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Changes in organic matter composition during composting of two digested sewage sludges.
T Hernández1, G Masciandaro, J I Moreno
1Department of Soil and Water Conservation and Waste Management, Centro de Edafología y Biología Aplicada del Segura (CEBAS-CSIC), P.O. Box 164, 30100 Espinardo-Murcia, Spain. mthernan@cebas.csic.es
Waste Management (New York, N.Y.)
|December 17, 2005
Summary
Composting sewage sludge with sawdust reduces labile organic matter and microbial activity, resulting in a more stable compost. Pyrolysis analysis revealed limited humification, suggesting specific chemical ratios are better indicators of sludge compost transformation.
Area of Science:
- Environmental Science
- Soil Science
- Biotechnology
Background:
- Sewage sludge composting is crucial for waste management and resource recovery.
- Understanding organic matter transformation during composting is key to producing stable, high-quality compost.
- Pyrolysis-gas chromatography offers insights into the chemical structure of organic matter.
Purpose of the Study:
- To investigate the changes in organic matter composition during the composting of sewage sludge mixed with sawdust.
- To evaluate the effectiveness of chemical and microbiological parameters, alongside pyrolysis-gas chromatography, in monitoring composting processes.
- To assess the degree of humification in the resulting composts.
Main Methods:
- Composting of aerobic and anaerobic sewage sludge with sawdust in outdoor piles.
- Monitoring of chemical (volatile organic matter, water-soluble C) and microbiological (respiration) parameters.
- Analysis of organic matter chemical structure using pyrolysis-gas chromatography at various composting stages (1, 30, 60, 90 days).
Main Results:
- Volatile organic matter and water-soluble C decreased, indicating mineralization of labile fractions.
- Microbial respiration declined, correlating with increased compost stability.
- Pyrolysis analysis showed an increase in aromatic compounds (acetonitrile, acetic acid, phenol) but a low degree of humification, characterized by high polysaccharide and alkyl content.
- Established humification indices for soil organic matter were not suitable for poorly evolved sludge composts.
Conclusions:
- Composting transforms sewage sludge by reducing labile organic matter and increasing aromaticity, though humification remains limited.
- Microbiological and chemical parameters effectively track composting progress and compost stability.
- Modified pyrolysis-based ratios, focusing on carbohydrate derivatives and aromatic compounds, are more sensitive for assessing transformations in sludge composts.