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Assessment of the effects of greywater reuse on gross solids movement in sewer system

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.

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Assessment of the effects of greywater reuse on gross solids movement in sewer system

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  1. Assessment of the effects of greywater reuse on gross solids movement in sewer system Roni Penn 1 EranFriedler 1 , Manfred Schütze 2 1. Environmental, Water & Agricultural Eng. Faculty of Civil & Environmental Eng. Technion – Israel Institute of Technology Haifa, Israel 2.ifak- Institutfuer Automation und Kommunikation Magdeburg, Germany

  2. 70% Domestic consumption 30-40% 60-70% Blackwater Greywater(GW) Toilets Dark Light Kitchen sink Dishwasher Washing machine? Bath Shower Washbasin 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 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. B A Types of homes contributing WW “GWR” home “Conventional” home

  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 SIMBA 6 • Flat • densely populated • coastal area • neighborhoods sewer pipes ~ 6 km • Separate sewer 7

  8. Scenarios examined Effects of GWR on: Separate sewer systems, Sludge released at 8:00, Toilet flush volume: (1) 9L full, 6L half (2) 6L full, 3L half • Flow characteristics • Gross solids movement sewer blockages? 8

  9. 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 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 0 4 8 12 16 20 24 T [h] 0 4 8 12 16 20 24 T [h] 0 4 8 12 16 20 24 T [h] 0 4 8 12 16 20 24 T [h] Diurnal pattern LINK 36 LINK 71 FLOW [m3/min] LINK 97 LINK 154 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 0 VELOCITY [m/s] 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 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 PROPORTIONAL DEPTH (d/D) [-] 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 FROUDE [-]

  10. Gross solid transport GWR domestic WW - reduces  flows with in the sewer system – reduced higher rate of blockages? • 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. Gross solid transport – upstream (Walslkiet al., 2011) Pulse to move solid with attenuation, short duration Flow to move solid no attenuation, long duration 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. 0.27 0.38 0.35 0.28 0.39 0.33 • Gross solid transport - upstream 0.85 0.05 0.1 0.02 0.22 0.76 0.78 0.03 0.19 0.02 0.21 0.77 0.82 0.05 0.13 0.78 0.04 0.17 0.18 0.36 0.46 0.11 0.38 0.51 0.75 0.03 0.21 0.66 0.1 0.24 0 0.14 0.86 0 0.06 0.94

  13. Gross solid transport - downstream • Critical Tractive Force TF (Walski et al., 2004) • Average boundary tractive stress K 0.867 (N/m2) d diameter (mm) for a discrete design sand particle of 2.7 specific gravity tractive stress (Pa), density of liquid (kg/m3) R hydraulic radius (m) • For: discrete grit particle • Transported often enough d=6mm 𝝆=1000

  14. Modeling gross solid transport Generator module Velocity SIMBA

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

  16. THANKS FOR LISTENING! • QUESTIONS?

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