energy optimization trends in biosolids management...• case studies • whole plant optimization...

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Energy Optimization Trends in Biosolids Management

By Duyen Tran, ENV SP and Todd O. Williams, P.E., BCEEJune 6, 2018

DOE Webinar – Biosolids Energy Recovery

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Residuals Resource Recovery


• Fayetteville, Arkansas Case Study• What are the industry trends?

– Improved quality due to regulatory and public concerns– Nutrient recovery– Energy efficiency/optimization– Interest in non-land-based alternatives and future

technology development

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Case Study - Fayetteville, AR Biosolids Operations

• 2 WWRFs, total design 22.6 MGD• 670 acres biosolids management site

– Fertilizer production/sale– Irrigation and nutrient uptake, hay

harvesting/marketing– Application of water treatment

residuals

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History of Fayetteville Biosolids Management

1988 to 2003 – land application2003 to 2011 – landfill2012 to current – class A biosolids

– Process ~ 21,000 wet tons of sludge/yr

– Produce ~3,000 dry tons of fertilizer

– Generate ~ $60K in fertilizer sales/year

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Specific Options Comparison

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Solar House Drying Cycle

1. De-watered biosolids are trucked to the site & emptied into the “Unload Basin”

3. Solids are then spread as evenly as possible inside the houses

4. Then the ‘moles’ are turned loose to do their thing!

2. Solids are then loaded into the spreader or hauled directly into the houses with the skid-steer loader

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Thermal Drying to Class A Biosolids

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Costs

• Total capital cost is $8M– $6M for solar dryers– $2M for thermal dryer

• Actual savings is ~$500,000 in 2017 compared to landfilling

• Produces beneficial reuse products

• Solar drying reduces overall drying energy cost by ~50%

• Reduces carbon footprint

Benefits

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Residuals Resource Recovery Lessons Learned

•Sludge Composition is critical•Odor Issue•Dust Issue•Preventive Maintenance

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Looking for The Next Big Thing –Energy Reduction Alternatives

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• What are the trends?– Improved quality due to regulatory and public concerns

• Class B to Class A– Nutrient Recovery– Energy efficiency/optimization

• Advanced anaerobic digestion– Thermal hydrolysis

• Co-Digestion (FOG and HSW) to generate more biogas– Biogas for driving CHP and biogas upgrading

• Case Studies• Whole plant optimization

– Carbon redirection– Interest in non-land-based alternatives and future technology development

• Gasification• Pyrolysis• Hydrothermal liquefaction• Supercritical water oxidation

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Phosphorus Recovery / Struvite Management

• A component of sustainable nutrient management and resource recovery

• Produces P fertilizer that has value– Worth about $40 per ton on open market

• Minimize impact of sidestream, especially at Bio-P WWTPs

• Drastically reduces struvite issues• Control Ca and Mg in the biosolids for best results• Several vendor systems available

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PrimaryClarifier

FinalClarifier

AnaerobicDigester Dewatering

Incineration

RAS

WAS

Centrate/Filtrate

Ash

PrimarySludge

Potential Locations for Nutrient Recovery at Water Resource Recovery Facilities

N and P recovery

P recovery

N and P recovery

Bio-P Process

P recovery

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Pre-Digestion Mechanistic Principles for Reducing Solids Generation Evaluated in 2010 WERF Study • Biological Combination Process

– Cannibal• Physical Process

– Thermal Hydrolysis (Cambi)– Pressure Release (Crown)– Shearing (ABS Kady)

• Physical/Chemical Process– Microsludge

• Pulsed Electric Process– OpenCel

Lots of Conclusions but….only Thermal Hydrolysis installations are growing

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Thermal hydrolysis

Hygienization (Class A Biosolids)...No FC Regrowth and Low Odour

Dewaterability ...dryer cake and less solids = big volume reduction

Improvement of sludge

biodegradability...sludge reduction & biogas production

Viscosity ...easier to pump and can load digester at higher %TS

Benefits of Thermal Hydrolysis

Reduction in Anaerobic

Digestion Reactor Volume

Much higher VSLR (4-6 kg/m3/day) and reaction kinetics

Increase in biogas yield and methane

content... More energy production

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Thermal Hydrolysis is a Proven Technology Worldwide THP Systems Jan 1, 2016, Compliments of Cambii

* = operating; **operating & expanded, (*) closed down (pilot/decommissioned), *? Uncertain operating status. All other under design/construction

Over 70 Operating THPPlants Worldwide

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Thermal Hydrolysis Vendor SystemsVendor Full-Scale

FacilitiesBuilt (const.)

Capacities of Installed Base

DT/day

Since

Cambi - THP 53 (+4) 6 to 360 1995

Veolia - BioTHELYS 6 (+2) 3 to 100 2004

Veolia - Exelys 1 (+3) 10 to 66 2014

Sustec - TurboTec 2 (+0) 20 to 35 2012

Haarslev 2 (+1) 20 to 25 2014

CNP - Pondus 8 (+0) 5 to 20 2005

Lysotherm 2 (+0) 3 to 33 2016

TOTAL 2017 74 (+10) 3 to 360 1995

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WEF/NBP Study Released in July 2013

• About half of all wastewater is processed using anaerobic digestion

• 5127 Water Resource Recovery Facilities (WRRF) were surveyed, majority above 1 MGD (about 1/3 of all)

• Plenty of opportunity exists for development of energy recovery at WRRF’s in the next decade.

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FOG and HSW Addition to Digesters and CHP is Trending up•3 Times as many WRRF’s are without Anaerobic Digestion (AD)

as those with AD

•3 Times as many WRRF’s with AD do not generate power or drive plant equipment as those that do

•6 Times as many WRRF’s do not import FOG or high strength waste to feed digesters as those that do

• Plenty of opportunity exists for development of energy recovery at WRRF’s in the next decade. This is a big trend.

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Residuals Resource Recovery Biogas with Addition of Fats, Oil & Grease (FOG)

50 dry tons/day solids > 600,000 ft3/day of biogas $4,800/day energy value

55,000 gal/day FOG @ 5% solids + 50 dry tons/day solids > 952,000 ft3/day of

biogas $7,600/day energy value

+ $1,022,000/yr energy value with FOGF. Wayne Hill WRC, Gwinnett County, Georgia

Douglas L. Smith Middle Basin FacilityJohnson County, Kansas

50% of Plant Power Needs Met

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The Resource Recovery Model

Biosolids Fertilizer

Biodiesel

Renewable Electricity

Recycled WaterWastewater

Organic Wastes

Food Waste

Fats, Oils, and Grease

Wastewater Treatment

Plant

Nutrient Harvesting

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Renewable Energy Expansion

• Installed in 1985• Met 40-50% of demand

(2-2.5 MW net gen)• Frequent flaring of excess

biogas

Expansion (+1 turbine)

• Meets 100-200% of demand (5-10 MW net gen)

• Sell excess green energy

• Reduces air and GHG emissions

• Increases operational reliability

Original Facility (3 engines)

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First WWTP in U.S. to Become a Net Electricity Provider

2013

Generation: 6MW

Demand: 5MW

Net Sales = 1MW

Electrical Grid

Wastewater Treatment Plant

Net Electricity Provider

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Process Schematic of DC Water’s New Biosolids Program with TH and CHP

Dewatering

Lime

Store &Loadout

Class B

DAFTs

Mix

R

R

Screening and Pre-Dewatering

FinalDewatering

RecycleProcessing

R

LoadoutCambi™ THP

Steam Biogas

Biogas Treatment and CHP

Emissions

MesophilicAnaerobicDigestion

Class A

Power

R

R

GravityThickeners

Blend Tank

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Program Benefits

Reduce biosolids quantities by more than 50%

Improve product quality (Class A)

Generate 13 MW (net 10 MW, or ~40% of total grid draw) of clean, renewable power

Cut GHG emissions by a third

Saving millions of dollars annually since the facility began operating in early 2015

Reinventing Biosolids

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Green Bay Resource Recovery and Electrical Energy (R2E2) Project

R2E2 will generate 70% to 75% of overall facility power and heating requirements when it is fully operational in 2018

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VandCenter Syd (VCS), Denmark

• 3rd largest water and wastewater company in Denmark. Headquartered in Odense.

• Operates 7 WTPs and 8 WWTPs with 2,125 miles (3,400 km) of conveyance

• Ejby Mølle WWTP:

– 385,000 PE BNR facility

– 76 percent energy self-sufficient in 2011

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Ejby Mølle WWTP Energy Optimization Project Objectives

• Contribute towards achieving VCS’s corporate goal of energy self-sufficiency and carbon neutrality by 2014

• Identify energy optimization opportunities (EOOs):

– Short-term, readily implementable scenarios to reduce energy consumption and/or increase energy generation, and decrease greenhouse gas emissions

• Identify and document all options, including longer term opportunities for future consideration

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Availability of detailed historic energy consumption and generation data was key in the evaluation of optimization opportunities

Screen, Grit, and Grease3.88% Primary Treatment

3.09%Pumping to

Trickling Filters2.15%

Pumping to Activated Sludge5.80%

Trickling Filters -Stage 2 pumping

7.30% Trickling Filters -Recirculation pumping

4.73%Trickling Filters -

WAS/Humus Pumping0.01%

Trickling Filters - Return Pumping to Act Sludge

0.64%

Activated Sludge -Anaerobic Zone Mixers

1.78%Activated Sludge -

Oxidation Ditch Aeration39.35%

Activated Sludge -Oxidation Ditch Mixing

2.09%

Activated Sludge -RAS Pumping

0.86%

Activated Sludge -WAS Pumping

0.22%

Activated Sludge - Other0.24%

Effluent Filters10.43%

Sludge Storage1.56%

Anaerobic Digestion3.83%

Thickening/Dewatering Centrifuges

6.44% Other5.59%

Ejby Mølle WWTP 2011 Annual Average Electricity Consumption

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A whole plant mass/energy model and screening criteria led to an EOO short-list

• Adopted screening criteria – Readily implementable; Primarily

process modifications– Significant impact on energy profile;

Proven elsewhere• Short-listed EOOs

– Implement chemical enhanced primary treatment (CEPT)

– Operate at shorter BNR system solids retention time (SRT)

– Decommission TFs and convert TF clarifiers to CEPT for wet weather treatment

– Reduce effluent filtration operation to 12 hours per day

• Longer term Improvements for positive net energy status

– Co-digestion of high strength waste in 2014

– Implemented deammonification for N removal in sidestreams in 2014; mainstream in 2015

– Replaced oxidation ditch mechanical aerators with fine bubble diffused aeration

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Implementation of several EOOs achieved energy self- sufficiency in 2014

Electrical Energy

Electrical + Heat Energy

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What is Carbon Redirection and why would a utility be Interested in applying it?• The diversion of biodegradable material away from the influent to a secondary treatment system

• The Good:– Lower energy usage– More biogas for beneficial use– Less biosolids production– Smaller bioreactors/more bioreactor capacity– Sets plant up for future technologies like mainstream Anammox

• The Bad:– Makes conventional nitrogen removal in secondary treatment more difficult because less carbon is

available for denitrification

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Examples of Carbon Redirection

• The diversion of biodegradable material away from the influent to a secondary treatment system

BOD5Raw

Sewage

Oxygen/Air$$$

BOD5Raw

Sewage

Oxygen/Air

$

BOD

5

BOD5

Primary Treatment

Carbon Redirection

Conventional

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Examples of Carbon Redirection

• Realizing energy savings requires anaerobic digestion, or no digestion– Aerobic digestion would just move power from the liquids to the solids train

BOD5Raw

Sewage

Oxygen/Air

$

BOD

5

BOD5

Primary Treatment

Anaerobic Digestion

Digester Gas

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Impact of Primary Clarification (1 MGD Facility)

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Growing interest in non-land application based alternatives and future technology development

Emerging technologies for biosolids management as defined by the US EPA

with suggested updates by Jacobs

• Established – Technologies widely used (i.e. generally more than 25 facilities in operation) are considered well established.

• Innovative – Technologies meeting one of the following qualifications: (1) have been tested at a full-scale demonstration site; (2) have been available and implemented for less than 5 years; (3) have some degree of initial use (i.e. implemented in less than twenty-five utilities)

• Embryonic – Technologies in the development stage and/or tested at laboratory or bench scale. New technologies that have reached the demonstration stage, but cannot yet be considered to be established

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EmbryonicGenifuel - Hydrothermal Liquefaction

and Catalytic Gasification

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Genifuel Status

• Proof of Concept Bench testing at Pacific Northwest National Laboratory

• Bench Tested Primary, Waste Activated and Digested Sludges

• Yield of 25-37% crude oil on mass basis, 39-59% on carbon basis

• High methane content (>75%) in gas• Metro Vancouver is participating (it was

your sludge that was tested!)• Looking for full scale demonstration

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Embryonic – Aquacritox Supercritical Water Oxidation

• Complete conversion of organics in less than a minute

• Complete conversion of N possible at higher temperatures (540°C)

• Planned pilot testing in Orange County, CA

• Water above 374°C (700°F) and 221 bar (3,000 psi), reaches supercritical state

• Eco-Innovation Initiative funded demo is being developed in Cork, Ireland

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Embryonic – KORE Encore Pyrolysis

• Ran pilot at LA San Districts for 5 years

• Full scale demonstration project is under construction, on line late 2016

• Thermo chemical pyrolysis that generates a liquid fuel.

• Biochar• Syngas is transformed by

Fischer-Tropsch process to produce advanced biofuels such as bio-diesel

• Patented process with turnkey developers.

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Summary

• What are the trends?– Improved quality due to regulatory and public concerns

• Class B to Class A– Nutrient Recovery– Energy efficiency/optimization

• Advanced anaerobic digestion– Thermal hydrolysis

• Co-Digestion (FOG and HSW) to generate more biogas– Biogas for driving CHP and biogas upgrading

• Whole plant optimization– Carbon redirection

– Interest in non-land-based alternatives and future technology development• Gasification• Pyrolysis• Hydrothermal liquefaction• Supercritical water oxidation

www.jacobs.com | worldwideJune 4, 2018

© Copyright Jacobs

Thank You

Todd Williams, [email protected] Tran, [email protected]

energy optimization trends in biosolids management...• case studies • whole plant optimization...

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