1. 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

2. 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
Domestic consumption
70%
Greywater (GW)
60-70%
Blackwater
30-40%
Toilets
Dark
Kitchen sink Dishwasher
Washing machine?
Light
Bath Shower Washbasin
Potential reduction of GWR
Toilet ~ 30%
Toilet +garden irrigation ~ 40%

3. 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?

4. 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

5. Types of homes contributing WW
“GWR” home
“Conventional” home A B

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. SIMBA 6 The chosen neighborhood 15,000 residents Flat
densely populated
coastal area
neighborhoods sewer pipes ~ 6 km
Separate sewer 7

8. Scenarios examined Separate sewer systems, Sludge released at 8:00,
Current
situation
Extreme situation
To be expected 1 2 3 4 5
GWR type
& penetration proportion
(1) NR
100% 0%
70%
(2)
RWC
30%
15%
(3)
RWC+IR
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:
Flow characteristics
Gross solids movement
sewer blockages? 8

9. PROPORTIONAL DEPTH (d/D) [-]
Diurnal pattern
LINK 36
LINK 97
LINK 71
LINK 154
FROUDE [-]
FLOW [m3/min]
VELOCITY [m/s]
PROPORTIONAL DEPTH (d/D) [-]
0.5 1 5
4.5 4
3.5 3
2.5 2
1.5
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
1.4
1.2
0.8
0.6
0.4
0.2
0.7
0.3
0.1
T [h]

10. 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.)

11. no attenuation, long duration with attenuation, short duration
Gross solid transport – upstream (Walslki et al., 2011)
Flow to move solid
no attenuation, long duration
Pulse to move solid
with attenuation, short duration
𝑽=𝒂𝑺𝑮/ 𝑺 𝟎.𝟐
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

12. Gross solid transport - upstream
0.02
0.22
0.76
0.28
0.39
0.33
0.06
0.94
0.11
0.38
0.51
0.14
0.86
0.18
0.36
0.46
0.27
0.38
0.35
0.02
0.21
0.77
𝟑.𝟓× 𝟑×
0.85
0.05
0.1
0.78
0.03
0.19
0.66
0.1
0.24
0.78
0.04
0.17
0.75
0.03
0.21
0.82
0.05
0.13

13. Gross solid transport - downstream
Average boundary tractive stress
Critical Tractive Force TF (Walski et al., 2004)
𝝉=𝝆𝒈𝑹 𝑺 𝟏𝟎𝟎
𝝉 𝒄 =𝒌 𝒅 𝟎.𝟐𝟕𝟕
d=6mm 𝝆=1000 𝒌𝒈/𝒎 𝟑
𝝉 tractive stress (Pa),
𝝆 density of liquid (kg/m3)
R hydraulic radius (m)
K (N/m2)
d diameter (mm) for a discrete design sand particle of 2.7 specific gravity
For: discrete grit particle
Transported often enough

14. Modeling gross solid transport
Generator module
SIMBA
Velocity

15. 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
Middle links
Downstream links
Small amounts of WW discharged
additional houses discharge WW
full movement in all scenarios
no GWR
GWR
Higher proportions of the day for full movement
67% of the day full / partial movement
76% of the day no movement

16. THANKS FOR LISTENING!
QUESTIONS?

17. Effects of GWR on domestic sewage
Parameter No
GWR WC
WC + Irrig
Flow
l/(cap·d)
138
102 81
COD load
g/(cap·d)
148
137
130
TSS load 87 85 83
NH4-N load
2.9
2.8
PO4-P load 10
9.8
Bio. + Phys. Treatment
(RBC) 17

18. SIMBA model
Hydrodynamic simulations- solves the full Saint Venant differential equations 18

19. SIMBA model
The subsystem for inflow to a single node in the hydrodynamic model 19

21. Diurnal pattern LINK 36 LINK 97 LINK 71 LINK 154 Concentrations COD
3500
3000
2500
2000
1500
1000
500 80 70 60 50 40 30 20 10
180
160
140
120
100
2400
2200
1800
1600
1400
1200
800
600
400
Concentrations
COD
[mg/l]
NH4+-N
TSS
PO43--P
T [h]

22. Gross solid transport - upstream
Velocity
Only solids with full movement
solids move <<< liquid
𝑽 𝒔 𝑽 𝒇 =𝟏.𝟗𝟓 𝑺𝑮 −𝟐.𝟓 𝑺 𝟎.𝟐𝟓 𝑸 𝟏.𝟐
Vs velocity of the solid (m/s)
Vf velocity of the liquid (m/s)

23. Conclusions Q, V, (d/D) - Two main peaks significant morning peak
smaller evening peak
COD & TSS concentrations - morning peak
NH4+-N & PO43- -P - night peak
Different use patterns of contributing appliances
A decrease in the daily maximum flow and an increase in the daily minimum flow were found as a result of the attenuation and shift in time of the flows occurring aseptically in long pipes, which are in this case, the links located at the outlet of the neighborhood.
When no additional wastewater is discharged to the sewer - the momentary, daily average and minimum values continue to increase, while the maximum values do not show a specific trend.
velocity - no specific patterns of its momentary, daily maximum, minimum and average increase/decrease were found, this is since the velocity is influenced by the flow and geometry of the pipes.
Further, low momentary velocities and proportional depth were found in links located upstream; this is because of the combination of the small pipe diameter and the small number of residents discharging their WW to those links. 23 23

24. Conclusions
GWR: toilet flushing: saves 26% of the daily water consumption
GWR: toilet flushing & irrigation: saves 41%
Higher GWR:
Instantaneous: Q, V, (d/D)  decrease
Highest reduction –
peak usage hours
Vmax > Vmin  low possibility of negative effect on blockages rate (?)
d/D decrease  connect additional homes to existing sewers
construct smaller systems (under some circumstances)
Pollutants loads  decrease (treatment)
Pollutants concentrations  increase (since higher decrease in flows)
Sludge release (in morning peak)  COD & TSS concentration peak (smaller peak in PO43--P)
daily average, maximum and minimum concentrations of the pollutants examined also increased. This was as a result of the decrease in flow and hardly any changes in the pollutants loads
Some decrease in the diurnal pollutants loads -in the peak water consumption times, aspectual in the morning.
Greater reuse – Greater reduction
The peak of the sludge release- accurse before the consumption peak 24 24

25. Conclusions Gross solid transport: Upstream links Middle links
Downstream links
Small amounts of WW discharged
additional houses discharge WW
full movement in all scenarios
Higher proportions of the day for full movement
no GWR
GWR
75% of the day full / partial movement
65% of the day no movement