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

Monika Zubrowska-Sudol,Piotr Krawczyk,Katarzyna Sytek-Szmeichel,Agnieszka Bisak

doi:10.3390/en15020555

Monika Zubrowska-Sudol, Piotr Krawczyk + Show 2 more

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https://doi.org/10.3390/en15020555

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Journal: Energies	Publication Date: Jan 13, 2022
Citations: 5	License type: CC BY 4.0

Affiliation: Warsaw University of Technology

Abstract

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 (εL) used in disintegration was accompanied by an increase in the release of organic compounds from sludge (SCOD increased from 211 ± 125 mg O2/L for εL = 0 kJ/L to 6292 ± 2860 mgO2/L for εL = 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 εL 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 εL 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.

Highlights

After Poland’s accession to the structures of the European Union and the adaptation of Polish law to the EU, the handling of municipal sewage sludge has become one of the basic problems of wastewater treatment plants (WWTP), and one of the most challenging environmental and logistic issues in the country
At least 32% of gross final energy consumption in the EU is required to come from renewable energy sources (RES) by
Anevaluating increase inthe thisrelease indicator suggests converfrom activated sludge flocs is soluble. An increase in this indicator suggests conversion sion of the solid phase to the soluble phase, resulting in an increase in sludge bioavailaof the solid phase to the soluble phase, resultingbiogas in an increase in sludge bioavailability, bility, and it may result in increased production in the anaerobic diand it may result in increased biogas production in the anaerobic gestion process

Summary

Introduction

After Poland’s accession to the structures of the European Union and the adaptation of Polish law to the EU, the handling of municipal sewage sludge has become one of the basic problems of wastewater treatment plants (WWTP), and one of the most challenging environmental and logistic issues in the country. As well as constituting waste, wastewater sludge can be a source of renewable energy. Poland as a country has assumed certain obligations resulting from the climate and energy package, among other sources. Pursuant to these obligations, at least 32% of gross final energy consumption in the EU is required to come from renewable energy sources (RES) by

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