Biofiltration. Area/person? Designs?

Just throwing out a question regarding biofiltering grey/blackwater in reed beds. How large an area of reed bed would you calculate per person?
Have been looking for a while for this information, but this has got to be the #1 place to ask 
Also, do you know of a good place to look at design drawings for reed beds (looking for something very concrete and practical).

Do you have any experience with incorporating any of the following?:
-  Fresh water clams
-  Mycofiltration
-  Azolla ferns or other N-fixing plants


Thanks.

Black water can go into a cess pool (outhouse) and be buried over every few years to make an asparagus bed. The problem with putting blackwater into a reed bed, or some similar low containment area is that that practice kills millions of people every year. Even if the water never gets into the drinking water you might have a flood that could put raw sewage on your garden, that is why peasants ate porridge, they had to cook everything until it was safe to eat. Freshwater clams would also be a tempting but horrible food source, because time breeds complacency. I think that Urine diverting toilets have been successfully coupled with BSF bins in such a way that the BSF eat the humanure and they can then be directed to a reed bed or similar environment but keeping seepage from getting into the water is a serious concern. You want lots of good loam between the blackwater and the freshwater. Remember you don't just have to look out for your community, you also have to protect the people downstream from you as well.

Thanks. I actually found what I was looking for here:
http://en.wikipedia.org/wiki/Constructed_wetland

In an efficient reed bed you'd only need 3m²/person. If one would enclose this space in a greenhouse or a plastic tunnel you'd prolong the efficient filtration time in temperate areas. If you also use gravel that absorbs and holds heat you could keep the reed bed active even during the winter (At least in my climate), assuming you do not use any extras like lighting and "artificial" heating etc.

Check out the wikipedia article, it looks very positive.