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Study of the Factors Affecting the Competition Between Floc-Formers and Filaments

Author: WangZhongZuo
Tutor: PengYongZhen
School: Beijing University of Technology
Course: Environmental Science and Engineering
Keywords: Zoogloea bacteria Filamentous bacteria Sludge settling Low dissolved oxygen Sludge micro-expansion
CLC: X172
Type: Master's thesis
Year: 2011
Downloads: 148
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Abstract

Sludge bulking essentially unbalanced microbial competition of two major categories of the the activated sludge zoogloea bacteria and filamentous bacteria. Blooms of filamentous bacteria cause sludge bulking; filamentous bacteria are too small, however, activated sludge will lack skeleton, acicular floc, the water was a haze. Recently, a study showed that low dissolved oxygen can lead to sludge micro-expansion. Moderate number of filamentous bacteria in the sludge in the state, will not affect the secondary settling tank dewatering, but also make the water very clear, but also save aeration energy consumption. Based on this, the research group, Professor Peng Yongzhen Low dissolved oxygen sludge micro-expansion energy conservation theory and methods. The key to the application of the technology is that the the balance zoogloea bacteria and filamentous bacteria compete. Visible, in-depth study is necessary competition between floc bacteria and filamentous bacteria in a variety of environments. In this thesis competition starting from the research zoogloea bacteria and filamentous bacteria around the major factors affecting the expansion of sludge, the system examines the the sludge bulking mechanism under various situations. Dominant filamentous bacteria in sludge bulking system, the effect of different factors identified using small test SBR simulate a variety of processes in different operation modes, and explore the feasibility of sludge micro-expansion in the different operating modes. To hypoxic micro-expansion of the practical application of the energy-saving technology to provide a theoretical basis and experimental basis. The main findings of the paper are as follows: 1. Settings the full aerobic running and front hypoxia running two sets of SBR reactor, control of dissolved oxygen and water inlet time, run way bacteria and filamentous bacteria zoogloea the impact of competition. The full aerobic running way can easily lead to a vicious sludge bulking. Low substrate concentration gradient, regardless DO level of expansion very quickly, the expansion rate of up to 34.0 mL / (gd), only two sludge retention time (SRT = 15 d), the SVI that more than 1000 mL / g. High substrate concentration gradient low DO inflated, slightly slower rate of expansion. High substrate concentration gradient normal DO, sludge settling properties to maintain good, but vulnerable to impact and lead to sludge bulking. Front the hypoxia running way analog tired / anoxic selectors have a significant role in the improvement of sludge settling. Low DO, high substrate concentration gradient sludge settling is still good, SVI is about 50 ~ 60 mL / g. Low DO appropriate to reduce the concentration gradient of the substrate can be achieved stable micro-expanded, SVI is between 120 to 220 ml / g. 2 - supply rate from substrate consumption level of the expansion rate of the similarities and differences in the different operation modes analysis, consumption - supply rate hypothesis driven expansion that occurred outside the floc some kind of substrate diffusion into the floc a certain position within a rate less than the premises microbial consumption rate of this substrate. Nearer the surface of the floc, the greater the concentration gradient of the substrate, the diffusion rate is also greater. Therefore, in this position of the microorganisms will grow to a place closer to the surface of the floc. Filamentous bacteria can be faster because of its advantage on the morphology and growth of one-dimensional characteristics close to the surface of the floc, and even lend a floc, which won the competition with zoogloea bacteria. 3 full aerobic environment of low substrate concentration, sodium acetate, glucose as a carbon source in the reactor sludge vicious expansion breeding more filamentous bacteria; starch as the carbon source within the reactor, but not trigger the sludge malignant expansion, SVI is maintained at less than 300 mL / g. Sludge expansion rate of sodium acetate, glucose, followed by starch slowest confirmed the hypothesis of consumption - supply rate. 4 the normal DO run water in front hypoxia short time, a separate nitrogen deficiency or phosphorus deficiency alone sludge up to three sludge retention time (SRT = 15d) yet swell. Has yet to occur in non-filamentous bulking the phosphorus deficiency systems to non-phosphorus influent run two sludge age; nitrogen deficiency to nitrogen-free influent sludge bulking. Nitrogen deficiency substrate storage capacity of the system is higher than the P Deficiency system. Replaced by nitrogen or phosphorus-free influent were lower in the two-reactor sludge storage capacity of the substrate. Hypoxic micro expansion under the sludge floc, filamentous bacteria take even form a network among the floc precipitation from the netting effluent COD and turbidity were only 16.7 mg / L and 4.8 NTU significantly lower than normal sludge. Hypoxic micro-expansion can save at least 10% of the aeration energy consumption. Nitrification performance and phosphorus removal performance is not due to low DO worse. Fluorescence in situ hybridization (FISH) analysis showed that, after long-term anaerobic / aerobic running, the number of denitrifying bacteria under low DO is even greater than the number of nitrifying bacteria under high DO. Sludge under low DO anaerobic phosphorus release and more fully, more than 20% of the total number of bacteria phosphorus accumulating bacteria. Using conventional staining and FISH were identified on the the system advantages expansion filamentous bacteria, expansive full aerobic running way the filamentous bacteria sludge advantage Thiothrix, 1851 type, 021N, S. natans. Micro-expansion front hypoxia dominant filamentous bacteria in the sludge 0092 type.

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