Li,

>Q: The objective of the research is to remove P from the
>effluent from rainbow trout ponds. What is the treated water for?

A: Coldwater fish production is quite different than warmwater fish
production in ponds. Trout are produced in cement raceways (like cement
streams) and the amount of P in the water does not affect the growth of
fish. The concern is after the water leaves the facility and enters the
streams. A little extra nutrients can enhance production in the natural
streams also, but too much degrades the water quality and that is what
we are trying to prevent.
 
 

>Q: Ambient phosphorus concentrations in pond water are usually
>quite low. P is introduced into ponds in fertilizers to stimulate
>phytoplankton blooms, enhance the abundance of natural food
>organisms, and promote greater aquacultural production.
>It seems that there is no need to do this for rainbow trout in U.S.
>Am I right?

A: You are right. The only feed they get is that which the
grower feeds them, they are "tigers", not vegetarians.
 

>Q: The triangle filter is able to remove about 80% of the P excreted
>by the fish with the biosolids, leaving about 20% of the P in
>the effluent. I'm interested in this. Could you explain it in detail?

A: Most of the P excreted by the fish (80%)  is contained in the
solids and the solids are removed using various types of filters or
settling basins. The rest of the P is either soluble organic or
inorganic P or P in solids to fine to capture.
 

Paul
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Paul R. Adler, Ph.D.
USDA-ARS
45 Wiltshire Road, Kearneysville, WV 25430 USA
Web site http://afrsweb.usda.gov