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What is greywater?

Guidance for Greywater Use for Small-Scale Irrigation Nicola Rodda University of KwaZulu-Natal School of Life Sciences. What is greywater?. All non-toilet domestic wastewater: Bath / shower / handbasin Laundry Kitchen Toilet wastewater ( blackwater ) NOT included.

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What is greywater?

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  1. Guidance for Greywater Use for Small-Scale IrrigationNicola RoddaUniversity of KwaZulu-NatalSchool of Life Sciences

  2. What is greywater? • All non-toilet domestic wastewater: • Bath / shower / handbasin • Laundry • Kitchen • Toilet wastewater (blackwater) NOT included. • Some definitions also exclude kitchen wastewater. • Sewered areas: greywater represents about 75% of total wastewater.Unsewered areas: greywater represents up to 100% of total wastewater.

  3. Uncontrolled greywater is an environmental and health hazard. Photos K. Carden, UCT

  4. Why use greywater for irrigation? • Water scarcity. • Pressure on freshwater sources. • Potential benefit of greywater use for irrigation • environmental. • water, nutrients. • food security, informal employment.

  5. Concerns about the use of greywater for irrigation • Human health. • Plant growth and yield. • Ability of soil to support plant growth.

  6. Guidance for greywater irrigation • Guide to Managing Uncertainty and Risk • Greywater Quality: Guide to Greywater Constituents • Greywater Quality: Mitigation of Greywater Quality • Greywater Quantity: Guide to Irrigation Volumes

  7. Guide to Managing Uncertainty and Risk • A hazard becomes a risk only when people, plants or soil come in contact with it (exposure). • For example: • Hazard may be harmful microbes (‘germs’). Risk of illness exists if microbes are ingested by people. • To prevent the risk (illness) - remove microbes from greywater. - prevent microbes from coming into contact with hands or crops. - make sure that microbes on hands or crops are removed or killed.

  8. Guide to Managing Uncertainty and Risk • So risk can be managed by: • Removing hazards in greywater (improve quality). • Preventing people/plants/soil from coming into contact with hazards in greywater (exposure barriers).

  9. Guide to Managing Uncertainty and Risk • Three categories, depending on how risk is managed. Category 1: No greywateranalysis or treatment; Strict barriers to exposure. Category 2: Minimum greywateranalysis so that greywater quality is controlled; Slightly less strict barriers. Category 3: Full greywateranalysis; Least strict barriers.

  10. Category 1: No analysis or treatment Household level irrigation use No analysis; No treatment Kitchen greywater Laundry greywater Bath/shower/basin greywater Wash water Rinse water Can be used for irrigation in accordance with restrictions R1, Table 7.1 Not recommended for irrigation use

  11. Restrictions for Category 1 Restrictions relating to health impact • Do: • Wash hands and arms well with soap after handling greywater. • Use bathwater water and laundry rinse water only. • Use all greywater within 24 hours of collection. • Grow only non-food plants or food plants with crops that will be cooked before consumption. • Use irrigation methods that minimise contact of greywater with above-ground plant parts. • If using on lawns, avoid direct human contact for 8 hours after irrigation. • If using on crops, stop irrigating with greywater 2 weeks before harvesting. • Reduce volume of greywater per application if ponding occurs on surface of irrigated ground, or if water runs off the surface. • Wash all crops well in soapy water after harvest and dry in sunlight. • Peel and cook crops prior to consumption. • .

  12. Restrictions for Category 1 Restrictions relating to health impact • Do not: • Do not use greywater falling in this category of use restrictions for any form of communal gardening. • Do not use greywater if someone in the household has an infectious disease.

  13. Restrictions for Category 1 • Restrictions relating to impacts on plant growth and yield • Restrictions relating to soil and environmental deterioration

  14. Category 2: Minimum analysis Minimum analysis of greywater to be performed Communal greywater irrigation Greywater irrigation by a single household Y Is greywater irrigation feasible according to greywater generation rate? N Bath/shower/basin greywater Kitchen greywater Laundry greywater Minimum of mulch filter to reduce levels of solids and of oil and grease ? Y N Not recommended for irrigation use Y Does greywater comply with quality guidance for minimum analysis? N N Not recommended for irrigation use Is greywater going to be treated? Y Does greywater after treatment comply with quality guidance for minimum analysis? N Y Can be used for irrigation in accordance with restrictions R2 , Table 7.2

  15. Category 2: Minimum analysis • Same groups of restrictions as for Category 1, but less strict. • For example: This greywater can be used for communal gardens

  16. GreywaterQuality: Guide to GreywaterConstituents • Minimum analysis • Electrical Conductivity (EC) • Sodium Adsorption Ratio (SAR) • E. coli • pH • Full analysis • Minimum analysis plus • Boron • Chemical Oxygen Demand (COD) • Oil and grease • Suspended solids • Total inorganic nitrogen • Total phosphorus

  17. Greywater Quality: Mitigation of GreywaterQuality • Integrated mitigation practices (part of irrigation). • Greywater treatment systems.

  18. Greywater Quality: Mitigation of Greywater Quality Integrated mitigation practices: • Irrigation method. • Improvement of soil. • Leaching (rinsing with water). • Planting tolerant plants. • Accepting smaller/fewer crops. • Using greywater only when there is no rain.

  19. Rural / semi-rural small plots eThekwini Municipality

  20. Greywater treatment systems: Examples Tower gardens - Rural villages From Crosby C. (2005). The Water Wheel, January/February 2005, 10-13.

  21. ‘Agritubes’ – informal settlements eThekwini Municipality

  22. Greywater treatment: Mulch tower Buffalo City Municipality; UKZN pilot study

  23. Greywater treatment: Resorption bed, infiltration zone Buffalo City Municipality; UKZN pilot study

  24. The importance of people!! • Greywater use works only if the people using it are committed to making it work. • Commitment means: • Greywater use holds value for the users. • Users are involved from the beginning. • Users are given the information and training to use the system properly. • Users have somewhere to go with questions and problems.

  25. Acknowledgements • Funding • Water Research Commission • eThekwini Municipality • National Research Foundation • Stockholm Environment Institute • Research partners • Prof Neil Armitage and Mrs KirstyCarden, UCT • Students of School of Biological and Conservation Sciences (Life Sciences), UKZN • Lumka Salukazana, Siobhan Jackson , Preshanthie Naicker, Graham Taylor

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