Abstract: A double screen or double-rack grate for use in the extra-fine screening of waste waters includes two rows of rods in laterally staggered arrangements with one row positioned behind the other in the direction of flow of waste water to be screened. Each rod of one row has a hydrodynamic cross section defined by a thickened head portion. Such row of rods is positioned downstream of a first row of rods including rods with substantially rotationally symmetrical cross sections.

Abstract: An interceptor for the continuous removal of solid matter from a mixture of solids and liquids includes a screening drum rotating while in operation in a given direction of rotation. The mixture is fed to the outer surface of the jacket of the drum, whereby the liquid enters the drum and solid matter remains on the outer surface of the drum jacket. A solids discharge device is provided adjacent the outer surface of the drum to remove deposited solid matter. At least the lower half of the screening drum is surrounded by a tank to which a mixture inlet is connected. A liquid outlet is connected to the interior of the screening drum. The level of the mixture in the tank is controlled in such a way that it is above the level of the cleansed liquid inside the screening drum. The mixture introduced into a flow chamber surrounding the drum jacket flows substantially in the same direction as the direction of rotation of the drum.

Abstract: A security bar rack for installation in the inlets or outlets of water-treatment plants or power stations comprises a number of hollow tubes. A conductive indicator element with uninsulated external surfaces is stretched within each tube and extends over its entire length. Each indicator element is provided with a separate monitoring circuit which actuates a signal element in a way that a detectable alarm signal is emitted if any change takes place in the dielectric condition of the indicator element/tube assembly. In addition a second signal element is provided which is controlled by the monitoring circuit so as to produce a detectable signal to indicate that the device is in a state of readiness to produce an alarm signal.

Abstract: An electric fish-scaring device for water inlet and extraction structures contains several main and counter-electrodes below the surface of the water and which are connected to a voltage supply unit. To monitor operation, at least one simulator electrode is positioned at a predetermined distance in front of the main electrodes.