Integrating Bulk and Molecular Analyses with PCA to Elucidate OM Dynamics in Treated Sludge: Insights for Sustainable Waste Management

Abstract

Abstract Effective sludge treatment is essential for sustainable waste management, addressing environmental protection, public health, and resource recovery objectives. This study investigates the stabilization dynamics of five treated sludge products—raw thickened, digested, dried, limed, and composted sludge—using an integrated approach combining bulk characterization, molecular analysis, and principal component analysis (PCA). Bulk parameters including dry matter, volatile matter, chemical oxygen demand, and electrical conductivity provided an overall assessment of sludge properties and stabilization status. Meanwhile, molecular characterization of organic matter (OM) by thermochemolysis coupled with gas chromatography and mass spectrometry identified specific biomarkers that revealed the biochemical transformations occurring during treatment. The integration of bulk and molecular datasets enabled a comprehensive evaluation of sludge stabilization by linking macro-scale properties with molecular-level processes. PCA highlighted relationships among sludge types, bulk parameters and molecular markers, allowing differentiation of sludge products according to their degree of stabilization. Rather than serving as a predictive classification tool, PCA provided an effective diagnostic framework for distinguishing reactive, transitional, and stabilized sludge products and for identifying the dominant processes governing their evolution. From an engineering perspective, the proposed approach offers a practical framework for identifying sludge management by supporting treatment optimization, assessment of stabilization efficiency, evaluation of land application suitability, and identification of opportunities for resource or recovery strategies. Overall, this study demonstrates that combining bulk and molecular analyses with multivariate statistical tools improves the understanding and assessment of sludge stabilization processes, contributing to more sustainable sludge treatment and valorization strategies.