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

Research on the Excess Sludge Femantation under the Continuous Flow

Author QiMing
Tutor DuMaoAn
School Harbin Institute of Technology
Course Municipal Engineering
Keywords volatile fatty acids (VFAs) waste activated sludge (WAS) fermentativeacid production alkaline pretreatment
CLC X703
Type Master's thesis
Year 2013
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Fermentation of waste activated sludge (WAS) has been on one of top issues ofsludge recycling. The production of volatile fatty acids (VFAs) in this process willsupply externally carbon source to enhance the removal of nitrogen and phosphorus.Meanwhile, it can also be employed as chemical materials to produce many highadded-value products in some industries. During this fermentation of WAS,macromolecule organic matters can be transformed into available VFAs rather thancarbon dioxide. It will not only reduce its environmental pollution but also meet therequirements of the reduction and recycling as well as the stability of WAS.In this study, mainly used the continuous flow reactor CSTR, the WAS werefermented with the technique of alkaline pretreatment, after its fermentation, thesupernatant could be used as the inflow of CSTR. Via changed the temperature, pH,the load of inflow and the inhibitor of the continuous fermentation of the sludgeprocess, to explore the impact of these key factors on system operation and to seekthe optimal factors of VFAs yielding. And under conditions of continuous flow tostudy WAS hydrolysis and acidification kinetics.First was called A condition, operating temperature was45℃, the pH of inflowwas7.0, and the load of the inflow was1000mg/L and2000mg/L (counted byprotein). In this condition, the maximum VFAs production could reach1417.8mgCOD/gVS (1d) and1348.3mg COD/gVS (13d) respectively, and theVFAs-producing efficiency were202.5mg COD/gVS and192.6mg COD/gVSrespectively, average utilization of protein were54.78%and59.08%respectively,average utilization of polysaccharides were37.08%and41.14%respectively.Second was called B condition, operating temperature was35℃, the pH ofinflow was10.0, and the load of the inflow was1000mg/L and2000mg/L (countedby protein). In this condition, the maximum VFAs production could reach1252.8mg/L (4.5d) and1764.1mg/L (2.5d) respectively, and the VFAs-producingefficiency were179.0mg COD/gVS and252.0mg COD/gVS respectively,average utilization of protein were67.43%and56.70%respectively, averageutilization of polysaccharides were42.93%and49.19%respectively.Last was called C condition, this condition was based in the B condition,dosing0.012%chloroform (Inhibiting the activity of methanogenic bacteria) and8.0g barium chloride (Inhibition of the activity of sulfate-reducing bacteria) and theload of the inflow was1000mg/L and2000mg/L (counted by protein). In thiscondition, the maximum VFAs production could reach1939.9mg/L (4.5d) and2066.3mg/L (2.5d) respectively, and the VFAs-producing efficiency were277.1 mg COD/gVS and295.2mg COD/gVS respectively, average utilization of proteinwere67.43%and56.70%respectively, average utilization of polysaccharides were34.10%and38.81%respectively.Through simulated sludge hydrolysis process dynamics in the process of wasteactivated sludge fermentation, the degradation of protein and carbohydrate wereconformed to first-order model. It can also be observed that VFAs production in thefermentation of WAS during this experiment conformed to the first-order model.

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