Changes in Nitrification Inhibitory Properties Due to pH Neutralization of Organic Chelate Agent DEA

Abstract

The problem that the nitrification process does not proceed at sea-based landfill sites has been identified. The suspected cause is the organic chelate agents which are used for the treatment of heavy metals in incineration fly ash. It has been found that these organic chelate agents decompose near neutral pH, but the decomposition process and the resulting products are not well understood. In this study, we hypothesized that the organic chelate agent DEA decomposes to produce allylthiourea. We conducted experiments to determine whether allylthiourea is produced during the DEA decomposition process and to understand changes in nitrification inhibitory properties during this process. While the concentration of DEA decreased due to decomposition, the TOC value remained nearly constant, indicating that it did not fully decompose to carbon dioxide and intermediate products are present. However, the production of allylthiourea during the decomposition process was not identified. Results from the nitrification inhibitory properties experiments suggest that the intermediate products have nitrification inhibitory properties and that these intermediates may further decompose into other intermediate products during the decomposition process.