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Organic matter transformations and kinetics during sewage sludge composting in a two-stage system
Dorota Kulikowska1, Ewa Klimiuk
1University of Warmia and Mazury in Olsztyn, Department of Environmental Biotechnology, Słoneczna St. 45G, 10-709 Olsztyn, Poland. dorotak@uwm.edu.pl
Bioresource Technology
|October 8, 2011
Summary
Composting sewage sludge with rape straw and grass amendments impacts temperature and organic matter. Higher temperatures during composting are crucial for forming humic acids (HA) and achieving better humification.
Area of Science:
- Environmental Science
- Soil Science
- Waste Management
Background:
- Municipal wastewater treatment plants generate dewatered sewage sludge, a potential resource requiring effective treatment.
- Composting is a viable method for sludge stabilization and nutrient recovery.
- The use of agricultural byproducts like rape straw and grass as amendments can improve composting efficiency.
Purpose of the Study:
- To investigate the effect of different proportions of rape straw and grass amendments on the composting of dewatered sewage sludge.
- To analyze the impact of feedstock composition on temperature, organic matter degradation, and humic substance formation.
- To determine the factors influencing humic acid (HA) formation and the degree of humification.
Main Methods:
- A two-stage composting system was employed, including an aerated bioreactor and a turned windrow.
- Dewatered sewage sludge was composted with varying ratios of rape straw and grass.
- Temperature, organic matter degradation, and humic substance content (including HA) were monitored throughout the process.
Main Results:
- Feedstock composition significantly influenced bioreactor temperature and organic matter degradation.
- Total humic acid (HA) content increased over time, but labile HA remained a small fraction.
- A low degree of humification (R-type HA) was observed, with temperature being the key factor for HA polymerization.
Conclusions:
- The ratio of rape straw and grass amendments affects sludge composting performance.
- Thermophilic temperatures are essential for promoting the polymerization of fulvic acids into humic acids and enhancing humification.
- Optimizing composting conditions, particularly temperature, is critical for maximizing humic substance formation in sludge compost.
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