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

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

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

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

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

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

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

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

Seeding and Ramp Up Feed

Digester pH

Solids Concentration in Digesters

Alkalinity Trends

Digester Ammonia

Digester Cameras

Visible Differences

Understanding Foam Conditions

Observing Mixing Patterns & Foam

Digester Settling 1 minute 90 minutes 4 hours

Hydrolyzed Sludge Settling 1 minute 90 minutes 28 hours

Sludge feed to BFP

Polymer Dosing for Final Dewatering

Dewatered Solids Results

Capture efficiency remains excellent

Fecal Coliform Results (Dewatered Biosolids)

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

Ammonia Load Return to Plant

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

Blue Plains AWTP Main Process Train Project Questions?