loading page

Anaerobic co-digestion of mixed activated sewage sludge and fruit and vegetable waste on two-stage digester stability
  • +1
  • Herald Wilson Ambrose,
  • Ligy Philip,
  • G.K. Suraishkumar,
  • Tushar Sen
Herald Wilson Ambrose
Curtin University Bentley Campus
Author Profile
Ligy Philip
Indian Institute of Technology Madras
Author Profile
G.K. Suraishkumar
Indian Institute of Technology Madras
Author Profile
Tushar Sen
Edith Cowan University - Joondalup Campus
Author Profile

Abstract

Co-digestion of mixed waste activated sludge (MWAS) and fruit and vegetable waste (FVW) was studied in a two-stage (thermophilic followed by mesophilic) semi-continuous anaerobic digestion to evaluate anaerobic digester performance and stability. A mixing ratio of 75% MWAS and 25% FVW showed a 1.6-fold increase in overall methane yield and achieved 0.38 FOS/TAC ratio (volatile fatty acids to alkaline buffer capacity) compared to mixture of 50% MWAS and 50% FVW. Application of hybrid (MW-H2O2) pretreatment in the former mixing ratio increased sludge solubilisation by 33% and consequently enhanced overall methane yield by 2.17-fold. The treated digester showed increased process stability with a FOS/TAC ratio of 0.26 as a consequence of buffer capacity offered by released biopolymers during pre-treatment. The generation of superoxide radicals during digestion was studied and found to negatively correlate with sludge bioactivity. Two-stage digestion also minimizes the issue of high acidification due to co-digestion involving FVW.