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The Research on Enhancement of Anaerobic Digestion Using Addition of Zero Valent Iron

Author: LiuZuoWen
Tutor: ZhangYaoBin；ChenShuo
School: Dalian University of Technology
Course: Environmental Science
Keywords: Anaerobic Zero-valent iron Granulation Decolorization Hydrolysis and acidification
CLC: X703
Type: Master's thesis
Year: 2011
Downloads: 206
Quote: 0
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Abstract

Anaerobic biological treatment technology capable of generating the energy available in the degradation of pollutants at the same time, is widely used in the wastewater treatment process. Granular sludge formation is the main features of the upflow anaerobic sludge bed reactor, because it has a higher biological treatment capacity. However, the sludge particles require a longer time, and therefore a method to enhance this process has been extensively studied. Anaerobic fracture azo bond in the treatment of dyeing wastewater demonstrated economic and environmental friendliness, but higher concentrations of dye wastewater, and its performance will be substantially reduced. Further, the hydrolysis acidification as an anaerobic pretreatment means, in practical applications, also faces the problem of poor treatment effect. Zero-valent iron as a good reducing agent, by strengthening the anaerobic atmosphere to improve the anaerobic digestion treatment effect corresponding research in the subject. Based on experimental and theoretical studies of the subject, we can draw the following conclusions: 1, built-in electric field enhanced zero-valent iron anaerobic reactor can speed up the process of anaerobic granular. Experiments in three parallel reactor: the electric field enhancement of the built-in zero-valent iron anaerobic reactor (R1), the zero-valent iron anaerobic reactor (R2) and common anaerobic reactor (R3). When a 1.4 V voltage is applied to R1, in the next four days the COD removal rate increased from 60.3% to 90.7%, while the particle size of 38 days by 151.4μm growth to 695.1μm. R2 and R3 in the COD removal efficiency and the increase in particle size is smaller than R1. The electric field enhanced cushioning effect of the zero-valent iron and facilitate maintaining a low redox potentials within the reactor. In addition, the electric field increases the dissolution of divalent iron ions and the production of extracellular polymeric substances. These are conducive to the role of methanation and particles. The scanning electron micrographs show that the type the granular sludge inside and outside the distribution of microorganisms in the R1. Fluorescence in situ hybridization experiments showed that the R1 in the relative abundance of methane-producing bacteria was significantly higher than the R2 and R3 reactor. The above results suggest that the coupling of the electric and zero-valent iron can effectively promote sludge granulation. 2, the electric field enhancement of the built-in zero-valent iron anaerobic reactor can improve the printing and dyeing wastewater treatment. Experiments in three parallel reactor: the electric field enhancement of the built-in zero-valent iron anaerobic reactor (R1), the zero-valent iron anaerobic reactor (R2) and common anaerobic reactor (R3). Electric field enhanced built-in zero-valent iron anaerobic reactor R1 has the highest COD and color removal. Raise the applied voltage can enhance the treatment effect of the R1. The scanning electron micrographs show that the particles in R1 is dealing with high concentrations of dye wastewater sludge remains complete and solid structure, but R3 granular sludge already broken. The methanogenic bacteria abundance fluorescence in situ hybridization experiments show that R1 significantly higher than the R2 and R3. Deformation gel electrophoresis showed electric and zero-valent iron coupling structure of microbial populations, in particular, plays a key role in the anaerobic bleaching flora. 3, cast iron powder added to the hydrolysis acidification reactor so as to strengthen the role of the paragraph study. The results show that the iron powder dosing can significantly improve the efficiency of hydrolysis acidification. When the hydraulic retention time is reduced from 6 h to 2 h dosing iron powder hydrolysis acidification reactor (A1), the COD removal rate and degree of acidification are each preferably stable at 45-56% and 84-91% between, and the reference reactor (A2) performance were clearly decreased from 45% to 25% and from 65% down to 30%. The iron powder can be optimized to the type of acid production, reduce Titanium representing difficulties of propionic acid is formed. Iron powder added to make hydrolysis acidification reactor A1 propionate total volatile fatty acids reduce the proportion of 14% -20%, and the content of acetic acid and butyric acid, respectively, an increase of 8% -11% and 6% -9%. These role in promoting the subsequent methanation process of the reactor A1, A2 subsequent methanation process while the reactor was found higher concentrations of propionic acid accumulation. The abundance of iron powder so that the ferredoxin 17-fold increase in activity of the protein, which helps to accelerate the process of acid production; fluorescence in situ hybridization experiments confirmed that the iron powder is added to make the hydrolysis acidification reactor acetogen significantly improved, which Titanium content results in higher reactor is consistent. Strengthening effect on the hydrolysis and acidification, the iron powder can reduce subsequent processing load, to form a more favorable form of organic acids play a significant role, is expected in the pretreatment of wastewater, the two-phase anaerobic fermentation and even more effective application of sludge fermentation.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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