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Hydroxylamine addition impact to Nitrosomonas europaea activity in the presence of monochloramine
Citation:
Wahman, D. G. AND G. E. Speitel Jr. Hydroxylamine addition impact to Nitrosomonas europaea activity in the presence of monochloramine. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 68:719-730, (2015).
Impact/Purpose:
Investigate the impact of hydroxylamine on the activity of Nitrosomonas europaea in the presence of monochloramine.
Description:
In drinking water, monochloramine may promote ammonia–oxidizing bacteria (AOB) growth because of concurrent ammonia presence. AOB use (i) ammonia monooxygenase for biological ammonia oxidation to hydroxylamine and (ii) hydroxylamine oxidoreductase for hydroxylamine oxidation to nitrite. Monochloramine and hydroxylamine react, providing AOB a potential benefit by removing the disinfectant (monochloramine) and releasing growth substrate (ammonia). Alternatively and because biological hydroxylamine oxidation supplies the electrons (reductant) required for biological ammonia oxidation, this abiotic reaction represents a possible inactivation mechanism by consuming hydroxylamine and inhibiting reductant generation. As a first step to investigate the abiotic monochloramine and hydroxylamine reaction’s impact on AOB activity, the current study used batch experiments with Nitrosomonas europaea (AOB pure culture), ammonia, monochloramine, and hydroxylamine addition. To decipher whether hydroxylamine addition benefitted N. europaea activity by (i) removing monochloramine and releasing free ammonia or (ii) providing an additional effect, a previously developed cometabolism model was coupled with an abiotic monochloramine and hydroxylamine model for data interpretation. N. europaea maintained ammonia oxidizing activity when hydroxylamine was added prior to complete ammonia oxidation cessation. The impact could not be accounted for by monochloramine removal and free ammonia release alone and was concentration dependant for both monochloramine and hydroxylamine. In addition, a preferential negative impact occurred for ammonia versus hydroxylamine oxidation. Overall, these results suggest an additional benefit of exogenous hydroxylamine addition beyond monochloramine removal and free ammonia release.
