The export of fresh blueberries is an important productive activity in Chile, in terms of the lab... more The export of fresh blueberries is an important productive activity in Chile, in terms of the labour employed, the number of hectares cultivated and the resulting trade flow with the northern hemisphere. The export of fresh blueberries requires planning based on early estimates of the yield of the orchard. The growers keep plots with plants of more or less the
The kinetics of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) could be di... more The kinetics of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) could be differentiated during simple respirometric and titrimetric assays. The following properties were applied: NOB are more sensitive at low concentrations of oxygen than AOB, and it is only during the ammonium oxidation catalyzed by AOB that protons are released.
Partial nitrification to nitrite has three practical advantages: lower oxygen consumption, lower ... more Partial nitrification to nitrite has three practical advantages: lower oxygen consumption, lower need for organics and lower sludge production. In order to develop a stable partial nitrification a novel operational strategy was studied in a sequencing batch rotating disk reactor under oxygen concentrations lower than 1.0 mg/L throughout 270 days. The strategy was based on a supervisory pH control and an automatic interruption of aeration at the endpoint of ammonia oxidation. The supervisory control enabled the maintenance of a concentration of 3-4 mg NH 3 -N/L for optimal growing of ammonia oxidizing bacteria. For this reason on-line monitoring of sodium carbonate consumption was implemented during nitrification. The results showed that it is possible to reach a stable partial nitrification with high nitrite accumulations of 84-88% during long-term assays, and a relatively high ammonia conversion rate of 1.45-4.25 kg NH 4 + -N/(m 2 day). A high impact was observed by decreasing the oxygen concentration from 1.0 to 0.8 mg O 2 /L; the ammonium removal rate declined significantly from 4.25 to 1.62 kg/(m 2 day). The molecular analyses by dot-blot hybridizations with 16S rRNA revealed the presence of more than 95% of Nitrosomonas sp., and only 5% of Nitrobacter sp. during the initial phase of the biofilm formation.
This work proposes a supervisory control system based on an optimization layer to calculate the o... more This work proposes a supervisory control system based on an optimization layer to calculate the optimum pH and dissolved oxygen (DO) set-points for the SISO controller, maintaining the process at stable partial nitrification. Takagi-Sugeno fuzzy multimodels were implemented to estimate ammonium degradation and nitrite accumulation from on-line DO and pH values, and updated using off-line measurements. An activated sludge reactor was operated successfully over 115 consecutive days with the supervisory control system, achieving ammonium degradation and nitrite accumulation values higher than 95% and 80%, respectively. The on-line estimates of the multimodels showed a prediction error of less than 7% at steady state operation, and reflected the tendencies shown in experiment to be caused by changes in pH value and DO concentration.
The export of fresh blueberries is an important productive activity in Chile, in terms of the lab... more The export of fresh blueberries is an important productive activity in Chile, in terms of the labour employed, the number of hectares cultivated and the resulting trade flow with the northern hemisphere. The export of fresh blueberries requires planning based on early estimates of the yield of the orchard. The growers keep plots with plants of more or less the
The kinetics of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) could be di... more The kinetics of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) could be differentiated during simple respirometric and titrimetric assays. The following properties were applied: NOB are more sensitive at low concentrations of oxygen than AOB, and it is only during the ammonium oxidation catalyzed by AOB that protons are released.
Partial nitrification to nitrite has three practical advantages: lower oxygen consumption, lower ... more Partial nitrification to nitrite has three practical advantages: lower oxygen consumption, lower need for organics and lower sludge production. In order to develop a stable partial nitrification a novel operational strategy was studied in a sequencing batch rotating disk reactor under oxygen concentrations lower than 1.0 mg/L throughout 270 days. The strategy was based on a supervisory pH control and an automatic interruption of aeration at the endpoint of ammonia oxidation. The supervisory control enabled the maintenance of a concentration of 3-4 mg NH 3 -N/L for optimal growing of ammonia oxidizing bacteria. For this reason on-line monitoring of sodium carbonate consumption was implemented during nitrification. The results showed that it is possible to reach a stable partial nitrification with high nitrite accumulations of 84-88% during long-term assays, and a relatively high ammonia conversion rate of 1.45-4.25 kg NH 4 + -N/(m 2 day). A high impact was observed by decreasing the oxygen concentration from 1.0 to 0.8 mg O 2 /L; the ammonium removal rate declined significantly from 4.25 to 1.62 kg/(m 2 day). The molecular analyses by dot-blot hybridizations with 16S rRNA revealed the presence of more than 95% of Nitrosomonas sp., and only 5% of Nitrobacter sp. during the initial phase of the biofilm formation.
This work proposes a supervisory control system based on an optimization layer to calculate the o... more This work proposes a supervisory control system based on an optimization layer to calculate the optimum pH and dissolved oxygen (DO) set-points for the SISO controller, maintaining the process at stable partial nitrification. Takagi-Sugeno fuzzy multimodels were implemented to estimate ammonium degradation and nitrite accumulation from on-line DO and pH values, and updated using off-line measurements. An activated sludge reactor was operated successfully over 115 consecutive days with the supervisory control system, achieving ammonium degradation and nitrite accumulation values higher than 95% and 80%, respectively. The on-line estimates of the multimodels showed a prediction error of less than 7% at steady state operation, and reflected the tendencies shown in experiment to be caused by changes in pH value and DO concentration.
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Papers by C. Muñoz