Assessment of N2O emission from a photobioreactor treating ammonia-rich swine wastewater digestate

Mezarri et al., October, 2013

 

Abstract – This study investigated the interactions between naturally occurring bacteria and the microalgae Chlorella vulgaris within a lab scale photobioreactor treating ammonia-rich swine wastewater digestate effluent. Nitrification and denitrification were assessed by targeting ammonia monoxygenases (amoA), nitrate (narG), nitrite (nirS), nitric oxide (norB) and nitrous oxide (nosZ) reductases genes. Oxygen produced from microalgae photosynthesis stimulated nitrification. Under limiting carbon availability (i.e., <1.44 for mg TOC/mg NO2-N and 1.72 for mg TOC/mg NO3–N), incomplete denitrification led to accumulation of NO2 and NO3. Significant N2O emission (up to 118 μg N2O–N) was linked to NO2 metabolism in Chlorella. The addition of acetate as external carbon source recovered heterotrophic denitrification activity suppressing N2O emission. Effluent methane concentrations trapped within photobioreactor was removed concomitantly with ammonia. Overall, closed photobioreactors can be built to effectively remove nitrogen and mitigate simultaneously greenhouse gases emissions that would occur otherwise in open microalgae-based wastewater treatment systems.

 

Click here to access the article at ScienceDirect

Labex Korea on Twitter and Facebook

Correlating denitrifying catabolic genes with N2O and N2 emissions from swine slurry composting

By Angnes et al.

Abstract – This work evaluated N dynamics that occurs over time within swine slurry composting piles. Real-time quantitative PCR (qPCR) analyzes were conducted to estimate concentrations of bacteria community harboring specific catabolic nitrifying-ammonium monooxygenase (amoA), and denitrifying nitrate- (narG), nitrite- (nirS and nirG), nitric oxide- (norB) and nitrous oxide reductases (nosZ) genes. NH3-N, N2O-N, N2-N emissions represented 15.4±1.9, 5.4±0.9, and 79.1±2.0% of the total nitrogen losses, respectively. Among the genes tested, temporal distribution of narG, nirS, and nosZ concentration correlated significantly (p < 0.05) with the estimated N2 emissions. Denitrifying catabolic gene ratio (cnorB+qnorB)/nosZ ⩾ 100 was indicative of N2O emission potential from the compost pile. Considering our current empirical limitations to accurately measure N2 emissions from swine slurry composting at field scale the use of these catabolic genes could represent a promising monitoring tool to aid minimize our uncertainties on biological N mass balances in these systems.

Source: ScienceDirect, 7th May, 2013
Follow us on Twitter and Facebook