THESIS
2015
121 pages : illustrations (chiefly color) ; 30 cm
Abstract
The characteristics of various sulfate-rich wastewaters, including pH, temperature, and
salinity, are typically determined by domestic activities and industrial processes from
which they originate; these can be far from the physiological optima of anaerobic
microorganisms. Sulfate conversion biotechnologies (SCBs) have been developed for
treating various sulfate-laden domestic and industrial wastewaters. For anaerobic
treatment, the concentration of biomass and contact between pollutants and bacteria are
considered the main factors dictating overall treatment capacity. Internal hydrodynamic
properties can be adjusted via reactor configuration to improve the contact, but any high
concentration of biomass cannot be reached easily through physiochemical means. The
efficiency of th...[
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The characteristics of various sulfate-rich wastewaters, including pH, temperature, and
salinity, are typically determined by domestic activities and industrial processes from
which they originate; these can be far from the physiological optima of anaerobic
microorganisms. Sulfate conversion biotechnologies (SCBs) have been developed for
treating various sulfate-laden domestic and industrial wastewaters. For anaerobic
treatment, the concentration of biomass and contact between pollutants and bacteria are
considered the main factors dictating overall treatment capacity. Internal hydrodynamic
properties can be adjusted via reactor configuration to improve the contact, but any high
concentration of biomass cannot be reached easily through physiochemical means. The
efficiency of the bioreactor is also highly dependent on ambient conditions and fluctuant
characteristics of the influent. Compact and resilient sulfate-converting granular sludge
systems may offer a promising solution to overcoming these constraints in the
implementation of SCB biotechnology. Previous researchers Hao et al. (2013) developed
sulfate reducing granular (SRG) sludge with synthetic sewage. A real-world sewage trial
is essential to scale up this new technology, as real sewage not only contains complex
pollutants but also fluctuates in its characteristics, representing a significant challenge as
far as successful research and development of SRG.
This study attempted to apply sulfate reducing granular (SRG) sludge to real saline
sewage. Two reactors, a sulfate-reducing up-flow sludge blanket (SRUSB) and a
continuous stirred tank reactor (CSTR), were adopted for comparison purposes. Granular
sludge was successfully developed in both reactors with average diameter of SRG of 200-300 μm, settling velocity of 7-19 m/h, porosity of 0.01 ml/g, and specific area of 18.8-24 m
2/g. The hydraulic retention time (HRT) decreased to 2.2 and 2.8 h in the SRUSB and
CSTR, respectively, corresponding to respective organic loading rates of 3.8 and 3 kg
COD/m
3. Regarding the COD removal efficiency, CSTR achieved 5% greater than that of
SRUSB (~75%). CSRT also showed advantages of faster startup, less accumulation of
inert matter, and simpler operation than SRSUB during the development of SRG. The
sulfate reducing bacteria (SRB) abundance in the granular sludge of SRUSB reached 29.3%
of the total sequences, while the SRG in the CSTR showed higher SRB abundance (45%),
most likely owing to different substrate distribution patterns. The SRG developed in the
CSTR one month earlier than the SRUSB due to implementation of dual selection forces
mixing and upflow velocity.
Sulfide oxidation bacteria (SOB) and acidogens dominated the mature/stable SRB
granules, and the related microbial pattern was proven independent of substrate (synthetic
or real sewage) or reactor type (SRUSB or CSTR). The particular microflora were found
to be controlled by the reactor type, however. Reactor type dictates the substrates and
internal flow pattern, thus influencing the microbial structure of the granules. The
dominant SRB genus (Desulfobacter, 25%) in the SRUSB granules belongs to the
complete organic oxidation group, while the non-complete organic oxidation SRB genus
was detected in the CSTR.
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