Nitrous oxide and methane emissions from different treatment processes in full-scale municipal wastewater treatment plants

Abstract

Nitrous oxide (N2O) and methane (CH4) are two important greenhouse gases (GHG) emitted from biological nutrient removal (BNR) processes in municipal wastewater treatment plants (WWTP). In this study, three typical biological wastewater treatment processes were studied in WWTP of Northern China: pre-anaerobic carrousel oxidation ditch (A+OD) process, pre-anoxic anaerobic-anoxic-oxic (A-A/ A/O) process and reverse anaerobic-anoxic-oxic (r-A/ A/O) process. The N2O and CH4 emissions from these three different processes were measured in every processing unit of each WWTP. Results showed that N2O and CH4 were mainly discharged during the nitrification/denitrification process and the anaerobic/anoxic treatment process, respectively and the amounts of their formation and release were significantly influenced by different BNR processes implemented in these WWTP. The N2O conversion ratio of r-A/ A/O process was the lowest among the three WWTP, which were 10.9% and 18.6% lower than that of A-A/A/O process and A+OD process, respectively. Similarly, the CH4 conversion ratio of r-A/ A/O process was the lowest among the three WWTP, which were 89. I% and 80.8% lower than that of A-A/ A/O process and A+OD process, respectively. The factors influencing N2O and CH4 formation and emission in the three WWTP were investigated to explain the difference between these processes. The nitrite concentration and oxidation-reduction potential (ORP) value were found to be the dominant influencing factors affecting N2O and CH4 production, respectively. The flow-based emission factors of N2O and CH4 of the WWTP were figured out for better quantification of GHG emissions and further technical assessments of mitigation options.

Archaeal Diversity in Biofilm Technologies Applied to Treat Urban and Industrial Wastewater: Recent Advances and Future Prospects

“…These authors also suggested that the methanogens found in the aerated WWT plants investigated in their study may simply survive under oxygen exposure and be restricted in their activity to the anoxic areas of the plants, or just play structural roles in cell-aggregate development as they are proposed to do in GS. Archaea have also been detected in other aerated WWT systems [72–76]. …”

“…Despite their strictly anaerobic metabolism, it has been found that methanogenic Archaea are often part of the microbiota of aerated WWT systems [72–76], and a few studies have also reported their presence in aerated MBR [16,102]. The presence of anaerobic Archaea under aerated conditions is explained by the anoxic microenvironments created by the flocs’ stratification, located in the core of the aggregates.…”

Energy benchmarking in wastewater treatment plants: the importance of site operation and layout

“…Direct GHG emissions from OD processes have not been measured in this study but nitrous oxide and methane emissions are of relevance and should be accounted for. [21] Ferric chloride was dosed at Site 2 and it was assumed it would still be dosed, however, it is also expected that this would now be prior to the use of the PSTs instead of prior to the OD, and therefore this value was not affected. The size, number and capital cost of the PSTs required to treat the influent in Site 2 was completed using Southern Water design and cost models.…”

Activated Sludge – 100 Years and Counting

“…The IPCC Guidelines take a first principles approach to estimating wastewater CH 4 emissions based on the maximum CH 4 yield from a given quantity of organics and a correction factor to account for the likely realization of this maximum CH 4 production along a given treatment and discharge pathway (Doorn et al, 2006). Compared to N 2 O, CH 4 emissions from wastewater systems have been much less well researched and there are relatively few published studies (Wang et al, 2011a;Ren et al, 2013;Willis et al, 2012;Daelman et al, 2013). Compared to N 2 O, CH 4 emissions from wastewater systems have been much less well researched and there are relatively few published studies (Wang et al, 2011a;Ren et al, 2013;Willis et al, 2012;Daelman et al, 2013).…”