TABLE OF CONTENTS Pages Symposium 1 - the National Sea ...

dioxide (1) and un-ionized ammonia (3), at a given alkalinity (2), will set the minimum
operating pH and the maximum allowable TAN (4). Note that alkalinity is unchanged by
carbon dioxide addition or removal. Stripping carbon dioxide increases pH levels as the
total carbonate content of the water is decreased, shifting the inorganic carbon system’s
acid-base equilibrium as bicarbonate releases carbonate ions (Summerfelt et al., 2000b).
Therefore, following a constant alkalinity line in Figure 4 (top graph), the water’s pH
could be increased by some fraction of 1 pH-unit if stripping reduced a portion of the
carbon dioxide. Note, make-up water alkalinity is the controlling factor determining water
reuse rates in partial-reuse systems. Water supplies with lower alkalinity levels would
allow for much higher accumulations of total ammonia-nitrogen than a more alkaline
water supply, such as used in this study. Therefore, coldwater fish farms located in
regions that contain groundwater with low alkalinity, such as portions of North Carolina,
Maine, and British Columbia (to name a few), could operate partial-reuse systems with
make-up water flow rates < 5% of the total system flow rates.
Literature Cited
Mudrak, V. A. 1981. Guidelines for economical commercial fish hatchery wastewater
treatment systems. pgs 174-182 In: Proceedings of the Bio-engineering Symposium for
Fish Culture. American Fisheries Society, Bethesda, MD.
Noble, A.C. and S.T. Summerfelt. 1996. Diseases encountered in rainbow trout cultured
in recirculating systems. Annual Review of Fish Diseases 6:65-92.
Summerfelt, S. T., J. Davidson, M. B. Timmons. 2000. Hydrodynamics in the ‘Cornelltype’
dual-drain tank. In: 3 rd International Conference on Recirculating Aquaculture (July
19-21, 2000, Roanoke, VA). Virginia Tech, Blacksburg, VA.
Summerfelt, S.T., B.J. Vinci and R. H. Piedrahita. 2000b. Oxygenation and carbon dioxide
control in water reuse systems. Aquacultural Engineering 22: 87-108.
Timmons, M.B., S.T. Summerfelt, and B.J. Vinci. 1998. Review of circular tank
technology and management. Aquacultural Engineering 18(1):51-69.
Tsukuda, S., R. Wallace, S. Summerfelt, and J. Hankins. 2000. Development of a third
generation acoustic waste feed monitor. In: 3 rd International Conference on Recirculating
Aquaculture (July 19-21, 2000, Roanoke, VA). Virginia Tech, Blacksburg, VA.
Wedemeyer, G. A. 1996. Physiology of Fish in Intensive Culture. International Thompson
Publishing, New York, New York.
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