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Anaerobic Technology in Texas: History, Trends, and Outlook
Leonard E. Ripley, Ph.D., P.E., BCEE Senior Process Engineer
Texas Water 2011 – Gloyna Breakfast
April 8, 2011 – Fort Worth
• In Texas: Permian sea deposits
Back to the Beginning …
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 2
• Lagoons, septic tanks, Imhoff tanks
• High(er) rate anaerobic treatment:
– Covers to contain/recover biogas
– Heating to accelerate process
– Mixing
CHAPTER 1:
ANAEROBIC DIGESTION OF MUNICIPAL SLUDGE
Early Approaches to Covers
Dorr Digester: fixed cover suspended from a truss bridge, with mixing mechanism, and heating pipes mounted to wall.
Downes (“PFT”) Digester: variable sludge volume,
floating cover, heating coils mounted to wall.
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 4
A Texas Anaerobic Timeline
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
1925 1930 1935 1940
Fort Worth: Riverside
WWTP - 1928
San Antonio: Rilling Road
WWTP - 1930
El Paso: Haskell
WWTP - 1935
Austin: Govalle
WWTP - 1937
Dallas: Central
WWTP - 1939
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 5
Fort Worth Riverside WWTP
• Original Imhoff plant: 1922
Dorr
PFT
• 5 Dorr digesters: 1928 & 1936
• 4 PFT digesters: 1945 & 1950
• Flow diverted to Village Creek WWTP: 1976
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 6
Riverside Dorr Digesters
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 7
Digester #3 --, overgrown, but roof still intact
< < Security detail
San Antonio Rilling Road WWTP
• Original plant: 1930
• Four Dorr digesters Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 8
Austin Govalle WWTP
• Plant constructed: 1937
• Four digesters (2+2) with concrete roofs
• Later converted to sludge holding tanks
• Decommissioned: 2006
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 9
• Very common treatment scheme across Texas:
Then, trickling filters …
• Built as recently as 1970 in Terrell; two rectangular digesters added in 1983
Primary
Anaerobic Digesters
Tr. Filter Tr. Filter Final
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 10
• Better mixing: gas lances, pumped recirculation
• External heat exchangers
Technology Developments: 1950s
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 11
Rehabilitate or convert?
Beaumont digesters: 1970 - 2001
Cleburne digester: 1960’s – 1987 converted 1994
Key factors:
• Expensive rehab cost
• 3-4₵/kW-hr power cost
• O&M simplicity
• Odor issues
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 12
Rehabilitate or convert?
San Angelo WWTP
• Digesters constructed: 1959
• Converted to aerobic: 1975
• New digesters built: 2003; old digesters converted to WAS & digested sludge tanks
• Significant odor reduction Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 13
Who’s Digesting Now?
0
50
100
150
200
250
300
Houston SanAntonio
Dallas Austin FortWorth
El Paso
PLA
NT
CA
PAC
ITIE
S (
MG
D)
TEXAS CITIES WITH POPULATION > 500,000
187
250
150 166
94
561 Red patterns: Anaer. digestion
Black patterns: other
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 14
• 39 plants: 0.378-200 MGD, no primaries
• 69th St plant handles ~half of system sludge: gravity thickeners, dewatering centrifuges, and natural gas-fired flash dryers
Houston Solids Management
Anaerobic Technologies in Texas – Leonard Ripley 4/08/11: Slide 15
Who’s Digesting Now?
0
10
20
30
40
50
60
70
80
Arlington Plano CorpusChristi
Lubbock Garland Irving
PLA
NT
CA
PAC
ITIE
S (
MG
D)
TEXAS CITIES WITH POPULATION > 200,000
NTMWD
42.7
64
TRA TRA
31.5
Red patterns: Anaer. digestion Black patterns: other
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 16
CHAPTER 2:
ANAEROBIC TREATMENT OF INDUSTRIAL WASTEWATERS
Anaerobic Technologies in Texas – Leonard Ripley 4/08/11: Slide 18
Baby Steps … Hormel Plant
• Meat packing plant in Austin, MN -- 1965
• Anaerobic contact process (suspended growth)
– Very “low” organic loading rate ≈ 1 kg COD/m3-d (62 lb/1000 ft3-day) … compare to activated sludge
– 97% BOD removal
Anaer. Reactor
Clarifier
Degas
RAnS≈2Q
• Anaerobic Filter
– McCarty & Young (Stanford)
– Random or oriented media
– First “prototype” system in 1970
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 19
Key Milestone: Retained Biomass
• Granular sludge reactors
– Lettinga, et al (Delft, Holland)
• Upflow Anaerobic Sludge Blanket
• Expanded Granular Sludge Bed
• Internal Circulation reactor
– Suitable for soluble wastes
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 20
Anaerobic Filters: A Texas First!
• Celanese Celrobics system (1970’s)
– Upflow reactor w/ plastic pall rings
– Biomass controlled by sparging N2 gas
– Patents based on pH/alkalinity control
• Vernon, TX (guar gum waste) – 1977
– COD loading = 10-12 kg/m3-day (624 lb/1000 ft3-d)
• Pampa, TX (organic acids) – 1981
– COD loading = 12-15 kg/m3-day (749 lb/1000 ft3-d)
• Bishop, TX (alcohols) – 1981
Major brewery in Fort Worth (1995) -- reduced organic load to city’s WWTP by 10%
Major brewery in Houston (1999), installed system for surcharge reduction
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 21
Granular Reactor: Paques IC
• Internal circulation reactor (upper/lower zones)
• Organic loading rate ≈ 30 kg COD/m3-day (1870 lb COD/1000 ft3-day)
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 22
Granular Reactor: Biothane EGSB
• Hereford (2006)
– Panda Ethanol
– 0.69 MGD flow
– 0.119 MG package plant
– 90% SCOD removal
• Schulenberg
– Confidential facility
Typical package plant (identical to Hereford’s)
• Huckabay Ridge – near Stephenville (2007)
• 8 thermophilic reactors, each 0.92 MG
• Feed: dairy manure + liquid wastes
• Product: pipeline quality gas
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 23
Microgy Energy: Bigger in Texas!
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 24
Beacon Energy Plant
• First choice for treatment: Microgy facility
• Designed “hybrid” reactor, with dissolved nitrogen flotation for flocculent biomass
• Started operation in 2008
• Biodiesel plant in Cleburne
• Residuals:
– Glycerin
– Organic acids
EQ
DNF
BIOREACTOR
CHAPTER 3:
ANAEROBIC PROJECT DRIVERS
• Energy reduction
– Aerobic digestion
– Solids reduction → less diesel fuel for hauling
• Improved dewaterability … polymer, fuel
• Energy production
– Electricity to offset aeration power demand
– Heat … can be used for sludge drying
• Odor reduction • Greenhouse gasses, carbon footprint, etc.
Anaerobic Drivers (in Texas)
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 26
• Capital costs … very equipment-intensive
• Management of high-strength return streams
• Effect on biological phosphorus removal
• Perception of odor issues
• Perception of process
instability/difficulty
Anaerobic Anti-Drivers
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 27
CHAPTER 4:
COMING SOON … TO A PLANT NEAR YOU?
• Egg-shaped digesters (ESD’s)
• First US installation: Terminal Island WRP (1985)
• Many plants in US, but none (yet) in Texas
Options for Improved Mixing - 1
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 29
< Terminal Island - by Long Beach, CA
Pinellas Co. – St. Petersburg, FL
Options for Improved Mixing - 2
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 30
LMM disks at Hornsby Bend
• Jet mixing – internal nozzles & external pump
• Linear Motion Mixers (LMM’s) - axial “plunger” in center of digester … low power requirement
• Internal combustion engines, gas turbines, microturbines – all need careful gas prep, but:
• Generate ≈30 kWe/MGD, waste heat →digesters
Co-Generation (Combined Heat Power)
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 31
Waco -- 3 ea: 500 kW IC engine/gen sets Dallas -- 4.2 MW IC engine/gen sets
Fort Worth -- 2 ea: 5 MW gas turbines
• Thørso, Denmark – built 1994 … thermophilic
• Treats WWTP sludge, fish wastes & pig manure
• Digested solids trucked back to farmers
Co-Digestion of Trucked Wastes
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 32
Receiving Bldg >>
<< Slurry Pit >>
Digesters
Biogas
Mech Bldg
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 33
Co-Digestion: Pinellas Co., Florida
• County adopted grease program – concentrated grease trucked to WWTP
• Biogas to pelletizer
Digester performance:
Biogas flow
∆ VSS
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 34
Co-Digestion: Waco
• Adding food processing wastes & FOG
• Increased biogas production by 25-30%
• Provides 50% of gas for sludge drying
Truck Unloading
Receiving Tank
Ron Sieger Biosolids
Award Winner
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 35
Co-Digestion: Fort Worth
• Constructing co-digestion receiving/feed system
– New linear-motion mixers in six digesters
– Additional biogas for steam generation/blowers
• Selected industries & plant scum
• Two reactors in series
– Acidification: HRT = 1-2 days
– Methanogenesis: HRT ≈ 10 days
• Increased VSS & pathogen destruction; less foaming
• DuPage County plant in 1988
Two-Phase Digestion (Acid/Gas)
• Texas plants evaluating acid/gas: – Dallas Southside
– Waco Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 36
Acidification Tank at 12 MGD Woodridge
Greene Valley plant in DuPage County, Illinois
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 37
Class A Pathogen Reduction
• Acid/Gas digestion may produce Class A pathogen quality, but only by Alt 3 (testing)
• EPA considering eliminating Alt 3
• Alternative 1, time/temp), can meet Class A but only with batch digestion … (Terminal Island) 0
5
10
15
20
25
30
130 135 140 145
Req
uir
ed C
on
tact
Tim
e (h
ou
rs)
Contact Temperature (°F)
REQUIRED TIME vs TEMP FOR ALTERNATIVE 1
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 38
Other Options, Technologies …
Thermal Hydrolysis
(Cambi)
???
Sonication
(Crown)
HAZWASTE Detox.
Anaerobic / Aerobic
Temperature Phased (TPAD)
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 40
MSW “Dry” Digestion: Electricity
• OWS plant in Brecht, BE
• “Green” waste @ 35% total solids, no dilution
• Influent blended ~1:8 w/ effluent recycle (25% TS)
• Steam injection to reach thermophilic range
• Fed with ram pump
• Generates ~400 kW, plus low-grade steam
• Fermentation of MSW biomass to organic acid salts (no methanogenesis)
• Conversion of acid salts to ketones & alcohols
• Conversion of alcohols to gasoline or jet fuel
• Bench, pilot, demo-scale
• Full-scale: 2013
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 41
MSW Fermentation to Fuel
Demonstration Plant outside Bryan
1. Anaerobic technologies evolving – many choices
2. Major drivers for anaerobic treatment in Texas:
– Avoided costs … electricity, diesel fuel, surcharges
– Energy production … electricity and heat
– Greenhouse gasses, carbon footprint
3. Obstacles:
– Capital costs
– Concentrated return streams
4. Opportunities for synergy with MSW streams
Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 42
Conclusions
Be ready for the unexpected!
Into the Future …
Questions, comments, additions?