N:dlzc D:aol T:com (dlzc) wrote:
Dear Gregg:

"Gregg" wrote in message
...
...

Hi Dave,
I have a friend who has designed some very high
efficiency bubble diffusers (originally designed for
O2 transfer). Since the diffusers are ceramic


I've seen and used porous teflon membranes too...


and can be easily fitted with ozone resistant fittings,
I was wondering if you thought there would be a good market for
bubble diffusers as a replacement for
injectors. (90% O2 transfer efficiency in 8' of water
IIRC) They have an incredible turn down ratio. ( I
can't remember the exact operating pressure ~20"
water IIRC) When I worked on the diffusers, I
noticed there was a lot of reluctance to try an
unproven technology esp in water treatment.


Diffusers have been used in municipal water treatment since the
early 1900s.

Turndown ratios for diffusers are on the order of 50%, which is
fine for some applications. If the growing bubble is filled too
slowly, it doesn't distribute over the whole surface... just on
the "high spots".


Some were sold for special applications and proved
very effective. I know he has some ideas for
improving transfer efficiency even further - but could
this be a solution to a problem nobody wants to solve?

Thanks in advance for any input,


There is a great lot of competition in diffusers. If you can do
it without polymeric seals of any sort, you will have a leg up on
the competition.

I personally *hate* diffuser systems. The diffusers are
constantly requiring service, since ozone will cause iron (among
other things) to go insoluble right on the diffuser. This
requires a full shutdown of the process to remove / replace /
refurbish. Then you have to build huge tanks for contacting.
And you have to make sure the manifold is level and
self-draining. And you require high flow rates, or multi-tier
delivery manifolds for large gas turn-down ratios. Finally, with
large exposed volumes you get very high dissolved oxygen levels,
which pose serious corrosion problems in municipal systems.

I'll put my salesman's hat on for a second, even though the
company I used to work for doesn't work out of Arridzona any
more. Injector systems reside outside the contacting area,
allowing service on components without draining (or wearing a
wetsuit). Injector systems can be arranged to deliver ozone in
just a few tens of feet of pipe... even for huge flow rates, and
mixed to get (in most cases) better then 95% mass transfer.
Injector systems can even be made to keep DO levels close to
ambient saturation, so that you don't end up with air binding in
filtration systems downstream.

Salesman's hat comes off...

I added 100 ppd of ozone at 12 wt% to a 350 gpm semiconductor
wastewater flow stream, got about 99% mass transfer (very high
instantaneous demand), and only took about 60 sq feet of floor
space including contacting and destruction of excess gas.

Diffusers don't require additional power to contact. But that
really is their only benefit. Sorry.

David A. Smith


Thanks for your input Dave.
It's good to hear from the other side!
- Don't be sorry! It's good to here solid advice before throwing money &
time down the drain.
I'd like to provide a few more details about the diffuser (We made
standard ceramic disc, dome & Sanitare type diffusers for municipal
waste water systems - they have fairly low transfer efficiencies as do
teflon membranes ( per internal O2 transfer testing in 30' water column)
This is a ceramic membrane diffuser system -fine ceramic membrane coated
on a large pore ceramic body which acts as a plenum. A 3/4"or 1" NPT SS
fitting is used - screws right in - the diffusers are balanced for DWP
- that is - they can be manufactured to very tight tolerances unlike
standard diffusers. The end result is- you don't wind up with dead or
low flow diffusers in the grid. (If it's plumbed correctly!!) even
though they have a very flat Flow vs P curve. These membranes are also
designed to prevent clogging (A long explanation is required)
I talked with him last night - the diffuser can get 100% transfer in
short column depths 8ft so no ozone destruction is needed.
Having said all that - There is still a hell of a lot of expensive
plumbing required and maintenance would be a pain.
He's not looking at selling systems - just diffusers...
With the additional info - do you think there is any benefit?


Gregg