Alternative binder materials and its application in concrete sewer structures for possible reduction in Fat, Oil and Grease related

Sanitary Sewer Overflows

Samrin Ahmed KusumMohammad Pour-Ghaz, Joel Ducoste

NC-AWWA 17th Annual Spring Symposium, 2018

2

A piece of London’s 130 ton Fatberg! 3

FOG buildup inside sewer lines

Who is responsible?

Why do we care?

Rapid Urbanization Growth in FSEs

Grease Inceptor

Poor GI managementInefficient GI performance

Domestic Kitchen/ Restaurants

Excessive use of dish washing detergent

Result of FOG deposition Sanitary Sewer Overflows

Result of FOG deposition Sanitary Sewer Overflows

SSOs impactEnvironmental impact

Public health hazard

Why do we need to study and fight FOG now more than ever?

Replace/Rehab Sewer, $42,072

New Collector Sewer, $25,828

New Interceptor Sewer, $18,663

Clean Watershed Needs Survey Report, 2012

Numbers in Million dollars!

Provide sustainable sewer collection system

No or less FOG formation and deposition

Causes no SSOs related to FOG

FOG Formation Mechanism

Saponification reaction

Fat, oil and grease are semi-solid or liquid at room temperature

85% of FOG Samples contained calcium ion

Fat or Oil (Triglycerides)

FOG formation = Solidification of FOG inside sewer lines?

LCFFAs – Long chain free fatty acids Calcium ion

Hydrolysis Free fatty Acids Glycerol

Calcium ion Calcium Soap WaterFree fatty Acids

FOG Formation Mechanism

FOG on water

surface

Slow chemical hydrolysis inside

sewer lines FFA (Free Fatty Acid)

Saponification

Calcium ion (Ca2+)

Wastewater Concrete

FOG on water

surface

Laboratory Based FOG Formation

He et al. 2013. Water research, 47, 4451-4459.

• Synthetic laboratory wastewater made with different fatty acids, Canola oil and distilled water

• No calcium added!

Concrete is made of• Binder (Cement + water)• Aggregate (coarse and fine)

Cement- when hydrates

C3S + H2O → CH + CSH

C2S + H2O → CH + CSH

Bad glue Good glue

Cement constituents areC3S – Tri-calcium silicatesC2S- Di-calcium silicatesC3A- Tri-calcium aluminatesC4AF- Tetra-calcium aluminoferrites andCaSO4- gypsum

Aggregates

Calcium hydroxide Calcium silicate hydrates

• Around 20-25% of cement hydrates is CH

• Around 75-80% of cement hydrates is CSH

Leaches calcium faster under corrosive media or pure water

Leaches calcium slowly under corrosive media or pure water

Alternative Binder Benefits

Our goal

• Reduce CH• Increase CSH

How?

• Add Pozzolans• Pozzolanic reaction: Pozzolans coverts CH into CSH

Silicates from Pozzolans + CH → CSH

PozzolansFly ashMetakaolinSilica FumeSlagCalcinated Shale

Image from inindianawater.org

Merom coal plant and ash pond in Indiana

Image from sain.nbii.govKingston fly ash pond spill, Tennessee

Why Fly Ash?

Byproduct of coal fired power plant

Why Fly Ash?

Byproduct of coal fired power plant

Inexpensive and available

Why Fly Ash?

Byproduct of coal fired power plant

Inexpensive and available

Has pozzolanic properties – converts CH into CSH

Why Fly Ash?

Byproduct of coal fired power plant

Inexpensive and available

Has pozzolanic properties – converts CH into CSH

Provides concrete durability

Methodologies and Test Results

Methodologies

Two high volume fly ash cement paste and one pure cement paste sample-

CP0FA – 0% fly ash + 100% cement

CP50FA – 50% fly ash + 50% cement

CP75FA – 75% fly ash + 25% cement

Test Conducted

Thermogravimetric analysis (TGA) test

Test ConductedDissolution or Leaching test

pH meterAcid supply

Stirrer

Sample

Available CH% in samples• Increasing trend of CH

content for CP0FA as hydration period increases.

• Decreasing trend for CP50FA and CP75FA indicates effective pozzolanic reaction between cement and fly ash.

0

5

10

15

20

25

30

0 50 100 150C

H, g

ram

per

gra

m o

f bin

der (

%)

Hydration period (days)

100% cement + 0 % fly ash

50% cement + 50% fly ash

25% cement + 75% fly ash

Calcium Leaching100% cement + 0 % fly ash100% cement + 0 % fly ash

50% cement + 50 % fly ash

0

5

10

15

0 10 20 30 40 50

Cum

ulat

ive

calc

ium

leac

hing

(mg/

l/g)

Time (Days)

50% cement + 50 % fly ash

100% cement + 0 % fly ash

25% cement + 75 % fly ash

Compressive Strength

42 44

23

0

10

20

30

40

50

CP0FA CP50FA CP75FA

Com

pres

sive

Stre

ngth

(MP

a)

• CP75FA- low compressive strength

• Durable• Cheaper• Applicable to low

strength structures

Reduced FOG formation

100 % cement concrete 25 % cement + 75% fly ash concrete

Nothing that attached to the surface!

Summary

Use of FA to replace cement in concrete structures-cost effective sustainable solution

Clean Watershed Needs Survey-Total need in replacing sewer lines is $42,072M

Therefore, for the replacement of sewer lines, alternative binders will be effective to fight FOG related SSOs

Thank You

Any Question?

Saponification reaction between

LCFFAs – Long chain free fatty acids

and

Calcium ion

85% of FOG Samples contained calcium ion1

Ducoste et al 2008,

FOG Formation Precursors

Fat or oil

Calcium ion

Surface for deposition

Sources of Calcium-

• Wastewater• Sewer line construction material corrosion

Goal

Reduce CH

Increase CSH

How?

Add Pozzolans- Fly ash, metakaolin, silica fume etc.

Pozzolanic reaction: Pozzolans coverts CH into CSH

Silicates from Pozzolans + CH → CSH

Alternative binder materials and its application in concrete sewer structures for possible reduction in Fat, Oil and Grease related Sanitary Sewer OverflowsSlide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Why do we need to study and fight FOG now more than ever?FOG Formation MechanismSlide Number 11FOG Formation MechanismLaboratory Based FOG FormationSlide Number 14Alternative Binder BenefitsSlide Number 16Slide Number 17Slide Number 18Why Fly Ash?Why Fly Ash?Why Fly Ash?Why Fly Ash?Methodologies and Test ResultsMethodologiesTest ConductedTest ConductedAvailable CH% in samplesCalcium LeachingCompressive StrengthReduced FOG formationSummaryThank You��Any Question?Slide Number 33Slide Number 34FOG Formation PrecursorsSlide Number 36