Abstract: A hollow, floatable, hydrodynamically shaped member supports a screen in canopy-like fashion and is secured to a harness for being lowered into and raised from an effluent stream such as in a closed sewage system. The member floats on the stream and floating substances therein are collected by the screen for subsequent analysis or the like, as may be required for pollution control or related purposes. The harness includes a line for tethering the floatable member so that said member rises and falls with the rising and falling of the stream level. The hollow, floatable member has a removable cap, whereby ballast can be added or removed for adjusting the buoyancy thereof.