Abstract
The method of land disposal was subjected to a field test. An irrigation of wastewater was kept continued from January 1972 to June 1977 at a mean rate of 3001/ (m-trench-d). The soil permeating water was sampled by three soil-permeating-water sampling devices set at a depth of 120 cm and analyzed together with original wastewater. The average removal of nutrients in soil permeating water based on the original wastewater was registered as 95.0% biological oxygen demand (BOD), 50.6% total nitrogen (T-N), and 87.2% total phosphorus (T-P). Soil samples were collected from the wastewater permeating area at each 50-cm-mesh point in the range of 50 to 280 cm in depth and of 600 cm in width and analyzed together with soil samples collected from the control plot. The concentration of T-P in soil samples increased significantly in the region directly below trench 1 (T1) in the range of 60 to 100 cm in depth as compared with that in the control plot. However, no remarkable increase in the concentration of T-N and total carbon (T-C) could be observed even in the soil samples collected from directly below T1.
