Thermal Hydrolysis Pretreatment (THP) Considerations

1. Thermal Hydrolysis Pretreatment (THP) Considerations November 17th, 2015 For a 15 Dry Ton per Day WRF Thomas Nangle, PE CDM Smith 2015 Annual Conference Raleigh, NC

2. Presentation Overview

3. 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

4. Background on THP

5. THP and Cake Product Odor (Novak, 2012)

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

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

8. Other Drivers for THP + AD • ½ Digester Capacity Needed • Higher % solids loading rates • Lower SRTs • Decreased Solids Hauling & Increased Biogas • Increased % VSR • Increased Dewaterability

9. 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

10. Simplified Process Flow of THP for Franklin, TN

11. Advantages & Challenges of Thermal Hydrolysis Pretreatment Advantages • Minimal Odor in Digested Cake • Class A, minimal regrowth • Reduce required digester capacity • Increased Solids Destruction • Increased biogas production • Improved Dewaterability • Reduce Hauling Costs Challenges • More equipment to maintain • Pressure vessels and high pressure steam • Depending on state may need special licensed operators • Regs typically require annual pressure vessel inspection • High strength side streams • Rapid rise risk • Two dewatering steps

12. Key Considerations for a 30 DTPD Facility

13. Thermal Hydrolysis(THP) THP Ancillary Systems Electricity to Plant Hot Water to Treatment Processes CHP System Pre-Dewatering Natural Gas Steam Post-Dewatering Additional Drying or Beneficial Reuse Sludge Cooling Heat Exchangers Mesophilic Anaerobic Digestion Side Stream Treatment Sludge Recirculation Liquids Process Nutrient Recovery

14. 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

15. Various Methods of Producing Steam • Boiler to produce steam • CHP system to reuse biogas • CHP System to Generate all Steam Biogas Biogas Natural Gas CHP Anaerobic Digester Hot Water Anaerobic Digester CHP Thermal Hydrolysis Boiler Steam Steam Hot Water Thermal Hydrolysis Natural Gas

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. Questions?Nanglet@cdmsmith.com