Open AccessA Control System to Simulate Diel pH Fluctuation in Eutrophic Aquaculture Ponds
Author(s) -
Hargreaves John A.,
Sheely Laura D.,
To Filip S.
Publication year - 2000
Publication title -
journal of the world aquaculture society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 60
eISSN - 1749-7345
pISSN - 0893-8849
DOI - 10.1111/j.1749-7345.2000.tb00889.x
Subject(s) - eutrophication , aquaculture , diel vertical migration , recirculating aquaculture system , sodium hydroxide , carbon dioxide , environmental science , fish <actinopterygii> , environmental chemistry , biology , environmental engineering , nutrient , ecology , fishery , chemistry
.— The toxicity of substances that vary in toxicity through time (daily) as a function of pH are not effectively assessed with static renewal test methods. A control system to simulate diel pH fluctuation in eutrophic aquaculture ponds was established in a flow‐through, wet‐laboratory setting. Water (100 L/ min) was conditioned in a packed column of 3.81‐cm Pall rings prior to distribution to 48 189‐L fish tanks. Control system components included a distributed data acquisition and control system, a personal computer, and various pH control devices. pH values greater than that of influent water (pH 8.0) were achieved by additions of concentrated sodium hydroxide solutions; pH values less than that of influent water were achieved by additions of carbon dioxide gas. Two data acquisition and control software strategies were developed to control pH: one from pH 7.4 to 8.0 and the other from pH 8.0 to 9.6. The basic control strategy involved comparison of a projected pH value to a set point. A moving linear regression was used to forecast the pH value that would result following base or gas addition, and the rate of chemical addition was adjusted accordingly. The system has resulted in acceptable pH control (deviation < 0.1 pH unit), indicating the potential utility of a relatively simple control system for evaluation of fish physiological response to the characteristically dynamic environment of eutrophic aquaculture ponds.