Phosphorus removal in a
marine prototype, recirculating aquaculture system
Y.
Barak, E. Cytryn, I. Gelfand, M. Krom, J. van Rijn-2003
Aquaculture, 220(1-4): 313-326
Abstract:
Phosphorus dynamics were examined in a prototype,
zero-discharge, marine-recirculating system. Operation of the system without
discharge of water and sludge was enabled by recirculation of effluent water
through two separate treatment loops. Surface water from the fish basin was
pumped over a trickling filter in one loop, while bottom-water was
recirculated through a sedimentation basin followed by a fluidized bed
reactor in the other treatment loop. Ammonia oxidation to nitrate in the
trickling filter and organic matter digestion together with nitrate
reduction in the sedimentation basin and fluidized bed reactor were the main
biological features of this treatment system. Orthophosphate concentrations
did not exceed 15 mg PO4–P/l in the culture water during more
than 1 year of system operation. Much of the phosphorus was retained within
the sedimentation basin and fluidized bed reactor. In these treatment
stages, the phosphorus content of organic matter was as high as 17.5% and
19%, respectively. High concentrations of total phosphorus and low
concentrations of soluble orthophosphate were measured in the initial stages
of sedimentation under oxic and anoxic conditions, suggesting that most of
the phosphorus was associated with organic matter. Depletion of oxygen and
nitrate in the sludge layers of the sedimentation basin coincided with
sulfate reduction to sulfide and a release of soluble orthophosphate. The
observed phosphorus dynamics in this marine system supported findings from
previous studies in which it was demonstrated that denitrifiers underlie
phosphorus immobilization under these conditions.
(Department of Animal Science, Faculty of
Agricultural, Food and Environmental Quality Sciences, The Hebrew University
of Jerusalem, P.O. Box 12, Rehovot 76100, Israel, e-mail of J. van Rijn: vanrijn@agri.huji.ac.il)