|WILLS, PAUL - Harbor Branch Oceanographic Institute
Submitted to: Book of Abstracts World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2009
Publication Date: 3/1/2010
Citation: Pfeiffer, T.J., Wills, P.S. 2010. An evaluation of a micro programmable logic controller for oxygen monitoring and control in tanks of a recirculating aquaculture system [abstract]. Book of Abstracts World Aquaculture Society. p.778.
Technical Abstract: Control of dissolved gases, especially oxygen is an essential component of recirculating aquaculture systems. The use of pure oxygen in a recirculating aquaculture system creates supersaturated concentrations of dissolved oxygen and can reduce fish production costs by supporting greater fish and feeding loading rates. As a result water flow requirements are lowered thereby reducing pumping costs, tank size, and water treatment equipment. The components required to setup the PLC oxygen monitoring and control system can be divided into five categories: (1) the oxygen sensors; (2) the relay output modules for solenoid control; (3) the micro programmable controller for input/ouput control functions; (4) the communication device - a operator touch screen panel; and (5) the software programming for the PLC. The PLC and touch screen panel were setup to monitor and control oxygen levels in sixteen 3.05 m diameter (1.2 m deep) tanks using the PLC ladder logic program. The control program actuated solenoids to supply oxygen to in-tank ceramic ultra-fine bubble diffusers (30 cm in length) and maintain the percent saturated levels in the tanks between high and low set points. High and low level set points were set at 150 and 110% saturation respectively. Oxygen to the in-tank emergency diffusers is also controlled by the program if tank dissolved oxygen levels fell below the low level set point which was set at 100% and deactivated when in tank dissolved oxygen levels were above 120%. The micro PLC and compatible components provide a cost efficient and suitable means of tank oxygen monitoring and control for the aquaculturist looking for an alternative to off-shelf industry technology.