WASTE SOLIDS REDUCTION TECHNOLOGIES

December 4, 2009

Timothy Shea, Ph.D., PE, BCEE, Julian Sandino, Ph.D., PE

Why Reduce Sludge Generation?

•  Reduce costs (capital and O&M) in sludge processing and ultimate disposal/reuse.

•  Maximize potential benefits of sludge processing (e.g. optimized energy balance in WWTP)

•  Reduce carbon footprint

Secondary Enhancements

PS to Digestion

WAS to Digestion

Primary Treatment

Activated Sludge

Plant Effluent

Secondary Treatment Headworks

Plant Influent

Solids Handling

Dewatering/ Disposal

• Extended Aeration • Cannibal™ •  Biolysis®O

• Homogenization • Sonication • Thermal Hydrolysis

• Thermophilic Digestion • Phased Digestion • Acid/Enzymatic Hydrolysis

CannibalTM

•  USFilter Cannibal™ builds on the “extended aeration” concept

CannibalTM

•  Biological Solids Destruction – Continuous –  cycling ML between the main plant and I/C tank –  anaerobic/aerobic cycling in the I/C tank

•  Physical Solids Separation – Intermittent –  250-micron fine screens – organic material – Hydrocyclone units – inerts/grit material –  20 to 30 percent of the solids reduction

•  Solids Inventory Purging – Annual –  low yield (0.1 lb TSS /lb BOD)

CannibalTM

•  Small to medium size plants (w/o anaerobic digestion …)

•  Major Cost Items –  covered I/C tanks and appurtenances (pH and ORP

meters, mixer, ) –  odor control system – SSM

•  Recent Cost quote for Fillmore, CA (1.8 mgd): –  $1.1Million USFilter supplied equipment –  excludes 0.5MG concrete tank, piping, odor

control, I/C tanks decanter, sludge pumps, etc.

CannibalTM

•  Advantages –  waste solids reduction –  processing and hauling costs reduction –  integration with most AS systems possible

•  Disadvantages –  Single vendor –  more complex system –  odor issues (I/C reactor and screens) –  biogas value of volatile solids LOST –  not applicable to conventional biological phosphorus

removal systems

Digestion Pretreatment

PS to Digestion

WAS to Digestion

Primary Treatment

Activated Sludge

Plant Effluent

Secondary Treatment Headworks

Plant Influent

Solids Handling

Dewatering/ Disposal

• Extended Aeration • Cannibal™ • Biolysis®O

• Thermal Hydrolysis •  Pressure Release

• Thermophilic Digestion • Phased Digestion • Acid/Enzymatic Hydrolysis

•  Disrupt cellular/ organic material that is slower to breakdown: –  Increase hydrolysis of complex organics and production of

VFAs and hydrogen –  Increase digestion rates & stability –  Increase gas production –  Increase volatile solids (VS) reduction –  Reduce solids for dewatering & reuse/disposal –  Reduce filamentous foaming –  Reduce viscosity –  Improve dewatering

•  Lesser value in hydrolyzing primary sludge

Digestion Pretreatment – Why?

Thermal Hydrolysis: CAMBI

•  Origins in Norway •  High pressure-high temperature process: thermal

hydrolysis of dewatered sludge under pressure using live steam.

•  Hydrolyzed and pasteurized sludge digested at greater VSLRs (smaller vessels).

•  Heat recovery minimizes the energy consumption. •  Application in mid-size treatment works (100 mgd

capacity range) at Aberdeen, Scotland and Ringsend, Dublin.

• Class A biosolids • Reduced volume

• >35% solids • 60 V.S. destruction

Methane

Dewatering 35-40% DS Dewatering 30 - 37% DS

Pre-Heat Tank

Flash Tank

Steam

Reactor

1 Solids are dewatered To ~15 %

5 Reactor pressure is rapidly released,flashing solids to the flash tank. • Flashing causes cells to

rupture • Steam is returned to

Pre-Heat • Hydrolyzed solids have reduce

viscosity

Anaerobic Digester • 60% C.O.D. conversion

• 50% reduction in digester volume • increased gas production • foaming eliminated

Pressure in reactor is reduced to 60 psi. • Steam is returned to Pre-Heat 4

2 Solids mixed with return steam and Water, so about 12%

8-10 % solids digester feed at 1 00 o F

Solids are heated by direct steam addition to 320 o F and 90 psi for 45 minutes • Class A time v. temp. • Organic compounds are

solubilized

3

CAMBI at Ringsend WWTP •  1,200,000 population equivalent •  40,000 dry tons per year (81%VS) •  Dewatering (15%TS) •  Thermal (steam) hydrolysis with

heat recovery (for digesters) •  Anaerobic digestion (60% VSD)

Biogas co-generation w/ heat recovery

•  Digested sludge (50%VS) to dewatering and heat drying

CAMBI Claimed Performance

Parameter Mesophilic AD

CAMBI + Meso AD

Digester Feed (%TS) 4-6 12-15

VSLR (kg VS/m3/d) 1.5 3.5

VS Destruction (%) 40-55 55-65

Pathogen content Class B Class A

Dewatered Cake TS (%) 20-25 30-35

Thermal Hydrolysis

•  Advantages: – Enhanced VSLRs – Requires smaller digesters – Produces a Class A biosolids –  Improved dewaterability of digested solids – Total destruction of microbiota from WAS,

thereby reducing/eliminating foaming in digesters.

Thermal Hydrolysis

•  Disadvantages: – Process complexity (substantial contractor

retrofit at Aberdeen and Ringsend). – The process requires the use of high pressure

steam, a need that has not been met well in municipal treatment works in the United States.

– There is considerable cost uncertainty with the process given the problems encountered.

Pressure Release

•  Macerate WAS to homogenize •  Increase pressure (12 Bar) with PC pump •  high pressure mixer, flow into disintegration

nozzle. •  As the flow exits the nozzle, cavitation

occurs rupturing cell structure •  Sludge can be passed through system three

times before discharge to the digesters.

Pressure Release

Vendor claims •  A minimum 20%

increase in Biogas production.

•  A minimum 15% reduction in dehydrated sludge volume

•  Carbon augmentation for BNR

Crown Disintegrator Wiesbaden WWTP - 60m3/hr

Homogenization/Pressure Release - MicroSludgeTM

•  NaOH to weaken cell membranes and reduce viscosity (pH 9 to 10)

•  Chopper pump to break up agglomerates

•  Screen to 800 µm to remove non-cellular debris

•  Homogenizer pressure 82,700 kPa (12,000 psig) for cell lysis

Questions?