Methane emission estimates using chamber and tracer release experiments for a municipal waste water treatment plant

Abstract

Abstract. This study presents two methods for estimating methane emissions from a waste water treatment plant (WWTP) along with results from a measurement campaign at a WWTP in Valence, France. These methods, chamber measurements and tracer release, rely on Fourier transform infrared spectroscopy and cavity ring-down spectroscopy instruments. We show that the tracer release method is suitable for quantifying facility-and some process-scale emissions, while the chamber measurements provide insight into individual process emissions. Uncertainties for the two methods are described and discussed. Applying the methods to CH 4 emissions of the WWTP, we confirm that the open basins are not a major source of CH 4 on the WWTP (about 10 % of the total emissions), but that the pretreatment and sludge treatment are the main emitters. Overall, the waste water treatment plant is representative of an average French WWTP.

Statistical atmospheric inversion of local gas emissions by coupling the tracer release technique and local-scale transport modelling: a test case with controlled methane emissions

“…Based on infrared spectroscopy, the high precision of the system (precisions of 3 ppb and < 600 ppt for methane and acetylene, respectively, on a 2 s interval) is due to its very long path length ( 20 km) and the small size of its measurement cell (< 35 mL). Mobile measurements with this instrument have already been successfully taken and published in previous studies (Mønster et al, 2014;Yver Kwok et al, 2015), demonstrating the potential of this method. The measurement error encompasses the precision stated above but also the fact that the acetylene and methane are not measured at the exact same time and frequency.…”

“…The mean and standard deviation SD tr of the n tr different results are used as the best estimate and uncertainty assessment for the source quantification. Note that, strictly speaking, the exact quantification of the uncertainty in the mean estimate should be SD tr / √ n tr , which will be used here, even though SD tr is often used (Yver Kwok et al, 2015). These statistics allow us to account, at least partly, for the potential temporal variations of the emissions, for the measurement and background errors, and for the potential impact of the non-perfect collocation of the sources in the selected measurement transects.…”

“…In general, there is no correlation between the prior uncertainties in the methane emissions from different targeted sources within a site, since they generally correspond to different processes (e.g. the aeration process and the clarification process in wastewater treatment plants; Yver Kwok et al, 2015). Therefore, here, the B matrix is set up diagonally.…”

“…However, a precise estimate of the methane emissions from these sites based on atmospheric techniques could help their operators to mitigate their emissions as part of their local action plans in the context of climate change. Instantaneous estimates of the emissions through a dedicated measurement campaign can help to detect and provide a useful order of magnitude for sources that are generally poorly known (Yver Kwok et al, 2015). The results from series of campaigns can be extrapolated to estimates for long timescales.…”

“…Typical methane-emitting sites due to anthropogenic activities include waste-processing plants (wastewater treatment plants and landfills), oil and gas extraction and compressing sites and farms (Czepiel et al, 1996;Marik and Levin, 1996;Yver Kwok et al, 2015). These sites contain widespread and heterogeneous sources (like the basins in waste water treatment plants, the cells in landfills and the livestock in farms) and are prone to fugitive leakages (especially in the oil and gas sectors).…”