Ž .
Aquaculture 183 2000 269–284 www.elsevier.nlrlocateraqua-online
Removal of aquaculture therapeutants by carbon adsorption
1. Equilibrium adsorption behaviour of single components
S.J. Aitcheson, J. Arnett, K.R. Murray , J. Zhang
Department of Mechanical and Chemical Engineering, Heriot-Watt UniÕersity, Edinburgh EH14 4AS, UK Accepted 6 September 1999
Abstract
This paper presents data on batch equilibrium adsorption onto the coal-based activated carbon Ž
. 207EA Sutcliffe Speakman of Malachite Green, formalin, Chloramine-T and Oxytetracycline.
These substances are widely used in aquaculture to control fish parasites and disease, but few data were previously available on their adsorption behaviour. In addition, equilibrium adsorption data
Ž .
for carbon 207EA are presented for the mixed dissolved organic carbon DOC typically present in the water where fish are reared, as well as for
D
-glucose. Together, these data permit the design of carbon adsorption treatment units that will remove both therapeutants and DOC without causing
stress to the fish stock. It further removes the need for land-based recycle systems to discharge these mixed effluents untreated to the environment. q 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Carbon-adsorption; Aquaculture; Chloramine-T; Formalin; Malachite Green; Oxytetracycline
1. Introduction
Classical intensive recycle aquaculture systems commonly use nitrifying biological Ž
. filtration to clean up the recirculating water Westerman et al., 1993 . These filters also
Corresponding author.
Tel. q44-131-449-5111
ext. 4719;
fax: q44-131-451-3129;
e-mail: cpekrmhw.ac.uk
0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž
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effectively remove suspended solids and control dissolved organic carbon DOC levels Ž
. Boller and Gujer, 1986 . Diseases are often controlled by the addition of organic
chemical therapeutants, either directly to the water or in the fish feed. Unfortunately, these biological filters are not designed to remove therapeutants and the shock loading
of the therapeutants on the filters may destroy the nitrifying bacteria and thereby lead to unacceptable stress to the fish stock. Therefore, it is common practice simply to purge
recycle aquaculture systems once therapeutants have been added, and only to resume normal effluent treatment and recirculation once the therapeutants have been removed.
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. Murray and McEvoy, 1990 .
As a classical unit operation for the removal of DOC and colour in potable water Ž
. treatment, activated carbon filtration Henry and Weinke, 1996; Kiely, 1997 has also
been used extensively for post ozone or chlorine treatment. It is clear that it has the potential to effectively remove DOC and certain therapeutants, i.e., Malachite Green,
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from fish farm waste waters Alderman, 1985 . This would effectively prevent the release of these pollutants to the environment whether as a purge from an intensive
aquaculture system or, for that matter, any land-based operations for disease treatment, Ž
particularly as there is concern and doubt about their fate in the ecosystem Bjorkland et .
al., 1990; Coyne et al., 1994; Kerry et al., 1994; Smith, 1996; Herwig et al., 1997 . To design carbon filters, this requires fundamental experimental data on the equilibrium
adsorption behaviour with respect to activated carbon of the main components of the effluent. However, while DOC removal using carbon filters is often reasonably well
characterised empirically, very few adsorption data are available for therapeutants. This paper, therefore, presents experimental data on the batch equilibrium adsorption of the
following commonly used therapeutants: Oxytetracycline, Malachite Green, formal-
Ž dehyde and Chloramine-T, onto the coal-based activated carbon 207EA supplied by
. Sutcliffe-Speakman . Data are also presented for DOC for the same carbon. These data
can be used directly to model multicomponent adsorption of DOC q therapeutant mixtures onto carbon filters. They may also indicate the likely competitive adsorption
behaviour of the therapeutants onto carbonaceous matter in the environment, such as might occur in sediment close to fish cages moored in natural water bodies.
2. Materials and methods
