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 75degreesC 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 50degreesC. However, higher temperatures increased the rate of phosphorus crystallisation and the volatilisation of ammonia. A temperature of 50degreesC was enough to eliminate faecal coliforms and Campylobacter spp., but 60degreesC was needed for the efficient destruction of Clostridium perfringens. Consequently, an operating temperature of 60degreesC appears to be a good compromise. Under these conditions, the BOD5 decreases from 50.5 to 1.0 g L-1, yielding a 98% removal. (C) 2003 Elsevier Ltd. All rights reserved.