Gas analysis reveals novel aerobic deammonification in thermophilic aerobic digestion

Abstract

A laboratory-scale thermophilic aerobic digester was operated with piggery wastewater. The operating temperature varied from 50-70 degrees C. It has been found that excessive nitrogen removal occurred in the laboratory-scale thermophilic system at various HRTs. Nitrite and nitrate were not observed in the effluent. Gas measurement reveals the presence of significant amount of N2O along with NH3 gas. The rational production of N2O gas in accordance with temperature and HRT suggests that biologically mediated deammonification processes significantly contribute to the N removal. Although further microbiological investigation is required to clarify the exact nitrogen removal mechanism, the large production of N2O gas seems to be a result of the existence of a rapid growing heterotrophic deammonification process in the thermophilic system.

Review of the use of aerobic thermophilic bioprocesses for the treatment of swine waste

“…An argument that is often presented to support the use of AT processes is a faster specific transformation rate of organic material at high temperature, which should mean smaller bioreactors (Kambhu and Andrews, 1969;Yi et al, 2003). However, experiments have not always supported this hypothesis.…”

“…occasions the presence of nitrous oxide (N 2 O) in the gas phase of a laboratory AT bioreactor treating swine waste (Yi et al, 2003;Lee et al, 2004). Increase of N 2 has also been noted, but nitrite and nitrate were absent from the effluent.…”

A robust nitrifying community in a bioreactor at 50 °C opens up the path for thermophilic nitrogen removal

“…Long-term thermophilic aerobic bioreactor studies focused mainly on the oxidation of organic compounds. The major nitrogen removal mechanisms in those systems were assumed to be ammonia volatilization (65 ± 14%) and nitrogen assimilation into biomass (14 ± 4) (Yi et al, 2003;Kurian et al, 2005;Abeynayaka and Visvanathan, 2011a, b). As neither nitrite nor nitrate was ever measured in these bioreactors at 45-60°C, there is no evidence that nitrification took place in these thermophilic systems.…”

Pathogen destruction and stabilization of sewage sludge in thermophilic digestion for its agricultural use. Effects on plants and soli microbial community

“…Regarding the biogas production, the TAnD digester showed average values from 0.86 to 1.02 Nm 3 kg -1 VS -1 destroyed, which is within the expected range for anaerobic digestion of wastewater sludge [36] and comparable to those obtained by other authors during thermophilic anaerobic digestion [11,17]. Biogas composition of the TAnD digester showed an average methane content of 62% being similar or even higher, than concentrations previously reported in other studies [17,32], while the mesophilic anaerobic digester of Molina de Segura WWTP had a methane concentration around 60% (data not shown).…”

“…One of the reasons that are often presented to support the use of aerobic thermophilic reactors is their faster specific transformation rate of organic material at high temperature, which would permit the use of smaller bioreactors [36]. The elemental analysis of the raw and digested sludge showed average values for TN, TP and TK of 51, 29 and 3 g kg -1 in raw sludge and of 65, 26 and 8 g kg -1 in ATAD-digested sludge respectively.…”