November 17th, 2015

Thermal Hydrolysis Pretreatment (THP)

ConsiderationsFor a 15 Dry Ton per Day WRF

Thomas Nangle, PECDM Smith

2015 Annual Conference Raleigh, NC

Presentation Overview

Presentation Overview

Background on Thermal Hydrolysis Pretreatment Relevance Definition Advantages & Challenges

Key Considerations for 30 DTPD Installation Ancillary System Considerations

Pre-dewatering Steam Production Digesters Post Dewatering

Enhancing Class A Product Co-Digestion with FOG Redundancy

Questions

3

Background on THP

THP and Cake Product Odor (Novak, 2012)

5

Regrowth and Sudden Increase in Digested and Centrifuged Biosolids

6 See Also WERF Report “Examination of Reactivation and Regrowth of Fecal Coliforms in Centrifuge Dewatered, Anaerobically Digested Sludges”

THP Regrowth and Sudden Increase vs. Other Class A Processes (Higgins, 2012)

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Other Drivers for THP + AD

½ Digester Capacity Needed Higher % solids loading rates Lower SRTs

Decreased Solids Hauling & Increased Biogas Increased % VSR Increased Dewaterability

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Definition of Thermal Hydrolysis Pretreatment

Lysis = The disintegration of a cell by rupture of the cell wall or membrane.

503 rules for Class A through Alt 1 – Time and Temperature Pasteurization 70 degrees C for 30 minutes Thermal Hydrolysis 165 degrees C for 20 minutes

Sterilize vs Pasteurize Pasteurization reduces the number of viable pathogens so they are

unlikely to cause disease. Sterilization is any process that kills or removes all forms of life.

Thermal Hydrolysis sterilizes sludge through lysis via heat and flashing Less viscous = easier to pump, mix, and dewater

Higher loading rates Higher % solids dewatered cake

Already hydrolyzed = Lower SRTs and Higher %VSD

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Simplified Process Flow of THP for Franklin, TN

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Advantages & Challenges of Thermal Hydrolysis Pretreatment

AdvantagesMinimal Odor in Digested CakeClass A, minimal regrowthReduce required digester capacityIncreased Solids DestructionIncreased biogas productionImproved DewaterabilityReduce Hauling Costs

ChallengesMore equipment to maintainPressure vessels and high pressure steam

Depending on state may need special licensed operators

Regs typically require annual pressure vessel inspection

High strength side streamsRapid rise riskTwo dewatering steps

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Key Considerations for a 30 DTPD Facility

THP Ancillary Systems

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Pre-Dewatering

Thermal Hydrolysis

(THP)

Steam

Mesophilic Anaerobic Digestion

Post-Dewatering

Sludge Cooling Heat Exchangers

Sludge Recirculation

Side Stream Treatment

Additional Drying or Beneficial Reuse

Liquids ProcessNutrient Recovery

CHP System

Electricity to Plant Hot Water to

Treatment Processes

Natural Gas

Pre-Dewatering Considerations

THP heats incoming sludge via steam injection ↑ mass of sludge (biosolids + water), ↑ steam required

Each supplier has their own percent solids “sweet spot”: Cambi ~16% Kruger/Veolia’s Exelys is 22% or greater

Considerations WAS only limits of

Dewaterability Small plant with one THP

train. Cake Storage vs Ability to

divert cake solids

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Various Methods of Producing Steam

Boiler to produce steam CHP system to reuse biogas

CHP System to Generate all Steam

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Thermal Hydrolysi

s

Thermal Hydrolysi

s

SteamSteam

BiogasBiogasAnaerobic Digester

Anaerobic Digester

BoilerBoiler

Hot Water

Hot Water

Natural GasNatural Gas

CHPCHP

Thermal Hydrolysi

s

Thermal Hydrolysi

s

BiogasBiogas

Anaerobic Digester

Anaerobic Digester

Hot

Wat

erH

ot W

ater

CHPCHP

SteamSteam

Natural GasNatural Gas

Steam Production & Application Considerations

Beneficial use of low grade heat. Building heating (digester bldg.) Heating of FOG Preheating steam generator water for more efficiency Preheating dilution water Digester heating during THP downtime

CHP system can be optimally designed to provide required steam based on what other resources are most valuable. Electricity Generated Hot Water Produced

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Anaerobic Digester Considerations

Rapid Rise Higher Gas Productions Up to 10-15% volume

expansion Mixing System

Less viscous sludge Solids will settle faster Provide mixing system vendors

with hydrolyzed sludge rheology

Heating Sources Normally incoming sludge During startup and THP

downtime, alternative heat source is needed

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Post Dewatering Considerations

Compared to MAD ~10% increase in dewatered cake solids Post-Dewatering filtrate Ammonia levels double (2,200-2,800 mg/L)

Technology Considerations Centrifuge Belt Filter Press (high ammonia levels, would want to enclose the press for odor

control – similar cost to screw presses if you take into account the cost of enclosure).

Screw Press (1st THP application that we know of, when factoring in ) Side Stream Ammonia treatment

Equalization High Rate Nitrification Process or Proprietary Processes

SHARON ANITA Mox Anammox InNitri Others

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Market for Class A End Product

Begin with the end in mind Additional equipment:

Sludge Screens Removes undesirables – cleaner

Class A product to market Increases uptime of downstream

equipment. Supplemental Drying/Pelletizing

Dryer product - higher value Less mass to haul off site

You have a great Class A product, now what? Sell/give to 3rd party distributer

(Franklin route) Brand the product and start

marketing! “Promoting Your Product:

Marketing Tips and Techniques to Stimulate Biosolids Sales and Distribution.” WEF Webcast

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Co-Digestion with FOG

Few existing THP installations treat FOG FOG needs to be treated to Class A

Can be accomplished different ways, Separate pasteurization of FOG

Lower temps require less energy input Additional equipment needed, economies of scale with redundancy (larger

the loads, better bang for the capex) Comingled with sludge and thermally hydrolyzed.

Heating to higher temps, Potential issue with heat exchanger fouling (Cambi solved with sludge

recirculation, now standard) Limited additional equipment needed. More complicated THP feed logic

Screening of FOG Protect equipment and enhance Class A end product

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Redundancy Considerations

Smaller Plants (≤30 DTPD) can be processed by one small THP train. Two trains provide redundancy, but lower utilization of equipment & ROI One train provides better ROI, but increased risk (limited redundancy)

Cannot bypass THP to digesters (Why redundancy is important) Contamination of tanks and pipes risk Class A. Tanks don’t have capacity because of longer SRTs associated with MAD Upset of digester (change in feed characteristics and loading).

Redundancy by component Vessels don’t need much redundancy, and are a high capital cost item Mechanical equipment require frequent maintenance, must have

redundancy to limit unplanned downtime. Annual inspection of pressure vessels

Sludge storage Divert of pre-dewatered sludge

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Questions?Nanglet@cdmsmith.com