprised of approximately 1,000 individual grinder pumps, five central pumping stations and 15.4 miles of low pressure force mains, discharges an influent wastewater to the treatment facility that averages 250 mg/l of BOD and 240 mg/l TSS. The Authority decided that to meet corrective measures required by PA DEP, the existing Schrieber facility would be converted for aerobic sludge digestion and storage and a new facility that could meet the future organic and hydraulic capacity needs of the Authority and the Chesapeake Bay watershed nutrient loading limits proposed for existing wastewater treatment discharges as part of a single project.
The new facility consists of two continuous fill, SBR tanks, preceded by a fine screen to remove inorganic solids, and a Trojan UV 3000 disinfection unit. The SBR tanks receive raw influent continuously, while treated effluent is discharged to the UV unit for a maximum 60 minute period out of a 4.8 hour treatment cycle. A baffle wall, which isolates approximately 15% of the SBR tank volume, prevents short-circuiting of the influent wastewater by directing the influent flow to the base of the tank and spreading it across the entire width of the basin. This pre-react volume, which is aerated with the rest of the tank volume, also acts as a high F:M selector to control the growth of filamentous bacteria. As a safety feature of this process, there is no floating equipment within the SBR basins. All equipment is mounted to the tank walls and can be maintained without entering the basin. The tanks’ fine bubble diffusers are grid mounted to the basin floor, but unlike a true batch SBR system, the ICEAS process can operate using a single basin without process modifications or effluent degradation, allowing a basin to be drained for diffuser maintenance, if necessary.
To meet the Chesapeake Bay Strategy nutrient loading limits, the new facility is equipped with mechanical mixers, in-tank dissolved oxygen sensors, and VFD-controlled blowers so that aeration can be controlled by the dissolved oxygen concentration in the basins during the react period of the treatment cycle. This prevents over-aeration during aeration periods of the react cycle, allowing the dissolved oxygen to quickly crash during anoxic periods in the cycle. Alternating periods of oxic react and anoxic react generate nitrate and denitrify the nitrate created, respectively. Nitrogen gas produced by denitrification is stripped during a final aeration period prior to settling.
The new facility was seeded on October 2, 2007. Two weeks later, on October 16, 2007 the facility was operating normally and meeting all of its NPDES discharge limits as well as meeting the anticipated nutrient discharge limits. Analytical results of the new facility’s effluent after 14 days of operation were as follows:
CBOD – < 2 mg/l
TSS – 7 mg/l
NH3-N – 0.38 mg/l
Fecal Coliform – < 2/100 ml
Phosphorus – 0.7 mg/l
Total Nitrogen – 3.1 mg/l
Construction cost of the project was less than $ 5.25 per gallon of treatment capacity.
The existing Schrieber process facility was experiencing periodic organic overloading. The community’s collection system, comprised of approximately 1,000 individual grinder pumps, five central pumping stations and 15.4 miles of low pressure force mains, discharges an influent wastewater to the treatment facility that averages 250 mg/l of BOD and 240 mg/l TSS. The Authority decided that to meet corrective measures required by PA DEP, the existing Schrieber facility would be converted for aerobic sludge digestion and storage and a new facility that could meet the future organic and hydraulic capacity needs of the Authority and the Chesapeake Bay watershed nutrient loading limits proposed for existing wastewater treatment discharges as part of a single project.
The new facility consists of two continuous fill, SBR tanks, preceded by a fine screen to remove inorganic solids, and a Trojan UV 3000 disinfection unit. The SBR tanks receive raw influent continuously, while treated effluent is discharged to the UV unit for a maximum 60 minute period out of a 4.8 hour treatment cycle. A baffle wall, which isolates approximately 15% of the SBR tank volume, prevents short-circuiting of the influent wastewater by directing the influent flow to the base of the tank and spreading it across the entire width of the basin. This pre-react volume, which is aerated with the rest of the tank volume, also acts as a high F:M selector to control the growth of filamentous bacteria. As a safety feature of this process, there is no floating equipment within the SBR basins. All equipment is mounted to the tank walls and can be maintained without entering the basin. The tanks’ fine bubble diffusers are grid mounted to the basin floor, but unlike a true batch SBR system, the ICEAS process can operate using a single basin without process modifications or effluent degradation, allowing a basin to be drained for diffuser maintenance, if necessary.
To meet the Chesapeake Bay Strategy nutrient loading limits, the new facility is equipped with mechanical mixers, in-tank dissolved oxygen sensors, and VFD-controlled blowers so that aeration can be controlled by the dissolved oxygen concentration in the basins during the react period of the treatment cycle. This prevents over-aeration during aeration periods of the react cycle, allowing the dissolved oxygen to quickly crash during anoxic periods in the cycle. Alternating periods of oxic react and anoxic react generate nitrate and denitrify the nitrate created, respectively. Nitrogen gas produced by denitrification is stripped during a final aeration period prior to settling.
The new facility was seeded on October 2, 2007. Two weeks later, on October 16, 2007 the facility was operating normally and meeting all of its NPDES discharge limits as well as meeting the anticipated nutrient discharge limits. Analytical results of the new facility’s effluent after 14 days of operation were as follows:
CBOD – < 2 mg/l
TSS – 7 mg/l
NH3-N – 0.38 mg/l
Fecal Coliform – < 2/100 ml
Phosphorus – 0.7 mg/l
Total Nitrogen – 3.1 mg/l
Construction cost of the project was less than $ 5.25 per gallon of treatment capacity.
Lake Meade Municipal Authority
Lake Meade Waste Water Treatment Facility 0.350 MGD
Nutrient Removal meeting the Chesapeake Bay Criteria. |
Lake Meade Municipal Authority
Lake Meade Municipal Authority WWTF Design.
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