Bacterial Response to Salts in an Anaerobic Dairy Lagoon

Abstract

ABSTRACT THE objective of this study was to develop the elec-trical conductivity parameter as a field tool in measuring the effect of salt accumulation on biological activity in livestock lagoons. Various concentrations (0.02N-0.8N) of Na, K, Mg, Ca, and NH4 were added as chloride salts to samples of sludge and effluent taken from an active anaerobic dairy lagoon. The salt-sludge-effluent mixtures were placed into small biological reactors where gas production over a 24-h period was monitored. Salt concentrations were expressed as electrical conductivities. The relationship between biological activity in an anaerobic dairy lagoon as affected by the addition of increasing amounts of the cations Na, K, Mg, Ca, and NH4 can be expressed by the general equation, This equation can be used as a model for managing salt concentrations in dairy lagoons. From the model, it appears that the salt content in a dairy lagoon should be managed to maintain an electrical conductivity in the range of 4.0-8.0 mmhos/cm. Allowing the salt content to exceed an electrical conductivity greater than 10-13 mmhos/cm could result in a large reduction in biological activity. The toxicity order of the cations tested was found to be (increasing toxicity): Ca, Mg, Na, K, NH4. The order of toxicity appeared to be strongly influenced by the effects of antagonism and synergism.