Growth-rate inhibition of acetoclastic methanogens by ammonia and pH in poultry manure digestion

• Published in: Biological wastes 1990, Vol.32 (4), p.285-297
• Main Authors: Hunik, J.H., Hamelers, H.V.M., Koster, I.W.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Environmental Technology; Fundamental and applied biological sciences. Psychology; Milieutechnologie; Mission oriented research; Physiology and metabolism; Sectie Milieutechnologie; Sectie Proceskunde; Sub-department of Environmental Technology; Sub-department of Food and Bioprocess Engineering
• ISSN: 0269-7483
• DOI: 10.1016/0269-7483(90)90060-6

The maximum growth rate ( μ m ) of acetoclastic methanogens was measured at ammonia concentrations between 0·55 and 0·74 mol/liter (7·7 and 10·4 g ammonia-N/liter) and a pH between 7·80 and 7·93. The observed μ m varied between 0·0046 and 0·0000 h −1 under these experimental conditions. The μ m was calculated by monitoring the gas production rate of batch reactors under conditions of substrate saturation (maximum growth rate in prevailing environment); the acetate concentration during all experiments was above 0·025 mol/liter (1·5 g/liter). It was shown that the pH and total ammonia concentration are the predominant inhibition factors for acetoclastic methanogens under these conditions. The best mathematical description for the inhibition of the growth rate is given by an equation which contains the total ammonia concentration as well as the pH, and this description was significantly better than a description using a calculated free ammonia concentration. The results can be used to calculate a minimal hydraulic retention time for acetate degradation in poultry manure digesters.