Venturi Aeration, Inc.

Venturi Aeration Oxygenator Unit As Pre-aeration for Bioclere Trickling Filters

The Bioclere™ Trickling Filter Treatment Unit is designed to treat wastewater that has already undergone primary treatment for the removal of solids in a primary settling tank. Additional treatment may provide removal efficiencies adequate to discharge effluent to surface water (under certain conditions) or provide relief to overloaded, failed or clogged soil absorption systems and/or reduce the size of required drainfield/leachfield.

The Bioclere™ trickling filter consists of a bed of highly permeable media to which microorganisms are attached and through which wastewater is trickled. The Bioclere™ uses a patented plastic filter media in a randomly packed configuration. The influent wastewater is passed from the primary settling tank, where most of the solids are separated from the untreated waste. While the Bioclere™ is most commonly a stand-alone unit, there are applications where the influent wastewater flow from the primary settling tank has certain characteristics that would require additional or enhanced pretreatment. In those cases, a Venturi Aeration Oxygenator unit is used in a pre-aeration tank to achieve reductions designed to reduce the biological loading on the Bioclere™. This reduces the overall capital cost of the total project, and increases performance of the combined system.

Pre-aeration of the influent wastewater in a separate aeration tank using a Venturi Aeration Oxygenator unit has many benefits for Bioclere™ systems:

1. Dissolved Oxygen: The liquid being processed through the venturi aerator unit is saturated with dissolved oxygen (DO). The discharged liquid is highly oxygenated with DO levels ranging between 5.0 mg/l and 7.5 mg/l.

2. Mixing and Equalization: The discharge from the venturi aerator unit mixes and equalizes the influent liquids with the contents of the tank. Any solids are kept in suspension by circulating the tank contents at 2 fps using the velocity of the discharge.

3. Odor Control: Imbedded malodorous and corrosive hydrogen sulfide from organic material is readily oxidized into soluble SO4, a non-odorous form of sulfur.

4. BOD Reduction: Pre-aeration induces large amount of dissolved oxygen into the aeration tank to effect BOD5 reduction from nascent bacteria in the sanitary wastestream to levels at which the Bioclere™ can be effective; this is usually < 500 mg/L.

5. Nitrification: With excess amounts of dissolved oxygen in the aeration tank, nitrification begins in the aeration tank enhancing the Bioclere™ unit’s performance.

6. Flotation of FOG: Conditioning with the Venturi Aeration Oxygenator causes imbedded fats, oils and grease (FOG) to separate and float to prevent their migration into the Bioclere™ unit.

7. Temperature: The Venturi Aeration Oxygenator has the ability to reduce the temperature of the influent wastewater. In field tests of the Venturi Aeration Oxygenator device with septage, temperature reductions have been documented to range between 2° and 6° C in summer months. Reducing elevated temperatures of the process liquid increases the solubility of dissolved oxygen, thus allowing for greater amounts of DO to achieve targeted biological reductions.

8. Non-chemical pH Control: As the nascent bacteria become active aerobically they produce carbon dioxide as a digestive byproduct. The increase in carbon dioxide lowers the pH. This increase in acidity can stress micro-organism performance in the Bioclere™ unit. Since the venturi aerator concurrently strips carbon dioxide (CO2) while oxygenating the liquid, a steady state pH is maintained on the liquids being decanted into the Bioclere™ unit.

9. Hydraulic Shear: Solids that migrate from the primary settling tank are conditioned in the venturi aeration device to increase their surface to enhance digestion.

10. Strips VOCs: The venturi aeration device protects the biomass on the trickling filter media by stripping certain weak Henry’s Constant VOCs that are characteristic of cleaning chemicals or detergents that degrade bacterial activity in the Bioclere™ unit.

There are many applications for Bioclere™ units, not all of them require pre-aeration. However in those cases where pre-aeration is required, a computer model has been developed to calculate the desired amount of dissolved oxygen that would be needed in pre-aeration to achieve targeted reductions in BOD5 for the influent wastewater. The computer model can assist the consulting engineer in the proper sizing of the aeration tank and venturi aeration oxygenator device to ensure desired reductions are achieved.

The pre-aeration tank does not use a submersible pump to provide the recirculation of the liquids to the venturi aeration device, because 1. Submersible pumps are not designed for continuous operation, and 2. Submersible pumps would transfer their heat from operation into the liquid being treated thereby reducing the solubility of dissolved oxygen in the process wastewater.

Summary: The addition of a Venturi Aeration Oxygenator unit in a pre-aeration and equalization tank can greatly enhance the performance of the Bioclere™ system allowing it to treat larger quantities of wastewater than could otherwise be achieved without adding additional Bioclere™ units to split the influent flow. This reduces overall project costs and increases efficiencies. Because of the many specific benefits listed above from pre-aeration, the Venturi Aeration Oxygenator should be utilized for preconditioning difficult wastestreams. The Bioclere™ is a class 1 device that cleans wastewater well in excess of secondary treatment requirements. The Venturi-Aeration Oxygenator unit is the preferred pre-aeration device for difficult wastestreams.