Evaluation of single and two stage anaerobic digestion of landfill leachate: Effect of pH and initial organic loading rate on volatile fatty acid (VFA) and biogas production

Single and Two Stage Anaerobic Digestion of landfill leachate. [Display omitted] •Assessment of Single and two stage AD of leachate with varying pH and IOL.•Highest VFA yield was obtained at IOL of 48 g/L at acidic (5.5) & alkaline (11) pH.•Acetic acid was dominant at acidic pH whereas it was butyric acid at alkaline pH.•IOL of 48 g/L and 6 g/L yielded highest methane in single & two stage respectively.•Overall increase of 21% COD removal efficiency can be achieved in two stage AD. This work aims to evaluate the impact of pH and initial organic load (IOL) in terms of Chemical Oxygen Demand (COD) of landfill leachate for the production of value added products during single and two stage anaerobic digestion (AD). It was observed that at an optimal IOL of 48 g/L, acetic acid was dominant at pH 5.5 whereas it was butyric acid at pH of 5.5–6.0 and 10–11. The yield of Volatile Fatty Acids (VFA) was dependent on IOL and it was in the range of 0.26 to 0.36 g VFA/(g COD removed). Methane was also harvested during single and two stage AD and found that it was varying in the range of 0.21–0.34 L CH4/(g COD removed) and 0.2–0.32 L CH4/(g COD removed) respectively. An overall increase of 21% COD removal was noticed in two stage AD in comparison to single stage.