Transcript Clean Up of Sewage Lakes

Cleanup of Sewage Lakes:
Case Studies in Jeddah and Riyadh
• Background
• Jeddah Sewage Lake
– Drivers and project
overview
– Recommended plan
– Clean-up Completion
• Al-Nazeem Sewage
Lake (Riyadh)
– Project overview
– Sediment
management
– Clean-up status
• Project’s Benefits
• Septage issues in
nearly all Cities
– ~50 % of
population
served by central
collection
systems
– Country-wide
issue that is
independent of
city size
• No inventory available for sewage lakes
• Jeddah
– Only 6 percent of municipal planning area is currently
sewered
– ~140,000 m3/day hauled by tanker trucks
• Riyadh
– ~50 percent of population on central collection system
• Wastewater pumped from cesspits and trucked to
sewage lake
– Air pollution from trucks
– Significant energy
investment in trucking
• Background
• Jeddah Sewage Lake
– Drivers and project
overview
– Recommended plan
– Clean-up Completion
• Al-Nazeem Sewage
Lake (Riyadh)
– Project overview
– Sediment
management
– Clean-up status
• Project’s Benefits
• Received 1500 to 2000
tanker trucks/day
• Up to 50,000 m3/day
of sewage
• Lake grew to 2.8 km2
in surface area
• May 2010
– Custodian of the Two Holy Mosques
King Abdullah bin Abdulaziz issued a
royal decree ordering that the
hazardous Sewage Lake be emptied
within 1 year
– NWC took responsibility for the
project
July 25, 2010
• June 2010
– NWC hires Lake Contractor
• July 2010
– Water evacuation efforts initiated
– Planning consultant hired
• October 2010
– Lake Evacuation completed
• November 2010 to July 2011
– Sediment clean-up
October 2, 2010
• Flood Management
– Removal of the Sewage Lake Dam
• Water Management
– Evacuation of the Lake
– Water Use and Agricultural
Activities
• Sediment Management
– Characterization
– Treatment/Management
alternatives
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Regulatory Requirements
Mitigation Needs
Recommended Plan
Plan Supervision
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• Additional sediment
depth sampling
points
– 125 measurements
• Sediment depths
– Main Lake – <0.5 m
– West Lake - <1.2 m
• Sediment volume
– Main Lake
• 300,670 m3
– West Lake
• 84,724 m3
Total Volume = 385,000 m3 •
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Characteristics of silty
clay
~ 3-5 cm thick
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• Main Lake Data
– Data indicated meeting
KSA criteria for
agricultural use of sludge
and US EPA “Exceptional
Criteria”
– A few sites with elevated
petroleum hydrocarbons
• Secondary Lake
– Showed sediments also
met KSA and EPA Criteria
– Did show general
contamination by
petroleum hydrocarbons
Open Water and Wetlands Ecosystem
Planted Forest
Upland Ecosystem
• Continued drying of sediments
– Use mineral material as a drying agent
– Sample new areas as can be accessed
• Mix thinner sediments in place
– When sufficiently dry
• Excavate thicker sediments
– Spread in upper areas of the Main lake with thin
deposits
• Mix sediments that have been spread
• Conduct “Site Release Sampling Plan”
– Verification of site safety
• Excavate sediment material littered with trash from
former conveyance channel and dispose at a land fill
Stratified Sediment Before Mixing
Topsoil Condition After Mixing
Organic Sediment
20 cm
<50% Organic Matter
~0.75 g/cc
Mixed Topsoil
Tillage
<25% Organic Matter
~1.0 g/cc
Mineral Soil
10 cm
<1% Organic Matter
~1.5 g/cc
Subsoil
Subsoil
16
30 cm
Stratified Sediment Before Mixing
Topsoil Condition After Mixing
Tillage
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• October 2010
– Lake Evacuation completed
• November - December
– Sediment drying and mixing
activities
– Additional sediment
characterization
• December-February 2011
– Completion of report
documentation
– Additional rainfall events
partially refilling the lake to
~2m depth
• March – August 2011
– Pumping to evaporation
ponds
– Continued sediment drying
and mixing activities
– Completed site release
sampling
29 March 2011
• Lake evacuation
– Delayed because of
availability of pumps
– Started in March 2011
– Completed in May 2011
• Sampling grid
– Final grid included 205
cells
– Thick vegetation along
margins prevented
sampling of infrequently
flooded areas
• Total Organic Carbon – low levels indicating sediments are stable
• Metals – maximum values <12% of criteria
• Microbiological
– Fecal Coliform – Maximum value of 24 MPN/g versus standard of 1000
MPN/g
– Parasite eggs – None detected
• Petroleum Hydrocarbons
– Only 3 sites showed some values exceeding levels of 2000 mg/kg for Total
Petroleum Hydrocarbons
– Additional mixing and re-sampling significantly reduced levels
Cleanup plan was executed and site release sampling demonstrated
site was safe for turnover back to the municipality
• Background
• Jeddah Sewage Lake
– Drivers and project
overview
– Recommended plan
– Clean-up Completion
• Al-Nazeem Sewage
Lake (Riyadh)
– Project overview
– Sediment management
– Clean-up status
• Project’s Benefits
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• Lake has been used for
approximately 20 years
• Received
– 1000 to 1500 trucks per
day
– ~20,000 to 30,000 m3/day
• Mixture of Domestic and
Industrial Waste
– Domestic waste eliminated
in January 2011
– Industrial waste eliminated
in Mid-May 2011
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• Lake area is ~3.5 km2
• When cleanup began in
June/July 2011 – very
little water remained
• Cleanup focus
– Sludge characterization
– Sludge drying
– Sludge treatment
• Lake are divided into 4
zone with 39 separate
lakes
• Characterization focus
– Metals
– Microbiological indicators
– Petroleum hydrocarbon
fractions
– Volatile and Semi-volatile
compounds
• Results
– Zones 3 & 4 – no results
exceed criteria
– Zones 1 & 2
• Metals and
hydrocarbon issues at
several locations
• Clean-up has involved
excavation, mixing and
combining with clean
sand
• Lake contractor is
conducting verification
sampling
• Upon completion – site
release sampling will be
conducted by an
independent laboratory
• Background
• Jeddah Sewage Lake
– Drivers and project
overview
– Recommended plan
– Clean-up Completion
• Al-Nazeem Sewage
Lake (Riyadh)
– Project overview
– Sediment management
– Clean-up status
• Project’s Benefits
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• NWC Efforts have eliminated
two long standing health
hazards
• Detailed investigations have led
to environmentally sensitive
solutions
• Jeddah Lake project recognized
with GLOBAL WATER
INTELLIGENCE Reuse Project of
the Year (reuse of sludge to
enhance soils)
Cleanup of Sewage Lakes:
Case Studies in Jeddah and Riyadh