Energy efficient aeration

Aeration in wastewater treatment typically involves the use of electrical energy to drive either a surface mounted mechanical aeration system or a compressed air diffused air aeration system.  Each general system type has it advantages, process limitations and efficiency, while at the same time there are divergant views on what constitutes the optimum system.

Without taking sides it is generally agreed that deeper finer bubbles are more efficient than shallower coarser – by virtue of the physics of gas exchange in liquids.  And it is also accepted that specific mechanical aeration systems exhibit differential efficiency based on system specific design issues.  These include applied power, rotational speed, basin depth and mixing interactions.

The job of an aeration system in activated sludge is to both mix and aerate and the basin configurations tend to impose the greatest process selection pressure wrt the selected technology and its optimal application.  At this point while a slight simplification we would suggest that shallow basins select for surface aeration, deep basins for diffused aeration, and medium depth basins – well they require very careful system selection.

What is not in any doubt is the following –

An activated sludge basin benefits from adequate mixing such that there is no precipitation.

The biomass flocculation is inhibited by excessive shear.

With dissolved oxygen control and system loading as a fixed element the biggest determinant of efficiency if the OTE of the installed aeration system.

It has become fashionable to try to get away from these basic truths for commercial reasons but when you strip out all the advertising copy aeration comes down to selecting the system with the lowest shear, complete homoginisation and the highest OTE.  In our view the reality of this is that there should be no talk of efficiency, suitability or efficacy until the particular capabilities of a system in relation to shear, homoginisation and OTE have been declared.

And that in a nutshell is why ENSEN promote the INVENT range of aerations systems, from the first time we asked these difficult questions on our client behalf until our most recent meeting Invent have been open and forthcoming about the real capability of their systems.  the fact that they have a large installed base, fantastic testimonials, excellent technical backup and high quality manufacturing are just the icing on the cake.