Disintegration of flushable wet wipes

DISINTEGRATION OF
FLUSHABLE WET WIPES IN
WASTEWATER SYSTEMS
Fatih KARADAGLI, Ph.D.
Associate Professor
Department of Environmental Engineering
Sakarya University, Turkey
ORGANIZATION
BACKGROUND AND RESEARCH PROBLEM
PHYSICAL CHARACTERIZATION OF WET WIPES
PHYSICAL DISINTEGRATION
Theory, Mathematical Modeling, and Experimental Testing
TRANSLATION OF RESULTS TO SEWER SYSTEMS
CONCLUSIONS AND FUTURE
Time
line
2001-2003
Team
Collaborator
Goal
Prof. Bruce E.
Rittmann and Fatih
Karadagli (Graduate
Student) of
Northwestern University
Dr. Drew C. McAvoy of
Environmental R&D
Departmant at Procter and
Gamble Co.
1- Theoretical and mathematical model
development for physical disintegration
2- Experimental testing with tampons
1- 3-Dimensional flow modeling of the shakeflask experimental system,
2004-2007
Prof. Bruce E.
Rittmann and Dr.
Fatih Karadagli
Dr. Drew C. McAvoy,
and John E. Richardson
of Blue Hill Hydraulics,
Inc.
2007-2011
Dr. Fatih Karadagli
and Mr. Beytullah
Eren
Meral Tirak and Besim
Kaplan of GeorgiaPacific-Eczacibasi (Turkey)
Disintegration of toilet papers in wastewater
systems
2014-
Dr. Fatih Karadagli,
Dr. Beytullah Eren
Prof. Bruce E. Rittmann,
Biodesign Institute at
Arizona State University
Disintegration of flushable wet wipes in
wastewater systems
2- Estimation of flow velocity, kinetic energy,
and Reynold’s number of fluid motion in the
experimental system
Flushable Wet Wipes
Product variety
Baby cleansing
Toddler wipes
Product Structure or Composition
Cellulosic fibers (wood, tencel)
Cotton fiber
Patient wipes
Adult wipes
Latex fiber
Binding chemicals
Feminine wipes
Facial cleansing
Fragrances
Flushable Wet Wipes – North America
Flushable Wet Wipes - Europe
Adverse Effects In Sewer Networks
•
•
•
•
•
Food waste – Fat, oil, and grease (FOG)  FOG deposits
Detergents, cleaning agents, personal care products
Water flow characteristics – flow rate and velocity
Pipe characteristics – slope, diameter, and pumping stations
In streets – Sanitary sewer overflows
• Rainfall and surface debris, root penetration,
By courtesy of
Mr. Barry Orr,
Wastewater treatment
operations
City of London
Consequences and Problems
50,000 SSOs and 400,000 basement backups per year in the USA
Microbial & Chemical Threats : Chlorea, Giardasis,
Chryptosporidiosis, and Hepatitis
Financial problems due to cloggings and equipment failures
Research Questions

How do wet wipes disintegrate?

Can we identify disintegration patterns?

Do sewer systems support transport and disintegration of
wipes?

Environmental feedback to manufacturers

Consumer expectations vs. environmental impacts
Characterization of wet wipes
Physical disintegration
Translation of results to sewer systems
CHARACTERIZATION
OF WET WIPES
SAMPLES OF FLUSHABLE WIPES FROM NORTH AMERICA
Product Category
Brand Name
Product Name
Manufacturer /
Distributor
Baby
Pampers
Kandoo
P&G
Baby
Charmin
Freshmates
P&G
Adult
Scott
Scott Naturals
Kimberly-Clark
Adult
Cottonelle
FreshCare
Kimberly-Clark
Adult
Cottonelle
Ultra ComfortCare
Kimberly-Clark
Adult
Kirkland Signature
Moist Flushable Wipes
Costco
Adult
GreatValue
Flushable Wipes
Walmart
Adult
Equate
Flushable Wipes
Walmart
Feminine
Equate
Personal Cleansing Cloths
Walmart
Patient
Tucks
Medicated Cooling Pads
McNeil-PPS
Patient
Equate
Hemorrhodial Pads
Walmart
Patient
Preparation H
Medicated Wipes
Wyeth Consumer
Healthcare
SAMPLES OF FLUSHABLE WIPES FROM EUROPEAN UNION
Country
Brand Name
Product Name
Manufacturer / Distributor
Austria
Clever
Feuchtes toilettenpapier
Pantos Productions- und Vertriebsges
Austria
Quality First
Feuchtes toilettenpapier
Albaad Deutschland GmbH
Austria
Tempo
Sanft & Pflegend
SCA
Austria
Hakle
Clean Comfort
Kimberly-Clark/Hakle
Austria
Hakle
Natütlich pflegend
Kimberly-Clark/Hakle
Germany
Favora
Kamille Feuchtes toilettenpapier
Albaad Deutschland GmbH
Germany
Favora
Sensitiv Feuchtes toilettenpapier
Albaad Deutschland GmbH
Germany
Hakle
Clean Comfort
Kimberly-Clark/Hakle
Germany
Hakle-Cottonelle
Pure Sensitive
Kimberly-Clark/Hakle
Hungary
Alouette
Kamille Feuchtes toilettenpapier
Dirk Rossmann Co.
Holland
Albert Heijn
Voching ToiletPapier
Albert Heijn Co.
Italy
Fria
Carta Igienica Umidificata
Diva International S.r.i, Spello (PG)
Finland
Lambi
Kosteuspyyhe
Metsa Tissue Oyj
France
Nivea Baby
Toddies
Beiersdorf
France
Pampers
Kandoo
P&G
England
Andrex
Washlets To Go
Kimberly-Clark
England
Sainsbury’s
Flushable Toilet Tissue Wipes
Sainsbury’s Supermarket Ltd
England
Tesco
Moist Toilet Tissue
Tesco Stores Ltd
SAMPLES OF FLUSHABLE WIPES FROM FAR EAST
(JAPAN, CHINA, AND SOUTH KOREA)
Product Category
Brand Name
Product Name
Manufacturer /
Distributor
Adult
Haso
Adult sheets
Haso Ltd.
Baby
Haso
Skin-care baby wipe
Haso Ltd.
Adult
Pigeon
Habisasu
Pigeon Ltd.
Baby wipes
Pigeon
Baby wipes
Pigeon Ltd
Physical Properties Used for Categorization
Sheet mass (g)
Sheet surface area (mm2)
Thickness of a sheet
Sheet volume (mm3)
Basis weight (g/m2): Weight per surface area = Sheet mass / sheet surface area
Specific volume (dm3/kg): Volume per unit mass = Sheet volume/sheet
mass
Thickness Measurements
Physical Properties of Flushable Wet Wipes from North America (as received)
I.D.
Sheet Mass
(mg/sheet)
Surface Area
(Length x Width)
(mm2)
Basis Weight
(g/m2)
Sheet
Thickness
(µm)
Sheet
Volume
(mm3)
Specific
Volume
(dm3/kg)
Range
1830 - 5807
4475 - 27440
170-616
227 - 611
2099 - 8206
1.0 – 1.6
Average
4513
19982
265
351
6385
1.4
NA-SN-4
4889
23680
206
305
7218
1.5
Adult – SFT
NA-SN-6
4571
23607
194
316
7448
1.6
Adult
Additional
Info.
Physical Properties of Flushable Wet Wipes from North America (dry state)
I.D.
Sheet Mass
(mg/sheet)
Surface Area
(Length x Width)
(mm2)
Basis Weight
(g/m2)
Sheet
Thickness (µm)
Sheet Volume
(mm3)
Specific
Volume
(dm3/kg)
Moisture
(%)
Range
307-1797
4416-26030
59-92
263-712
2069-14015
4.1-7.8
63 – 86
Average
1332
18861
72
440
7809
6.0
72
NA-SN-4
1797
22196
81
631
14015
7.8
63
NA-SN-6
1631
22125
74
449
9943
6.1
64
Physical properties of flushable wipe samples from European
Countries (as received)
I.D.
Sheet Mass
(mg/sheet)
Surface Area
(Length x Width)
(mm2)
Sheet Volume
(mm3)
Specific
Volume
(dm3/kg)
Range
2853-5196
19998-26880
117-244
150-397
3343-9314
0.8-2.7
Average
4363
23384
188
297
6952
1.6
EU-SN-14
3943
22154
178
255
5654
1.4
Basis Weight Sheet Thickness
(g/m2)
(µm)
Additional
Info.
Toddler wipe
Physical properties of flushable wipe samples from European
Countries (dry state)
I.D.
Sheet Mass
(mg/sheet)
Surface Area
(Length x Width)
(mm2)
Sheet Volume
(mm3)
Specific
Volume
(dm3/kg)
Moisture
(%)
Range
1020-1599
19500-25350
48-69
174-378
4128-8836
3.7-6.8
61-76
Average
1335
22323
60
299
6650
5.0
69
EU-SN-14
1052
20200
52
352
7114
6.8
73
Basis Weight Sheet Thickness
(g/m2)
(µm)
PHYSICAL DISINTEGRATION
Theory
Physical disintegration is controlled by

Solid characteristics – density, fiber matrix, mechanical strength –
represented with disintegration rate coefficient (k)

Turbulence in water – shear forces that break up solids – represented with
Reynold’s Number (Re) = depth(d)·water velocity(v)·density(ρ)/ viscosity(µ)
Time = 0
Main product
Time = t1
Intermediate size solids
Time = t2
Small size solids
Size Ranges:
Main
Product
(>12 mm)
(8-12) mm
f1
(4-8) mm
f2
f3
8-12 mm
f4
f5
4-8 mm
f6
(<4) mm
MATHEMATICAL MODEL
Mass Balance Equations for a Batch System:
d
[

12
mm
]


k
Re[

12
mm
]
1
dt
d
[(
8

12
)
mm
]

f
k
Re[

12
mm
]

k
Re[(
8

12
)
mm
]
1
1
2
dt
d
[(
4

8
)
mm
]

f
k
Re[

12
mm
]

f
k
Re[(
8

12
)
mm
]

k
Re[
4

8
)
mm
]
2
1
4
2
3
dt
d
[(

4
)
mm
]

f
k
Re[

12
mm
]

f
k
Re[(
8

12
)
mm
]

k
Re[(
4

8
)
mm
]
3
1
5
2
3
dt
MATHEMATICAL MODEL

The model has been tested previously with tampons and
toilet papers

It should capture disintegration of wet wipes

We conducted experiments with various wipe samples to
obtain for disintegration coefficients (k) and distribution
ratios (fj)

We used the model to capture disintegration patterns of
the wipe samples
Disintegration
Experiments
Representative Discharge Rates of Wet
Wipes and Water
WIPE DISCHARGE RATES:
Average of 1 sheet, and a maximum of 2 sheets per flush (4-6) L.
WATER DISCHARGE RATES:
Minimum of 1 and maxium of 5 flushes per person per day.
4-6 litres of water per flush, and, 4 to 30 litres of water per person per day.
Maximum - 2 sheets are discharged with one flush (4-6) L per day:
2 sheets / 4 L = 0.5 sheet / L – Experimental testing
Experimental case: 2 sheets with 1 flush (4 L) of water
EXPERIMENTAL TESTING
½ Sheet of Wet Wipe
1 L tap water into 2.8 L Fernbach
Flask
Rotating Shaker - Turbulence
Sampling – Wet Sieve Analysis
Sampling - Wet Sieve Analysis
Dry mass measurements
12 mm
8 mm
Experimental Results

Day 0
Day 9
Day 5
Day 10
Day 0
Day 3
Day 6
Day 10
Intermediate and small size
solids (47%)
Large size solids = Intact main
product (53%)
After 3 hours
EXPERIMENTAL AND MODELING
RESULTS
Experimental and Modeling Results
PRODUCT: F-NA-No-4 (0.5 sheet/L at 200 rpm)
A
B
C
D
Disintegration rate coefficients and fractional distribution ratios
PRODUCT: F-US-No-4
Fractional distribution ratios (fi)
ki·Re
8 - 12 mm
4 - 8 mm
<4 mm
Total
(hour-1)
%
%
%
%
> 12 mm
0.5
75
15
10
100
8 - 12 mm
1.24
25
75
100
4 - 8 mm
0.11
100
100
Solid size range
TRANSLATION OF RESULTS
TO WASTEWATER SYSTEMS
Comparison of Experimental
System to Sewer Environment

Comparison of turbulence levels in experimental setup (200 rpm) to
those of partial flow conditions in sewer pipes

Compute and compare Re numbers between the two systems
%60
%10
Turbulence levels in sewer pipes
Turbulence levels in rotating fluid in
the experimental system
Estimated Parameters
Mean Kinetic Energy:
KEmean = ΣmiVi2 / M
Average velocity:
(a)
(b)
Vave = SQRT (KEmean)
Reynold’s Number:
Re = Vave· d · ρ / µ
(c)
(d)
Re Numbers for 1 L water rotating at 64-300 rpms
90000
80000
y = 270.28x - 1135.2
R² = 0.9407
70000
Re Number
60000
50000
40000
30000
20000
10000
0
0
50
100
150
200
250
300
Rotations
per minute
rpm (1/minute)
Re at 200 rpm =>
Re = 270,3*(200) – 1135,2 => Re = 52900
350
Representative Sewer Pipes
Pipe type
Diameter
(inches)
Notes
Household drains
4-6
Small sewer pipes
8-12
8 inch is the smallest sewer pipe in
the USA
Mid-size sewer pipes
15-20
Suitable for city streets with low
population density, e.g., Tempe,
Mesa
Mid-to-large size sewer pipes
24-40
Suitable for densely populated
streets
Reynold’s Number for wastewater flow in pipes
Re = (v·r·w) / 
Where v: flow velocity, r: hydraulic radius, : wastewater density, and : viscosity
Manning’s Equation for flow velocity:
v = (1/n) · r(2/3) · s(1/2)
Where n: pipe coefficient, r: hydrualic radius, and s: pipe slope
%60
%10
Pipe Diameter
Hydraulic radius (rpartial) (cm)
Flow velocity at partial flow (vpartial) (cm/sn)
% 10 fill-ratio
% 60 fill-ratio
% 10 fill-ratio
% 60 fill-ratio
(rpartial-10)
(rpartial-60)
(vpartial-10)
(vpartial-60)
6 – 15
0,95
4,16
0,94
0,71
8 – 20
1,27
5,55
0,88
0,68
12 – 30
1,91
8,33
0,88
0,68
15 – 40
2,54
11,10
0,93
0,68
18 – 45
2,86
12,49
0,90
0,66
20 – 50
3,18
13,88
0,87
0,65
24 – 60
3,81
16,65
0,91
0,65
28 – 70
4,45
19,43
0,94
0,65
32 – 80
5,08
22,20
0,94
0,68
(inch - cm)
Pipe Diameter
(inch - cm)
Re Number
Corresponding Rotational Speed
(dimensionless)
(1/minute)
Minimum
Maximum
Minimum
Maksimum
6 – 15
8840
29209
37
112
8 – 20
10070
39582
45
151
12 – 30
16562
56283
65
212
15 – 40
23485
75138
91
282
18 – 45
25572
81814
99
307
20 – 50
27484
89054
106
334
24 – 60
34280
106643
131
399
28 – 70
41211
125934
157
470
32 – 80
47265
148678
179
554
Re value in our experimental system (52900) is comparable with average Re
value (49200) of waste water flow in small-to-mid size sewer pipes
Conclusions and Future

Only a few wipe samples disintegrate completely, while most
wipes show partial or no disintegration

Building drains (D: 4-6 inches) and small sewer pipes (D: 8-20
inches) are critical parts of sewer networks where disintegration
will be limited under most flow conditions.

In most sewer pipes (D: 20 – 40 inches), wet wipes will
disintegrate very slowly under low flow conditions as in summer
days.
Conclusions and Future

Performance criteria and standards must be developed for
flushable products to ensure sustainability of wastewater
systems

Consumer expectations must be evaluated along with
environmental concerns to optimize a product’s functional
and environmental performance.
Conclusions and Future

Disintegration rate coefficients and fractional distribution ratios can be
integrated into existing sewer models to predict how flushable products will
behave in sewer systems. Below is an example for tampons.
PUBLICATIONS
Water Environment Research, 2009, 81 (5), pp. 459 - 465
Water Environment Research, 2012, 84 (5), pp. 424 - 433