Ammonia levels needn’t become a problem
Here’s how to handle them using a Venturi Aerator
Higher than anticipated ammonia levels at this WWTP, due to higher than anticipated organic loadings on the system was a problem that needed to be resolved.
Ammonia from the DC influent to the primary septic tank ranged between 55 mg/L and 85 mg/L depending on the time of year. It was discovered that the water going into the trickling filter was also void of DO, low in pH, and had ammonia two to three times higher than the design loadings of 25-30 mg/L.
Flows ranged from 76,000 to 135,000 litre per day [L/D]. Further, there was insufficient alkalinity to support the metabolic reductions of ammonia by the resident bacteria in the wastewater and on the filter media.
A 15,000 litre poly tank was placed on-site as an aeration tank along with a two-inch Venturi Aerator unit with a small centrifugal pump. The Venturi -Aerator unit is designed to add dissolved oxygen (DO) from an ambient air source.
During the cold winter months the Venturi added DO up to 8.0 to 9.5 mg/L and in the very hot summer months DO ranged from 3.5 to 5.0 mg/L. This difference is due to water temperature and the reduced solubility of oxygen in warm and hot water.
The Venturi Aerator was placed in a slightly submerged discharge (600mm) so the kinetic energy of the discharge would spin and mix the contents of the tank. Liquids were pumped into the top of the tank at 60 litres per minute [L/M] displacing an equal volume of treated effluent out of the bottom of the tank.
The pH was also being raised by some stripping of CO2 by the Venturi Aerator from 6.7-6.9 up to 7.2-7.5. This allowed nitrification to occur in the aeration tank, which has a 4 hour hydraulic retention time before being transferred into treatment trains.
A siphon break was added and used to add the required additional alkalinity. A total of 7kg of bicarbonate was added daily and dosing was controlled by a small peristaltic metering pump.
The entire treatment process time was two days from when the wastewater was pumped into the aeration tank until it reached a very large leaching field.
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WHAT IS A VENTURI AERATOR?
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The EchoStorm water aerator from Gorman-Rupp offers the benefits of safety, reliability and ease of access to water aeration applications.
Because these units are mounted on the bank [instead of floating on the water or being submerged in it], access is much less complicated and safer, while delivering oxygen transfer outcomes.
The EchoStorm water aerator benefits::
- No cranes or row boats for maintenance
- Easily accessed
- Less downtime
- Reliable and easy to maintain
- Easily scalable and low cost of ownership
- Thorough mixing – no dead spots
- High SOTR (Standard Oxygen Transfer rate)
- Oxygenated water
These aeration units are used in conjunction with Gorman Rupp self-priming centrifugal pumps to deliver solutions for the following applications:
- Lagoon and basin water aerator
- Oxidation ditch aeration
- Lake destratification and algae control
- Odour control
- Sludge digestion
- Septage treatment
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The Gorman-Rupp Super T Series self-priming centrifugal wastewater/sewage pump has been the world benchmark for this technology since 1963 (>50 years). They have been designed for economical, trouble-free operation, with superior solids handling capability and a large inspection cover to access pump internals for service or blockage removal.
Advantages include:
- Self-Priming pump has the ability to mount high and dry above the wet well (not in it)
- Low cost of ownership
- Greatly reduced OH&S issues – no more working over water/heights/cranes/heavy swinging weights
- Surface-mounted pumps with easy access for monitoring or service
- Advanced safety features including pressure relief valve to protect operators
- Improved maintenance features to greatly reduce maintenance time and costs, with removable rotating assembly
- A variety of materials of construction to handle abrasive and/or corrosive fluids
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The Gorman-Rupp Super T Series pump with Eradicator™ Solids Management System are a series of self-priming centrifugal pumps designed specifically for handling municipal and industrial wastewater containing stringy, difficult-to-pump, solids in suspension (such as wet wipes, rags and feathers).
They have been designed for economical, trouble-free operation, with design features that deliver superior solids handling capability and a large inspection cover to access pump internals for service or blockage removal. Gorman-Rupp Super T Series wastewater and sewage pumps have been used for pumping of WAS and RAS and for digester recirculation with great success in wastewater treatment plants around the country, as well as food process plants, paper mills and other heavy industries. The Eradicator™ system advances the solids handling capabilities of this range.
Advantages include:
- Ability to mount high and dry above the wet well [not in it]
- Low cost of ownership
- Greatly reduced OH&S issues
- Easy access for monitoring or service
- Advanced safety features to protect operators
- Improved maintenance features to greatly reduce maintenance time and costs, with removable rotating assembly
- A variety of materials of construction to handle abrasive and/or corrosive fluids
