an advanced urban water management concept: graywater separation sybil sharvelle september 11, 2008
TRANSCRIPT
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
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
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
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
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
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.)