Nitrous oxide (N2O) has become a global concern as it is found to have global warming potential 310 times higher than carbon dioxide (CO2) and has a longer lifespan in atmosphere. It has been reported that water reclamation plant (WRP) engaging biological nutrients removal (BNR) processes can significantly increase urban N2O emissions, where N2O is produced from both nitrification and denitrification stages as an intermediate. This implies that WRPs could be contributing to global warming considerably more than currently expected. Till now, only a few studies have been dedicated to this issue mostly due to the challenge of quantifying gaseous nitrogen greenhouse gas emissions from open or covered wastewater surfaces in treatment tanks in a WRP. As a response to the governmental concern of climate change, a study on online monitoring of N2O emissions from Singapore WRPs has been conducted. A surface emission isolation flux chamber has been modified based on the USEPA standard method for the in-situ measurement of the surface emission of N2O from full-scale BNR processes. This newly established prototype has been used for a group of realtime online monitoring at aerobic/anoxic BNR reactors in the past one and half year at two WRPs in Singapore – Changi Water Reclamation Plant (CWRP) and Ulu Pandan Water Reclamation Plant (UPWRP). Comprehensive 24-h N2O emission profiles of BNR processes in both plants were obtained successfully. From the online monitoring data, N2O emission fractions of incoming nitrogen loading were calculated to be 1.88±0.116% and 0.168±0.026% from CWRP and UPWRP, respectively. Meanwhile, corresponding mixed liquor characteristics including nitrite, nitrate and dissolved oxygen concentrations were analyzed.
|School:||National University of Singapore (Singapore)|
|Department:||Civil And Environmental Engineering|
|School Location:||Republic of Singapore|
|Source:||DAI-B 77/06(E), Dissertation Abstracts International|
|Subjects:||Civil engineering, Environmental engineering|
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