Chloramine and Nitrite- who knew?

[TwoTankAmin]

I had bookmarked this paper and then forgotten about it.

Keshvardoust P, Huron VAA, Clemson M, Barraud N, Rice SA. Nitrite production by ammonia-oxidizing bacteria mediates chloramine decay and resistance in a mixed-species community. Microb Biotechnol. 2020 Nov;13(6):1847-1859. doi: 10.1111/1751-7915.13628. Epub 2020 Jul 30. PMID: 32729670; PMCID: PMC7533321.

Abstract​

As water distribution centres increasingly switch to using chloramine to disinfect drinking water, it is of paramount importance to determine the interactions of chloramine with potential biological contaminants, such as bacterial biofilms, that are found in these systems. For example, ammonia-oxidizing bacteria (AOB) are known to accelerate the decay of chloramine in drinking water systems, but it is also known that organic compounds can increase the chloramine demand. This study expanded upon our previously published model to compare the decay of chloramine in response to alginate, Pseudomonas aeruginosa, Nitrosomonas europaea and a mixed-species nitrifying culture, exploring the contributions of microbial by-products, heterotrophic bacteria and AOBs to chloramine decay. Furthermore, the contribution of AOBs to biofilm stability during chloramination was investigated. The results demonstrate that the biofilm matrix or extracellular polymeric substances (EPS), represented by alginate in these experiments, as well as high concentrations of dead or inactive cells, can drive chloramine decay rather than any specific biochemical activity of P. aeruginosa cells. Alginate was shown to reduce chloramine concentrations in a dose-dependent manner at an average rate of 0.003 mg l-1 h-1 per mg l-1 of alginate. Additionally, metabolically active AOBs mediated the decay of chloramine, which protected members of mixed-species biofilms from chloramine-mediated disinfection. Under these conditions, nitrite produced by AOBs directly reacted with chloramine to drive its decay. In contrast, biofilms of mixed-species communities that were dominated by heterotrophic bacteria due to either the absence of ammonia, or the addition of nitrification inhibitors and glucose, were highly sensitive to chloramine. These results suggest that mixed-species biofilms are protected by a combination of biofilm matrix-mediated inactivation of chloramine as well as the conversion of ammonia to nitrite through the activity of AOBs present in the community.

full paper here https://pmc.ncbi.nlm.nih.gov/articles/PMC7533321/

In short- when there are the bacteria that oxidize ammonia present, they act to reduce chloramine. When there is nitrite present, it actively makes the chlormine decay faster. In a cyleled tank there are mixed species biofilms where the nitrifying bacteri live. ANd even though we test ammonia and nitrite at 0, that is because the bacteria deal with them. But, this means there is an ongoing creation of ammonia and nitrite in most tanks which are immediately handled by microorganisms. But, that does not mean the short lived nitrite doesn't interact with the chloramine.