Remediation

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Remediation

• Technical Sustainability of
• Brownfield Land RemediationWork Packages E and I
• Michael Harbottle and Sinéad Smith
• Cambridge University Engineering Department

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Are currently used remediation technologies
sustainable?

• Reuse of land is a sustainable practice
• Impacts of remediation technologies can be
  significant
• but these arent often considered

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Objectives of Work Package E Robust
Sustainable Technical Solutions to Contaminated
Brownfield Sites

• Assess and compare the sustainability of some
  currently used remediation technologies (using
  past remediation projects)
• Investigate potential improvements to these
  technologies through experimentation,
  concentrating on durability and long-term
  behaviour

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Literature Review

• Increasing emphasis on wider effects (especially
  environmental) in current guidance (e.g. EA
  reports, CLR11) although unclear on transfer to
  industry
• Encouragement for bringing sustainability into
  remedial option selection (e.g. CLARINET
  reports), although no consensus on how to go
  about this practically
• 11 case studies on assessment of remediation
  techniques have been identified.

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Sustainability Criteria

• Future benefits outweigh cost of remediation
• Environmental impact of the implementation
  process is less than the impact of leaving the
  land untreated
• Environmental impact of the remediation process
  is minimal and measurable
• Timescale over which the environmental
  consequences occur, and hence intergenerational
  risk, is part of the decision-making process
• Decision-making process includes an appropriate
  level of engagement of all stakeholders

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Sustainability Assessment Method

• Criterion 1 Multi-criteria analysis (MCA)
  based on EA method

• Criteria 2-4 Examination of individual impacts

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Case study S/S vs. dig dump

• Stabilisation/Solidification (S/S) and dig dump
  (on the same site)
• MCA indicates that S/S performed better than dig
  dump on criterion 1
• S/S also had less impact than leaving the land
  untreated (the no action option)

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Case study S/S vs. dig dump

• Relative impacts (criteria 2-4)
• S/S emits more greenhouse gases, but produces
  less waste and uses less transport
• Containment in both cases, but with S/S the soil
  is reused more effectively, more quickly

(Harbottle et al, 2005)
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Case study comparison of five technologies
(preliminary results)

• S/S, soil washing, bioremediation, cover system
  and dig dump (on different sites)
• MCA score indicates that S/S performs better
  under criterion 1

(although deleterious effect of offsite disposal
in all but S/S)
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Case study comparison of five technologies
(preliminary results)

• Relative impacts (criteria 2-4)
• S/S low transportation, low waste production,
  but high greenhouse gas emissions and energy
  consumption
• Soil washing high emissions, high energy use
• Bioremediation low emissions, low material use
• Cover system low waste production, low duration,
  low material use
• Dig dump high transportation, high material
  use, high waste production

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Laboratory and site work

• Stabilisation/solidification
• Properties of novel cements
• S/S with bioremediation
• Encouragement of biodegradation within solidified
  matrix
• Use of novel cements combined with addition of
  nutrients and other additives

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Laboratory and site work

• Barrier walls
• Use of innovative materials to improve durability
• Deep soil mixing with bioremediation
• Soil mixing to encourage biodegradation at depth
• Site trials in Thames Gateway

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WP E and WP I durability of remediation

• Both WP E and WP I address long-term performance
  and durability
• An important aspect of long-term performance and
  durability is the potential impact of a changed
  climate
• Adaptation of current remediation methods may be
  required

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Objectives of Work Package I Impact of Climate
Change on Pollutant Linkage

• Quantify the short- and long-term impact of
  climate change on contaminated land and
  containment systems, through experimentation
  (CUED)
• Evaluate the effect of climate change on
  pollutant linkage (FR)
• Develop any required adaptation design strategies
  (BRE)
• Examine adaptive response of key brownfield
  stakeholders (CEM/UoR)
• Integration into guidance document

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Changes to the UK climate

• UK Climate Impacts Programme has produced climate
  scenarios for the 21st century
• Hotter, drier summers
• Warmer, wetter winters
• Increased storminess, heavier rainfall
• Increased risk of pollutant linkages forming

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Changes to seasonal precipitation in the South
East (UKCIP Report 2002)
Summer
Winter
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Impacts
Desiccation of surface soil
Dry, cracked soil changes infiltration capacity
Hot dry weather
Infrequent, intense rain storms
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Impacts
Diurnal freeze-thaw cycles cause surface
desiccation
Saturated ground
Depth of frozen ground
Warm wet weather
Diurnal freeze-thaw cycles
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Impacts
Rising groundwater levels- clean groundwater
becomes contaminated
Increased biological activity
Warm wet weather
Fluctuating groundwater
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Impacts on contaminated soils and containment
systems

• Both positive and negative impacts are expected
• Net result depends on magnitude of impact and
  severity of climate conditions
• Aim of investigation
• Identify the most damaging climate scenarios
• Apply scenarios to contaminated soils and
  containment systems
• Hence develop any required adaptation design
  strategies

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Lab work climate scenarios

• Temperature extremes
• Summer 2050 (27C) and 2080 (31C)
• Winter 2050 (0C) and 2080 (2C)
• Precipitation
• Summer no rainfall, infrequent high rainfall,
  frequent low rainfall
• Winter saturated conditions (i.e. flooding)
• Cyclic wet-dry and freeze-thaw conditions

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Lab work soils and containment systems

• Real contaminated site soils
• Typical low-permeability cover system
• Compacted sand-bentonite
• Compacted clay
• Stabilised/solidified contaminated soil
• Soil from a bioremediated site
• Contaminated soil remediated with combined
  immobilisation (with compost-zeolite binder) and
  bioremediation (bioaugmentation)

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Lab work short- and long-term scenarios

• Short-term scenario 2 years of extreme
  conditions in real time
• Site and model soil
• Soil aged to 2050 and 2080
• Various accelerated ageing methods used depending
  on system
• Long-term scenarios applied during accelerated
  ageing process
• Samples aged by approx. 15 years in 6 months
• Analysis of samples for physical, mechanical,
  chemical and biological properties

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Conclusions

• WP E and WP I both aim to improve understanding
  of sustainability
• WP E aims to find ways to reduce impacts of
  remediation techniques and addresses their
  long-term performance
• WP I is investigating impacts of climate change
  and any adaptation measures required

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Acknowledgements

• Funders
• EPSRC
• Cambridge Commonwealth Trust
• Contributors
• May Gurney
• CIRIA
• Partner of WPs E I