Water quality and rainbow trout performance in a Danish Model Farm recirculating system: Comparison with a flow through system

• Published in: Aquacultural engineering Vol. 40; no. 3; pp. 135 - 143
• Main Authors: d’orbcastel, Emmanuelle Roque, Blancheton, Jean-Paul, Belaud, Alain
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2009; [Amsterdam]: Elsevier Science; Elsevier
• Subjects: aeration; ammonia; Animal aquaculture; animal growth; Animal productions; biofilters; Biological and medical sciences; carbon dioxide; Energy cost; equipment design; equipment performance; fish farms; Flow rate; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; mortality; nitrites; Oncorhynchus mykiss; organic matter; oxidation; power requirement; recirculating aquaculture systems; Recirculating system; solids; stocking rate; toxicity; Treatment system; Trout; water flow; Water quality; Treatment system; Flow rate; Energy cost; Trout; Water quality; Recirculating system; Performance; Oncorhynchus mykiss; Environmental engineering; Vertebrata; Energetic cost; Pisces; Recirculating flow; Open systems; Models; Aquaculture
• ISSN: 0144-8609; 1873-5614
• DOI: 10.1016/j.aquaeng.2009.02.002

The objective was to compare water quality and fish growth and mortality in a pilot scale recirculating system (RS) and a control tank in flow through system (FTS). The RS was designed after the Danish Model Trout Farm and operated with a make up water renewal rate of 9 m 3 kg -1 of fish produced. RS water quality did not decrease significantly with water flow rate decrease in the RS. During the experiment, the RS water treatment system presented solids removal efficiency of 59.6 ± 27.7% d −1, ammonia oxidation of 45 ± 32 g m −3 d −1, oxygenation yield of 392 ± 132 g of O 2 kWh −1 and CO 2 degassing of 23.3 ± 11.9% pass −1. In the RS, nitrite concentration was 0.15 ± 0.07 mg l −1, close to the toxicity threshold; a N 2 supersaturation phenomenon was measured, probably due to the air injection depth. The biofilter and sedimentation area management has to be improved to avoid organic matter decomposition and release of dissolved elements. Even if no N 2 over-saturation apparent effect on fish performance and aspect were detected, the airlift depth has to be modified in the case of industrial development of the RS. Some improvements of the water treatment system, especially on the airlift and sedimentation area, are suggested. Concerning fish growth, no significant differences were observed between the RS and the FTS. No pathologies were detected and cumulative mortality rates (0.1%) were similar to the farm's usual data. There were no significant effects of water flow rate decrease in the RS on fish performance and energy savings were recorded to be 0.7 kWh kg −1 of fish produced between RS 1 and RS 2. The global energy cost of the RS was 3.56 kWh kg −1 of fish produced (0.107 € kg −1 of fish produced). Even if the energy consumption of the water treatment system can be improved, the results confirm that recirculating system can be used for industrial trout on growing, without fish performance deterioration.