Embed Size (px)
Citation preview
Assessment of the effects of greywater reuse on gross solids
movement in sewer system
Roni Penn 1 Eran Friedler 1 , Manfred Schütze 2
1
1. Environmental, Water & Agricultural Eng.Faculty of Civil & Environmental Eng.
Technion – Israel Institute of TechnologyHaifa, Israel
2. ifak- Institut fuer Automation und KommunikationMagdeburg, Germany
IntroductionShortage of fresh water is a serious worldwide
problem
Domestic consumption
70%
Greywater (GW)
60-70%
DarkKitchen sink Dishwasher
Washing machine?
Urban consumption (Israel)
Over 700*106 m3/year- The sector consuming the largest amount of freshwater
LightBath
Shower Washbasi
n
2
Blackwater
30-40%
Toilets
Potential reduction of GWR
Toilet ~ 30%
Toilet +garden irrigation ~ 40%
IntroductionGWR research focused, on a single-house scale, on recycling
systems and possible sanitary and environmental affects.
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
Effects on domestic WW quantity and quality, on urban
wastewater collection systems and on urban wastewater
treatment plants (WWTP)
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
Introduction
“GWR” home “Conventional” home
GW SourceGW SourceGW Source
GW SourceToilet
flushingGW Source
Selected for reuse Not reused
On-site
treatment
SludgeScumetc
Blackwater
Garden irrig.
Overflow
Sewer
WWTP
GW SourceGW SourceGW Source
GW SourceGW SourceGW Source
GW SourceToilet
flushingGW Source
Selected for reuse Not reused
On-site
treatment
SludgeScumetc
Blackwater
Garden irrig.
Overflow
Sewer
WWTP
GW SourceGW SourceGW Source Toilet
flushing
Raw GW
Not reused
Sewer
WWTP
Blackwater
GW SourceGW Source
GW SourceGW SourceGW Source Toilet
flushing
Raw GW
Not reused
Sewer
WWTP
Blackwater
GW SourceGW Source
A B
5
Types of homes contributing
WW
6
Effect of GWR- quantity and quality
effectsQuantity 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
7
Flat
densely populated
coastal area
neighborhoods sewer pipes ~
6 km
Separate sewer
15,000 residents
SIMBA
6
The chosen neighborhood
Scenarios examined
Currentsituation
Extreme situation
To be expected
1 2 3 4 5
GWR type& penetration proportion
(1) NR
100% 0% 0% 70% 70%
(2)RWC
0% 100% 0% 30% 15%
(3)RWC+IR
0% 0% 100% 0% 15%
Separate sewer systems,
Sludge released at 8:00,
Toilet flush volume: (1) 9L full,
6L half
(2) 6L full, 3L
half
Effects of GWR on:
sewer blockages?
• Flow characteristics• Gross solids movement
Diurnal patternLINK 36 LINK 97 LINK 71 LINK 154
FR
OU
DE
[-
]F
LO
W
[m3/m
in]
VE
LO
CIT
Y
[m/s
]P
RO
PO
RT
ION
AL
D
EP
TH
(d
/D)
[-]
00.5
1
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1.4
1.2
1
0.8
0.6
0.4
0.2
00.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1.4
1.2
1
0.8
0.6
0.4
0.2
0 0 4 8 12 16 20 24T [h]
0 4 8 12 16 20 24T [h]
0 4 8 12 16 20 24T [h]
0 4 8 12 16 20 24T [h] 9
Gross solid transport
GWR domestic WW - reduces flows with in the sewer
system – reduced higher rate of blockages?
Upstream: based on model by Walslki et al., 2011.
Downstream: based on model based on tractive force
(TF) (Walski et al., 2004.)
Upstream Downstream
Flow Intermittent More steady
Solids Larger,un-submerged
Smaller, submerged
different approaches for each part of the sewer:
10
11
SG specific gravity S slope of pipe Q flow (L/s) V volume of pulse (L)a 0.45: full - partial movement a 18: full - partial movement
0.25: no movement - partial movement 10: no movement - partial movement
𝑸= 𝒂𝑺𝑮/𝑺𝟎.𝟐
Pulse to move solid with attenuation, short duration
Flow to move solid no attenuation, long duration
𝑽=𝒂𝑺𝑮 /𝑺𝟎 .𝟐
Gross solid transport – upstream (Walslki et al., 2011)
36
48
57
97
107
71
85
154
85
Outlet pipe
𝟑 .𝟓×𝟑×
Gross solid transport - upstream
0.020.220.76
0.280.390.33
00.060.94
0.110.380.51
00.140.86
0.180.360.46
0.270.380.35
0.020.210.77
0.750.030.21
0.820.050.13
0.660.10.24
0.780.040.17
0.850.050.1
0.780.030.19
Critical Tractive Force TF (Walski et al., 2004)
Average boundary tractive stress
𝝉=𝝆 𝒈𝑹( 𝑺𝟏𝟎𝟎 ) 𝝉𝒄=𝒌𝒅
𝟎 .𝟐𝟕𝟕
K 0.867 (N/m2) d diameter (mm) for a discrete design sand particle
of 2.7 specific gravity
• For: discrete grit particle
• Transported often enough
tractive stress (Pa), density of liquid (kg/m3) R hydraulic radius (m)
13
Gross solid transport - downstream
d=6mm =1000 𝝆
Modeling gross solid transportGenerator
module
SIMBA
Velocity
Conclusions
Gross solid transport:
Upstream linksSmall amounts of WW discharged
no GWR 67% of the day full / partial
movement
GWR
76% of the day no movement
Middle linksadditional houses
discharge WW
Higher proportions of the day for full
movement
Downstream links
full movement in all scenarios
GWR: toilet flushing: saves ~25% of the water consumption
GWR: toilet flushing & irrigation: saves ~40%
Higher GWR:
• d/D decrease connect additional homes to existing
sewers
construct smaller systems
Highest reduction – peak usage hours
•Instantaneous: Q, V, (d/D) decrease
