Effect of variation in the C/N plus P ratio on anaerobic digestion

摘要

The importance of the balance between the nutrients in the anaerobic digestion process was assessed at laboratory scale. A soluble synthetic solution was used as substrate. The variable used to monitor the proportion of nutrients in the substrate was the [C]/[N + P] ratio expressed as equivalents of each element. A blank assay with a constant ratio of 53 and three experiments in which this variable was modified in the range 53-1 were performed. An increase in the concentration of nitrogen and phosphorus both separately and in combination was observed. The most relevant results show a loss of N in the biogas in the form of NH3 for concentrations of around 400 mg N soluble/L in the liquid phase of the reaction, and a loss of soluble phosphorus in the form of calcium phosphate due to precipitation at concentrations above 250 mg P soluble/L, regardless of the experimental procedure. No significant effects were observed in the production of biogas for a ratio in the range 53-40, while biogas production decreased by 8% for a ratio of 20 when both N and P increased in the best of cases and by up to 46% when only N increased. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38: 228-236, 2019