Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

Ronald F. Malone

Abstract

A computerized algal turbidostat was designed and constructed for use in aquaculture facilities requiring a continuous feed source. Continuous cultures, maintained in the exponential growth phase by the continual introduction of fresh media, exhibit a steadystate nature easily adaptable to computer automation and optimization processes. These characteristics, in contrast to batch culture methods, result in both reduced land and labor requirements; an important consideration for commercial applications wherein algal production occupies as much as 40 percent of a facility in both space and cost. The turbidostat system consisted of two 0.6 m$\sp3$ growth chambers supported by a central monitoring block and pressurized dosing apparatus, and operated from a single air/vacuum piston pump. System processes were executed by a computer control system interfaced to input and output devices through an analog to digital converter. The software program, "Supervisor", written in Turbo Pascal 4.0, provided: (1) system control and monitoring, (2) high rate data collection and storage and (3) reduced operational costs through the displacement of manual labor. The core control and monitoring algorithm contained a central supervisor that mitigated the temporal demands of simultaneous processes. System operation depended on the interaction between the photocell and computer to maintain high standing crop concentrations and appropriate harvest rates leading to high production levels. Investigations were undertaken to: (1) demonstrate the capabilities of the control system in maintaining growth conditions conducive to high production levels and (2) collect baseline optimization data for Chaetoceros muelleri (Chaet 10) under varying temperature and lighting conditions. No significant difference (P $<$ 0.05) was detected between computer estimated standing crop concentrations and analytically measured total suspended solids (TSS). This result indicated the reliability of the computer/photocell combination. An average production level of 221 g/m$\sp3$/day-dry wt was obtained for Chaetoceros muelleri (Chaet 10) under continuous lighting from 250W metal halide lamps and at a temperature of 30$\sp\circ$C, which resulted in a 400-500% increase in production levels over traditional outdoor pond cultures. The turbidostat system has been implemented and is undergoing "semi-commercial" evaluation within a greenhouse bivalve hatchery located on Skidaway Island, Savannah, Georgia; an affiliation of the University of Georgia, Marine Extension Service.

Pages

277

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