MESOPHILIC ANAEROBIC DIGESTION OF ANIMAL WASTE AND E.COLI REDUCTION

Yi Wang , Pramod Pandey

ABSTRACT: Anaerobic digestion (AD) is one of the preferred method for treating animal wastes, and emphasize of this study is to investigate E. coli reductions in AD system. The AD is widely applied in developing countries such as China and India. The AD has been also used in developed countries such as USA and Germany for treating animal waste, particularly, dairy manure. Both thermophilic (≈50-55 ⁰C) temperature and mesophilic temperature (≈35-37 ⁰C) AD systems are used; however, mesophilic AD is more common than the thermophilic AD because of no requirement for external energy to increase the temperature in mesophilic AD system. The advantages of AD system include the productions of biogas (a source of renewable energy), and digestate (used as a fertilizer). Another benefit of the AD is that it helps in controlling animal waste born pathogen and pathogen indicator (such as E. coli) reductions. Additional studies are needed to investigate E. coli reductions in the AD system. This study was focused on understanding of E. coli reduction in the AD, which was operated in mesophilic temperature conditions. Subsequently, models were developed to calculate E. coli reductions. Two different types of animal manure feedstocks were used for calculating E.coli reduction. In the first feedstock, liquid slurry from solid manure (scrapped manure) was prepared in the lab, while the second feedstock includes flushed dairy manure (i.e., liquid manure) collected from dairy lagoons located in dairy farms. Results of observation and model showed the AD system reduces E. coli level substantially; however, the reduction level depends on the incubation time.

Keywords: pathogen, anaerobic digestion, mesophilic temperature, animal waste, E. coli.