Aquacultural Engineering 49 (2012) 1–9 Contents lists available at SciVerse ScienceDirect Aquacultural Engineering journa l h omepa g e: www .elsevier.com/locate/aqua-online Use of biomass for the removal of heavy metals at low concentrations from freshwater for Chilean Atlantic salmon farms E. Aspé ∗ , M. Roeckel, K. Fernández Chemical Engineering Department, Universidad de Concepción, Casilla 160-C, Corrreo3, Concepción, Chile a r t i c l e i n f o Article history: Received 26 July 2011 Accepted 11 January 2012 Keywords: Heavy metals Salmon fry Biomass use a b s t r a c t In Chile and Norway, countries with the highest salmon production in the world, salmons have developed chronic diseases due to toxicity problems from free metallic ions. Aluminum (Al) and iron (Fe) were found to be present in freshwaters used by the Chilean salmon industry. In this work, different alternatives for Al and Fe removal were compared to achieve the required standards in salmon culture. Manganese (Mn) removal was also assessed since Fe and Mn removal can be accomplished in a single process. Since cellulose production (a principal economic activity in Chile) and the sawmill industry generate Pinus radiata bark as a waste product, this study also analyzed its application as an adsorbent of precipitate Al, Fe, and Mn in comparison with the traditional method of granular filtration. Al(OH) 3 precipitation was achieved by pH exchange. For precipitation of Fe and Mn oxides, two alternatives were analyzed: (i) oxidation by the presence of dissolved oxygen and pH exchange and (ii) pH exchange by CO 2 injection and oxidation produced by chemical filtration. Fe and Mn in solution, at low concentrations (less than 1 mg/L) presented a maximum precipitation at pH equal to 8.7, different from the value they presented individually. The separation efficiency of the three processes: (a) oxidation and filtration in column packed with P. radiata bark; (b) oxidation and granular filtration (smaller particle size); (c) CO 2 injection and chemical and granular filtration were of 93, 97 and 98%, for Fe and of 97, 99 and 29% for Mn, respectively. In all the studied alternatives, Fe concentrations less than 0.1 mg/L, compatible with salmon life, were obtained; in contrast for Mn, it was only possible to reach an adequate concentration for salmon life with the granular filter for smaller particle sizes. The optimum pH of Al precipitation was 6.4 and the column filled with P. radiata bark achieved Al concentration values less than 0.01 mg/L, limit value for salmon farms, obtaining removal efficiencies greater than 99.5%; in contrast, in the granular filter, the average obtained for cycle efficiency was 80.3%. Only the column filled with P. radiata bark achieves Al and Fe concentrations compatible with salmon life. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Chile and Noruega are the countries with the highestsalmon production in the world. In Chile, annual export volumes are close to 4,000,000, producing currency over 1500 million dol- lars. Even when removal of heavy metals in water to achieve the required standards for human water consumption is a solved issue in the literature (Nordell, 1965; Faust and Aly, 1998; Sommerfeld, 1999; Unda, 1963), there are no reports of metal removal related to salmon culture. In both Chile and Norway, a proportion of salmon producers have chronic or episodic metal toxicity problems (Kristensen et al., 2009; Aspé et al., 2009). In Chile, in salmon pro- duction, water from groundwater wells (32%), natural springs (40%) and rivers (28%) is used and Al and Fe are the main heavy metals ∗ Corresponding author. Tel.: +56 41 2204534; fax: +56 41 2243750. E-mail addresses: easpe@udec.cl, estrellaaspe@gmail.com (E. Aspé). present in these waters (Kristensen et al., 2009). The concentration limits of heavy metals for drinking water (human consumption) and for salmon farms are shown in Table 1. Heavy metal presence in water is the result of their lixiviation due to the action of rainwater on soil and volcanic rocks (Gray, 2008), moving into natural water courses, and possibly reaching fish farm inffluents. In water, metals can form complexes, which can be classified in ionic pairs, inorganic complexes and organic complexes. The presence of free metal ions or methyl–metallic complexes results in much higher toxicity than less soluble com- plexes (Novotny, 2003). The metal effect on fish produces lethargic and disoriented swimming; an increase of the opercular rhythm; change in color; spiral swimming; pseudo feces; sudden death; pale liver and hep- atomegaly (Blazer, 2000). Metal presence affects mainly fish gills because they are the first organs that contact metals in the water (Pandey et al., 2008). Additionally, fish are highly vulnerable due to the large superficial area, which facilitates interaction and fast 0144-8609/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaeng.2012.01.002