Wastewater Management: P bl O i ?Problem or Opportunity?

CEE357 SeminarCEE357  SeminarNovember 29, 2012

H. David Stensel, PhD, PEH. David Stensel, PhD, PEUniversity of Washington

Overview of PresentationOverview of Presentation

• Traditional Wastewater Treatment Activities

• Sustainable technology in wastewater treatment

• Energy production and utilization in wastewater treatment

Codigestion for increased methane production• Codigestion for increased methane production

• Phosphorus recovery

Domestic Wastewater Management in U.S.Domestic Wastewater Management in U.S.

• About 22 000 publically owned wastewaterAbout 22,000 publically owned wastewater treatment systems for 75% of the United States population treat aboutStates population treat about

• ~30 billion gallons of wastewater per day60 illi lb /d f i b t• ~60 million lbs/day of organic substances

• ~11 million lbs/day of nitrogen• ~2.5 million lbs per day of phosphorus.

Conventional Pollutants in Wastewater

Constituent Unit Value (typical)Constituent Unit Value (typical)Solids, total (TS) mg/L 390 -1230 (720)

Dissolved, total (TDS) mg/L 270 – 860 (500)

Suspended solids, total (TSS) mg/L 120 – 400 (210)

Biochemical oxygen demand(BOD) 5 d 20°C

mg/L 110 – 350 (200)(BOD) 5-d, 20°C

Total organic carbon (TOC) mg/L 80 – 260 (140)

Chemical oxygen demand mg/L 250 – 800 (450)(COD)Oil and grease mg/L 30 – 90 (60)

Total Nitrogen (TKN) mg/L 25-75 (40)g ( ) g ( )

Total Phosphorus (TP) mg/L 4 – 9 (6)

Elements of Conventional Wastewater TreatmentElements of Conventional Wastewater Treatment

Energy Hog

Biomethane

Looks like a work of art!

Water and Wastewater Utilities and Municipal Energy Usesp gy

At CDM, We Don’t Make the Energy Savings. We Make the Energy Savings Better.J. Peters, P.E. 1*, BCEE, Chris Varnon, P.E. 1, Dean Towery2, WEFTEC, 2008

Traditional Goals for Wastewater Treatment

• Protect public Health– Minimize discharge of pathogensMinimize discharge of pathogens

• Protect environmental healthMinimize oxygen deficit in surface waters– Minimize oxygen deficit in surface waters

• Organic loads• Eutrophication due to nutrient enrichment• Eutrophication due to nutrient enrichment

• Recreational and beneficial uses of water

Cuyahoga River, (Cleveland Ohio)(Cleveland, Ohio)

Convenient  disposal for industrial d i i l tand municipal wastes

Famous for river on fire ‐1969

Helped pass the 1972 Clean Water Act

Fish Kill in China due to Oxygen lDepletion

What are the effects of excess nutrients?

Low oxygen levels in water.

photo of dead fish(webpage electronic photo image, EPA;( p g p g35 mm slide, Kent Mountford, CBPO)

Not to be outdoneCHESAPEAKE BAY FISH KILL

Algae Biomass ProductionAlgae Biomass ProductionALGAE COMPOSITION: C106 H263 O110 N16 P

C:N:P Ratio = 106:16:1

1 Lb of P can produce 106 Lbs of Algae Biomass &1 Lb of P can produce 106 Lbs of Algae Biomass &1 Lb of N can produce 16 Lbs of Algae Biomass

1 Lb of Algae Biomass = 1 24 Lbs of COD (BOD )1 Lb of Algae Biomass = 1.24 Lbs of COD (BODu)

Therefore: 1 Lb P can generate 131 Lbs of COD,5 mg/L effluent P can generate 655 mg/L COD, and

1 Lb N can generate 19.8 Lbs of COD,1 Lb N can generate 19.8 Lbs of COD,20 mg/L effluent N can generate 397 mg/L of COD.

These focused on effluent goalsThese focused on effluent goals

• Increasing interest on other issuesEnergy needs and carbon footprint– Energy needs and carbon footprint

– Greenhouse gas emissionsS t i bl t h l– Sustainable technology

What is Sustainability?Sustainability?

“PreservingPreserving Resources for future 

generations”generationsEnergyEnergy SocialSocial

Greenhouse GasGreenhouse GasEnvironmental StewardshipEnvironmental Stewardship

“Evolving Urban Water and d l dResidual Management Paradigms:

Water Reclamation and Reuse, Decentralization, Resource Recovery”by Dr. Daigger with CH2M HILL ‐at WEFTEC, 2008

1 Water reclamation and reuse

Sustainability Criteria for Wastewater Treatment

1. Water reclamation and reuse

2. Reduce process energy demands

3. Recover energy

4 Reduce release of greenhouse gases (CH and4. Reduce release of greenhouse gases (CH4 and CO2) at WWTP or off-siteat WWTP or off site

5. Recover nutrients; nitrogen, phosphorus

Potable Water ReuseTechnology Exist and demonstrated for reclaimed water, ~2.5% currently used

Potable Water Reuse

16

Reduce Process Energy Demands

Port Orchard Karcher Creek WWTP Reducing Energy Demand and Energy 

Recoveryy

HYDROVOLT SYSTEM

Energy is available from Wastewater is available as gyheat or by conversion of organic material (COD)

Constituent Unit Value

Wastewater, heat MJ/0C-1000 m3 4,200,basis

,

Wastewater, COD b i

MJ/kg COD 12 - 15basis

• Conversion of COD to energyConversion of COD to energy• Thermal oxidation- need to reduce water content• Anaerobic degradation – water not a problem

Bi th• Biomethane

Methane UseMethane Use

• Generally needs cleaningGenerally needs cleaning– CH4, CO2, H2S, siloxanes

• Can be used to make electricity on• Can be used to make electricity on siteS d t h t di t t 350C• Some used to heat digesters to 350C

• Used in city vehiclesy• Added to natural gas pipeline – King

County South Plant – Renton. WACounty South Plant Renton. WA

Municipal Anaerobic DigestionBiomethane ProductionBiomethane ProductionBacteria digest solids to produce methane and carbon dioxid

Typically 20 ft3 methane gasTypically ~ 20 ft3 methane gasPer ft3 of feed!About 65% methane

CODIGESTIONCan add other communityWastes to increase biomethaneWastes to increase biomethane Output – i.e. food wastes,restaurant oils and grease

Waste solids flow in

Corona, California

Wastewater Energy Availablebiodegradable COD = 320 mg/L

50,000Effluent delta T = 100C

WWT bCOD

40,00075% E for heat pump

WWT Heat

m3

42,000 MJ

31 500 MJ

30,000

J/10

00 m 31,500 MJ

20,000

M

10,0004,160 MJ

0Energy Source

Evaluation of wastewater biodegradable COD t A tiCOD to energy - Assumptions

• 35% removal of bCOD in primary treatment35% removal of bCOD in primary treatment• 50% of influent bCOD oxidized in activated

sludgeg• 85% of bCOD fed to digesters converted to CH4

• 100 Hp/Million Gallon-d of wastewater treated100 Hp/Million Gallon d of wastewater treated• 30% efficiency from methane to electricity• 50 1 kJ/g CH• 50.1 kJ/g CH4

About 33% of wastewater plant energy need can be provided by biomethane to

5,000

need can be provided by biomethane to electricity

WWT bCOD4 1604,000

WWT bCODEnergy NeedBiomethaneElectricalm

3

4,160

3,000

Electrical

J/1

000

m

2,1602,000M

J ,1,700

0

1,000 650

0Energy Need and Sources

Opportunities for and Benefits of Combined Heat and Power (CHP) at WastewaterHeat and Power (CHP) at Wastewater

Treatment FacilitiesU.S. EPA (April 2007)

• ~1,000 facilities have influent flow >19,000 m3/d (~5.0 Mgal/d)

• 544 use anaerobic digestion• 106 use methane for heating or electricity (76 use CHP)

N t th t ith h t f l t i t• Note that with heat recovery from electric generators about 80% of heat value is used.

How can more methane be d d?produced?

• Increase bCOD removal in primaryIncrease bCOD removal in primary treatment

• About 25% of waste organics are not• About 25% of waste organics are not converted – technology to convert this carboncarbon.

• Find other waste sources to add to the bi di tanaerobic digester

– Co-Digestion

CodigestionCodigestion

• Add other local wastes to municipal panaerobic digesters

• Fats oils grease (FOG) food processing• Fats, oils, grease (FOG), food processing, distillery, beverage, biodiesel, food wastes etc

• High concentration, small volume, 50‐g , ,200 g COD/L

UW Activitiesd f b d lCodigestion of biodiesel wastes

Control Digester Biodiesel Waste Co-Digester

SRT (days) 15 15WPS + WAS

Avg. Daily Load4,600

mg bCOD / LReactor / Day4,600

mg bCOD / LReactor / Dayg y g y g yBiodiesel Waste Avg. Daily Load - 1,840 mg bCOD/L/day

(29% of total bCOD load)

Co-Digester: 15 day SRT with15-day SRT with

daily biodiesel waste additionsadditions

Example of Questions with CodigestionExample of Questions with Codigestion– Methane production efficiency of waste?

H i t f d ll t d t d f d t di t ?– How is waste feed collected, stored, fed to digester? – Inhibition

• Is acetoclastic methanogenesis (Vmax) inhibited by glycerol?a• No inhibition by glycerol at 11,200 mg sCOD / L and below

– Acclimation• Is glycerol readily degradable in sludge digestion?Is glycerol readily degradable in sludge digestion?• Glycerol degradability improves with acclimation time

– DegradabilityIs biodiesel waste fully degradable in anaerobic digestion?• Is biodiesel waste fully degradable in anaerobic digestion?

• Biodiesel waste is 100% biodegradable in acclimated sludge

Examples of codigest substratesUW lab study (Heidi and John)

Table 1: Description of Co-digestion Substrates Parameter Description

Substrate A scum material collected from CTP’s primary clarifiers

Substrate Bflower and vegetable wastes collect from a pilot source separation programSubstrate B source separation program

Substrate C blood product from the processing of animals

Substrate Ddissolved air floatation sludge from the rendering processSubstrate D process

Substrate E grease trap material (brown grease)

Substrate Fliquor from a tallow separation tank of a chili, soup and salad dressing manufacturing plantSubs a e a d sa ad d ess g a u ac u g p a

Substrate Gdissolved air floatation sludge from a chili, soup and salad dressing manufacturing processconfectionary waste, sugar, caramel, nuts, butter and

Substrate H chocolateSubstrate I bear, wine, soda and juice waste products

Waste Characteristics affect methane production. Fats oil and grease (FOG) have high energy output

Theoretical Gas Production from Different Organic Waste Components (Li et. al. (2002))

Gas

Fats, oil and grease (FOG) have high energy output

Component Reaction of Methane Fermentation

Gas Production

m3-biogas/kg

CH4 % in

Biogasbiogas/kg

Lipids (Fats)

C15H90O6 + 24.5 H2O 34.75 CH4 + 15.25 CO2

22.9 69.5

Carbohy (C H O ) H O 3 CH 3 CO 13 3 50Carbohydrates (C6H10O5) + nH2O 3n CH4 + 3nCO2 13.3 50

Proteins C11H24O5N4 + 14.5 H2O 8.25 CH4 + 3.75 CO2 + 4 NH4

++ 4HCO314.8 68.8

2 4 3

Another exciting resource recovery h htopic – Phosphorus Recovery

(MODIFIED) BARDENPHO PROCESSAnother problem turned into an opportunity

ANAEROBIC

INFL

Another problem turned into an opportunity

INFL.

AEROBIC

ANOXIC

WAS

ANOXIC

Anaerobic contact selectsfor bacteria that store largeWAS

RASGravity 

ThickenerGravity 

Thickener AnaerobicDigestion

for bacteria that store largeamounts of P and thus P removalwithout chemicals

Centrate / FiltrateCentrate / FiltrateDewatering

BUT -anaerobic digestionP released, struvite can formscaling problems, need to deal

47

Biosolidsg p ,

with P in recycle – add chemicals

Phosphorus RecoveryPhosphorus Recovery• Need enhanced biological phosphorus removal

processprocess• Solids digestion releases phosphorus• Controlled formation and removal of struvite inControlled formation and removal of struvite in

digester solids dewatering liquid– (MgNH4PO4) – control pH and add Mg

P tl d O h fi t U S f ilit O t P• Portland, Oregon has first U.S. facility – Ostara Process• Biological phosphorus removal process on liquid

stream• Excellent fertilizer, also high in nitrogen• 60% of domestic waste phosphorus recovered

2P Recovery

Reactor

(Mg2+)

Treated Side StreamSide Stream

Plate Settler

Hydrocyclone

Pelletizer

P recovery Product

Complete Mixed Reactor based Phosphorus Recovery Process (MultiForm)(MultiForm)

Wastewater is a resource!!

– Water reuse– Organic material conversion to biomethane– Other codigestion wastes can be handled at g

wastewater treatment facilities– Heat recovery from effluent and electricity

d tiproduction– Phosphorus recovery is feasible

Sustainable technology important to utilities– Sustainable technology important to utilities– Requires integrated and comprehensive

design evaluationsdesign evaluations