Education for sustainable development (ESD) plays an increasing role in environmental education policy and practice. In this article, we show how sustainable development is mainly seen as a goal that can be achieved by applying the proper processes of learning and how this learning perspective translates sustainability issues into learning problems of individuals. We present a different perspective on education for sustainable development and emphasize the importance of presenting issues of sustainable development as 'public issues', i.e. as matters of public concern. This shifts the focus from the competences that citizens must acquire to the democratic nature of the spaces and practices in which participation and citizenship can develop.
The role of microbial consortia on the removal of manganese (Mn) was examined on sand from three different Belgian rapid sand filters for the treatment of ground water. Microorganisms closely associated with deposits of Fe and amorphous Mn precipitates were observed by SEM and EDAX techniques on sand from the filters able to remove Mn efficiently. Bacterial counts were performed. Of the CFU enumerated on PYM-medium, 25-33% displayed Mn-oxidizing activity.Batch cultures were set up by inoculating a Mn-containing, low organic medium with sand from one of the filters. Microbial growth resulted in the formation of Mn-removing bacterial flocs and a pH increase. Suppression of microbial growth by addition of azide, kanamycin, or by autoclaving reduced removal of Mn(2+) from 0.5 mM/day to 0.05-0.11 mM/day. Buffering the pH of the medium at 7.5 (0.1 mM Hepes) decelerated the Mn removal but did not halt it, whereas microelectrode measurements revealed a clear pH drop of about 0.7 units inside bacterial flocs. In the absence of Mn(2+), the pH drop was only 0.4 units. The auto-catalytic removal of Mn by the Mn oxide coated filter sand was not sufficient to explain the Mn removal observed. Inactivated cells were not capable of a pronounced autocatalytic Mn removal. Experiments with enrichment cultures indicated that the Mn-removing capacity of the microbial sand filter consortia was not constitutive but was promoted by preadaptation and the presence of a substratum. These results clearly link Mn oxidation in rapid sand filters to microbial processes.
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