Carbon Footprint Analyses of Wastewater Treatment Systems in Puducherry

Abstract

Carbon footprint analysis is a method to quantify the life cycle Greenhouse Gases (GHGs) emissions and identify the measure to reduce climate change impacts. The Intergovernmental Panel on Climate Change (IPCC) has identified that the global warming and climate change which is one of the most important issues in the domain of environment are caused by the excessive emission of Greenhouse Gases (GHG) mainly constituting Carbon dioxide (CO2), Methane (CH4) and Nitrous oxide (N2O). The municipal wastewater treatment plant receives wastewater for treatment and finally discharges the treated effluent. The emissions of GHG during the treatment of wastewater as well as during the treatment process of sludge and also for energy generation are known to be on-site GHG emissions. Off-site GHG emissions are generated due to transportation and disposal of sludge, off-site energy and chemical production. In Puducherry, the municipal wastewater is being treated using oxidation ponds, Upflow Anaerobic Sludge Blanket (UASB) and Sequencing Batch Reactor (SBR). Wastewater treatment using Sequencing Batch Reactor (SBR) technology is one of the state-of-the art wastewater management systems. In this technology equalization, biological treatment and secondary clarification are performed in a single reactor in a time control sequence. The emissions of GHG from the Oxidation ponds of 12.5 MLD, UASB reactor of 2.5 MLD and SBR of 17 MLD were assessed based on the IPCC guidelines and the total emissions of GHG in terms of equivalent of CO2 were compared. The performance of the SBR is more efficient and the emissions of GHG are less than the emissions in the UASB as well as in oxidation ponds. The emission of GHG in SBR is about 60% of the existing treatment systems of oxidation ponds and UASB thus a reduction of 40% GHG emission could be achieved.