Sam Levy (ardag-w11@ardag.ardom.co.il) wrote:
>Q1: It seems to me that a similar nutrient stripping process
>occurs in the floating raft configuration used by Dr Rakocy
>in the Virgin Islands.  In this configuration the plants are
>reared on polystyrene floats with holes.  The roots sit in
>the water to be treated as it flows down a channel of 30 cm
>water depth.  Plants are harvested from one end of the channel
>and new seedlings are placed in the opposite end.
>
>I would like to ask you for a comparison of strengths and
>weaknesses between your conveyor system and a float
>system--especially as related to nutrient uptake, plant health,
>efficiency and/or speed of processing the effluent.

A1: I have not grown plants in the raft system and I have not
seen Jim's system in particular, so I can't comment on comparing plant
health, etc. But I do know that nutrients are very high in his system
and the effluent from the plant system is recycled back to the fish
system, so removal of nutrients to very low levels is not necessary. We
are discharging our effluent, so nutreint removal to very low levels is
important. But managing the raft system like a conveyor does allow him
to have a stable plant biomass removing a relatively constant amount of
nutrients from the fish system.

>Q2: Also, were any studies conducted where the effluent from the
>conveyor system was re-used in the trout culture system?

A2: No, we did not reuse or recirculate the water from the plant
system back to the trout system.

Paul R. Adler, Ph.D.
USDA-ARS, Kearneysville, WV 25430 USA