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ผู้เขียน หัวข้อ: Analysis of sedimentation and resuspension processes of aquaculture biosolids us  (อ่าน 1585 ครั้ง)
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« เมื่อ: มีนาคม 03, 2014, 02:05:08 PM »

Analysis of sedimentation and resuspension processes
of aquaculture biosolids using an oscillating grid

Ingrid Masalo? a, O` scar Guadayol b, Francesc Peters b, Joan Oca a,*
a Departament d?Enginyeria Agroalimenta`ria i Biotecnologia, Universitat Polite`cnica de Catalunya (U.P.C.),
Av. Canal Ol??mpic s/n, 08860 Castelldefels, Catalunya, Spain
b Institut de Cie`ncies del Mar, CMIMA (CSIC), Pg. Mar??tim de la Barceloneta 37-49, 08003 Barcelona, Catalunya, Spain
Received 24 October 2007; accepted 13 January 2008
Abstract

Sedimentation and resuspension processes of aquaculture biosolids (non-ingested feed and faeces) are analysed using vertically oscillating grids as a source of turbulence in fluid tanks. An oscillating grid system consists of a container in which a grid is stirred vertically generating a well-known turbulent field that is function of amplitude and frequency of oscillation, distance between grid and measurement point, and mesh spacing of the grid. The grid used in this study had a mesh spacing of 1.2 cm, and was calibrated using different amplitudes (1, 1.5 and 2 cm), frequencies (from 1 to 6 Hz) and distances (2.4, 2.7 and 3 cm). After calibration, the turbulence needed to resuspend biosolids and to maintain them in the water column following different times of consolidation, and with biosolids of different origin, was analysed. It was observed that the turbulence needed to resuspend aquaculture biosolids increased with the time of consolidation. When the turbulence was decreased after a resuspension process, the next sedimentation of biosolids showed a hysteretic behaviour: turbulence needed to resuspend a fixed percent of biosolids from the tank bottom is substantially higher than that needed to maintain the same percentage suspended in the water column. Differences in resuspension behaviour of biosolids originated in different tanks were also observed. The method provides useful information that can be compared with turbulence generated by fish swimming activity, in order to determine the culture conditions, which can promote self-cleaning conditions in a particular tank.
# 2008 Elsevier B.V. All rights reserved.

Keywords: Turbulence; Fish faeces; Solid waste; Resuspension; Oscillating grid
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