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

Abstract

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