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Formation and Modeling of Aerobic Granules under Low Hydrodynamic Shear Force

Author: DongFeng
Tutor: ZhangHanMin
School: Dalian University of Technology
Course: Water Science and Technology
Keywords: Aerobic granular sludge Denitrifying phosphorus removal Hydraulic shear Mathematical model
CLC: X703
Type: Master's thesis
Year: 2011
Downloads: 120
Quote: 0
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Abstract


Aerobic granular sludge microbial self-organized gathering macro particulate matter, has the advantages of good precipitation performance, high Biological ownership, strong resistance to organic load capacity, while nitrogen and phosphorus removal can be achieved in the same unit. The subject studied under conditions of low aeration intensity aerobic granular sludge process, explore the aerobic granular sludge in dealing with low organic load and low C / N ratio of the formation as well as the nature of the wastewater, analysis impact aerobic granular sludge treatment the formation of the key factors. Anaerobic / aerobic / anoxic the sequencer instructions reaction is (SBR) cultured in low aeration intensity (SGV = 0.6cm / s) and low organic loading (influent COD of 150 to 200 mg / L) conditions aerobic granular sludge. 50 d after successful a smooth dense aerobic granular sludge. When the granular sludge d (0.9) is increased to 1 mm, aerobic granular sludge becomes unstable. Speculated that the small size of granular sludge is more stable, more adapted to the low concentration wastewater treatment in small hydraulic shearing. Water N-NH4 and P-PO43-concentrations less than 1 mg / L, and the water N-NO3-concentration is gradually reduced with the process of the particles of the reactor. Cycle experiments showed that the most influent organic matter in the anaerobic stage is removed and found to exist within the aerobic granular sludge simultaneous nitrification and denitrification and bioaugmentation phosphorus removal. Phosphate accumulating bacteria (PAOs) are mainly distributed in the outer layer of the aerobic granular sludge culture granular sludge denitrification and phosphorus removal characteristics, aerobic phosphorus uptake rate of 26.2 mg P-PO43-/ (gVSS · h), hypoxia phosphorus uptake rate 8.9mgP-PO43-/ (gVSS · h). Biofilm mathematical model and mathematical model of the activated sludge as a basis for the establishment of a one-dimensional mathematical model of aerobic granular sludge, and simulate removing nutrients, changes in particle size, the reactor cycle performance as well as aerobic granular sludge within the dissolved oxygen (DO) and flora. Analog organics Ss concentration and effluent concentration of N-NH4 decreased to stabilize around 50 d and 50 d after simulated effluent concentrations were less than 25 mg / L and less than 1.5 mg / L. Analog water N-NO3-concentration show a reducing trend with increasing particle size. When the particle size increased by 1.1 mm analog 30 d 100 d 2.5mm, the granular sludge hypoxia area corresponding increase in total nitrogen (TN) removal efficiency from less than 60% to 91% The final simulation water N-NO3-concentration decreased to less than 3 mg / L. Aerobic granular sludge system, the oxygen mass transfer resistance, the simulation of the outer layer of granular sludge dissolved oxygen concentration and inner layer of low concentration, and dissolved oxygen characteristics of aerobic granular sludge within the changes over time, the particles inside simultaneous nitrification and denitrification. Early in the aerobic metabolism of aerobic granular sludge activity is high, the analog oxygen mass transfer depth of about to 100 to 200 μm; in aerobic final analog oxygen mass transfer depth of 800μm. Analog autotrophic bacteria is mainly distributed in the outer layer of the particles of the high concentration of dissolved oxygen, heterotrophic bacteria distributed throughout the particles. Simulate the growth characteristics of aerobic granular sludge under different hydraulic shear strength similar divided into initial growth, stable growth and mature and stable three stages. Granular sludge equilibrium particle size decreases with increasing aeration intensity. Hydraulic shear stress greater, the smaller the particle size of the mature aerobic granular sludge. High dissolved oxygen and quickly reduce the settling time to get adequate oxygen and nutrient substrate for the growth of beneficial aerobic granular sludge.

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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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