Assessment of leachable and persistent dissolved organic carbon in sludges and biosolids from municipal wastewater treatment plants

• Published in: Journal of environmental management Vol. 307; p. 114565
• Main Authors: O'Keeffe, Juliette, Akunna, Joseph
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2022
• Subjects: Biosolid; Biosolids; Dissolved Organic Matter; Leaching; Persistent organic pollutants; Sewage; Sludge; TOC; Waste Disposal, Fluid; Water Purification; TOC; Sludge; Persistent organic pollutants; Biosolid; Leaching
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2022.114565

Environmental regulation of organic pollutants has not kept pace with the growth in the number and diversity of legacy and emerging organic substances now in use. Simpler and cheaper tools and methodologies are needed to quickly assess the organic pollutant risks in waste materials applied to land such as municipal wastewater treatment sludges and biosolids. This study attempts to provide these, using an approach that consists of chemical leaching and analysis of dissolved organic carbon and determination of its biodegradability by measuring persistent dissolved organic carbon. Primary and secondary sludges, dewatered sludge cake, and anaerobically and thermally treated biosolids obtained from various types of municipal wastewater treatment plants were used in the study. The study found little variability in the levels of dissolved organic carbon leached from primary sludges obtained from different municipal wastewater treatment plants but found significant differences for secondary sludges based on levels of nitrification at the municipal wastewater treatment plants. As predicted treated biosolids leached less dissolved organic carbon than untreated dry sludges but had relatively higher proportions of persistent or poorly biodegradable dissolved organic carbon. Across all tested sludges and biosolids persistent dissolved organic carbon ranged from 14 to 39%, with biosolids that have undergone anaerobic digestion and thermal treatment more likely to contain greater relative proportion of persistent dissolved organic carbon than untreated sludges. The approach presented in this study will be useful in assessing the effectiveness of current and widely employed sludge treatment methods in reducing persistent organic pollutants in biosolids disposed on land. •Dissolved organic carbon leaches in appreciable quantifies from wastewater residues.•Leached non-biodegradable dissolved organic carbon may indicate persistent organics.•Leached dissolved organic carbon decreased with nitrification and thermal treatment.•Persistent dissolved organic carbon from wastewater residues ranged from 14 to 39%.•Persistent dissolved organic carbon was higher in treated wastewater residues.