Measuring dinitrogen gas emissions from a lagoon treatment system

Abstract

A method for collecting dinitrogen gas emissions from open pond waste treatment systems was developed. The method was critically tested in a laboratory for sources of air contamination to ensure reliable gas measurements. A laboratory experiment was done to estimate the rate at which dissolved dinitrogen would be stripped out of solution due to non-dinitrogen bubbles rising through the water column. A volumetric mass transfer coefficient for the process was estimated for clean water. The gas collection method was implemented in a partially aerated lagoon treatment system for dinitrogen and methane gas sampling. The volumetric mass transfer coefficient found in the laboratory for clean water was adjusted to compensate for field gas production rates, temperatures and wastewater quality to estimate the rate of stripped dinitrogen from the partially aerated lagoon. The estimated rate of stripped dinitrogen was subtracted from the total measured dinitrogen flux to estimate the dinitrogen produced biologically. Results from laboratory testing revealed that dinitrogen can be measured with low amounts of dinitrogen atmospheric contamination (0.57% N₂) and the preliminary field results suggest that biological denitrification did occur at this lagoon treatment system.