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Article
Stability Analysis of an Activated Sludge Bioreactor at a Petrochemical Plant at Different Temperatures
International Journal of Chemical Reactor Engineering (2006)
  • Sergio A. Martínez
  • Miriam G. Rodríguez
  • Miguel A. Morales
Abstract

The Mexican petrochemical industry, Morelos S.A. de C.V. is one of the biggest and most important petroleum industries in Mexico and in Latin America. It has an activated sludge system to treat its wastewater flow, which is about 7000m3/d. The wastewater contains volatile organic carbon substances classified as toxic. The old surface aeration system was changed for fine bubble diffusers; however, one major drawback of the new aeration system is that the temperature in the bioreactor has increased due to the compression of the air, which at the compressor exit reaches up to 85oC. This effect produces a temperature in the aerated bioreactor of 32oC during the fall, whereas in the spring and summer, the bioreactor temperature reaches higher values than 40oC. The high temperatures reduce the microorganisms’ activity and cause higher volatilization rates of volatile compounds, among other effects, which affect the performance of the biological treatment. In this work we performed a stability analysis at different equilibrium points in different scenarios of temperatures, recycle flowrate and wastage flowrate. The eigenvalues of the state matrix of dynamical model of the petrochemical wastewater treatment were evaluated. The model describes the effect of the temperature on the soluble and volatile pollutants removal rate, heterotrophic organism growth rate, oxygen uptake rate and biomass concentration in the settler. The model was obtained from tests that were done in laboratory reactors with 14 L of capacity, which were operated at different temperatures (from 30oC to 45oC), with the same conditions as the actual system. Simulations were done based on the model obtained manipulating the operation variables Qw and Qr. The stability analysis was also done to the reactor without recycle (Qr = 0 m3/d). In all the cases the stability analyses was performed. The stripping of VOC´s is an important process of COD removal at high operation temperatures.

Keywords
  • petrochemical,
  • activated sludge,
  • stability,
  • temperature
Publication Date
December, 2006
Citation Information
Sergio A. Martínez, Miriam G. Rodríguez and Miguel A. Morales. "Stability Analysis of an Activated Sludge Bioreactor at a Petrochemical Plant at Different Temperatures" International Journal of Chemical Reactor Engineering Vol. 3 (2006)
Available at: http://works.bepress.com/sergio_martinez/1/