Comparison of mesophilic and thermophilic methane production potential of acids rich and high-strength landfill leachate at different initial organic loadings and food to inoculum ratios

• Published in: The Science of the total environment Vol. 715; p. 136658
• Main Authors: Begum, Sameena, Juntupally, Sudharshan, Anupoju, Gangagni Rao, Eshtiaghi, Nicky
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2020
• Subjects: Anaerobiosis; Bioreactors; Fatty Acids, Volatile; Initial organic loading; Lag phase; Landfill leachate; Mesophilic; Methane; Temperature; Thermophilic; Water Pollutants, Chemical - analysis; Initial organic loading; Mesophilic; Thermophilic; Landfill leachate; Lag phase
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.136658

Landfill leachate (LL), which can contaminate both ground and surface water is a major global environmental issue. The aim of the present study was to investigate the biomethane potential (BMP) of a high-strength LL with low pH (5.0), high solids concentration (16%), and high organic matter (170 g/L of chemical oxygen demand (COD); 55 g/L of volatile fatty acids (VFA)) with ammonia nitrogen (NH3-N) (17 g/L). We investigated the BMP of LL at four different initial organic loadings (IOL) of 170 g/L, 85 g/L, 42.5 g/L and 21 g/L of COD and Food to inoculum (F/I) ratios of 0.5; 1; 2 and 3 at mesophilic (35 ± 2 °C) and thermophilic temperatures (55 ± 2 °C). We found that the highest cumulative CH4 could be obtained at an IOL of 42.5 g/L of COD regardless of the F/I ratio and temperature. The highest methane content results in biogas at an IOL of 42.5 g/L were 72% and 74% at mesophilic and thermophilic temperatures respectively. About 80–100% of cumulative methane was produced within 15 days in thermophilic reactors, and 40–72% in mesophilic reactors. The kinetic study revealed a fourfold reduction of lag phase in thermophilic compared to mesophilic reactors. The methane yield and organic matter removal rate increased as the concentration of IOL in LL decreased from 170 g/L to 21 g/L regardless of temperature. There exists an inverse correlation between IOL and organic matter removal efficiency. About 80% COD reduction was obtained at mesophilic temperature, and 90% at thermophilic temperature, at an IOL of 42.5 g/L and 21 g/L of COD. The modified Gompertz model showed a good fit to the experimental data, with R2 > 0.98 in all cases. Overall, the findings of this study conclude that treatment of acids rich and high-strength LL both at mesophilic and thermophilic temperature is feasible at an optimum IOL of 42.5 g/L of COD. However, treatment of LL at thermophilic temperature outperformed compared to mesophilic over the digestion time. [Display omitted] •Comparison of mesophilic and thermophilic AD of high strength landfill leachate.•>80% of methane was generated within 15 days in thermophilic reactors.•Lag phase reduced by 4 times in thermophilic reactors compared to mesophilic.•Inverse correlations exist between organic loading and organic removal efficiency.•Optimal methane yield was obtained at 42.5 g/L of COD regardless of F/I ratio.