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°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°C. However, higher temperatures increased the rate of phosphorus crystallisation and the volatilisation of ammonia. A temperature of 50°C was enough to eliminate faecal coliforms and Campylobacter spp., but 60°C was needed for the efficient destruction of Clostridium perfringens. Consequently, an operating temperature of 60°C 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.