CE292A_Fall 2009 1

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

CE 292A – Technologies for Sustainable Communities

Fall 2009

Diego Cobos RoaRyan Casey

October 12, 2009

CE292A_Fall 2009 2

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

Contents

•Introduction

•Description of System

•Quality of Greywater

•Current Practices

•Advantages and Disadvantages

•Application Example

•Conclusions

CE292A_Fall 2009 3

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

Contents

•Introduction

•Description of System

•Quality of Greywater

•Current Practices

•Advantages and Disadvantages

•Application Example

•Conclusions

CE292A_Fall 2009 4

Introduction (I)Current Wastewater Management

WWTP

Energy & associated cost

Nutrients and Phosphorous

Graywater ~60-70% of total producedBlackwater

CE292A_Fall 2009 5

Introduction (II)Alternative Wastewater Management

WWTP

Reduced Energy & associated cost

Nutrients and Phosphorous

Graywater ~60-70% of total producedBlackwater

Tre

atm

ent

CE292A_Fall 2009 6

Introduction (III)Alternative Wastewater Management for Isolated Homes

Anaerobic Digester

Energy Production

Graywater ~60-70% of total producedBlackwater

Compost Production

Wetl

and

CE292A_Fall 2009 7

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

Contents

•Introduction

•Description of System

•Quality of Greywater

•Current Practices

•Advantages and Disadvantages

•Application Example

•Conclusions

CE292A_Fall 2009 8

Description of System

Leaks9.5 gal/cap/d,

13.7%

Dishwashers 1.0 gal/cap/d,

1.4%

Faucets 10.9 gal/cap/d,

15.7%

Clothes Washer 15.0 gal/cap/d,

21.6%

Bath 1.2 gal/cap/d,

1.7%

Toilets 18.5 gal/cap/d,

26.7%

Other Domestic 1.6 gal/cap/d,

2.3%Shower

11.6 gal/cap/d, 16.7%

Source: AWWARF (2006)

Source Greywater Production, gal/d (L/d)

Bath 4.8 (1.3)

Shower 46.4 (12.2)

Washer 60.0 (15.8)

Faucets 43.6 (11.5)

Other 6.4 (1.7)

Total 161 (42.5)

CE292A_Fall 2009 9

Description of System (II)

Sources

Treatment

End Use

Source: DWR (1995)

CE292A_Fall 2009 10

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

Contents

•Introduction

•Description of System

•Quality of Greywater

•Current Practices

•Advantages and Disadvantages

•Application Example

•Conclusions

CE292A_Fall 2009 11

Constituent Range (mg/L)

COD 77 – 240

BOD 26 – 130

TSS 7 – 207

NH4-N 0.02 – 0.42

NO3-N <0.02 – 0.26

Total-N 3.6 – 6.4

Tot-P 0.28 – 0.779

Total coliform (CFU/100 mL)

6.0 x 103 –

3.2 x 105

Quality of Grey water

Source: Eriksson et al (2003). Friedler (2004)

•Kitchen sink contributes with 58%, 42% and 48% of VSS, CODt and BODt, respectively•Washing machine contributes with 40% of the sodium total daily load, 37% of the phosphate, and 22% of CODt•Dishwasher contributes 5% of the flow, but has high concentrations of boron and phosphate•COD concentrations in greywater can reach 1,000 mg/l•Fecal coliforms of about 104 to 106 CFU/100ml can be produced in greywater

CE292A_Fall 2009 12

Quality of Grey water (II)

The composition of greywater depends on quality and type of available freshwater supply and household activities. Greywater can contain soaps, food particles, oil, hair, pathogens and traces of chemicals (Crites and Tchobanoglous, 1998).

The physical, chemical and biological characteristics of greywater of interest are:

•pH and alkalinity

•Salinity and Sodium Adsorption Ratio

•Biological and Chemical Oxygen Demand

•Nutrients (Nitrogen, Phosphorous)

•Microbial content

•Oil and grease

•Household chemicals

CE292A_Fall 2009 13

Quality of Grey water (III)

Treatment of Greywater for reuse

Treatment options depend of end use of water, as well as source of the influent (toilet or no toilet, irrigation and/or toilet flushing). Some common treatments are:

•Direct membrane filtration •UV disinfection•Settling basin•Stand alone sand Filtration •Sand filtration•Membrane Bioreactor (MBR)

•For buildings, where less ‘natural’ space is available (but more money):•Fine screen•Equalization basin•Rotating biological contractor (RBC)•Sedimentation basin•Prefiltration storage tank•Sand filtration•disinfection

CE292A_Fall 2009 14

Quality of Grey water (IV)

Example of treatment with RBC (Biological Treatment). From Friedler et al (2006)

CE292A_Fall 2009 15

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

Contents

•Introduction

•Description of System

•Quality of Greywater

•Current Practices

•Advantages and Disadvantages

•Application Example

•Conclusions

CE292A_Fall 2009 16

•EBMUD currently supplies 8+ million gpd for irrigation, from industrial and building facilities.

•By 2020, EMBUD plans to supply an additional 8 million gpd.

•Mostly used in golf courses and parks, but plans to use them in new residential developments in Oakland are underway, with the objective of recycling up to 30 gpd for the EBMUD coverage area (about 20% of the per capita usage).

•Current regulations were developed from the California Plumbing Code, but will shift toward a more technical standard as the understanding of the process improves.

Current Practices in California

CE292A_Fall 2009 17

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

Contents

•Introduction

•Description of System

•Quality of Greywater

•Current Practices

•Advantages and Disadvantages

•Application Example

•Conclusions

CE292A_Fall 2009 18

Advantages - Disadvantages

•Economic value of greywater.

•Reduction of freshwater use in households.

•Reduction of burden to wastewater treatment plants.

•Uses in developing countries.

•Quality.

•Initial investment.

•Risks related to inadequate greywater reuse.

CE292A_Fall 2009 19

Advantages - Disadvantages (II) – Cost of System

•For buildings, the price of a greywater treatment and reuse system can add up to 0.5% of the price for buildings of 20+ apartments (Friedler et al., 2006).

•For isolated houses (example in following slides), the proportional cost can be much higher depending on the type of treatment.

Source: Friedler et al. 2006)

The system is therefore more cost-effective in buildings and complexes, which is where the highest freshwater demand occurs.

CE292A_Fall 2009 20

Application

•Problem: Typical family creating a grey water system

•Given

•Layout•Idealized

•Area: 1600 sf•Usage: 997 gpw

Family 1st floor Average family

Source (gal/day) (gal/day)

Bath 0 4.8

Shower 75 46.4

Washer 98 60

Faucets 60 43.6

Total 233 154.8 40’

House

x

x

x

Lawn

T

40’

CE292A_Fall 2009 21

•Cost:•DIY installation•Local Shopping

•Cost-Benefit•Low water rates

•Conclusion•Not suited for this example•Case by case basis

•Lawn area•Cost of installation•Housing condition

Item Cost ($) unit one time recurring (yr)

Water Tank (305 gal)* 1 195 PVC (dia: 2") 8x10' 80

PVC accessories variable 20 Water Filter 1 54

Filter Cartridge 1 16 16Hose (dia: 5/8") 1 30

Submersible Pump** 1 50 Total 445 16

Analysis

Cost

Option one time ($)recurring ($/mo) Benefit ($/mo) Recoup time (mo)

1 0 7.5 0 2 445 1.3 7.5 50

CE292A_Fall 2009 22

GREYWATER AS AN ALTERNATIVE TO SAVE WATER

Contents

•Introduction

•Description of System

•Quality of Greywater

•Current Practices

•Advantages and Disadvantages

•Application Example

•Conclusions

CE292A_Fall 2009 23

•Proper use of greywater can contribute to lowering the increasing demand rate of freshwater, as well as decreasing the burden on wastewater treatment plants.

•Greywater can be used for landscape irrigation and toilet flushing, which generally does not require the same quality as drinking water.

•Economically, greywater systems become more cost-effective as the number of users per treatment unit increases.

•Most current treatments are physical (filtration + disinfection), but the practice is transitioning to adding biological components for urban environments.

•This is a relatively new practice, and cost of treatment and installation is expected to decrease in the following years.

•From an LCA standpoint, the determination of impact of a greywater system depends on the treatment required. In general, ‘natural’ treatment processes have lower environmental impact than membrane based technologies.