The Applicability of the Wastewater Treatment Plant in Othfresen as Scientific Documentation of the Root-Zone Method

Abstract

Up to the present time documentation for the functioning of the root-zone method is almost exclusively based on data from the Othfresen plant in Western Germany, a 22.5 ha large wetland, which since 1974 has received municipal wastewater. The present paper describes the working experiences from Othfresen, and evaluates the applicability of the data from Othfresen as basis for the scientific documentation of the root-zone method in general. It is concluded that the data from Othfresen are useless in the documentation of the root-zone method for the following reasons: (a) The loaded area has not until 1985 been well-defined, (b) the soil in the treatment plant is very atypical (old mine debris), (c) a major proportion of the wastewater does not penetrate the soil, but distributes on the surface as overland flow, (d) the quality of the water in the “defined” outlet, i.e. a well consisting of a PVC-tube, has no relation to the treatment of wastewater in the area, and (e) the true effluent to the recipient is of varying quality, especially as far as nitrogen is concerned. It is therefore necessary to await results from well-controlled experimental treatment plants before the functioning and the applicability of the root-zone method can be properly evaluated.