A HYDROACOUSTIC WASTE FEED CONTROLLER FOR TANK SYSTEMS

The objective of this work was to develop a commercially viable method to reduce waste feed and thus improve production efficiency and reduc e discharge of solids and nutrients within tank based aquaculture syst ems. We developed and custom fabricated a feeding controller which use s ultrasound to detect uneaten feed and controls feeding events based upon appetite satiation as measured by the quantity of waste feed dete cted. During feeding, the developed device functions as a combination ultrasonic detector, feedback controller, and interval timer. The devi ce functions as a feedback controller by ultrasonically sampling the s tock tank effluent and turning off the feeder when an excessive amount of feed enters the effluent flow. After feeding has been inactivated, the ultrasonic waste feed controller operates as an interval timer an d provides a user selected delay between feedings. A custom hydroacous tic probe assembly was developed to detect uneaten feed. The controlle r can be calibrated by adjusting the transducer signal gain to detect signals resulting from feed pellets, while reducing signals resulting from faeces. The controller has an adjustable set-point for deactivati ng the feeder circuit based upon the number of feed pellets detected b y the transducer and a programmable delay time interval (from 5 to 160 min) to set the time between feedings. The controller also has an adj ustable sampling rate for detection at different pipe velocities and a n adjustable observation volume for use in standard 2, 3, 4 and 6 inch diameter effluent pipes. The cost in materials and labour to produce this waste feed controller was estimated at around $100 (U.S.).