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Re: phosphorus questions

On Sun, 21 Nov 1999, Stephen Lindsay wrote:
> a. I agree as previously stated on the list that smaller water changes made more
>     often will probably result in less removal of phosphorus than larger changes
>     made with longer intervals, because of the dilution in the former.

This depends on the relative size of the small, frequent changes and the
larger, less frequent changes.  15% water changes every week will remove
more than 25% water changes every two weeks.  15% water changes every week
will not remove as much as 30% water changes every two weeks.  But the
difference in this latter case isn't significant enough for me to worry
> b. Why do you suggest suppressing the phosphatase-catalysed reaction from
>     PPo to PPi apparently in preference to the similar reaction of DPo to PPi, since:
>    "some algae may be able to utilize DPo but plants cannot"? You then suggest
>    using algae to possibly aid that suppression.

First, I'm not sure I understand the question.  Second, the product in
both of these reactions is DPi, not PPi.  I suggest suppressing the
reaction from PPo to DPi to avoid the production of DPi.  I suggest
encouraging the reaction from DPo to DPi because DPo appears to be nothing
but algae food.  As DPi, at least plants will compete for the phosphorus.

The algae scrubber idea assumed that the scrubber could be built in such a
way that it didn't trap particulates, hence would not effect the PPo to
DPi reaction.
> c .When DPi attaches to laterite (for example), should this then be replaced at
>     appropriate intervals in the substrate as it becomes saturated? And could any
>     reverse reactions take place (or even in a filter)?

I wouldn't suggest rebuilding a substrate to replace the laterite, even if
it does become saturated with phosphorus.  In a filter the media should be
replaced regularly.  In fact, the sorption media probably shouldn't be
left in the filter full time because it will foul and lose effectiveness
fairly quickly.
> d.  Are anaerobic bacteria capable of acting on organic particulates from detritus
>     where it becomes trapped in a slower flow of water situation as in a trickle filter?
>     (And so solve the "flush" case you mentioned).

Anaerobic bacteria can work on particulates under low flow conditons.  In
fact, obligate anaerobes have been found living inside organic particles
suspended in fully aerated water.  However, reactions catalysed by
anaerobic bacteria are generally slower than by aerobic bacteria. Under
low flow conditions whatever phosphate is freed in an anaerobic reaction
should remain near the point of the catalysis and suppress further

Roger Miller