Energy-Positive Disintegration of Waste Activated Sludge-Full Scale Study

This study aimed to evaluate the effects of mechanical disintegration of waste activated sludge (WAS) on full scale anaerobic digestion, considering the possibility of obtaining a positive energy balance. The results showed that an increase in energy density (epsilon(L)) used in disintegration was accompanied by an increase in the release of organic compounds from sludge (SCOD increased from 211 +/- 125 mg O-2/L for epsilon(L) = 0 kJ/L to 6292 +/- 2860 mgO(2)/L for epsilon(L) = 180 kJ/L). Some of them were volatile fatty acids. The percentage share of WAS subject to disintegration was also documented as a crucial parameter affecting the efficiency of biogas production. An increase in the value of this parameter from 25% to 100%, even at much lower epsilon(L) used in disintegration (therefore with much smaller amounts of organic compounds released from sludge flocs) resulted in an increase in biogas production. Conducting disintegration of the entire stream of WAS directed to the fermentation tank at epsilon(L) 30 kJ/L resulted in an increase in biogas production by 14.1%. Such a surplus would allow production of approximately 360 kWh/d net electricity. Mechanical disintegration of thickened WAS therefore may be an economically justifiable strategy for the intensification of anaerobic sludge stabilisation.

Automated summary

This study evaluated the impact of mechanical disintegration of waste activated sludge on anaerobic digestion, and found that increasing the energy density used in disintegration resulted in higher release of organic compounds. The percentage of sludge subjected to disintegration was also identified as a crucial factor affecting biogas production efficiency.