10.4 Exsitu Liquid Phase

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10.4 Ex-situ- Liquid Phase
Materials are taken from the Textbook Hazardous
Waste Management. 2nd Ed. Legrega et al., McGraw
Hill
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Useful links
http//www.pubs.asce.org/WWWsrchkwx.cgi?Biofilm
http//www.pubs.asce.org/WWWsrchkwx.cgi?Filters
http//www.pubs.asce.org/WWWdisplay.cgi?5016176
http//www.pubs.asce.org/WWWsrchkwx.cgi?Designimp
rovements
http//www.frtr.gov/matrix2/top_page.html
http//www.frtr.gov/matrix2/section3/table3_7_fr.h
tml
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• Mixing regime
• Hydraulic retention time (HRT)
• Solid retention time (SRT)
• Total dissolved solids
• Other factors

• Equalization
• Chemical treatment
• Physical separation
• Conditioning

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Ex-situ-Liquid Phase

• Aerobic batch
• Anaerobic batch
• Continuous flow and aerobic suspended growth
• PAC
• Attached growth
• Submerged fixed-film
• Fluidized-bed

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10.4
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SBR
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Anaerobic batch system
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MBR

• Crossflow UF MLSS 30,000 mg/L
• MF MLSS 15,000 mg/L

http//www.ionics.com/technologies/mbr/index.htm
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RBC

• Bioreactors degrade contaminants in water with
  microorganisms through attached or suspended
  biological systems.
• In suspended growth systems, such as activated
  sludge, fluidized beds, or sequencing batch
  reactors, contaminated ground water is circulated
  in an aeration basin where a microbial population
  aerobically degrades organic matter and produces
  CO2, H2O, and new cells.
• The cells form a sludge, which is settled out in
  a clarifier, and is either recycled to the
  aeration basin or disposed.
• In attached growth systems, such as upflow fixed
  film bioreactors, rotating biological contactors
  (RBCs), and trickling filters, microorganisms are
  established on an inert support matrix to
  aerobically degrade water contaminants.

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10-5 Ex-situ-Slurry Phase
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Slurry Phase Systems

• In-situ
• Ex-situ

• Pretreatment
• Desorption
• Concentration of solids
• Mixing

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Pretreatment

• Enhanced desorption
• Surfactants and size reduction
• Waste consent ration
• Size fractionation

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Desorption

• Rate of degradation is a function of the
  concentration in solution rather than on the
  surface
• Microbial populations grow linearly rather than
  logarithmically

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Concentration of solids in reactor

• As low as 5 as high as 50 (dry weight)
• Typical 30-40

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Mixing (Agitation)

• Breakdown of solid particles
• Desorption of waste from solid particles
• Contact between organic waste and microorganisms
• Oxygenation of the slurry be aeration
• Volatilization of contaminants

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Mixer design

• Dual drive
• Axial flow impellers 20 30 rpm
• Rake arms 2 rpm

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Applications

• Wood-preserving wastes
• Contaminated soils

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Enhanced Bioremediation

• Typical Oxygen-Enhanced Bioremediation System for
  Contaminated Ground water with Air Sparging
• Oxygen-Enhanced H2O2 Bioremediation System
• Typical Nitrate-Enhanced Bioremediation System  

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Enhanced Bioremediation
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Oxygen Enhancement with Air Sparging

• Air sparging below the water table increases
  ground water oxygen concentration and enhances
  the rate of biological degradation of organic
  contaminants by naturally occurring microbes.
• Air sparging also increases mixing in the
  saturated zone, which increases the contact
  between ground water and soil.
• The ease and low cost of installing
  small-diameter air injection points allows
  considerable flexibility in the design and
  construction of a remediation system.
• Oxygen enhancement with air sparging is typically
  used in conjunction with SVE or bioventing to
  enhance removal of the volatile component under
  consideration.

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Oxygen Enhancement with Hydrogen Peroxide

• During hydrogen peroxide enhancement, a dilute
  solution of hydrogen peroxide is circulated
  through the contaminated ground water zone to
  increase the oxygen content of ground water and
  enhance the rate of aerobic biodegradation of
  organic contaminants by naturally occurring
  microbes.

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Nitrate Enhancement

• Solubilized nitrate is circulated throughout
  ground water contamination zones to provide an
  alternative electron acceptor for biological
  activity and enhance the rate of degradation of
  organic contaminants.
• Development of nitrate enhancement is still at
  the pilot scale.
• This technology enhances the anaerobic
  biodegradation through the addition of nitrate.
• Fuel has been shown to degrade rapidly under
  aerobic conditions, but success often is limited
  by the inability to provide sufficient oxygen to
  the contaminated zones as a result of the low
  water solubility of oxygen and because oxygen is
  rapidly consumed by aerobic microbes.
• Nitrate also can serve as an electron acceptor
  and is more soluble in water than oxygen.
• The addition of nitrate to an aquifer results in
  the anaerobic biodegradation of toluene,
  ethylbenzene, and xylenes.
• The benzene component of fuel has been found to
  biodegrade slower under strictly anaerobic
  conditions.
• A mixed oxygen/nitrate system would prove
  advantageous in that the addition of nitrate
  would supplement the demand for oxygen rather
  than replace it, allowing for benzene to be
  biodegraded under microaerophilic conditions.