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GREYWATER AS AN ALTERNATIVE TO SAVE WATER CE 292A – Technologies for Sustainable Communities

GREYWATER AS AN ALTERNATIVE TO SAVE WATER CE 292A – Technologies for Sustainable Communities Fall 2009 Diego Cobos Roa Ryan Casey October 12, 2009. GREYWATER AS AN ALTERNATIVE TO SAVE WATER Contents Introduction Description of System Quality of Greywater Current Practices

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GREYWATER AS AN ALTERNATIVE TO SAVE WATER CE 292A – Technologies for Sustainable Communities

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  1. GREYWATER AS AN ALTERNATIVE TO SAVE WATER CE 292A – Technologies for Sustainable Communities Fall 2009 Diego Cobos Roa Ryan 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 Energy & associated cost WWTP Nutrients and Phosphorous Graywater ~60-70% of total produced Blackwater CE292A_Fall 2009

  5. Introduction (II)Alternative Wastewater Management Reduced Energy & associated cost WWTP Treatment Nutrients and Phosphorous Graywater ~60-70% of total produced Blackwater CE292A_Fall 2009

  6. Introduction (III)Alternative Wastewater Management for Isolated Homes Energy Production Anaerobic Digester Wetland Compost Production Graywater ~60-70% of total produced Blackwater 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 Source: AWWARF (2006) CE292A_Fall 2009

  9. Description of System (II) Sources Treatment End Use CE292A_Fall 2009 Source: DWR (1995)

  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. Quality of Grey water • 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 Source: Eriksson et al (2003). Friedler (2004) 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. Current Practices in California • 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. 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. The system is therefore more cost-effective in buildings and complexes, which is where the highest freshwater demand occurs. CE292A_Fall 2009 Source: Friedler et al. 2006)

  20. 40’ Lawn 40’ x T House x x Application • Problem: Typical family creating a grey water system • Given • Layout • Idealized • Area: 1600 sf • Usage: 997 gpw CE292A_Fall 2009

  21. Analysis • 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 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. CE292A_Fall 2009

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