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| Author(s): |
Renata Medici Frayne Cuba
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD) |
| Defense date: | 2008-09-19 |
| Examining board members: |
Eugenio Foresti;
Catarina Simone Andrade do Canto;
Maria Bernadete Amancio Varesche Silva;
Silvana de Queiroz Silva;
Marcelo Zaiat
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| Advisor: | Eugenio Foresti |
| Abstract | |
Nitrogen removal via biological nitrification and denitrification was studied in a sequencing batch reactor submitted to aerate and anoxic periods. Methane was added as electron donor for denitrification in the anoxic periods. Different operational and nutritional conditions referred to as stages in this text were tested aiming to achieve the best nitrogen removal efficiency. When the reactor operated with high suspended biomass concentration (6 g/L), complete ammonia nitrogen oxidation was obtained in 6 to 3 hours aerobic periods and 16.5 to 4 hours anoxic periods defined for stage 1 and stage 2, respectively. However, denitrification was mainly associated with the use of endogenous metabolic byproducts instead of methane. In order to diminish endogenous material uptake, the biomass was immobilized in support material (polyurethane foam) and aerobic and anaerobic periods were reduced to 3 hours each (stage 3), followed by another reduction to 0.5 and 1.5 hours, respectively (stage 4). The highest nitrogen removal efficiencies (~35 %) were identified in this last stage, but only during the initial days of operation. The denitrification process using methane as electron donor was also studied under anoxic conditions, separately from nitrification by adding nitrate and nitrite as the oxidized nitrogen sources. In these experiments, nitrogen removal efficiencies were of 75% and 90%, but very low first order kinetic constants \'K IND.NO3\' = 0,007/h e \'K IND.NO2\' = 0,0278/h, respectively, were obtained with both the electron acceptors. The most provable number (MPN) tests carried out for methanotrophic bacteria quantification resulted in 5,1 x \'10 POT.3\' MPN/gVSS (stage 3 - suspended biomass) and 3,5 x \'10 POT.7\' MPN/gVSS (stage 4 - attached biomass). Therefore, the presence of a support media for biomass adhesion as well as more frequent aeration cycles enhanced the growth of such bacteria. Sulfate and chloride at concentrations of 100 mg/L, approximately, affected the nitrogen removal efficiency associated to methanotrofic process. The presence of methanotrops identified by molecular biology tests as Methylomonas sp was observed in samples taken from reactor in presence of oxygen and under anoxic operational conditions. (AU) | |