Biological Air Floatation (BAF) Plant
Biological Air Floatation Units should in theory be suitable for leachate treatment. Such plants have been trialled in the UK, but we do not know of any which have been taken forward to full scale operation.
A BAF Leachate Treatment Plant would be likely to comprise a two or three-stage aerobic bioreactor system, with pre-aeration and possibly flocculation, before the BAF Unit which forms the core treatment stage of the system. Tertiary treatment would be provided after the BAF unit in much the same way as in other biological systems.
The BAF Unit is an continuous flow aerobic bioreactor, and uses a submerged fixed film principle which creates an environment whereby bacteria grow in films on a surface immersed in the effluent stream and oxidise the biodegradable waste.
The bacteria grow on the surface of a patented, three dimensional media structure and are intensively aerated by a diffuser system which ensures that the entire bioreactor is evenly aerated and fully mixed, while avoiding blocking from excessive biomass build-up.
The resulting oxygen transfer is reported to be very efficient and ensures that the biofilm remains both thin and active, even in the event of shock loading.
These plants can be built to small footprints.
Possible reasons for the lack of popularity of BAF plants may be:-
- long term build-up and blockage of media;
- sensitivity to shock loading;
- high intensity treatment results in a much more rapid deterioration of effluent quality if the plant ceases to function correctly, than for long retention period SBRs. This may be a critical factor to waste management site operators which like the understandable “comfort” of knowing that as long as once daily even the the Weighbridge Clerk, if necessary, can visit the site before the once daily SBR discharge and test the whole day’s effluent with just one test strip. This fact obviates the need for any high technology at all in the traditional SBR system. Landfill operators have many other matters to worry about, and cannot afford the luxury of full time (and sometimes even part-time) plant operators.
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