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Study from Ben-Gurion University compares treated to non-treated greywater
Researchers at the Ben-Gurion University of the Negev (BGU) Zuckerberg Institute for Water Research published a new study in Chemosphere that shows reusing greywater in dry areas may require treatment for more efficient irrigation in arid sandy soils. Greywater includes any wastewater generated in households or office buildings except from the toilet. Greywater use has been proven safe for agriculture irrigation.
"Most of the scientific research and legislation efforts have focused on greywater's health risks, while less attention has been given to its environmental outcomes, including its effect on soil properties," said Amit Gross, head of the Department of Environmental Hydrology and Microbiology in the Zuckerberg Institute.
Gross and his team found that greywater does not infiltrate through the soil as easily as freshwater and is slower to reach plant roots. It also can cause water runoff leading to erosion.
"This condition, called ‘greywater-induced hydrophobicity,’ is likely temporary and disappears quickly following rainwater or freshwater irrigation events,” Gross said. “However, it is a more significant concern in arid lands with negligible rainfall as compared with wetter regions.”
According to the researchers, treating the greywater using biofiltration to degrade the hydrophobic organic compounds will eliminate the problem. In the study, the researchers examined how greywater induces soil hydrophobicity, as well as its degree and persistence. They created three greywater models using raw, treated and highly treated greywater to irrigate fine-grained sand compared to a freshwater control. The result was that only the raw greywater irrigated soil showed hydrophobicity, which could be mitigated with both moderately and highly treated solutions.
“Onsite reuse of greywater for irrigation is perceived as a low-risk and economical way of reducing freshwater use and as such, it is gaining in popularity in both developing and developed countries," Gross said. “As many government authorities are establishing new guidelines, the results of this study reinforce the recommendations to treat greywater before reusing for irrigation, particularly in arid regions.”
Other researchers who collaborated on the study were Ph.D. candidate Adi Maimon of the Department of Environmental Hydrology and Microbiology and Arye Gilboa of the French Associates Institute for Agriculture and Biotechnology of Drylands. Together with the Swiss Institute for Dryland Environmental and Energy Research, the institutes comprise BGU’s Jacob Blaustein Institutes for Desert Research on its Sede Boqer Campus.