Inderscience Publishers

Regrowth of bacterial pathogen indicators after advanced electro-osmotic dewatering of biosolids

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Applying an electrical field for 10 min to mechanically dewatered biosolids increased dryness to 35 to 45% and reduced
Escherichia coli
levels to/close to detection limits. Possible reasons for the regrowth of bacterial pathogens impacted by electro-osmotic dewatering are biosolids dryness, low pH and the generation of bacterial oxidants on the anode due to high temperatures. Testing for this with aerobic and anaerobic incubations resulted in more than four logs of
E. coli
regrowth in 2011, when biosolids harboured higher initial counts; whereas regrowth was not observed in 2012, when biosolids had lower
E. coli
counts. In 2011 experiments, however, addition of a nitrate salt prior to anaerobic incubations reduced regrowth by 1.4 logs. This indicates that other NO
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-respiring organisms could be competing with
E. coli
and diverting electrons away from the
E. coli
population. These results suggest that electro-osmotic dewatering and nitrate can play a role in controlling
E. coli
regrowth.

Keywords: bacterial regrowth, class A biosolids, electro-osmotic dewatering, EOD, aerobic incubation, anaerobic incubation, sustainable waste management, activated sludge

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