An Autothermal Thermophilic Aerated Bioreactor (ATAB) pilot plant operating on food processing wastes is being studied to identify the micro-organisms present. Incubations of teh wastewater stream from the wastewater holding tanks to sludge (biomass) from the Dissolved Air Floatation (DAF) plant and the ATAB pilot plant were carried out at both 30 deg and 60 deg to estimate the impact of the process on culturable microbes. It was found that resident culturable microflora in the wastewater stream did not survive the ATAB process. The bioreactors performance appears to be related to the presence of thermophilic organisms not previously detected in the wastewater feed. Molecular methods using Amplified Ribosomal DNA Restriction Analysis (ARDRA) are now being applied to analyse the thermophilic microbial communities diversity and to identify important members. It can be concluded that the high autothermal operating temperatures create a pasteurisation effect on resident microbial species, some of which are pathogens, in the wastewater stream. The heat produced in this process is potentially recoverable for reuse. The stabilised and pasteurised sludge may be useful for value adding products.
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