Mechanistic understanding of the NOB suppression by free ammonia inhibition in continuous flow aerobic granulation bioreactors

ABSTRACT The survival of Cryptosporidium parvum oocysts in soil and water microhabitats may be affected by the environmental production and release of free ammonia. The objective of this study was to determine the effects of increasing free ammonia concentrations and times of exposure on oocyst viability. Wild-type oocysts were obtained from naturally infected calf feces by chemical (continuous-flow) centrifugation and sucrose gradients. Ammonia (NH3) from a commercial solution was applied in concentrations ranging from 0.007 to 0.148 M. Exposure times ranged from 10 min to 24 h at a constant temperature of 24 ± 1°C. Viability of oocysts was determined with a dye permeability assay and an in vitro excystation assay (M. B. Jenkins, L. J. Anguish, D. D. Bowman, M. J. Walker, and W. C. Ghiorse, Appl. Environ. Microbiol. 63:3844–3850, 1997). Even the lowest concentration of ammonia decreased significantly the viability of oocysts after 24 h of exposure. Increasing concentrations of ammonia increased inactivation rates, which ranged from 0.014 to 0.066 h−1. At the highest concentration of ammonia, a small fraction of viable oocysts still remained. Exposure to pH levels corresponding to those associated with the ammonia concentrations showed minimal effects of alkaline pH alone on oocyst viability. This study shows that environmentally relevant concentrations of free ammonia may significantly increase the inactivation of oocysts in ammonia-containing environments.

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Unraveling the literature chaos around free ammonia inhibition in anaerobic digestion

Renewable and Sustainable Energy Reviews ◽

10.1016/j.rser.2019.109487 ◽

2020 ◽

Vol 117 ◽

pp. 109487 ◽

Cited By ~ 22

Author(s):

G. Capson-Tojo ◽

R. Moscoviz ◽

S. Astals ◽

Á. Robles ◽

J.-P. Steyer

Keyword(s):

Anaerobic Digestion ◽

Free Ammonia ◽

Ammonia Inhibition

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Nitrite accumulation in submerged biofilters - combined effects

Water Science & Technology ◽

10.2166/wst.1996.0453 ◽

1996 ◽

Vol 34 (3-4) ◽

pp. 371-378 ◽

Cited By ~ 10

Author(s):

F. Fdz-Polanco ◽

S. Villaverde ◽

P. A. Garcia

Keyword(s):

Ammonia Concentration ◽

Relative Activity ◽

Free Ammonia ◽

Effect Of Temperature ◽

Ammonia Oxidizer ◽

Ammonium Concentration ◽

Nitrite Accumulation ◽

Biological Aerated Filter ◽

Ammonia Inhibition ◽

Aerated Filter

The combined effect of temperature, pH and ammonium concentration over the nitrite accumulation phenomena in situations of free ammonia inhibition, their effect over the ammonia and nitrite oxidizer microorganiisms influence over the nitrification, have been studied in an Up-flow Biological Aerated Filter (UBAF). The free ammonia inhibition effect highly depends on the values of pH, temperature and ammonium concentration. For the same specific free ammonia concentration different values of temperature, pH and ammonium concentration bring about different nitrite accumulations. In conditions of no free ammonia inhibition and low values of temperature and pH, high ammonium concentrations bring about a higher relative activity of ammonia oxidizer microorganisms of the filter increases the nitratation efficiency in zones close to the outlet and will favour the nitrite accumulation in situations of free ammonia inhibition.

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