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Optimization of biological denitrification : kinetic analysis (CROSBI ID 487632)

Prilog sa skupa u zborniku | sažetak izlaganja sa skupa

Foglar, Lucija ; Briški, Felicita Optimization of biological denitrification : kinetic analysis // Croatian, Hungarian and Slovenian Symposium on industrial Microbiology and microbial ecology "Power of microbes in industry and environment" : Book of abstract / Mrša, Vladimir ; Hajsig, Danko (ur.). Zagreb: Prehrambeno-biotehnološki fakultet Sveučilišta u Zagrebu, 2002. str. 63-63

Podaci o odgovornosti

Foglar, Lucija ; Briški, Felicita

engleski

Optimization of biological denitrification : kinetic analysis

This study investigates biological denitrification of synthetic wastewater (SW) in a batch reactor. The effects of temperature and pH on the kinetics of nitrate removal were monitored under anoxic conditions with the use of the mixed bacterial culture. In the culture with the dominant three Pseudomonas strains, high denitrification rate was achieved even at initial concentrations of dissolved oxygen that were as high as 5.5 mg O2 dm-3. The first objective of this work was to adapt the mixed microbial culture for the removal of nitrate ions from SW. For that purpose, concentration of NO3-N in synthetic wastewater was increased stepwise from 100 to 500 mg NO-3-N dm-3. Complete denitrification with low accumulation of nitrite was achieved in SW. Furthermore, mixed bacterial culture was capable of complete removal of 500 mg NO-3-N dm-3 from synthetic wastewater during 5.5 hours. The produced nitrite ions during the experiments were between 0.30-1.70 mg NO-2-N dm-3, but terminal nitrite ions were as low as to 0.11 mg NO-2-N dm-3. In the second run, denitrification activity was monitored at temperature range of 250C to 350C and at different pH values (5.9-8.4). The initial nitrate concentration and initial biomass concentration were 200 mg NO-3-N dm-3 and 1.84 g VSS dm-3, respectively. At 15oC, nitrate removal was very slow and lasted for 18 hours. During first 3 hours 50.84% and 32.53 % of nitrate were removed from SW at 25oC and 20oC respectively. Complete denitrification was achieved in 5.5 and 9 hours, respectively. At 25oC and 30oC there was no significant difference. Furthermore, at 35oC complete denitrification was achieved in 3 hours, what was very fast compared to other tested temperatures. Although denitrification at 25oC was slower than at 35oC, for economical reasons the former temperature can be proposed as the operating temperature. In addition, with respect to nitrite accumulation, 25oC was the operating temperature of choice given that at this temperature there was lower accumulation of nitrite ions. Fundamental studies of denitrification have shown that optimal pH for denitrification is within neutral range (pH=7-8). Obtained results confirmed previous assumption. The complete denitrification of SW was fastest at pH=7.4, and lasted 5.5 hours. The decrease of the nitrate removal rate to 75 % was observed at the lowest and at the highest examined pH value of SW. However, at pH=6.8, time required for complete nitrate removal was slightly longer than at pH=7.4 and nitrite production was lower, so pH=6.8 was chosen as optimal parameter. A general kinetic model of nitrate removal is given in Equation: dt/dC = -kMmCn, where t is time in hours, M and m are biomass concentration (mg VSS dm-3) and its partial reaction order, C and n are nitrate concentration (mg NO-3-N dm-3) and its partial reaction order, and k is the specific denitrification rate with a unit depending on the values of m and n (mg (1-n) dm (m+n-1) / mg VSSm h). A kinetic analysis was developed to determine dependence of denitrification rate on biomass (first-order) and nitrate (zero-order) levels. The denitrification rate increased at the temperatures from 15-350C, which could be predicted by Arrhenius equation with the activation energy of 50, 12 kJ mol-1 and frequency factor of 1.08x1010 mg NO-3-N g-1 VSS h-1. For nitrate removal, the specific reduction rate (18.73 mg NO-3-N g-1 VSS h-1 at 25oC) indicated that microbial culture was capable of removing 200 mg NO-3-N dm-3 within a relatively short period. With respect to the tendency to rapid denitrification with low nitrite accumulation, the obtained mixed culture selected for denitrification of the synthetic wastewater gave very good results.

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Podaci o prilogu

63-63.

2002.

objavljeno

Podaci o matičnoj publikaciji

Croatian, Hungarian and Slovenian Symposium on industrial Microbiology and microbial ecology "Power of microbes in industry and environment" : Book of abstract

Mrša, Vladimir ; Hajsig, Danko

Zagreb: Prehrambeno-biotehnološki fakultet Sveučilišta u Zagrebu

Podaci o skupu

Croatian, Hungarian and Slovenian Symposium on Industrial Microbiology and Microbial Ecology: Power of microbes in industry and environment

poster

07.06.2002-09.06.2002

Opatija, Hrvatska

Povezanost rada

Kemijsko inženjerstvo