Dynamics of dissolved organic matter (DOM) in waste stabilization ponds: Insights into co-treatment of sanitary sewage and landfill leachate

Abstract

A thorough comprehension of dissolved organic matter (DOM) transformation in wastewater treatment plants is vital for their efficient operation and the production of high-quality effluent. However, little attention has been given to understanding DOM transformation and its potential impacts in stabilization pond systems, which heavily rely on biological processes. This study aims to fill this knowledge gap by investigating the transformations of DOM in stabilization ponds co-treating sanitary sewage and landfill leachate. A case study was conducted at the Ouro Branco WWTP in Brazil. Spectroscopic tools, including UV–Vis spectroscopy parameters (UV-254, URI), and molecular fluorescence (Excitation-Emission Matrix - EEM), were employed to assess the quality of organic matter. The findings revealed the prevalence of humic-like fluorophores associated with landfill leachate in all sampling points, including the final effluent. Notably, anaerobic ponds exhibited significantly higher fluorescence removal (peak A (80 %) > peak B (78 %) > peak C (76 %) > peak T (75 %)) compared to facultative ponds (peak T (29 %) > peak B (26 %) > peak C (19 %) > peak A (16 %)). The influent and final effluent displayed the most intricate DOM characteristics. While the influent characteristics were linked to the addition of landfill leachate, those of the final effluent were likely due to the release of soluble microbial products (SMPs).