FAST Septic System

[OlDave]

I've recently installed a FAST (Fixed Activated Sludge Treatment) system and was wondering if the blower has to run 24 hrs/day. In my neck of the woods, that works out to about $65.00/month for electric. If I could run it say 3 hrs on, 3 hrs off, that would certainly help. Thanks for any help
Dave

 

[LHA]

I assume a FAST is a flow-through/plug-type reactor, and not a batch reactor?

I can only speak to larger, extended aeration AS plants. They go septic very rapidly if air is turned off.

In general, though, it seems to me as if any flow-through AS system needs a constant aeration rate (as opposed to batch systems, which operate differently). This controls the life and eating cycles of the microbes, which must be held fairly constant. Knowing how easily these cycles are disrupted by even small variations of temp, pH, toxins or organic loading, I would have to say "Don't turn the air off".

Remember, amateurs built the ark...professionals built the Titanic. -Steve

 

[bimr]

Agree with lha post.

I will add that you may be able to lower the output of the blower if you have a variable speed or belt drive to optimize the installation.

The equipment as built was probably conservatively sized or possibly oversized for future expansion.

But once you have established the minimum requirements, you will not be able to operate below the minimum requirements.

 

[kchayfie]

Adding Dissolved Oxygen control to control the speed of a variable speed blower would further optimise the installation because you could react to changes in influent and keep blower output to the absolute minimum required.

 

[LivermoreCE]

Depending on the amount of oxygen needed you may be able to have the blower run intermittingly. If you are using the Biomicrobics control panel, there might be a dip switch that can be sent to control the off and on time of the blower. I have used these with ½ hour on and ½ hour off but received a smell complaint and then switched to full time on and the smell was not produced. When the blower came on, the air above the liquid blew out and was odor problem.