Anaerobic digestion of thermal pre-treated sludge at different solids concentrations--Computation of mass-energy balance and greenhouse gas emissions

J Environ Manage. 2015 Jul 1:157:250-61. doi: 10.1016/j.jenvman.2015.04.023. Epub 2015 Apr 22.

Abstract

The effect of thermal pre-treatment on sludge anaerobic digestion (AD) efficiency was studied at different total solids (TS) concentrations (20.0, 30.0 and 40.0 g TS/L) and digestion times (0, 5, 10, 15, 20 and 30 days) for primary, secondary and mixed wastewater sludge. Moreover, sludge pre-treatment, AD and disposal processes were evaluated based on a mass-energy balance and corresponding greenhouse gas (GHG) emissions. Mass balance revealed that the least quantity of digestate was generated by thermal pre-treated secondary sludge at 30.0 g TS/L. The net energy (energy output-energy input) and energy ratio (energy output/energy input) for thermal pre-treated sludge was greater than control in all cases. The reduced GHG emissions of 73.8 × 10(-3) g CO2/g of total dry solids were observed for the thermal pre-treated secondary sludge at 30.0 g TS/L. Thermal pre-treatment of sludge is energetically beneficial and required less retention time compared to control.

Keywords: Energy ratio; Mixed sludge; Net energy; Primary sludge; Secondary sludge; Thermal pre-treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteria, Anaerobic / metabolism*
  • Bioreactors
  • Conservation of Energy Resources
  • Greenhouse Effect
  • Hot Temperature*
  • Humans
  • Models, Theoretical
  • Sewage / chemistry*
  • Waste Disposal, Fluid / methods*

Substances

  • Sewage