Long-term nitrate removal through methane-dependent denitrification microorganisms in sequencing batch reactors fed with only nitrate and methane

Abstract

Denitrifying anaerobic methane oxidation (damo) bioprocesses can remove nitrate using methane as the electron donor, which gains great concern due to the current stringent discharge standard of nitrogen in wastewater treatment plants. To obtain an engineering acceptable nitrogen removal rate (NRR) and demonstrate the long-term stable ability of damo system under conditions of nitrate and methane, two sequencing batch reactors (SBRs) fed with only nitrate and methane were operated for more than 600 days at 30 °C. The NRR of 21.91 ± 0.73 mg NO3−-N L−1 day−1 was obtained which is, to the best of our knowledge, the highest rate observed in the literatures under such conditions. The temperature was found to significantly affect the system performance. Furthermore, the microbial community was analyzed by using real-time PCR technique. The results showed that the microbial consortium contained damo archaea and bacteria. These two microbes cooperated to maintain the long-term stability. And the number of damo archaea was higher than that of damo bacteria with the ratio of 1.77. By using methane as the electron donor, damo archaea reduced nitrate to nitrite coupled to methane oxidation and damo bacteria reduce the generated nitrite to nitrogen gas. The first step of nitrate to nitrite taken by damo archaea might be the limiting step of this cooperation system. SBR could be a suitable reactor configuration to enrich slow-growing microbes like damo culture. These results demonstrated the potential application of damo processes for nitrogen removal of wastewater containing low C/N ratios.

Effects of Antibiotics on the DAMO Process and Microbes in Cattle Manure

“…However, the DAMO process, which couples methane oxidation and the nitrogen cycle, has not been studied in cattle manure or other livestock production systems. DAMO microbes have been found in many natural environments or enriched reactors (Table ,,− ). For example, the concentration of the 16S rRNA gene of DAMO archaea ranged from 3.72 × 10 4 to 2.30 × 10 5 copies μg –1 DNA in lake and river sediments as well as in rice paddy soil DAMO archaea ranged from 0.28 × 10 6 to 3.9 × 10 6 16S rRNA gene copies g –1 dry weight bulk soil and 0.27 × 10 6 to 2.8 × 10 6 in the rhizosphere, while NC10 phylum bacteria was an order of magnitude lower .…”

Revisiting the Engineering Roadmap of Nitrate/Nitrite-Dependent Anaerobic Methane Oxidation

“…Since nitrate is ubiquitous in many natural and artificial environments, such as agricultural areas and WWTPs, , research on n-DAMO is of practical significance for the treatment of nitrate-containing wastewater. However, restricted by the relatively long doubling time of n-DAMO microorganisms, , the nitrogen removal rates of n-DAMO biomass were only 18–28 mg NO 3 – -N L –1 d –1 even at optimized conditions. − With the cultivation of biofilm that is efficient in biomass accumulation, a practical nitrogen rate of 1.02 kg N L –1 d –1 was achieved through the cooperation of n-DAMO archaea and n-DAMO bacteria . Such a high nitrogen removal rate indicates the practical application potential of the n-DAMO process in the treatment of nitrate-contaminated wastewater.…”

“…The selection of appropriate inoculum plays a decisive role affecting the enrichment duration and reactor performance. Various types of inoculum are used for the enrichment of n-DAMO microorganisms, such as freshwater sediments, agricultural land, paddy soil, coastal sediment, and WWTP sludge . The first n-DAMO culture was obtained from the inoculum of sediments of freshwater canal after 16 months of enrichment .…”

Significance of anaerobic oxidation of methane (AOM) in mitigating methane emission from major natural and anthropogenic sources: a review of AOM rates in recent publications

“…230 For systems with both nitrate-DAMO and nitrite-DAMO, similar AOM rates of 3 × 10 −6 to 11.5 μmol CH 4 cm −3 d −1 (ref. 28, 50, 53, 92, 122 and 231–234) were reported. Currently, the highest AOM rate observed in bioreactors with nitrogen removal as the objective was from coculturing of DAMO archaea and Anammox bacteria.…”