TY - JOUR
T1 - The effect of kaolin particles on the behavior of nitrifying activated sludge units
AU - Campos, J. L.
AU - Garrido, J. M.
AU - Méndez, R.
AU - Lema, J. M.
N1 - Funding Information:
The authors would like to thank the Spanish Commission of Science and Technology CICYT (Project AMB98-0658) and the European Union (TMR Project BIOTOBIO: Ref FMRX-CT97-0114) which have sponsored this research.
PY - 2002
Y1 - 2002
N2 - The effects of the addition of powered particles of kaolin to nitrifying activated sludge systems were studied. Kaolin was added to a nitrifying activated sludge reactor, during the operational phase, to observe the effects of this clay on reactor performance. The results were compared to those obtained from a similar unit operated without kaolin. The settling properties of the sludges from both units were similar (sludge volume index (SVI) of 14.5 ml/g VSS; zone settling velocity (ZSV) of 7.5 m/h), but the specific nitrifying activities of ammonia and nitrite oxidizing processes were enhanced up to 75% and 50%, respectively, when kaolin was added. The mechanism of action of kaolin was not clear. Additional ammonia, nitrite and nitrate adsorption tests showed that these compounds were not adsorbed by kaolin. This demonstrated that no beneficial effect was caused by adsorption of either substrates or products. Short-term activity tests also showed that the stimulating effects of kaolin on specific activity were not immediate. The effects of kaolin when nitrifying units were operated under unfavorable conditions were also evaluated: In a second set of experiments, a nitrifying unit was operated with low levels of dissolved oxygen (DO), with and without kaolin. The presence of kaolin exerted practically no effect on ammonia oxidation but nitrite oxidation slightly diminished. In a third set of experiments, a nitrifying unit was subjected to pH shocks (9, 10 and 11) over 3 h with pH then restored to 7.8. A pH shock of 11 caused a decrease of 60% in nitrifying activity for 12 days. When kaolin was added to this unit the efficiency of the system was completely restored in 4 days. Therefore, kaolin might be useful to restore damaged units.
AB - The effects of the addition of powered particles of kaolin to nitrifying activated sludge systems were studied. Kaolin was added to a nitrifying activated sludge reactor, during the operational phase, to observe the effects of this clay on reactor performance. The results were compared to those obtained from a similar unit operated without kaolin. The settling properties of the sludges from both units were similar (sludge volume index (SVI) of 14.5 ml/g VSS; zone settling velocity (ZSV) of 7.5 m/h), but the specific nitrifying activities of ammonia and nitrite oxidizing processes were enhanced up to 75% and 50%, respectively, when kaolin was added. The mechanism of action of kaolin was not clear. Additional ammonia, nitrite and nitrate adsorption tests showed that these compounds were not adsorbed by kaolin. This demonstrated that no beneficial effect was caused by adsorption of either substrates or products. Short-term activity tests also showed that the stimulating effects of kaolin on specific activity were not immediate. The effects of kaolin when nitrifying units were operated under unfavorable conditions were also evaluated: In a second set of experiments, a nitrifying unit was operated with low levels of dissolved oxygen (DO), with and without kaolin. The presence of kaolin exerted practically no effect on ammonia oxidation but nitrite oxidation slightly diminished. In a third set of experiments, a nitrifying unit was subjected to pH shocks (9, 10 and 11) over 3 h with pH then restored to 7.8. A pH shock of 11 caused a decrease of 60% in nitrifying activity for 12 days. When kaolin was added to this unit the efficiency of the system was completely restored in 4 days. Therefore, kaolin might be useful to restore damaged units.
KW - Activated sludge
KW - Ammonia adsorption
KW - Kaolin
KW - Nitrification
KW - Specific nitrifying activity
KW - pH shock
UR - http://www.scopus.com/inward/record.url?scp=0036132277&partnerID=8YFLogxK
U2 - 10.1016/S0960-8524(01)00136-5
DO - 10.1016/S0960-8524(01)00136-5
M3 - Article
C2 - 11800489
AN - SCOPUS:0036132277
VL - 81
SP - 225
EP - 231
JO - Bioresource Technology
JF - Bioresource Technology
SN - 0960-8524
IS - 3
ER -