Temperature and organic loading dependency of methane and carbon dioxide emission rates of a full-scale anaerobic waste stabilization pond

Abstract

CH 4 and CO 2 emission rates were measured in a full-scale anaerobic waste stabilization pond (AWSP) in Portugal and correlated with removed organic loading rate, and ambient air temperature. Strong correlation was found between biogas composition and removal efficiency. Correlation coefficients for CH 4 and CO 2 were 92.6% and 76.9%, respectively. The lowest liquid temperature at which the AWSP served as a primary sedimentation basin without any biological degradation, was found to be 11.7°C, with a total COD removal of 30%. First-order COD removal rate constant and temperature correction factor were 0.221 day −1 and 1.117, respectively. Biogas production rates varied between 28.68 and 83.17 l m −2 day −1. Average volumetric biogas production rate was 19.57 l m −3 day −1. Biogas volume changed during the day and 24 h-averaged value was 2.02 l m −2 h −1. Biogas conversion ratio was between 0.160 and 0.702 m 3 kg COD −1 removed. Percentages of CH 4 and CO 2 found in the biogas were between 52–80%, and 7–28%, respectively. CH 4 production rates varied between 18.18 and 48.74 l m −2 day −1 depending on influent COD loading and liquid temperature. CO 2 formation rates were between 3.08 and 9.79 l m −2 day −1. Mean CH 4 and CO 2 production were determined to be 82.34 and 14.40 m 3 day −1, respectively. Volumetric production rates for CH 4 and CO 2 were obtained to be 13.54 and 2.37 l m −3 day −1, respectively.