Developments in pre-treatment methods to improve anaerobic digestion of sewage sludge

  • P. Neumann
  • S. Pesante
  • M. Venegas
  • G. Vidal
review paper


During wastewater treatment, most organic matter is transferred to a solid phase commonly known as sludge or biosolids. The high cost of sludge management and the growing interest in alternative energy sources have prompted proposals for different strategies to optimize biogas production during anaerobic sludge treatment. Because of the high solid content and complex structure of sludge-derived organic matter, methane production during digestion is limited at the hydrolysis step. Therefore, large digester volume and long retention times of over 20 days are necessary to achieve adequate stabilization. Pre-treatments can be used to hydrolyze sludge and consequently improve biogas production, solids removal and sludge quality after digestion. This paper reviews the main pre-treatment processes, with emphasis on the most recent developments. An overview of the different technologies is presented, discussing their effects on sludge properties and anaerobic digestion. Future challenges and concerns related to pre-treatment assessment and implementation are also addressed.


Sewage sludge Hydrolysis Pre-treatment Biogas production Biosolids Anaerobic digestion 



Anaerobic digestion


Advanced thermal hydrolysis


Biochemical oxygen demand


Chemical oxygen demand


Capillary suction time


Disintegration degree




Dissolved organic carbon


Dry solids


Endocrine disrupting compounds


Extracellular polymeric substances


Feed/inoculum ratio


Fecal coliforms


Growth rate of solubilization


Helminth eggs


High pressure homogenization




Organic dry solids


Organic loading rate


Organic matter


Oxygen uptake rate


Peracetic acid






Soluble biochemical oxygen demand


Soluble chemical oxygen demand




Suspended solids


Specific resistance to filtration


Solids retention time


Sludge volumetric index


Total chemical oxygen demand


Total nitrogen


Thermally-phased anaerobic digestion


Temperature-staged biologically-phased anaerobic digestion


Total solids


Total suspended solids




Volatile fatty acids


Volatile solids


Volatile suspended solids


Waste activated sludge



This work was supported by Grant No. 21110449 from CONICYT (Chile), Grant CONICYT + PAI/2014 No. 781413004 and CONICYT/FONDAP/15130015. The authors also thank the Doctoral Network REDOC.CTA, MINEDUC Grant UCO1202 at the University of Concepcion. P. Neumann and M. Venegas thank to CONICYT for their Scholarship Program CONICYT-PCHA/Doctorado Nacional/2013-21130054 and CONICYT-PCHA/Doctorado Nacional/2016-21160100, respectively for supporting their Ph.D. studies at the University of Concepción.


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© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  1. 1.Engineering and Environmental Biotechnology Group, Environmental Sciences Faculty and Center EULA-ChileUniversity of ConcepciónConcepciónChile

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