Oxfiniti Super Oxygenation Box Trial at Wick St Lawrence

The OXFINITI wastewater treatment system is a proven technology for direct injection of oxygen from a generator more efficiently into an activated sludge process. No liquid oxygen or storage is required. This results in significant energy savings and enhanced quality benefits.

Wessex Water was selected for the trial which commenced in February 2015. The OXFINITI box was set up at the Wick St Lawrence stw activated sludge oxidation ditch plant. This serves approximately 20,000 PE using four surface aerators, floating aerator and two paddle aerators.

The Site's Oxidation Issues

The activated sludge process was struggling at times owing to high loads receiving insufficient aeration.
At peak load times the ditch was under-aerated commonly resulting in high ammonia levels
Even with additional aerators added to the original configuration the system was incapable of consistently meeting DO targets
Inlet flows to the works varied fivefold affecting oxidation

The Trial

The OXFINITI system was set up to test its efficiency in introducing oxygen into the wastewater and its effectiveness in providing enhanced treatment. This was compared to the existing aeration system.

Dissolved oxygen, ammonia, and sludge volumes were measured.

OXFINITI : Self-contained, portable system

The OXFINITI Solution

The OXFINITI system is housed within a self-contained 20 foot box. It can be integrated into a SCADA system, or run independently as it was in the Wessex Water trial. It can be operated delivering a base load or controlled to deliver its oxygen in response to changing dissolved oxygen demands in the basin.

Oxygen is directly injected from a generator into a side-stream taken from the ditch. The super oxygenated stream is then introduced into the effluent, where required, increasing the DO levels very quickly to the desired levels.

Significant power reduction using OXFINITI system

Power Reduction

In normal operation the four controlling surface aerators would cycle on and off to maintain an appropriate DO target in the basin. During the trial the OXFINITI box was set up to supplement the base load. OXFINITI delivered more than sufficient oxygen to meet the targeted DO levels.

The maximum power of the four floating surface aerators is 60kW and the OXFINITI box’s power at base load in contrast was 40kW. During the trial the use of the OXFINITI system operating alone resulted in significant energy savings of 21% as compared to normal operation of the works treatment process. Whilst running the OXFINITI system there were significant reductions in ammonia and sludge volume levels in the secondary clarifiers.

Conclusions

The trial showed that the use of the Oxfiniti system delivered significant cost and operational benefits compared to conventional aeration system:-

Operational energy and carbon savings - 21%
Positive Sludge Consolidation - sludge volumes reduced from 18% to 11%, a 40% reduction;
Power Requirements Lower - max power Oxfiniti 40kW, surface aerators max. power 60kW;
Water Quality & Plant Health significant improvements in visual appearance of the secondary clarifiers and micro-organism levels;
Significant Reduction in Ammonia Levels. The Oxfiniti system reduced ammonia levels very quickly compared to the existing surface aeration system.

clarifiers

Secondary clarifier before and after OXFINITI trial

Further Optimisation

The test conditions using a standard design box did not allow a full optimization of the Oxfiniti system on a plant that can be achieved with a long-term installation.

There are optimization alternatives in a permanent installation that could reduce the existing energy consumption of the Oxfiniti system by a further 50%. In this case it could reduce the total energy consumption of the Oxfiniti box from 40 kW to 20 kW

For the full report, download our technical papers

Technical Papers

Wick St Lawrence Case Study