Floating aerators cut ammonia levels

Leachate treatment is a key area in landfill management subject to increasingly stringent regulation. LAWE reports on technology available to assist site operators in meeting their obligations which continues into the long-term with provision for aftercare. In this case study Flucon Aerators Ltd reports on the use of its floating aerators to tackle high levels of ammonia in landfill leachate

Flucon was invited to investigate the possibility of improving the consistency of reducing the ppm level of ammonia in leachate extracted from a high altitude landfill site. The landfill site had two existing 15kW vertical paddle aerators, which were unable to cope with the fluctuating strength of the raw extracted leachate.

Flucon supplied two 11kW floating aerators, which are controlled by the ICAS Module, which includes a soft start option, that produces a gentle commencement of aeration with an intelligent self-cleaning aeration system.

In the event of amperage fluctuation, due to potential blockages of the suction end of the aerator, the sensor will switch off the aerator, start up the aerator in reverse and will eject any obstruction in the inlet. If the blockage persists the sequence will be repeated for a longer period. This feature prevents a potential motor burn out because the cleaning system is actioned by an increase of one and half times the normal running amperage. The soft start reduces the normal high start up amperage, which allows for a small generator to be used for mobile site work.

Rpm adjustment
When the aerators were first installed they were set to run at full rpm, resulting in the ammonia levels reducing to below 5ppm (Consent discharge level was 150 pm). However, the Environment Agency reported that foaming was occurring at point of discharge, this being caused by excessive aeration. The rpm of the aerator was reduced to correct the over aeration. The site now discharges at 25ppm.

Aerator features
The Flucon aerators discharge micro bubbles which aerate, mix and re-suspend mid-depth within the liquid mass. They are totally adjustable for depth and discharge angle and can be positioned to achieve maximum rotation with the lagoon.

The full depth aeration and scrubbing produces a very effective method of stripping ammonia in leachate.

BODS, COD, SSP are very effectively reduced. The splashing effect produced by vertical paddle aerators in cold weather caused the aerators to sink due to ice build up on the floats. There was loss of aeration due to sinking as a result of ice build up on the floats.

The non-splashing Flucon aerator is not affected by freezing conditions and it prevents ice forming on the surface of the lagoon giving continuous aeration and ammonia stripping.

Flucon adds that the aerator releases no odour or aerosol into the atmosphere.

It is stated to produce a consistent performance to comply with discharge consent levels.

The aerator can be installed and running in one hour.

The company adds that there is one moving part, which requires minimal maintenance (parts and labour). There is no costly gearbox, rotor or shafts and no expensive bearing lubrication.

No civil work is required and no emptying of ditch is needed for installation.

Lower whole life costs are also cited as is a lower kilowatt rating required when compared with other forms of aeration.

Range available
The range of aerators and mixers available includes Floating, Skid-mounted floating, Bridge-mounted and Aquatic. A range of cutter aerators is also available.

The patented Flucon aerator has been independently tested to American ANSI Standards. The range of Flucon aerators produces a dissolved oxygen transfer rate of 1.8kg/kW/hr in clean water.

In this case study the energy saving was 30 to 22kW which equals 27% energy saving.



Waste & resource management

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