enhancing the beneficial use of incinerator ash
TRANSCRIPT
Enhancing the Beneficial Use of Incinerator Ash
Rob Van Evra – City of Columbus DPU OWEA 2012 Biosolids Specialty Workshop Presentation
12:45-1:30 P.M. – Thursday, December 6, 2012
Columbus WWTP Incinerator Ash
• Ash generated by incineration of sludge in MHIs
• Ash collected in ash hoppers at bottom of incinerator
• Water added to ash hoppers to quench and transport
• Ash conveyed hydraulically in slurries to ash lagoons
Columbus WWTP Ash Lagoons History
• Pairs of ash lagoons at each WWTP
• Lagoons drained to excavate ash using heavy equipment
• Generally used sequentially - filling one lagoon at a time
• Generally one lagoon is drained and excavated at a time
• Lagoons used to store Incinerator Ash - up to 5 years!
Columbus WWTP Incinerator Ash History
o Ash historically had been sent to landfill for disposal
o Ash was used briefly in the past on baseball diamonds
o Ash has been tested in the past for beneficial uses as:
• Admixture for concrete
• Admixture for controlled density fill (CDF)
• Admixture for brick-making
Belden Brick Tests of JPWWTP Ash
Belden Brick Tests using SWWTP Ash
(Excavated from lagoons – great colors and
other qualities, but excessive moisture!)
Current WWTP Incinerator Ash Use
• Excavated ash is used by City of Columbus Compost Facility to make Com-Til Plus, a soil amendment version of our Com-Til mulch
• 4,200 wet tons/year used at the Compost Facility
• Ash adds finer texture when screened smaller with compost
• Ash dramatically reduces airborne ammonia during composting
• Excavated ash is also used by Kurtz Bros. for soil amendments
• 5,000 wet tons/year used by Kurtz Bros. under contract w/ City
Jackson Pike WWTP Ash Lagoons •Ash Lagoons separated from Scioto River by a high levee
•Ash Lagoons drain/overflow/pump to the Scioto River
•Lagoons do not flood except in extremely rare conditions
Southerly WWTP Ash Lagoons •Ash Lagoons in floodway of the Scioto River w/ low dikes
•Lagoons drain/overflow to the Scioto River
•Lagoons flood approx. annually during high Scioto River levels
New Regulations Coming Soon! New NPDES Limits on WWTP Ash Lagoon effluent
outfall locations to the Scioto River
NPDES Limits on Copper – 34 ug/l
NPDES Limits on Mercury – 1700 ng/l
Compliance deadline – August 1, 2013
Ash Lagoon Modification Project
CIP 333
• Capital Improvement Project designed to modify WWTP Ash Lagoons for compliance w/ lower NPDES effluent limits by August 1, 2013
• $18M budgeted for proposed ash lagoon modifications for both WWTPs
Proposed Design Solutions:
REROUTE LAGOON EFFLUENT • Keep lagoons next to Scioto River
• Build pump station and piping systems to pump lagoon drains to WWTP Outfalls
• Utilize mixing zone proximal dilution
Proposed Design Solutions:
MOVE AND ELEVATE LAGOONS • Move lagoons further away from river
• Move lagoons up and out of floodway
• Lagoon drains directed to Plant Effluent
Proposed Design Solutions:
CONCRETE LAGOONS • Construct “Bays” up and away from river
• Shorter-term storage/excavation cycles
• Lagoon drains directed to Plant Effluent
• Reuse of Sludge Concentrator Building?
Great engineering ideas, but
what if we have NO LAGOONS?
• Why are we storing ash?
• Why are we handling ash multiple times?
• Why use WWTP footprint for ash when we need land application storage for future?
Treatment Engineering gets to work - designing methods to:
• Dewater ash after it exits incinerators
• Make dewatering vessel transportable
• Transport ash directly to end user(s)
• Treat decant drainage from ash @ WWTP
• Deeper -
Use Prototype Ash Containers
• Rent Dewatering Roll-Offs for Pilot Test
• Test Two Roll-Offs w/ different Liner Screen Fabrics
• Mesh Size - 400 micron
• Mesh Size - 250 micron
Dewatering Roll-Off Containers
Ash Dewatering Pilot Test
Southerly WWTP ash pump outlets to ash lagoon flume
utilized for initial testing of the prototype ash containers
Dewatering Roll-Off Containers Positioned at the SWWTP Ash
Lagoon Flume
MOMENT OF TRUTH ASH DEWATERS AND DRAINS
ALMOST INSTANTLY!
BONUS DISCOVERY
Ash Filters Itself! Decant Effluent Low TSS
DEWATERING ASH WORKS! Results From Pilot Tests Provide Ideas:
• Liners helpful for drainage, but self-destruct during unloading operations
• Ash drains/filters itself well (and quickly!)
• How much outlet needed for drainage?
Drain Filter Experiment Provides Outlet Drain Size Roll-Off Drain Filter Experiments provide screen and outlet dimensions for drainage
USE DEWATERING TRAILERS!
Compost Facility and TE staffs design trailer tailgate modifications to the Facility’s Biosolids Tractor/Trailers
ASH TRAILER DESIGN
Design of Trailer Tailgate Filter
• Screen Filter attached to the interior of the tailgate allows interior screen to swing away free and clear of the ash dumping
• Screen sized to cross-section of trailer
SMOC Garage Fabricates Interior Tailgate Screen for Compost Facility Sludge Trailer
SMOC Garage Fabricates Tailgate Screen and Drain - Compost Facility Sludge Trailer
Tailgate Drain Valve Assembly out of harm’s way at rear exterior of tailgate
Ash delivered to your door - dry and fresh!
Ash Loadout Design Begins!
Jackson Pike WWTP personnel build entire ash loadout facility using existing plant materials,
tapping sludge piping currently routed to the JP ash lagoons
Jackson Pike WWTP completes 24-hour/day load-to-full tests!
Jackson Pike WWTP completes 24-hour/day load-to-full tests!
Jackson Pike Maintenance Staff modify and rebuild trailer filter
•Strengthen interior screen frame support
•Add filter cloth mounts to interior screen
•Repair leaks encountered during tests
Pauses in the Action • Jackson Pike Incinerators shut down for
the year – move tests back to Southerly
• Intermittent Operations at Southerly • Dry Summer/Low Flows/Low Solids Inventories
• Emissions Compliance Test Scheduling
• South Ash Lagoon Cleaning/Ash Removal
• Ash Lagoon Flume Gates Modified
• Removal of Fuel Oil Tank at New Loadout Area
Work Continues • Procure two additional sludge/ash trailers
• Route scrubber water and ash container decant streams through plant headworks and processes
• Observe Cold Weather Operation 2012-13
• Design and Install ash piping and exterior loadout at SWWTP Incinerator Building
• Fabricate Custom Roll-Off for 24-hour tests
Custom Roll-Off Container for Additional 24-Hour Testing at
WWTPs
My Sincere Thanks! Keith Brandon – Treatment Engineering
John Hoff – City Residuals Manager
Compost Facility and SMOC Garage
JPWWTP and SWWTP
TE FEM - Dan Pullen & Monica Powell
Malcolm Pirnie/ARCADIS
