| 摘要 |
PURPOSE:To surely prevent the contamination of underground water, by packing the bottom part of a trench having a cut-off tank with sand and forming a gravel layer on the sand and further forming a soil layer thereon. CONSTITUTION:When waste water having received purification treatment is supplied to a water sprinkling pipe 15 from an excretion treatment apparatus, said waste water is gravitationally penetrated into a sand layer 13 from a gravel layer 19 through-holes 14 and further penetrated into soil around a trench 1 from the sand layer 13 by capillary siphon action and a part thereof is evaporated into the open air from the ground surface GL. The remainder is penetrate to be replenished to underground water. Waste water is subjected to decomposition treatment by soil bacteria during penetration through the gravel layer 17 and soil.
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