Effects of Ammonia on Anaerobic Digestion of Simple Organic Substrates

Abstract

The effects of ammonia on mesophilic digestion of acetate, propionate, acetate‐propionate mixture, and lactate were studied in batch serum bottles. The un‐ionized ammonia nitrogen (UAN) affected the acetate‐utilizing microorganisms in the acclimated mixed cultures to a greater extent than propionate‐utilizing bacteria or other trophic groups. The inhibitory effects were less severe in batch reactors supplemented with sulfate, pointing to an antagonistic action of the sulfate‐reducing bacteria. Analysis of the inhibition pattern of methane/biogas production has shown that UAN displayed a moderate half‐kill dose in the range of 10 millimole and demonstrated a high sensitivity exponent. The latter suggests potential for a sudden failure response of an anaerobic system subjected to an increasing ammonia concentration in the reactor.