AN ADVANCED URBAN WATER MANAGEMENT CONCEPT: GRAYWATER SEPARATION

Sybil SharvelleSeptember 11, 2008

Separate Graywater Plumbing Graywater is relatively clean compared

to blackwater On-site residential reuse

Landscape irrigation Storage and coarse filtration

Toilet Flushing Minimal Treatment

Pathogen inactivation TSS reduction

Current Wastewater Management

WWTP

Energy & $$$

N & P

GraywaterBlackwater

Graywater Separation

GraywaterBlackwater

Anaerobic Digester

Green Energy

Compost

High NLow Pathogen

Advantages of Graywater Separation Reduced load to wastewater

treatment plant Reduced capital costs Reduced energy requirements

Water conservation Preservation of source waters

Water quality improvements

Recent Current and Studies at CSU

Research on a residential graywater system

Review of the literature on “Long Term Effects of Residential Landscape Irrigation using Household Graywater

Pilot testing the Effects of Residential Irrigation using Household Graywater

Wetland treatment of graywater Pilot studies on reuse of graywater from

university residence hall

Need for Water Reuse

Source: CO Department of Public Affairs, State Demographers Office, June 2003

Graywater Production

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

Household Graywater Production

(family of four, gpd)

- Bath 4.8 - Shower 46.4 - Washer 60.0- Faucets 43.6- Other 6.4

TOTAL 161 gpd 1128 g/wk

- Toilets 74 gpd 518 g/wk

- Irrigation 610 g/wk

(waters 300 plants or 1000 ft2 of grass)

Residential Reuse Potential

Greywater Generation of 87 gpcd

Cost Savings

($ per year)

Volume Reduction

(Gallons)

Cost Savings

($ per year)

Volume Reduction

(Gallons)

Bath, Shower 25,920 - - $51.48 21,451

Washing Machine 5,400 - - $2.23 931

Toilet Flushing 5,040 $6.30 5,040 - -

Outdoor Use 18,360 $22.95 18,360 - -

Totals $29.25 23,400 $53.72 22,382

Estimated Annual Per Capita Reduction in Demand and Treatment

SourceVolume

(Gallons per year)

Drinking Water Demand Waste Water Treatment

Waste Water Treatment $2.40/1000 gal

Drinking Water Treatment $1.25/1000 gal

Fort Collins Population 250,000 (2000 Census)

Million $ per year

Million GallonsMillion $ per

yearMillion Gallons

$7.31 5,850 $13.43 5,596

Graywater Quality

Constituent Range (mg/L)COD 77 – 240BOD 26 – 130TSS 7 – 207

NH4-N 0.02 – 0.42NO3-N <0.02 – 0.26Total-N 3.6 – 6.4Tot-P 0.28 – 0.779

Total coliform (CFU/100 mL)

6.0 x 103 –

3.2 x 105

Source: Eriksson et al., 2003

Application of Graywater for Household Irrigation

Course Filter

Storage Tank

Household Graywater Drip Irrigation

Graywater System

Irrigation well coarse screen

Graywater Irrigation

Pilot Testing on a National Scale

Application of Graywater for Household Irrigation

Many households use graywater for irrigation Current regulations are not based on science

Legal in California, New Mexico, and Arizona (not Colorado)

In depth studies on fate of graywater constituents and effects to plant health required to make informed decisions about graywater irrigation

Study funded by WERF and US Soap and Detergent Association to Examine the Long Term Effects of Using Household Graywater for Irrigation

Graywater Irrigation Project

Graywater Irrigation Project

3-year duration Samples collected at households with

systems in place for more than5 years New systems installed at households in

each state and monitored for three years Parameters Studied

Surfactants Antimicrobials Pathogens Plant health General soil quality parameters

Some Forward Thinking at CSU

Treat graywater in wetlands and combine with stormwater runoff for reuse non-potable needs (decentralized treatment and reuse)

Blackwater collection and treatment for water reuse and energy generation

Location for Graywater Treatment Lagoons

Graywater, Labwater and Blackwater Lines in Atmospheric Sciences Laboratory at CSU

The Wetlands Under Construction

Planting the Wetlands

Latest Graywater Application to a University Residence Hall

One floor (14 residential units) plumbed with: Graywater (sinks, showers, laundry)

separated from blackwater Toilets water supply separate from potable

water lines Experiments

Use raw (irrigation) water to flush toilets Use conditioned graywater to flush toilets

and for irrigation

Summary on Graywater

Graywater is a great source of water for reuse applications Not highly contaminated

Graywater use for irrigation has many benefits Water conservation Contains important nutrients for plant growth

WERF funded research will provide ability to make informed decisions about graywater use for irrigation

Sources: Palmquist & Hanæus 2004 & Eriksson et al. 2003

Separate Graywater: What Happens to Wastewater Characteristics?

Graywater Blackwater Domestic WWConsituent Range (mg/L) Range (mg/L) Range (mg/L)

COD 77 – 240 806 - 3138 250 - 800BOD 26 – 130 410 - 1400 160 - 300TSS 7 – 207 920 - 4340 390 - 1230

Total-N 3.6 – 6.4 130 - 180 20 - 70Tot-P 0.28 – 0.779 21 - 58 4 - 12

Treatment Options

• Aerobic– High removal of organic carbon, nitrification– Pathogens still present

• Extensive disinfection required for reuse– High oxygen requirements

• Anaerobic– Generation of methane – renewable energy– Pathogen inactivation

• Water reuse after treatment (high nitrogen content)– Removal of organic carbon – Higher maintenance

A Word on Waste to Energy

Anaerobic digesters are well developed technology for conversion of high BOD wastes to energy Generation of methane by bacteria from

carbon under anaerobic conditions Rise in prices and demand for renewable

energy has resulted in renewed interest

Urban Applications

Anaerobic digesters good method for blackwater treatment when graywater is utilized for irrigation or treated by wetland Water can be collected and treated for

potential reuse Can be combined with local industrial and

food processing wastes for increased methane potential

Anaerobic Digestion

High BOD Waste

Organics Acids

Acids CH4

High NutrientLow Odor

Waste

Anaerobic Environment

Cogeneration

Hot Water

CH4

Green Power

AD Energy Generation

For a neighborhood with 100 households, anaerobic digestion would produce enough energy to offset waste treatment energy requirements and 5% of energy requirements for the neighborhood 3 persons per household 60 gal/cap/day wastewater (40% blackwater) Household Energy Use: 33,595 kWh / year

Supplement with other alternative energy sources (wind, solar, etc.)

Questions?