Experiences of treating graywater by soil natural treatment systems have not been widely reported. In general terms, graywater has a lower concentrations of organic matter; nutrients (e.g. nitrogen), and microorganisms than combined wastewater; therefore, the graywater treatment capacity of soil should be evaluated. In this study, the performance of a natural soil treatment system was evaluated when shower graywater from a house located at Sapporo City, Japan, was treated by a layer of 30 cm of soil from the Hokkaido University Campus. Results showed very high removal efficiencies of chemical oxygen demand (98%) and Kjeldahl nitrogen (95%) at high infiltration rates (214 cm/d), which denotes that natural soil treatment systems could be a good alternative to treat lower load graywater.

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