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.

Adler, Paul [PAdler@afrs.ars.usda.gov] responded
>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.

Sam:
is the system in Virgin Islands in a greenhouse ?
I have not seen Dr Rakocy's paper and I am very interested to have a copy
by airmail or email, I also wish to contact her/him if email is available.

Sam and Paul, and others:
In an earlier message, I wrote:
>I am interested in treating brewery waster water with plants and would like
>your advice on this.
>
>(a) The total P in brewery wastewater is 7-14 mg/litre for breweries that
>use about 3-5 m3 of water per m3 beer produced (Swedish Environmental
>Protection Agency, 1991).  The total N in brewery WW is 45-65 mg/litre.
>(your trout effluent has 0.7 mg/l P and 25 mg NO3-N/litre). Temp. is 22-28 C.

I will be in Western Samoa in June and July to start a project where there
is a component on phyto-remediation of brewery wastewater. At the moment,
all wastewater is discharged directly into the ocean. A sedimentation tank
permits solid separation before the water goes into the ocean.

I have designed an IBS to use the solid and liquid wastes at this site. The
project will however only look at some components of the designed system
due to limited budget. These components include sub-systems for mushrooms,
poultry, earthworms and housefly maggots. The water component is to recycle
high pH water for use in the other sub-systems. While pH can be adjusted
using acidic wash water coming from the cleaning of fermentation tanks of
the brewery, at some stage, I felt that a phyto-remediation would be
needed. Though the wastewater may be used directly, passing it via an
aquatic system sounds sensible as a pre-treatment because we are dealing
with biological systems. If plants dont grow well in the water, it will
probably have some effect if used directly on the other bio-systems.

Thus I am attracted to Rakocy's shallow channel system.

Paul comment on Rakocy's system is:
>.....managing the raft system like a conveyor does allow him
>to have a stable plant biomass removing a relatively constant amount of
>nutrients

raft system is also used in living machines in greenhouse. I have seen
indoor channel systems in Osaka and Ostersund (Sweden), these have rooted
plants on a material and the water flows through it.

here is a question for Sam, Paul, Li, Julian and others:
with temperatures between 24-39 C in Samoa, could you recommend a few
aquatic plants that I should consider using ?
My list so far include: water hyacinth, duckweed (which are know are
available in Samoa), Salvinia, Pistia and Azolla.

I also welcome any other suggestions ....e.g. bamboo, (but in these plant
systems, water cannot be recycled).

regards
jacky