Origin, causes and effects of increased nitrite concentrations in aquatic environments

Literature frequently mentions increased nitrite concentrations along with its inhibitory effect towards bacteria and aquatic life. Nitrite accumulation has been studied for decades, and although numerous causal factors have already been commented on in literature, the mechanism of nitrite accumulation is not always clear. From the broad range of parameters and environmental factors reviewed in this paper, it is obvious that the causes and consequences of nitrite accumulation are not yet completely understood. Among others, pH, dissolved oxygen, volatile fatty acids, phosphate and reactor operation have been found to play a role in nitrite accumulation, which results from differential inhibition or disruption of the linkage of the different steps in both nitrification and denitrification. In the case of nitrification, this differential inhibition could lead to the displacement or unlinking of the ammonia oxidisers and nitrite oxidisers. In this paper, the idea is formulated that the nitrifier population forms a role model for the total microbial community. Increased nitrite concentrations would in this aspect not only signal a disruption of nitrifiers, but possibly also of the total configuration of the microbial community. [KEYWORDS: denitrification, nitrification, nitrite accumulation, nitrite toxicity]