Unlocking Resource Recovery at the Neuse River RRF with THP

NC AWWA-WEA Annual Conference

November 14, 2016

T.J. Lynch, City of RaleighAaron Brower, City of RaleighTim Woody, City of RaleighMichael Bullard, Hazen and SawyerAmy Hanna, Hazen and Sawyer

Neuse River Resource Recovery Facility

• Currently expanding from 60 mgd to 75 mgd

• Planning for expansion to 90 mgd (~ 2040)

• Aerobic digestion and lime stabilization onsite

• Composting offsite

Offsite Composting

Current Biosolids Outlets

Class B LiquidRaleigh Plus

Drivers for Change

Drivers for Change

• Age of Equipment

• Uncertainty of future Class B land application

Drivers for Change

• A strategic part of the City’s Climate Energy Action Plan

• Make enough digester gas to fuel over 3,000 passenger vehicles!

Decision to Convert to Anaerobic Digestion

• Covered and Uncovered Aerobic Digesters• 2.6 million KWhr/yr

Technology Evaluation

Technology Evaluation

Drivers for Change – Benefits of THP

Anaerobic digester volume ↓ Capital Cost ↓

Biogas production ↑ Revenue ↑

Volatile solids reduction ↑ and dry mass ↓ Hauling Cost ↓

Final cake solids ↑ Hauling Cost ↓

Low odor, Class A product Public Health ↑Environment ↑

Project Description

Thermal Hydrolysis Process (THP)

• A sludge “pressure cooker” operating at about 330F/165C (90 psig)

THP Benefits and Considerations

BENEFITS

• Decreased digester volume

• Increased biogas production

• Increased VSR

• High quality biosolids• Class A • Low odor

CONSIDERATIONS

• Stronger sidestream• Nitrogen• Phosphorus• COD

• Possible impacts to UVT• Pre-conditioning required• Sludge cooling• Rapid Volume Expansion

Proposed Biosolids Process

EQ

CLASS A CAKE STORAGE

FOG RECEIVING

SCREENINGS

LOW PRESSURE

GAS STORAGE

PS

SLUDGE SCREENS

SCREENED SLUDGE WET

WELL

PRE-DEWATERINGTHERMAL

HYDROLYSIS

COOLING SYSTEM

ANAEROBIC DIGESTERS

SLUDGESTORAGE

FINAL DEWATERING

SIDESTREAM NITROGEN REMOVAL

THICKENING

GAS CLEAN UP

BIOGAS

BOILERS

STEAM

RETURN TO HEAD OF PLANT

WAS

BLEND TANK

CAKEBIN

RNG PIPELINE INJECTION

SCREENINGS

PASTEURIZATION

TWAS

STEAM FROM BOILERS

FLARE

Sidestream Considerations

• Improved VSR across digestion increases nutrient mass loadings in the sidestream. (+20%)

• Deammonification offers a reduced energy and reduce carbon pathway for nitrogen removal.

• Dilution will be required with post-THP centrate because of toxicity and nutrient loading

Fats, Oils and Grease

Benefits of Co-Digestion

• Boost biogas production

• Divert waste from collection system

• Revenue

Market study of grease interceptor waste

• 2015: 30,000 gal/day, 2040: 60,000 gal/day

FOG

Co-DigestStorePasteurizeScreenReceive

Digester Gas Utilization

Project Benefits

Net Energy Production with Renewable Natural Gas

2+ MW hr/hr

CWSRF Green Reserve$50M @ 0%

MW

hr/

hr

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

2020

2021

2022

2023

2024

2025

2026

2027

2028

2029

2030

2031

2032

2033

2034

2035

2036

2037

2038

2039

2040

Resid

uals

Disp

osed

, DT/

yr

Current THP + MAD

THP reduces residuals mass for final disposal

NRRRF will reduce operating costs with THP

$-

$50

$100

$150

$200

$250

20-y

r NPV

Ope

ratin

g Co

sts a

nd R

even

ue (

$M, 2

016$

)

Current THP + MAD

Disposal Cost Labor Cost Maintenance Cost Operation Cost Revenue

Next Steps

• In detailed design

• Selecting CMAR Contractor

• Construction to begin Q3 2017

Thank You!