1. Starting From Scratch - Commissioning the First Thermal Hydrolysis Fed Digesters in North America
November 17, 2015
NC AWWA-WEA
Annual conference
Blue Plains AWTP Main Process Train
Peter Loomis CDM Smith
Engin Guven
CDM Smith
Christine deBarbadillo
DC Water

2. Starting From Scratch – Commissioning the First Thermal Hydrolysis Fed Digesters in North America
Agenda
Background and Objectives
Startup Methodology
Seeding and Ramp Up
Findings

3. Background 2.2 million water and wastewater customers in DC
Annual operating budget $300M+
$3.8B 10 Year CIP
1,100 employees
8 Time Winner of National Association of Clean Water Agencies Gold Peak Performance Award
DC Water is the largest power user in Washington, DC

4. Overview of Blue Plains AWTP
391 mgd average day capacity
~160 acres
Largest Advanced WWTP in the world
Serves DC, plus areas of Maryland and N. Virginia
Advanced secondary treatment – filtration, N and P removal
Discharge to Potomac

5. Main Process Train Project
Solids Blending Tanks
Sludge Screening
Pre-Dewatering
Dewatered Sludge Storage and Pumping
Thermal Hydrolysis (Cambi)
Sludge Cooling
Digestion
Digested Sludge Transfer & Holding

6. Commissioning Objectives
Initiate seeding of digesters with Class A biosolids
Maintain solids throughput (estimated at 300 dtpd at start of commissioning)
Continue Class B land application until Class A achieved and approved

7. Startup Methodology Fill all digesters ~60% with water
Heat water to 100°F
Continuous operation of HEX solids pumps for minimal mixing
Transport sludge and fill remaining volume of two digesters with class A seed sludge (~1% solids in each digester)
Continue heating digester with steam
Begin mixing with draft tube mixers (startup mixers over 12 hour period)
Begin feeding TH solids to first digester (overflow to adjacent digester)
Ramp up solids based on VS in digesters

8. Seeding and Ramp Up Results
First digester lower solids concentration
Initial sludge provided was more dilute
Steam added water to digester
Maintaining temperature required significant steam
Initial decline of pH and Alkalinity
Added alkalinity to first 2 digesters
Rapid increase in alkalinity after two weeks

9. Seeding and Ramp Up Feed

10. Digester pH

11. Solids Concentration in Digesters

12. Alkalinity Trends

13. Digester Ammonia

14. Digester Cameras

15. Visible Differences

16. Understanding Foam Conditions

17. Observing Mixing Patterns & Foam

18. Digester Settling
1 minute 90 minutes hours

19. Hydrolyzed Sludge Settling
1 minute 90 minutes hours

20. Sludge feed to BFP

21. Polymer Dosing for Final Dewatering

22. Dewatered Solids Results

23. Capture efficiency remains excellent

24. Fecal Coliform Results (Dewatered Biosolids)

25. Sidestream Impacts Solids and ammonia loading increased gradually
Stabilized at approximately 5% solids and 2600 mg/L Ammonia
Increased plant TKN load by 15% to 20% (~5 mg/L)
Methanol use increased by 6000 gal/day
DEMON facility under construction

26. Ammonia Load Return to Plant

27. Findings Supplemental Heat Required
Ramp up conservatively (max. 5% per day increase feed)
Supplemental alkalinity allows faster ramp up (initial drop in pH)
Digested solids not Class A for ~150 days (acclimatization)
High VSR (60%+)
Methane Concentrations 62%+
Reduced concentration is early sign of upset
Ammonia elevated
Rapid increases in feed can cause upset

28. Blue Plains AWTP Main Process Train Project
Questions?