TY - JOUR
T1 - Effects of the residual ammonium concentration on NOB repression during partial nitritation with granular sludge
AU - Poot, Vincent
AU - Hoekstra, Maaike
AU - Geleijnse, Mitchell A A
AU - van Loosdrecht, Mark C M
AU - Pérez, Julio
N1 - Accepted Author Manuscript
PY - 2016
Y1 - 2016
N2 - Partial nitritation was stably achieved in a bench-scale airlift reactor (1.5L) containing granular sludge. Continuous operation at 20 °C treating low-strength synthetic wastewater (50 mg N-NH4 +/L and no COD) achieved nitrogen loading rates of 0.8 g N-NH4 +/(L·d) during partial nitritation. The switch between nitrite-oxidizing bacteria (NOB) repression and NOB proliferation was observed when ammonium concentrations in the reactor were below 2–5 mg N-NH4 +/L for DO concentrations lower than 4 mg O2/L at 20 °C. Nitrospira spp. were detected to be the dominant NOB population during the entire reactor operation, whereas Nitrobacter spp. were found to be increasing in numbers over time. Stratification of the granule structure, with ammonia-oxidizing bacteria (AOB) occupying the outer shell, was found to be highly important in the repression of NOB in the long term. The pH gradient in the granule, containing a pH difference of ca. 0.4 between the granule surface and the granule centre, creates a decreasing gradient of ammonia towards the centre of the granule. Higher residual ammonium concentration enhances the ammonium oxidation rate of those cells located further away from the granule surface, where the competition for oxygen between AOB and NOB is more important, and it contributes to the stratification of both populations in the biofilm.
AB - Partial nitritation was stably achieved in a bench-scale airlift reactor (1.5L) containing granular sludge. Continuous operation at 20 °C treating low-strength synthetic wastewater (50 mg N-NH4 +/L and no COD) achieved nitrogen loading rates of 0.8 g N-NH4 +/(L·d) during partial nitritation. The switch between nitrite-oxidizing bacteria (NOB) repression and NOB proliferation was observed when ammonium concentrations in the reactor were below 2–5 mg N-NH4 +/L for DO concentrations lower than 4 mg O2/L at 20 °C. Nitrospira spp. were detected to be the dominant NOB population during the entire reactor operation, whereas Nitrobacter spp. were found to be increasing in numbers over time. Stratification of the granule structure, with ammonia-oxidizing bacteria (AOB) occupying the outer shell, was found to be highly important in the repression of NOB in the long term. The pH gradient in the granule, containing a pH difference of ca. 0.4 between the granule surface and the granule centre, creates a decreasing gradient of ammonia towards the centre of the granule. Higher residual ammonium concentration enhances the ammonium oxidation rate of those cells located further away from the granule surface, where the competition for oxygen between AOB and NOB is more important, and it contributes to the stratification of both populations in the biofilm.
KW - Mainstream conditions
KW - Nitrobacter
KW - Nitrospira
KW - pH gradient
KW - Stratification
UR - http://resolver.tudelft.nl/uuid:7380a63d-70db-419c-a30b-87390870b024
UR - http://www.scopus.com/inward/record.url?scp=84991211061&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2016.10.028
DO - 10.1016/j.watres.2016.10.028
M3 - Article
AN - SCOPUS:84991211061
SN - 0043-1354
VL - 106
SP - 518
EP - 530
JO - Water Research
JF - Water Research
ER -