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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 43343 (06)
- University: Sharif University of Technology
- Department: Chemical and Petroleum Engineering
- Advisor(s): Borghei, Mehdi
- Abstract:
- One of the most important parts of bacteria growth is specific concentration of nutrients added. Although the trace amount of heavy metals are required for bacteria growth, after a threshold concentration they may cause damage or kill the bacteria. Scientifically speaking, all these trace nutrients should be consider as a profitable source of energy for bacteria growth. There are several studies throughout pondering whether the advantages of using heavy metals, such as Zn, outweigh the drawbacks. It has been proven that heavy metals, especially, zinc salt, can improve microbial growth up to a specific threshold concentration. In this study, two upward submerged aerated reactors, which had 12 liters volume each, were used. One of them also was fed with different concentrations of zinc salt to consider how it will affect the COD removal during experiment. It should be noticed that two different retention time, 12 and 24 hours, were examined. The range of zinc salt added to the reactor was from 0.1 mg/lit up to o.7 mg/lit whereas influent COD differ from 750 mg/lit to 2250 mg/lit. According to these series of experiments, the efficiency of the system was around 86% to 92%. Notwithstanding the fact that heavy metal are toxic for microorganisms, they can increase the efficiency of treatment by devoting too much energy for bacteria growth. It should be considered that salt precipitation in produced sludge and pumice particles at high concentration decrease the effect of zinc salt as a complementary nutrient. In a nutshell, trace amount of heavy metals, zinc ion, can improve the efficiency of reactors in COD removal treatment but after a threshold concentration, which is around 0.5 mg/lit in these series of experiments, this additive ion may result harmful effect on bacteria growth and decrease the efficiency.
- Keywords:
- Heavy Metals ; Pumice Stone ; Submerged Biological Aerated Filter ; Zinc Salt
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