Case Study for Customer Location ND47:
Reservoir or Lake Use:
Municipal wastewater treatment system for a population 16,000.
System Overview and Reservoir:
The city’s wastewater lagoon system consists of 6 treatment basins. There are 2 total mix aeration basins (A1 and A2): each basin is 1 acre in area and 11 ft deep. Design loading was 935 lbs of BOD5/acre/day, with 60 hp of grid aeration operating 24 hrs/day in each aeration basin. Cell 1 is the primary cell, 43 acres in area, 3.5 ft deep, and a volume of 42 MG. Cell 2 is 43 acres in area, 3.5 ft deep, and a volume of 42 MG. Cell 3 is 58 acres in area, 12 ft deep, and a volume of 151 MG. Cell 4 is 29.7 acres in area, 20 ft deep, and a volume of 145 MG. None of these four cells had grid aeration installed. Flow rate: 1.6 MGD, with 100% to A1, then Cell 1, then Cell 2, then Cell 3, then Cell 4, then 100% periodically discharged. Total system detention time is about 240 days. Most critical discharge permit limits are 25 mg/L BOD, 30 mg/L TSS, and ammonia limits that vary from 5 to 10 mg/L depending on river flow.
Reported Problem Before SolarBee Installation:
Problems included high energy costs of 500 hp (for aeration, irrigation, and pumping) and the inability to discharge water - only 12% could be discharged due to ammonia limits and the rest had to be irrigated creating odor problems. The Overland Flow was causing riverbank erosion.
SolarBee Installation:
Date: between 1998 – 2006 installed various combinations; currently: Cell A1: one (1) SB10000v12, one (1) solar with battery SB10000U55, and two (2) solar only SB10000 machines; Cell 1: six (6) solar only machines equal to SB2500*, and three (3) solar only SB4000; Cell 2: five (5) solar only machines equal to SB2500*; Cell 3: five (5) solar only SB10000DM units; Cell 4: four (4) solar only SB10000DM machines.
Results:
Realized benefits of circulation have been numerous. SolarBees have eliminated 340 hp of aeration, unneeded irrigation, and transfer pumping equipment, with an energy savings of over $50K per year. Both better odor control and water quality have also been achieved. The BOD in Cells 3 and 4 is usually less than 5 mg/L, and water these cells is usually discharged when ammonia is 5-7 mg/L. All water can be discharged within permit limits and irrigation is now used only when desired by farmers. Cell A2 and the Overland Flow are all still functional but are being bypassed. The city lagoon system now meets discharge permits, and appears adequate for the town to double in population without any increases in capital or annual operating expenses, or a need to increase city sewer rates that have not changed since 1983. The city is very pleased with the consistently good water quality, better water management, reduced odors, and energy/economic savings achieved with SolarBees.
Updated: 05/16/2007
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