basford gas works remediation using soil washing technology
TRANSCRIPT
BASFORD GAS BASFORD GAS WORKSWORKS
REMEDIATION USINGREMEDIATION USINGSOIL WASHING TECHNOLOGYSOIL WASHING TECHNOLOGY
History of Basford Gas WorksHistory of Basford Gas Works
2.5 miles north-east 2.5 miles north-east Nottingham city centreNottingham city centre
Flood plain River LeenFlood plain River Leen
Operational 1854 – 1972Operational 1854 – 1972
Valuable by-productsValuable by-products
Decommissioned 1972Decommissioned 1972
1995 – 1997 site 1995 – 1997 site investigationsinvestigations
Major ContaminantsMajor Contaminants
Granular soil – soil Granular soil – soil washingwashing
Objectives of Remediation ProjectObjectives of Remediation Project
Acceptable contamination levelsAcceptable contamination levels
Selective excavationSelective excavation
Soil washingSoil washing
Minimise landfillMinimise landfill
Re-use clean soilRe-use clean soil
Minimise local disruptionMinimise local disruption
Minimise environmental impactMinimise environmental impact
Project ProcessesProject Processes
Preliminary investigationPreliminary investigation
Identify need for remediationIdentify need for remediation
Test suitability of soil washingTest suitability of soil washing
Detailed site investigationDetailed site investigation
Full scale remediationFull scale remediation
Performance assessmentPerformance assessment
Soil Washing - ProcessSoil Washing - ProcessRemove debrisRemove debrisMix with waterMix with waterParticle size separationParticle size separation- Contaminants bind to small particles- Contaminants bind to small particles- Small particles bind to larger particles- Small particles bind to larger particles- Washing processes separate small from large- Washing processes separate small from large
Gravity separationGravity separation- Removes high or low specific gravity particles e.g. heavy metal - Removes high or low specific gravity particles e.g. heavy metal containing compoundscontaining compounds
Attrition scrubbingAttrition scrubbing- Removes surface contaminant from coarse particles- Removes surface contaminant from coarse particles
Sequential washingSequential washing
Soil Washing - ApplicabilitySoil Washing - Applicability
Originally developed to remove PAH’s Originally developed to remove PAH’s and PCPand PCPAlso applies to:Also applies to: - Fuels- Fuels
- Pesticides- Pesticides- Various industrial - Various industrial
chemicals chemicals
- Metals- Metals
Removes a wide range of organic and Removes a wide range of organic and inorganic contaminants from coarse inorganic contaminants from coarse grained soilsgrained soils
Soil Washing as a solution at Soil Washing as a solution at Basford GasworksBasford Gasworks
Efficient technique for contaminant types Efficient technique for contaminant types (mainly hydrocarbons) and soil(mainly hydrocarbons) and soilWaste minimisation technique, reduced lorry Waste minimisation technique, reduced lorry movement offsite (23,000 to 8,000 movement offsite (23,000 to 8,000 movements)movements)14,500 movements saved compared to 14,500 movements saved compared to traditional dig and dumptraditional dig and dumpSignificant recovered quantities of ash & Significant recovered quantities of ash & clinker (steel and breezeblock clinker (steel and breezeblock manufacturing) using soil washingmanufacturing) using soil washing
Efficiency of Soil WashingEfficiency of Soil Washing
80.5% of input recovered as 80.5% of input recovered as clean for re-useclean for re-useThat unclean usually contained That unclean usually contained high coarse organic content high coarse organic content within gravel fractionwithin gravel fractionMost contaminants located in Most contaminants located in filter-cake - the higher the input filter-cake - the higher the input contaminant concentration the contaminant concentration the more effectively it is washedmore effectively it is washed15,000t of excavated 15,000t of excavated contaminated soil blended with contaminated soil blended with filter-cake to stabilize itfilter-cake to stabilize it Soil Washing Plant
Material ProcessingMaterial Processing
161,650 tonnes of material 161,650 tonnes of material supplied supplied Processing rate of 370t of clean Processing rate of 370t of clean output/dayoutput/day125,761t of clean material (sand & 125,761t of clean material (sand & gravel fractions) and 32,240t of gravel fractions) and 32,240t of filter cakefilter cake76% excavation was re-used 76% excavation was re-used (compared to 11% for traditional (compared to 11% for traditional methods)methods)Site restored to original ground Site restored to original ground levels (+/- 0.3m) with the addition levels (+/- 0.3m) with the addition of 81,402t clean fillof 81,402t clean fill
Clean soil from Washing Plant
Alternative SolutionsAlternative Solutions
No recommended alternativesNo recommended alternatives
Dig and dump would have been cheaper Dig and dump would have been cheaper – did not meet the requirements– did not meet the requirements
(Cost of soil washing was £21.11/t)(Cost of soil washing was £21.11/t)
Selective excavation (low cost, low Selective excavation (low cost, low technology) was also used in technology) was also used in conjunction with soil washing (higher conjunction with soil washing (higher cost, higher technology)cost, higher technology)
SummarySummary
Only solution to fulfil all objectivesOnly solution to fulfil all objectivesShowed that soil washing was effective on a Showed that soil washing was effective on a variety of contaminantsvariety of contaminantsReduced volumes transported offsiteReduced volumes transported offsiteMinimised disruption to local communityMinimised disruption to local communitySignificant quantities of recycled materialsSignificant quantities of recycled materials30% less energy compared to road haulage 30% less energy compared to road haulage 200,000t of contaminated material excavated, 200,000t of contaminated material excavated, this represents a substantial saving in landfill this represents a substantial saving in landfill void spacevoid spaceBetter results as voluntary projectBetter results as voluntary project