Re: is it possible to curb the ecological destruction from hurricane katrina?

Wow that's an interesting question Joe.  Hope my answer sheds some light.

I guess the first place to start is by mentioning that natural water 
systems such as rivers, the ocean and lakes, as you probably know, have 
ways of breaking down and/or processing their toxins.

These include the sun's radiation, dilution from incoming water, airation 
through air contact with the surface of the water and through movement 
(like the flow of river water over rocks or the wave action in the sea), 
biological processing through plants and micro-organisms and so on.

Clearly this event is outside the capacity of any short term processes of 
any natural system.  The only positive here is that the massive volume of 
water will allow for alot of dilution.

Over coming weeks, the water will continue to receed and the processes 
mentioned above will begin coping better.  Until then we can continue to 
expect some species to struggle (such as land animals trying to find dry 
land to live, sleep and eat) whilst others, particularly micro-organisms, 
may flourish.  This is often seen in the form of algal blooms after a 
organic pollution event or a break in a dry spell when fertilisers wash 
off nearby farm areas providing a massive increase in food sources.

Unfortunately, as you may know, these micro-organisms can multiple to 
toxic levels.

In answer to your question about filters, my view is that the natural 
systems in place are very efficient so we should try and work with them.  
History shows that when we try and implement something "better" the 
result is often some unforeseen cure that is worse than the original 
disease.  In other words, if you and I found some means and way of 
putting in some type of hypothetical filter we'd be wise to ensure we 
first understood the fine balance of the natural system.  You've made a 
good start by considering water flow as this is crucial.  Just look at 
all the environmental damage caused both down and upstream of dams.

If we decided against a permanent filter than our next best bet would be 
to filter out (or remove) as much of the toxins and waste from the area 
as possible.  By doing this we are relieving some of the strain on the 
natural systems in place and allowing them to get on with their job.  
This means trying to remove any spilled chemicals such as oil and petrol 
from cars, pesticides, industrial waste etc as well as organic solids 
including trees, animals carcases and unfortunately human bodies.

Hope that makes some sense and answers your question.