Quantifying direct carbon dioxide emissions from wastewater treatment units by nondispersive infrared sensor (NDIR) – A pilot study

Abstract

Treatment of nutrient-rich wastewater potentially results in direct release of greenhouse gases (GHGs) such as CO2, N2O or CH4 – and thus affects Waste Water Treatment Plant's carbon footprint. Accurate CO2 quantification is challenging due to various chemical, physical and operational conditions. A floating chamber equipped with a nondispersive infrared, single beam, dual wavelength sensor has been evaluated for a pilot approach to quantify fugitive CO2 emissions above different wastewater treatment units. Total average CO2 flux was 1182gCO2·m−2·d−1 with minimum and maximum fluxes of 829gCO2·m−2·d−1 and 1493gCO2·m−2·d−1, respectively. Total observed CO2 emissions were in 7 to 17kgCO2·PE−1·a−1 (average 12kgCO2·PE−1·a−1). The nitrification tank accounted for about 94.3% of the emissions, followed by secondary clarification (ca. 4.3%) and denitrification (ca. 1.4%), based on those average annual CO2 emissions per population equivalent (PE).