Using Anhydrous Ammonia During Anaerobic Digester Startup

The commissioning of anaerobic digesters without the benefit of a good quality seed sludge required pH control. Anhydrous ammonia was a viable alternative to conventional alkalis being virtually 100 per cent pure, having a low equivalent weight, and cheapest when expressed in terms of cost per unit of volatile acids. Although precautions were needed in its handling, the introduction of ammonia to a digester was relatively simple. Concentrations of ammonium ion of 1500-3000 mg per litre could be inhibitory, so careful monitoring was necessary. Two case studies of its successful use are described in detail.