What he proposes is a fermentation-air injection. Nothing more than a
small air pump (like the size on a large fish tank) 1/8"dia plastic /
tygon tubing connected to a porous ceramic block (sparge nozzle) in/on
the bottom of the tank to promote a relatively large surface/amount of
air bubbles. The air injection will promote aerobic fermentation and
the 'rise' of the bubbles in the fluid will constantly (but slowly) mix
the tankage - (called: sparging). This is equivalent to the very
common fermentation pilot scale air injection in the biopharm industry.
Saw a 'commercialzed' version of this at the Atlantic City boat show
about 4-5 years ago - dont remember the name of the displaying
manufacturer, just remember that it was well overpriced.

In article , Peggie Hall
wrote:

Gwynne Spencer wrote:
What would you think about running a small airpump that pumped air
into the discharge port of the holding tank (so that the air entered
at the bottom of the tank) to aerate the fluid in the tank?

Aerating the tank contents is a very effective means of eliminating
holding tank odor, but I dunno if just introducing it through the tank
discharge port would work...it's an idea I hadn't heard before. Thinking
out loud...

Effective aeration requires two things: 1. a pump big enough to aerate
the whole tank..and 2) a means of distributing air all the way across
the tank bottom. A small pump that only produces a single small column
of air would only create enough pressure to force odor out the vent.
You may have solved the issue of sending enough air horizontally across
the bottom of the tank...so if the pump were big enough it MIGHT work.

Otoh, any air introduced via the tank discharge wouldn't only go into
the tank, it would also go into the discharge hose(s). While that would
certainly help to prevent the hoses from permeating, I dunno whether
that would prevent enough air from going into the tank. And, there are
other concerns: how would you seal the connection to ensure it doesn't
leak? The pump would be subject to suction during pumpout...could that
suction damage the pump?

It's a VERY interesting idea, and one that certainly bears investigating
to find out whether it would work. If you'd like to draw up some design
specs, I'd love to see 'em.

Meanwhile, you might want to check out the Groco "Sweetank" aeration
system on their website at http://www.groco.net. On the surface, $200
seems very pricy...till you start costing out the components--a 1.7
litre/minute 12v pump, the perforated piping system and all the fittings.