Interestingly, the high level of particulate filtration coupled with
some relatively harsh, though easily rectifiable water qualities that are
created (e.g. low DO and redox; presence of sulphide) may provide
other useful processes, such as the control of pathogens and diseasecausing
organisms in recirculated systems. For example, the low levels
of sulphide that can be present in these filtration bed's anaerobic
discharge has been observed to dissipate very quickly (within minutes)
after release from the sand bed into an oxygenated water body. Neori
et al.
(2007) recently highlighted the rapid oxidation of sulphide in the
boundary layers between anaerobic and aerobic sediments, where
patches of white elemental sulphur were often visible. In the present
system,this white material also typically forms in the immediate stream
of water discharging from the sand beds. It is normally combined with a
slime or gel layer on adjacent surfaces, which is likely associated with
the bacteria involved in this sulphur deposition (e.g. Beggiatoa sp.
Nelson and Castenholz, 1981), or those utilising the sulphur after its
transition to an oxidised form. This sulphur-rich gel is also likely to
constantly form on the insides of the worms burrows, and probably
provides or is the base of an important food source for inhabiting
polychaetes and other benthic organisms (Reise, 1981), perhaps as it is
in areas directly adjacent to deep ocean hydrothermal vents (Van Dover
and Lutz, 2004)
Interestingly, the high level of particulate filtration coupled withsome relatively harsh, though easily rectifiable water qualities that arecreated (e.g. low DO and redox; presence of sulphide) may provideother useful processes, such as the control of pathogens and diseasecausingorganisms in recirculated systems. For example, the low levelsof sulphide that can be present in these filtration bed's anaerobicdischarge has been observed to dissipate very quickly (within minutes)after release from the sand bed into an oxygenated water body. Neoriet al. (2007) recently highlighted the rapid oxidation of sulphide in theboundary layers between anaerobic and aerobic sediments, wherepatches of white elemental sulphur were often visible. In the presentsystem,this white material also typically forms in the immediate streamof water discharging from the sand beds. It is normally combined with aslime or gel layer on adjacent surfaces, which is likely associated withthe bacteria involved in this sulphur deposition (e.g. Beggiatoa sp.Nelson and Castenholz, 1981), or those utilising the sulphur after itstransition to an oxidised form. This sulphur-rich gel is also likely toconstantly form on the insides of the worms burrows, and probablyprovides or is the base of an important food source for inhabitingpolychaetes and other benthic organisms (Reise, 1981), perhaps as it isin areas directly adjacent to deep ocean hydrothermal vents (Van Doverand Lutz, 2004)
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