Nitrogen and the Threshold Odor Number Produced by an Actinomycete Isolated from Lake Sediments

Abstract

The objective of this study was to determine environmental factors which favor the production of Threshold Odor Number (TON) by an Actinomycete (Streptomyces sp.) isolated from a reservoir with frequent taste and odor problems. The isolate was cultured under varying conditions of form and concentration of nitrogen. Geosmin produced by the isolate was identified by GC-MS. The effect of form and concentration of nitrogen was measured as TON by an odor panel. ANOVA indicated that the TON and the cell biomass varied with the concentration of nitrogen but not the form of nitrogen supplied. There was a significantly greater TON with higher concentrations (75 to 600 µg N l−1) of nitrate and ammonia nitrogen but not organic nitrogen. Cell biomass increased with nitrate and organic nitrogen but not ammonia nitrogen. On the other hand, TON per unit biomass (specific TON) varied with the form of nitrogen but not the concentration. Specific TON was greater with ammonia nitrogen than with either nitrate or organic nitrogen. Although the differences in specific TON with concentration were not significant, rank correlation analysis showed that high values of specific TON were associated with higher values of nitrate and ammonia nitrogen. These laboratory data support field observations that taste and odor episodes occur in the reservoir after rainfall events that supply pulses of nitrogen to the system.