IRON TRANS PORT AND REMOVAL DYNAMICS IN THE OXIDATIVE UNITS OF A - - PowerPoint PPT Presentation

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IRON TRANS PORT AND REMOVAL DYNAMICS IN THE OXIDATIVE UNITS OF A - - PowerPoint PPT Presentation

Nov 24, 2022 320 likes •535 views

IRON TRANS PORT AND REMOVAL DYNAMICS IN THE OXIDATIVE UNITS OF A P AS S IVE TREATMENT S YS TEM Dr. Leah Oxenford AS MR2017: Whats Next for Reclamation Average S ystem Influent Water Quality (3 seeps) n= 40 2004-2008 pre system

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IRON TRANS PORT AND REMOVAL DYNAMICS IN THE OXIDATIVE UNITS OF A P AS S IVE TREATMENT S YS TEM

  • Dr. Leah Oxenford

AS MR2017: What’s Next for Reclamation

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SLIDE 2

Average S ystem Influent Water Quality (3 seeps)

n= 40 2004-2008 pre system construction

Component Concentration Iron 191.0 ± 10 mg/ L Zinc 9.65 ± 1.0 mg/ L Manganese 1.60 ± 0.1 mg/ L Lead 62 ± 13 µg/ L Cadmium 15 ± 5 µg/ L

  • Q varies seasonally

400-700 L\min annually

  • Influent pH

5.95 ±0.06

  • Net Alkaline

393 ± 13 mg\L CaCO3

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SLIDE 3

Understanding Iron Chemistry

  • Iron removal and storage within oxidative

cells is based on two distinct processes:

  • Iron Oxidation –

Fe2+ oxidized t o Fe3+ 4Fe2+ + O2 + 4H+  4Fe3+ + 2H20

  • Iron Hydrolysis: Iron Precipit at ion

Fe3+ + 3H20  Fe(OH)3(s) + 3H+

Oxidation is the rate determining step. Rate influenced by iron concentration, pH, dissolved

  • xygen, and temperature.
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SLIDE 4

MRPTS Improves Water Quality of Tributary

Tributary Fe Loading Before System Installation: 71.3 kg Fe/day average After System Installation: 0.30 kg Fe/day

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SLIDE 5

MRPTS Fe Removal

Oxidative Unit

  • Cell 1
  • Removes 87 kg/ day
  • Cell 2S

/ S N

  • Removes 17.3 kg/ day
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SLIDE 6

Iron Removal Efficiency Profiling

  • To determine the spat ial dist ribution of iron

removal, sedimentation, and storage over time.

  • Provides essential insight into how the design of

the treatment cell may be refined to optimize processes favoring iron removal enhancement.

  • existing design
  • design of future passive treatment systems
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SLIDE 7

Building Progressive Removal Profile:

  • Horizontal Component
  • S

ample locations with increasing distance (time) from influent

  • Vertical Component
  • S

ample locations with increasing depth from surface

  • Temporal Component
  • S

ample collection with increasing time (seasonal, annual, 3-5 years)

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SLIDE 8

Progressive Iron Removal Dynamics

  • Progressive Removal
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SLIDE 9
  • Accumulation

Accumulation of Fe (2008-2015)

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SLIDE 10

Average Accumulation Depth Decreases With Increasing HRT within The Oxidative Unit

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SLIDE 11

Solids Characterization

  • Increased with HRT:
  • Particle size

Crystallinity

  • Only crystallinity

increased with increasing depth

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SLIDE 12

Amorphous vs Crystalline

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SLIDE 13

Crystalline Goethite Formation

  • Orthorhombic crystals
  • bserved in S

EM

  • RAMAN microscopy

verified as Goethite

  • Principle mineral phase
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SLIDE 14

S

  • lids Accumulation Inspires Rhodamine

Tracer S tudy (2009-2015)

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SLIDE 15

Rhodamine Tracer Study: (2015) Cell 1

  • Tracer S

tudy

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SLIDE 16
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SLIDE 17

Rhodamine Tracer Study: (2015) Cells 2

  • Tracer S

tudy

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SLIDE 18
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SLIDE 19

S ignificance of Work

  • Iron oxyhydroxide precipitates formed from the oxidation and

hydrolysis of Fe2+ accumulate within the preliminary oxidation cell (Cell 1) and the surface flow wetlands (Cells 2N/ 2S ) of MRPTS .

  • The accumulation of iron oxyhydroxides is not uniformly

distributed within each cell, with the first section of the cell favoring deeper deposits of material.

  • Thus far, performance has not been inhibited by solids

accumulation, but hydraulic conductivity of Cells 3N/ 3S impact HRT and water levels in the oxidative unit.

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SLIDE 20

Comments / Questions?