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Re: Aquatic Plants Digest V3 #33

At 03:48 PM 1/18/1998 -0500, Roger Miller wrote:
>isn't with the concept.  The problem is that the contact surface on the 
>biowheel and the contact time appear far too small to me.  The contact 
>surface in an actual trickle filter is much, much larger.

If you are talking about "bio balls"  (the orange plastic thingies) I
seriously doubt this.  My guess is that one bio ball has about 5-10 sq
inches of surface and that a gallon of them has on the order of 1-2K in2.
One ounce of 3u fibre has (if density of the plastic is 1.2) about 25cc of
volume with 2x10**-7 cm2 cross-sectional area and 10**-3 cm circumference,
so you get about 10**8 cms of fibers which has 10**5 cm2 area, or over 10x
the area of a gallon of bio balls in one little biowheel filter element.
And both filters provide adequate air exposure with 100% humidity.  If
anything the biowheel may have too little AIR contact time.  Transfer of
gases across the air-water interface is notoriously slow as is often
reported on this list.   George, please check to see if I am right to
within an order of magnitude.

Dave Gomberg	gomberg at wcf_com
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