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Biodegradability Studies of Atrazine in Bioreactor Receiving Low-Level COD Wastewater

Kamanmalek, Sara | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50370 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Borghei, Mehdi
  7. Abstract:
  8. Atrazine is widely used in the agriculture as an herbicide. Due to its high mobility, Atrazine leaks into the groundwater, surface waters, and drinking water wells. Many physical and chemical methods have been suggested for removing Atrazine from aquatic environments. However, these methods are very costly, have many performance problems, produce a lot of toxic intermediates which are very harmful and dangerous, and cannot completely mineralize Atrazine. In this study, biodegradation of Atrazine by microbial consortium was evaluated in the aquatic environment. In order to assess the Atrazine removal from the aquatic environment, Fixed-Bed biofilm reactor and Moving Bed Biofilm Reactor were fed with synthetic wastewater based on sucrose (200 mg/L) and Atrazine of various concentrations (C_in Atrazine=5,10,15,20 & 30 mg/L) at different hydraulic retention times (HRT= 5, 10 & 24 hrs). Moreover, the effects of the concentration of nitrogen sources on Atrazine removal was investigated.The maximum efficiencies for Atrazine was 87.5% in the Fixed-Bed biofilm reactor with an initial atrazine concentration of 30.0 mg/l, thus maintaining a hydraulic retention time (HRT) equal to 24 hours. By increasing the hydraulic retention time from 5 & 10 hours to 24 hours, the removal efficiency increased. Very minor influence was observed when Urea was added as additional nitrogen source. The maximum efficiencies for COD was 81.64% in the Fixed-Bed biofilm reactor. No further reduction of COD was observed after 10 hours. The COD reduction rate decreased slightly due to the nitrogen addition. The study findings showed that Stover-Kincannon model gave high correlation coefficients, which were 95.1% and 91.9% for Fixed-Bed biofilm reactor and Moving Bed Biofilm Reactor. Therefore, these models could be used in predicting the behavior or design of these reactors. Increasing the initial concentration of atrazine increased the removal efficiency. There was no significant inhibition of the mixed aerobic microbial consortia by the atrazine. Atrazine degradation depended on its initial concentration in the wastewater and the amount of atrazine in the influent. Although this system shows good potential for atrazine removal from aqueous environments, that remaining in the effluent does not yet meet international standards. Further research is required to make this system effective for removal of atrazine from the environment
  9. Keywords:
  10. Toxic Biodegradation ; Aerobic Treatment ; Herbicides ; Atrazine ; Moving Bed Biofilm Reactor (MBBR) ; Fixed Bed Bioreactor

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