CONVERTING DIGESTER GAS TO STEAM AND ELECTRICITY AT THE BLUE PLAINS AWTF MICHAEL B SHAFER, PE BLACK & VEATCH November 12, 2013 PRESENTED AT THE NC AWWA/WEA ANNUAL CONFERENCE 2013

Reduces hauling of biosolids by 50% Produces a Class A beneficial byproduct for use as a soil amendment Reduces annual O&M cost by $20M/year Cogen plant generates 15 MW of power ~ 30% of daily power demand for Blue Plains AWTP Reduces DC Water’s Green House Gas (GHG) emissions by 41% Provides DC one of the greenest projects on the East Coast DC WATER ANTICIPATES THE FOLLOWING BENEFITS: 2

Wastewater service to over 2 million people in DC, MD, VA Blue Plains AWTP – largest advanced WWTP in the world 370 mgd average annual flow 1,076 mgd wet weather Largest power user in Washington, DC 3 DC WATER AND SEWER AUTHORITY

1200 wet tons per day lime stabilized biosolids Agriculture – 39 counties in MD and VA Silviculture – 40,000 acres permitted in 8 Virginia counties Poplar plantation on a gravel mine Reclamation projects – three sites to date EXISTING BIOSOLIDS DISPOSAL 4

AERIAL OF BLUE PLAINS SITE 5 N I-295 BIOSOLIDS PROJECT SITE

3D RENDERING OF BIOSOLIDS SITE 6 I-295 N COMBINED HEAT AND POWER

Main Process Train Screening & Pre- Dewatering Final Dewatering Recycle Processing R R R Gravity Thickeners R R Class A Loadout Biogas Treatment and CHP Lime Thermal Hydrolysis Steam Biogas Emissions Store & Loadout Class B Dissolved Air Flotation Thickeners MixDewatering Mesophilic Anaerobic Digestion Electricity PROGRAM ELEMENTS 7 Combined Heat and Power Final Dewatering R = Return to plant

MAIN PROCESS TRAIN Solids Screening Building PreDewatering Building Thermal Hydrolysis Process Digesters (4) Digester Building Enclosed Flares MAJOR BIOSOLIDS MANAGEMENT PROGRAM COMPONENTS: 8 COMBINED HEAT AND POWER Turbine Building Gas Conditioning Bld. Gas Blower Bld. Siloxane Flare FINAL DEWATERING FACILITY Expansion of Existing Solids Processing Bld.

BIOSOLIDS AERIAL RENDERING 9 Combined Heat and Power Facilities Turbine Building Gas Conditioning Building Blower Building

PROJECT RENDERING 10

Pepco Energy Services (PES) – Prime DBO Contractor Ulliman Schutte Construction Black & Veatch PES has 15 year operations contract Extensive operations experience with combustion turbines DC Water reduces financial risks Volatile energy markets Schedule Benefits Early release of foundation design Early procurement DESIGN-BUILD-OPERATE 3 October 2012

PROCESS OVERVIEW Combustion Turbines Combustion Turbines Heat Recovery Steam Generator Electricity Duct Burner Heat Steam Heat Medium Pressure Digester Gas Exhaust High Pressure Digester Gas Water 12

Three Solar Mercury 50 Each unit rated at 5 MW at 13.8 kV Self-contained enclosure COMBUSTION TURBINES Recuperator Turbine Generator Exhaust Air Intake

Convert heat and water to steam Deliver 47,500 pph of steam to Cambi HEAT RECOVERY STEAM GENERATORS (HRSG) Turbine Exhaust Duct Duct Burner Section Stack Steam Drum

COMBUSTION TURBINES AND HRSG Steam Dump Condenser HRSG Duct Burner Combustion Turbine Deaerator

Auxiliary Boiler (backup supply) Water Treatment (RO and softener treatment) Deaerator Steam Dump Condenser SUPPLEMENTAL STEAM FACILITIES 18

WATER AND STEAM FLOW DIAGRAM Deaerator Dump Condenser Feed Water Pumps Condensate Pumps Makeup Water Excess Steam Auxiliary Boiler HRSG (TYP of 3) HRSG (TYP of 3) Natural/ Digester Gas Steam Turbine Exhaust Water Process Steam To Cambi Digester Gas Steam 19

TURBINE BUILDING FLOOR PLAN Steam Dump Condenser HRSG Auxiliary Boiler Combustion Turbine Deaerator Water Treatment Instrument Air System

TURBINE BUILDING LOWER LEVEL Auxiliary Boiler 13.8 kV Switchgear 480 V Electrical Control Room Remote I/O Mech Room Restrooms Combustion Turbine 21

GAS FLOW DIAGRAM Blowers Siloxane Removal Blowers Compressors Wet Scrubber Moisture Removal Moisture Removal Condensate MPDG to HRSG Duct Burner and Auxiliary Boiler HPDG to Combustion Turbines Natural Gas Flare Static Mixer Digester Gas Particulates 22

GAS FACILITIES Chiller Wet Scrubber Blowers Cooling Water HEX (2) Chilled Water HEX (2) Gas Reheat HEX (2) Regen Skid Siloxane Removal Compressors Siloxane Polishers Siloxane Flare

Impingement tray scrubber Remove particulates and foam Uses plant effluent spray WET SCRUBBER 24

Boost pressure (12 psi) for conditioning process Multi-stage centrifugal blowers Modulated to maintain upstream pressure in digesters GAS BLOWERS 25

Dry gas required for downstream siloxane removal Digester gas is saturated at ~ 100°F Series of heat exchangers to reduce gas to 40°F Plant effluent and chilled water used to cool gas MOISTURE REMOVAL 26

BLOWER BUILDING LAYOUT Chiller Wet Scrubber Blowers Cooling Water HEX (2) Chilled Water HEX (2) Gas Reheat HEX (2)

Siloxanes limit the useful life of the recuperator Primary removal system uses a regenerative adsorptive desiccant media Secondary system uses carbon polishers SILOXANE REMOVAL 28

Hot air used drive off VOCs from media Flare is used to incinerate off-gas SILOXANE REGENERATION & FLARE 29

Send high pressure digester gas (200 psi) to combustion turbines Rotary screw compressors Modulated to maintain pressure for the combustion turbines GAS COMPRESSORS 30

GAS CONDITIONING BUILDING Regen Skid Siloxane Removal Compressors Siloxane Polishers