The efficiency of sewage treatment in the ground bed under the subsurface sewage disposal field was tested in laboratory conditions using synthetic sewage. The ground bed was composed of dusty sand. The experiment determined the following indicators: suspended solids, BOD₅, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, phosphates and pH. In the sewage filtered through the ground bed a considerable increase in the concentration of nitrate nitrogen was observed. The values of other indicators of the treated sewage were within the standard range.

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