Effect of temperature on microbial population and performance of an aerobic thermophilic reactor treating cattle slurry and waste food

Abstract

This study was carried out to quantify and identify the presence of somatic coliphages, RNA coliphages, sulphite‐reducing clostridia, Clostridium tyrobutyricum or its related clostridia, faecal coliforms, enterococci and heterotrophs in a mixture of cattle slurry and waste food (whey and jam) that had undergone aerobic thermophilic treatment (ATT). We also investigated the influence of different factors, including pH, COD, temperature, odour removal, addition of waste food (whey and jam) and nitrogen losses, on the long‐term ATT process. The processes were conducted semi‐continuously with retention time of five days and with the waste food and slurry mixture (1:4) being added daily into the reactor. The experiments lasted seven days for each thermophilic temperature (50, 60 and 70 °C). Our work showed that, at the higher temperature of the ATT operation, the number of microorganisms declined much more rapidly than at the lower temperature and the final product was hygienically safe. The use of waste food (whey and jam) was beneficial because it buffered pH.