Constructed Wetlands for greywater reuse
Greywater includes all the domestic wastewater generated from a house excluded those from the toilet (called black water); therefore, grey water represents the majority of the potable water daily used by us and is much less polluted in comparison to black water. Constructed wetlands are recognized among the ideal techniques to treat greywater near the houses, without discharging them into public sewer and unlocking the potential of greywater reuse for activities requesting not potable water (e.g., irrigation, recharge of toilet flushing tanks, antifire, pavement cleaning).
Advantages 
- high removal efficiencies of organic pollutants and pathogens
- simple realization and functioning
- simple maintenance
- low CAPEX in comparison to compact technological solutions
- very low OPEX
- possibility to reuse treated greywater
- multiple possibilities of landscaping: gardens, terraces, roofs
Courtesy Jaime Nivala
More information
Greywater represents about 70% of the water consumed in houses. In comparison with blackwater, greywater is less polluted and easier to be treated and reused.
Greywater reuse
Since greywater is easy to be treated, they are valuable non-conventional water for uses not requiring potable water quality, such as:
- irrigation
- flushing toilet
- fire prevention system
- pavement cleaning
Role of constructed wetland
Constructed wetlands are one of the most promising nature-based solutions for the treatment and reuse of greywater, due to the following advantages:
- high removal efficiencies of organic pollutants and pathogens
- simple realization and functioning
- simple maintenance
- low CAPEX in comparison to compact technological solutions
- very low OPEX
- multiple possibilities of landscaping: gardens, terraces, roofs
Horizontal flow constructed wetland (HF) is one of the most adopted solutions for treatment and reuse of greywater, providing:
- organic load removal efficiencies of 80–90%, absolutely adequate for greywater treatment
- efficient disinfection
- simple construction and management
Due to the low pollutant load of greywater, nature-based solutions do not give any odour issue and are suitable for both indoor and outdoor application. Therefore, indoor CW can be also seen as an interesting occasion for aesthetic improvement of indoor spaces.
Example of outdoor CW for treatment and reuse of greywater (WC flushing), serving a small residential area of 280 inhabitants (Preganziol - TV, Italy), designed by IRIDRA
Example of indoor CW for treatment and reuse of greywater (WC flushing and gardening), San Francisco Public Utilities Commission: the “Living Machine” (USA)
Green wall pilot plant sited in Maharashtra Jeevan Pradhikaran head office (Pune - India) for treatment and reuse of greywater. Designed by IRIDRA and realized under the European funded project NaWaTech
References
IRIDRA's authors are highlighted in bold.
Masi F., El Hamouri B., Abdel Shafi H., Baban A., Ghrabi A., Regelsberger M. “Segregated black/grey domestic wastewater treatment by Constructed Wetlands in the Mediterranean basin: the Zer0-m experience”, Water Science & Technology, 61, 1, 97-105, 2010. doi:10.2166/wst.2010.780.
Masi, F., Bresciani, R., Rizzo, A., Edathoot, A., Patwardhan, N., Panse, D. and Langergraber, G. Green walls for greywater treatment and recycling in dense urban areas: a case-study in Pune. Journal of Water Sanitation and Hygiene for Development, , 2016.
Scheumann R., Masi F., El Hamouri B., Kraume M., “Greywater treatment as an option for effective wastewater management in small communities”, Desalination and Water Treatment, 4, 33–39, 2009.
