The influence of ammonium and methods for removal during the anaerobic treatment of poultry manure

The addition of exogenous NH₄Cl to poultry manure and synthetic medium was used to study the effect of ammonia-nitrogen on the activity and composition of a methanogenic consortium. Results indicated that the production of biogas and methane was not affected by the variation in NH₄Cl concentration within the range 2–10 g dm⁻³ (0·5–2·6 g N-NH₄ dm⁻³). At higher values of ammonium (10–30 g dm⁻³ or 2–8 g N-NH₄ dm⁻³) a significant decline in both parameters (by 50–60% for biogas and 80–90% for methane) was observed. A significant decrease in the numbers of bacteria of all physiological groups (especially proteolytic and methanogenic) was observed when more than 30 g NH₄Cl dm⁻³ (7·8 g N-NH₄ dm⁻³) was added to the fermentation medium. The addition of 10% (w/v) of powdered phosphorite ore enhanced the production of biogas and methane at NH₄Cl concentrations up to 30 g dm⁻³, and also changed the composition of the methanogenic consortium. A partial recovery in the numbers of proteolytic and methanogenic bacteria coupled with the decrease in the density of sulphate-reducers was observed. High concentrations (more than 50 g dm⁻³) of NH₄Cl seemed to cause irreversible inhibition of methanogenesis which could not be eliminated by the addition of phosphorites. ©1997 SCI