Bacterial destruction of sodium nitrite in open cooling water systems.

Corrosion is a problem that has plagued man ever since he turned to the use of metals; corrosion is defined as the destructive alteration of a metal by reaction with its environment. Corrosion, viewed in a broad sense, has two main causes; these are: 1. Chemical-a direct cause. In this instance, an attack occurs on refined metals by acids, chemical fumes, moisture, and air. 2. Biological-an indirect cause. This too is mediated by chemical action but, in itself, represents a unique case. Within this category are found corrosion problems due to the presence of microorganisms in industrial systems; the microorganisms of major importance include sulfur bacteria, iron bacteria, and ammonia, nitrate and nitrite utilizing bacteria. The presence of bacteria can result in conditions under which chemical corrosion occurs, whereas, in the organism's absence, corrosion ordinarily would not be found. A prime example of this situation is the microbiological attack and breakdown of a chemical substance used as an anticorrosion agent, which loss results in corrosion. The present paper reports on a problem of this type; specifically, the destruction of sodium nitrite in open cooling water systems. This study investigated: (a) the relationship between bacterial activity and nitrite utilization, (b) techniques for mass propagation of Nitrobacter agilis for use both as a pure culture inoculum for controlled experimentation and as a source of raw material for some basic physiological research, (c) chemical screening (laboratory-scale operation) as regards the compounds' effect on inhibiting nitrite oxidation by Nitrobacter agilis, and (d) the nitrite-stabilizing capacity of various chemicals in circulating waters of pilot plant cooling systems.