Case Studies

Report of EcoClear and EcoBac Performance

Algae and Suspended Solids Reduction
Ammonia and Phosphorus Reduction
Sludge Reduction 

Redwood Falls Wastewater Treatment Plant
City of Redwood Falls, Minnesota
USA

Background

The City of Redwood Falls City Engineer initially contacted ESI in September, 2000. The City Engineer requested information regarding improved treatment for suspended solids (TSS). High suspended solids levels were largely due to seasonal algae blooms. Additional interests included phosphorus reduction and sludge reduction.
The facility includes three 10 million gallon aerated ponds. The ponds consist of three cells, and are 10 feet in depth. The ponds flow in series and provide approximately 30 days retention time. Effluent from these ponds was previously discharged to the Redwood River, but is currently pumped to North Redwood Falls facility. The North Redwood Falls facility consists of three 5 million gallon aerated ponds run in series. At the North Redwood facility the flow from the Redwood Falls plant is mixed with industrial, pre-treated water. The effluent from the North Redwood facility is discharged to the Minnesota River.
The average daily flow of the facility is approximately 0.8 million gallons per day (MGD). The industrial flow that is mixed into the three 5 million gallon ponds is approximately 10% of the municipal flow into these ponds.

EcoClear System Set Up 

The bioreactor system installed at the Redwood Falls facility for improved nitrification and algae reduction is the EcoClear System 400. The system was installed in April, 2001. The system equipment consists of a 175-gallon bioreactor tank, two 300-watt submersible heaters, an aerator capable of approximately 0.5 CFM at 2.5 PSI, flexible plastic air lines, and medium pore air diffuser stones. Also included is a submersible pump and garden hose for use in dosing the product. The bioreactor was set up indoors near a 110-volt power source and a potable water source. The system products include three six-gallon pails of EcoClear Starter Concentrate and individual 4.5-pound bags of Biopack 400 powder.
At initial start up three pails of the concentrate were added to the bioreactor, and the tank was filled with water. The aeration stones were placed on the tank bottom, and the heaters were submersed and set to a temperature of 80 F. The aerator was started and one bag of BioPack 400 was added. After seven days of aeration the product was ready for dosing to the ponds.

EcoClear Product Dosing

After completion of each seven-day aeration cycle one half of the bioreactor tank volume was dosed to the inflow of Aeration Pond 2. One half of the tank volume remained in the tank to restart the refilled bioreactor after adding in one bag of BioPack 400 powder. The first dose to the ponds occurred in late May, 2001. Aeration Pond 2, which flows into Aeration Pond 3, received 87-gallons of product per week. The program has been in operation for many years beginning in April 2001.

Results of EcoClear Program

As a result of the EcoClear Program the Redwood Falls facility achieved an improved performance of the aerated ponds. As a result of the addition of the nitrifying bacteria, the growth of algae that had historically caused elevated TSS in the effluent did not occur. Historically, TSS in the effluent averaged approximately 40 ppm, and after the EcoClear Program TSS averaged less than 20 ppm. Phosphorus was also reduced significantly, achieving less than 1.0 ppm compared to at least 2.0 ppm in previous years.

EcoBac System Set Up

The bioreactor system installed at the Redwood Falls facility for sludge reduction is the EcoBac I System. The system was installed in May, 2001. The system equipment included one 55-gallon bioreactor tank, one 300-watt submersible heaters, an aerator capable of approximately 0.3 CFM at 2.0 PSI, flexible plastic air lines, and medium pore air diffuser stones. The bioreactor was set up indoors near a 110-volt power source and a potable water source. The system products include individual eight-ounce bags of EcoBac I powder.
At initial start up the tank was filled with water. The aeration stones were placed on the tank bottom, and the heater was submersed and set to a temperature of 80 F. The aerator was started and one bag of EcoBac I was added. After 48 hours of aeration the product was ready for dosing to the ponds.

EcoBac Product Dosing

After completion of each 48-hour aeration cycle the entire contents of the bioreactor tank was dosed to the pond needing treatment. Pond 1 was selected for treatment because this pond historically had the highest accumulation of sludge. The product was dosed to the inflow of the pond. The first dose to the pond occurred in May, 2001. The program consisted of a three times per week dose of 55 gallons of product to the pond, and has been in operation for many years beginning in May 2001.

Results of EcoBac Program

As a result of the EcoBac Program the Redwood Falls facility achieved a significant reduction in the sludge layer in Aeration Pond 1. As a result of the addition of the solubilizing enzymes and BOD reducing bacteria from the EcoBac system, the sludge was made more soluble for consumption by facultative bacteria in the pond.
Historically, sludge accumulation increased the depth of the sludge layer and periodic dredging of ponds was necessary. The lack of increased accumulation, in fact a significant reduction in the sludge layer of Aeration Pond 1, suggests that dredging can be delayed for a considerable time, thus avoiding expense and treatment disruption associated with dredging operations.

Conclusions

The EcoClear and EcoBac Programs at Redwood Falls WWTP have been in effect for multiple seasons, and the comparison of data and observations with previous years suggests that the programs have been effective in meeting the desired results.
With the EcoClear Program the addition of vast numbers of nitrifying bacteria into aerated treatment ponds improves the nitrification process, and in doing so reduces ammonia and other nutrients that provide the food source for a variety of filamentous and planktonic algae species. The result is a higher quality effluent for TSS, BOD, ammonia, and phosphorus.
With the EcoBac Program the addition of a continuous supply of active enzymes and facultative bacteria into aerated treatment ponds increases the bioactivity in the sludge layer. The result is a reduction in sludge accumulation, and a reduction in the depth of the sludge layer.


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