Identifier

etd-01222007-144953

Degree

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

Document Type

Dissertation

Abstract

A 40-L recirculating rotifer turbidostat (RRT) pilot system consisting of a rotifer reactor, biofilter, foam fractionator, feed container, harvester, and two air-lift pumps was designed to produce B. rotundiformis, a small (S-type) rotifer, that is increasingly demanded for production of small-gape marine finfish larvae. The system’s automatic monitoring (turbidity, pH, conductivity and temperature) and controlling (turbidity, pH, feeding and harvesting) were performed by a Rugid™ computer. A 4 (temperature) x 3 (salinity) study indicated that a 30oC/15 ppt treatment is the most favorable to the growth of B. rotundiformis. Under these conditions, the effect of harvest rate on rotifer system productivity was investigated with a feed ration of 1.3x105 cells Nannochloropsis oculata rot-1 d-1. Three 33-40 d pilot trials (mean stocking density: 742-946 rot mL-1) showed significant improvements in the daily rotifer harvest (1.68, 3.70 to 5.89 million rot d-1) and system volumetric productivity (0.09, 0.20 to 0.32 million rot L-1 d-1) with the increasing rotifer harvest rate (0.12, 0.21 to 0.37 d-1). Pilot trials demonstrated that the designed system functions in ammonia removal (mean TAN < 0.15 mg N L-1), foam/solids reduction, continuous harvesting, pH controlling (pH ≥ 8.0), and culture stability. The Monod constants for B. rotundiformis fed N. oculata were determined using non-linear regression and Lineweaver-Burk plots. A linear equation between μmax and harvest rate (H, 0.12-0.37 d-1) was introduced to modify the Monod equation. A mechanistic model was developed for the designed RRT system and solved using STELLA®. The RRT model was calibrated with three datasets. The economic analyses were compared between 40-L and up-scaling 1-m3 systems at 103 rot mL-1 stocking level. The production cost for one million rotifers was reduced from $3.01 to $0.70 for this volume up-scaling. It lowers to $0.14 for further five-time density up-scaling. Model simulations indicated a harvest rate of 0.35 d-1 for a stable rotifer production under the Pilot Trial 3 scenario, although 0.60-1.10 d-1 could achieve the maximum productivity. The rotifer economic model can function as a useful management tool.

Date

2006

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Kelly A. Rusch

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