Swine waste treatment by self-heating aerobic thermophilic bioreactors

Pig manure represents a very high-strength wastewater that is well suited for a self-heating aerobic thermophilic treatment. Here we report the use of 59-L Aerobic Thermophilic Sequencing Batch Reactors (AT-SBR) to study the treatment of pig manure with a HRT of 6 days. Temperatures up to 75 degrees C were reached without external heating by using Venturi-type aerators but these conditions were detrimental for the respiratory activity of the microflora. For COD removal, better performances were achieved when the temperature was limited to 50 degrees C. However, higher temperatures increased the rate of phosphorus crystallisation and the volatilisation of ammonia. A temperature of 50 degrees C was enough to eliminate faecal coliforms and Campylobacter spp., but 60 degrees C was needed for the efficient destruction of Clostridium perfringens. Consequently, an operating temperature of 60 degrees C appears to be a good compromise. Under these conditions, the BOD(5) decreases from 50.5 to 1.0 g L(-1), yielding a 98% removal.