The duckweed is eating the nutrient overload in the lagoon. I can't see any
harm that it is doing in the process. The only drawback I can see is that when
it dies it will fall to the bottom of the lagoon.

Duckweed is routinely havested for animal feed, although not very frequently
from human waste systems. It is susceptible to wind causing it to bunch up on
one side on the lagoon.

Dragging a wire, rope of long thin net across the lagoon is a normal way of
harvesting. Achor one end of the rope or net and walk the other end around the
lagoon as a pivot. This will likely have to be done weekly to keep it well
managed in warm weather.

I imagine there are chemical controls as well.

Cornelius A. Van Milligen
Kentucky Enrichment Inc