Modeling Carbon Dioxide, pH and Un-Ionized Ammonia Relationships in Serial Reuse Systems

Aquacultural Engineering
By: , and 



In serial reuse systems, excretion of metabolic carbon dioxide has a significant impact on ambient pH, carbon dioxide, and un-ionized ammonia concentrations. This impact depends strongly on alkalinity, water flow rate, feeding rate, and loss of carbon dioxide to the atmosphere. A reduction in pH from metabolic carbon dioxide can significantly reduce the un-ionized ammonia concentration and increase the carbon dioxide concentrations compared to those parameters computed from influent pH. The ability to accurately predict pH in serial reuse systems is critical to their design and effective operation. A trial and error solution to the alkalinity–pH system was used to estimate important water quality parameters in serial reuse systems. Transfer of oxygen and carbon dioxide across the air–water interface, at overflow weirs, and impacts of substrate-attached algae and suspended bacteria were modeled. Gas transfer at the weirs was much greater than transfer across the air–water boundary. This simulation model can rapidly estimate influent and effluent concentrations of dissolved oxygen, carbon dioxide, and un-ionized ammonia as a function of water temperature, elevation, water flow, and weir type. The accuracy of the estimates strongly depends on assumed pollutional loading rates and gas transfer at the weirs. The current simulation model is based on mean daily loading rates; the impacts of daily variation loading rates are discussed. Copies of the source code and executable program are available free of charge.
Publication type Article
Publication Subtype Journal Article
Title Modeling Carbon Dioxide, pH and Un-Ionized Ammonia Relationships in Serial Reuse Systems
Series title Aquacultural Engineering
DOI 10.1016/j.aquaeng.2008.10.004
Volume 40
Issue 1
Year Published 2009
Language English
Publisher Elsevier
Publisher location Amsterdam, Netherlands
Contributing office(s) Leetown Science Center
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Aquacultural Engineering
First page 28
Last page 44
Country United States
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