An elaborate model was developed to estimate on-site and off-site greenhouse gases (GHGs) generated
from wastewater treatment plants (WWTPs). The model was applied to a hybrid treatment system
(five-stage Bardenpho processes) treating 5500 m3 d1 of municipal wastewater with 200 mg L1
influent biochemical oxygen demand (BOD). A sensitivity analysis was performed to predict the potential
variability of GHG emissions from the WWTP. On-site GHG emissions related to biochemical reactions at
the system were estimated to be 8264 ± 678kgCO2e d1
. The major source of on-site GHG emissions was
the first aeration tank, and these were caused by the release of dissolved and accumulated GHGs by
air-blowing. Off-site GHG emissions related to electricity consumption, chemical production, and
transportation were estimated to be 4591 ± 576 kgCO2e d1
. Off-site production of chemicals to be used
on-site was identified as the primary source of the off-site GHG emissions. The recovery of biogas and its
reuse as electricity reduced the overall GHG emissions. The results obtained from the newly developed
model (10.6 kgCO2e$kg1
BOD) were 2.83e4.24 times greater than those obtained from previous studies.
From the results of this study, an appropriate methodology is proposed to accurately estimate GHG
emissions from WWTPs and tactics are outlined for reducing GHG emissions without reducing the
quality of treated wastewater.