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I l d id Sl d M t PlIsland-wide Sludge Management PlanSludge Processing Alternatives and Recommendations – Honouliuli WWTP
Review and Discussion
Project Background (2010-present)
• Defined sludge loadingsDefined sludge loadings
• Evaluated sludge options for all 9 WWTPs• Processing
H li• Hauling• Outlets
• Analyzed Risk, Reliability, and Redundancy
• Workshops w/ ENV WW , ENV Refuse, and DDC
• Screened out several options
Why should we care about Honouliuli WWTP?
• Fastest growing region in Oahu
• Second biggest WWTP on Oahu
S• Secondary treatment capacity to triple in 2024
• New developments around the WWTP
• Landfill will no longer except sludge• Landfill will no longer except sludge
H-POWER Introduction
• Owned by CCH, operated by Covanta• Receives & incinerates most of Oahu’s
residential and commercial wasteT t t bi
MBU = Mass Burn Unitk “Thi d B il ”RDF = Refuse Derived Fuel
• Two steam turbines• Generates 10% of Oahu’s electricity
aka “Third Boiler”300,000 tpy MSW
e use e ed ue300,000 tpy MSW each
Evaluation Findings
• The existing outlets do not provide enough capacity unless there is dryingg p g p y y g
• Drying is cheaper over the planning period
• Co-incineration of cake:
• recently implemented, limited operating data
• not practiced at RDF facilities
• Co incineration of dried biosolids successfully tested at H POWER• Co-incineration of dried biosolids successfully tested at H-POWER
• Significant amounts of energy can be recovered (tens of millions of $ worth over
the planning period)
Drying is recommended, but implementation and energy recovery is key
Outlets
Sludge Outlet Options
• Landfill • Synagro’s Land Application • H-POWER
Sludge Outlet Options
• Landfill • Synagro’s Land Application • H-POWER
S.I. Synagro Biosolids Reuse/Disposal
7% 5% 9%
2012 20135%
2%2014
88%
19%
72%93%88%
Cake Landfilled Pellets Landfilled Pellets Reused
Sludge Outlet Options
• Landfill • Synagro’s Land Application • H-POWER
S.I. Synagro Biosolids Reuse/Disposal
7% 5% 9%
2012 20135%
2%2014
88%
19%
72%93%88%
Cake Landfilled Pellets Landfilled Pellets Reused
Cannot rely on land application alone
Additional Processes are Required to Utilize H-POWER
Either:Either:
1. Additional processes at Honouliuli WWTP (thermal drying), or
2. Additional processes at H-POWER (cake receiving stations)
Energy Generation is Critical to Selecting the Best Option
Either:
1. Generate electricity and heat at Honouliuli WWTP (CHP, gas sale)
or
2. Generate electricity at H-POWER by providing additional high-
energy feedstock (dried biosolids)energy feedstock (dried biosolids)
Loading and Capacity Considerations
60,000
Annual Load Total DT/yr Annual Load without Sand Island DT/yr
2 RDF Dry Capacity
40 000
50,000
ons p
er year)
Excess!
30,000
40,000
/Cap
acity
(dry to
Good through planning
1 RDF Dry Capacity
MBU Cake + 1 RDF Dry Capacity
20,000
dge Prod
uctio
n/
Enough capacity through planning,excluding Sand Island
Sufficient for all till 2035
MBU + RDF Cake Capacity
10,000
Annu
al Slud
Almost at Capacity, Not sufficient past 2024
MBU Cake Capacity
MBU + RDF Cake Capacity
02015 2020 2025 2030 2035 2040 2045 2050
Year
p y, p
Loading and Capacity Considerations
Without drying at SI or HN, H-POWER cannot accommodate all CCH biosolids
Sludge Treatment Options
Two Options Evaluated in Detail
Option 1: Expanded Cake Receiving at H-POWER• MBU Cake Receiving & Feed Station• RDF Cake Receiving & Feed StationRDF Cake Receiving & Feed Station• HN Biogas → Onsite Electricity
Option 2: Thermal Drying at Honouliuli WWTP w/ H-POWER Receiving• MBU Cake Receiving & Feed Station• RDF Dry Receiving (no station required)• HN Biogas → Thermal Drying
Option 1: Cake Hauling
Option 1: Expanded Cake Receiving at H-POWER
Roll-off bins or dump trucks would be loaded with dewatered cake
Option 1: Expanded Cake Receiving at H-POWERDewatered cake from Honouliuli and other CCH WWTP would be hauled and fed to one of two cake receiving stations at H-POWER
Note:An MBU receiving station was recently constructed.
An RDF receiving station would be required for this option.
Option 1: Expanded Cake Receiving at H-POWER
Dewatered cake would be co-incinerated with MSW
Option 1: Expanded Cake Receiving at H-POWER
Ash would be removed and hauled as is current practice at H-POWER.
Option 1: Expanded Cake Receiving at H-POWER
In the event of H-POWER downtime, Honouliuli WWTP cake would be stored onsite
Option 1: Expanded Cake Receiving at H-POWER
Energy could be recovered from a new biogas CHP system at Honouliuli WWTP
Footprint Considerations – Option 1
64’ x 265’ Cake Storage Area
CHP
Option 2 Thermal Drying
Option 2: Drying at Honouliuli WWTP w/ H-POWER Receiving
Dewatered cake would be fed to a buffer silo or hopper
Cake from the hopper would be pumped t th it th l dto the onsite thermal dryer.
Option 2: Drying at Honouliuli WWTP w/ H-POWER Receiving
Biogas would be used as the dryer fuel to evaporate moisture from the cakeogas ou d be used as e d ye ue o e apo a e o s u e o e ca e
Indirect Drying – paddle or screw
Option 2: Drying at Honouliuli WWTP w/ H-POWER Receiving
Dried biosolids producted b oso ds p oduc
Option 2: Drying at Honouliuli WWTP w/ H-POWER Receiving
Dried biosolids would be conveyed to a storage silo
Option 2: Drying at Honouliuli WWTP w/ H-POWER Receiving
Trucks would be loaded w/ dried biosolids and hauled to H-POWERuc s ou d be oaded / d ed b oso ds a d au ed o O
Option 2: Drying at Honouliuli WWTP w/ H-POWER Receiving
Dried biosolids would be fed to the RDF burners and co-incinerated w/ MSW
Energy & revenue recovered via existingrecovered via existing HECO PPA
Option 2: Drying at Honouliuli WWTP w/ H-POWER Receiving
Ash would be removed and hauled as is current practice at H-POWER.
Footprint Considerations – Option 2
Thermal Drying
CHP
Thermal Drying Complex
Comparison of Options
Options and Sub Options Evaluated
Major ComponentsOptions
1a 1b 2a 2b 2c 2dMBU Cake Receiving X X X X X XRDF Cake Receiving X XThree indirect dryers (20 dtpd each) X X XThree indirect dryers (20 dtpd each) X X XTwo direct dryers (40 dtpd each) XHonouliuli Cake Storage X XHonouliuli Cake Receiving X X X XCHP 1,800 kW XCHP 500 kW XCHP 600 kW XAdditional Energy Recovery System X
2015-2040 Lifecycle Cost Analysis
2015-2040 Lifecycle Cost Analysis
Without CHP, Drying is the lowest costWith CHP, Drying is Still the LowestH‐Power Credit – Important for Dryer Economics!
Cake Hauling only Economical if Gas Beneficial Use is Maximized!
H-POWER Economics
The additional biosolids “fuel” will produce more electricity and $$$
• Receive all biosolids excluding SI WWTP (20-40 wtpd, Projections)• Dried biosolids HHV: 7,500 Btu/lb (Sampling Data)• Fuel electricity efficiency: 20% (ENV Refuse)• Fuel→electricity efficiency: 20% (ENV Refuse)• System uptime: 85% (ENV Refuse)• HECO PPA: $0.20/kW-hr, 81.5% to ENV Refuse (currently in place)
$• Tipping fee: $87.15/WT biosolids (ENV → Covanta)
~$1-2 MM/year additional from HECO → ENV Refuse
Cost Comparison
60
50
60lars
Option 1 ‐ No Drying + CHPOption 2 ‐ Drying + CHP
40
ions of d
oll
20
30
ost, in m
illi
10
20Co
0Capital Cost Capital + 25‐yr Operating Cost
But remember, Option 2 provides more capacity, redundancy
Option 2 Thermal Drying is Recommended
With t d i t H li li th i b k / tl t f• Without drying at Honouliuli, there is no backup process/outlet for Sand Island biosolids
• Drying opens up capacity at H-POWER that is not available for cake
• Co-incineration of dried biosolids at RDF tested successfully at H-
POWER
• Least cost option (significant reduction in operating cost)
• Potential future outlets
Option 1 Expanded Cake Receiving is Not Recommended
• Highly dependent on CHP electricity generation
• Insufficient cake receiving capacity at H-POWER
O h f k l lik l Other future cake outlets unlikely
• Co-incineration of cake at H-POWER
Recently implemented limited operating data Recently implemented, limited operating data
Maybe only available for MBU
• Cake storage is an odorous and labor intensive process
Option 2 Major Equipment Required
• Three indirect dryers (2+1) each sized for 20 dtpd
• Import cake receiving station
• Onsite cake conveyance
• Cake hopper (dryer feed)
Dried biosolids conveyance and silo• Dried biosolids conveyance and silo
• New building for dryers (demo existing Thermal Conditioning Bldg.)
• Digester gas cleaning equipment• Digester gas cleaning equipment
• Digester gas storage
• Auxiliary fuel tanku a y ue ta
Next Steps
• ENV/DDC proceed into planning, design, and construction
• H-POWER permit modifications
Discussion
Questions, comments, concerns…