Assessment of the effects of greywater
reuse on gross solids movement in sewer
system
Roni Penn 1
Eran Friedler 1 , Manfred Schütze 2
1.
Environmental, Water & Agricultural Eng.
Faculty of Civil & Environmental Eng.
Technion – Israel Institute of Technology
Haifa, Israel
2.
ifak- Institut fuer Automation und
Kommunikation
Magdeburg, Germany
1
Introduction
Shortage of fresh water is a serious worldwide problem
Urban consumption (Israel)
Over 700*106 m3/year- The sector consuming the largest amount of freshwater
70%
Domestic consumption
60-70%
30-40%
Greywater (GW)
Blackwater
Toilets
Light
Bath
Shower
Washbasin
Dark
Kitchen sink
Dishwasher
Washing machine?
Potential reduction of GWR
Toilet ~ 30%
Toilet +garden irrigation ~ 40%
2
Introduction
GWR research focused, on a single-house scale, on recycling systems and
possible sanitary and environmental affects.
Effects on domestic WW quantity and quality, on urban wastewater
collection systems and on urban wastewater treatment plants (WWTP)
overlooked
Questions to be asked:
• What could be the effects of GWR on urban WW collection systems and on
WWTPs?
• Are these effects positive or negative?
• How will they change with increasing penetration of on-site GWR?
3
Introduction
GW can contain non negligible concentrations of organic and microbial
contamination.
 Treatment of GW before reuse
• Prevent sanitary and environmental hazards
• Prevent aesthetic disturbance
Within the urban environment, GW "demand" < GW "production"

Treat and reuse the less polluted GW streams (SH, BT and WB)

The more polluted  discharge to the urban sewer system
4
Types of homes contributing WW
“GWR” home
“Conventional” home
B
A
Selected for reuse
GW Source
GW Source
GW Source
Not reused
GW Source
GW Source
Not reused
GW
Source
GW
Source
GW
Source
GW
Source
GW Source
Toilet
flushing
Toilet
flushing
Blackwater
Blackwater
On-site
Raw GW
treatment
Overflow
Sludge
Scum
etc
WWTP
WWTP
Garden irrig.
Sewer
Sewer
5
6
Effect of GWR- quantity and quality effects
Quantity effects
Wastewater flows released to the sewer
reduced
wastewater flows in the sewer network
reduced
wastewater flows to the WWTP
reduced
Quality effects
Treatment changes the quality of the wastewater discharged to the urban
sewer
Reduced flows (less dilution?)
7
The chosen neighborhood
15,000 residents
 Flat
 densely populated
 coastal area
 neighborhoods sewer pipes ~ 6 km
 Separate sewer
7
Scenarios examined
Current
situation
GWR type
& penetration
proportion
(1)
NR
(2)
RWC
(3)
RWC+IR
Extreme
situation
To be
expected
1
2
3
4
5
100%
0%
0%
70%
70%
0%
100%
0%
30%
15%
0%
0%
100%
0%
15%
Separate sewer systems,
Effects of GWR on:
Sludge released at 8:00,
• Flow characteristics
• Gross solids movement
sewer blockages?
Toilet flush volume: (1) 9L full, 6L half
(2) 6L full, 3L half
Diurnal pattern
LINK 36
FLOW
[m3/min]
0.08
0.07
0.06
PROPORTIONAL VELOCITY
DEPTH (d/D) [-]
[m/s]
LINK 154
5
5
5
4.5
4.5
4.5
4
4
4
3.5
3.5
3.5
0.05
3
3
3
0.04
2.5
2.5
2.5
2
2
2
1.5
1.5
1.5
1
1
0.01
1
0.1
0.5
0
5
0.5
0.5
1.40
0
1.4
0
1.4
0
1.4
1.2
1.2
1.2
1.2
0.03
0.02
FROUDE
[-]
LINK 71
LINK 97
1
1
1
1
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0
0.7
0
0.7
0
0.7
0
0.7
0.6
0.6
0.6
0.6
0.5
0.5
0.5
0.5
0.4
0.4
0.4
0.4
0.3
0.3
0.3
0.3
0.2
0.2
0.2
0.2
0.1
0.1
0.1
0.1
0
1.4
0
1.4
0
1.4
0
1.4
1.2
1.2
1.2
1.2
1
1
1
1
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0
0
4
8 12 16 20 24
T [h]
0
0
4
8 12 16 20 24
T [h]
0
0
0.2
4
8 12 16 20 24
T [h]
0
0
4
8 12 16 20 24
T [h] 9
Gross solid transport
GWR domestic WW - reduces  flows with in the sewer system –
reduced  higher rate of blockages?
Upstream
Downstream
Flow
Intermittent
More steady
Solids
Larger,
un-submerged
Smaller,
submerged
different approaches for each part of the sewer:
Upstream:
based on model by Walslki et al., 2011.
Downstream: based on model based on tractive force (TF) (Walski
et al., 2004.)
10
Gross solid transport – upstream (Walslki et al., 2011)
Pulse to move solid
with attenuation, short duration
Flow to move solid
no attenuation, long duration
𝑽 = 𝒂𝑺𝑮/𝑺𝟎.𝟐
𝟎.𝟐
𝑸 = 𝒂𝑺𝑮/𝑺
SG
Q
a
specific gravity
flow (L/s)
0.45: full - partial movement
0.25: no movement - partial movement
S
V
a
slope of pipe
volume of pulse (L)
18: full - partial movement
11
10: no movement - partial movement
84
83 8
2
81
80
79
78
77
76
Ori
fice
Orif
ice
e
154
e
ific
Or
154
Outlet
pipe
85
71
0.85
0.05
0.1
0.78
0.03
0.19
12
5
11
11 3
2
99
10
0
98
27
28
26
𝟑×
24
21
59 58
22
20
57
56
19
55
5
3
2
85
695
68 1
67
50
52
4
85
48
0.78
0.04
0.17
0.66
0.1
0.24
48 45
46
47
49
1
8484
81
80
81
79
83 82
83 82
80
79
78
77
76
75
74
73
11 10 9
33 32
12
34
8
13 23
35
31
108
14
109
22
7
107
30 16 15
21
6
106
17 29
123
20
28
5
105
27
4
19
104
122
103
3
26
121
18
129
102
120
2 1
25
101
128
119
127
100
24
118
126
99
117
54 53
98
55
116
56
97
52
57
62 61 60
115
59 58
69
96
68 51
114
95
67
50
113
66
112
94
153
49
93 92
7065
152
91
151
64
150
90
48 45
149 146
46
63
148
8988
47
147
145
87
144139
86
143
138
142
137
140
141
136
135134
133
132
131
130
125
72 71 111 110
124
44 4
3
42
41
40 39
38
0
0.14
0.86
63
6
54
53
7
66
65
70
64
18
8
11 10
9
85
flow
n
i
a
M
tion
c
e
r
di
94
1
15 5933 92
91
15 2
15 1
90
14 104
14 9 6
89
88
14 8
1
7
45
87
14 13
86
9
4
14 13
3
8
14
13
14 2
7
01
41
13
6
13 13
5 4
13
13 3
13 2
13 1
0
62 61 60
97
96
95
97
25
14
13 23
12
154
57
11
4
ce
44 43
41
40 39
37
42
38
37
36
0.11
0.38
0.51
11
5
11
6
11
7
11
8
11
9
Orifi
0
0.06
0.94
12
6
12
7
12
8
10
4
10
3
10
2
10
1
107
1
12 21
912
0
4
30 15
16
17 29
31
15
0.28
0.39
0.33
12
2
4
85
33 3
2
15
4
15
0.02
0.22
0.76
34
35
10
10 8
75
1 91
72 71 11 10 07
74 7
12 1
3
10
4
6
12
3
10
5
ific
Or
0.18
0.36
0.46
36
Gross solid transport - upstream
0.27
0.38
0.35
36
0.02
0.21
0.77
𝟑. 𝟓 ×
Main flow 0.82
0.05
direction 0.13
0.75
0.03
0.21
Gross solid transport - downstream
Average boundary tractive stress
Critical Tractive Force TF (Walski et al., 2004)
𝝉 = 𝝆𝒈𝑹 𝑺 𝟏𝟎𝟎
𝝉𝒄 = 𝒌𝒅𝟎.𝟐𝟕𝟕
𝝉 tractive stress (Pa),
𝝆 density of liquid (kg/m3)
R hydraulic radius (m)
K
d
•
For: discrete grit particle
•
Transported often enough
0.867 (N/m2)
diameter (mm) for a
discrete design sand particle
of 2.7 specific gravity
d=6mm 𝝆=1000 𝒌𝒈/𝒎𝟑
13
Modeling gross solid transport
Generator
module
Velocity
SIMBA
Conclusions
GWR: toilet flushing: saves ~25% of the water consumption
GWR: toilet flushing & irrigation: saves ~40%
Higher GWR:
•Instantaneous: Q, V, (d/D)  decrease
Highest reduction –
peak usage hours
• d/D decrease  connect additional homes to existing sewers
construct smaller systems
Gross solid transport:
Upstream links
Small amounts of WW
discharged
Middle links
additional houses
discharge WW
Higher proportions of
no GWR
GWR
the day for full
67% of the day 76% of the day
movement
full / partial
no movement
movement
Downstream links
full movement
in all scenarios
THANKS FOR LISTENING!
QUESTIONS?
16