Abstract: A hand tool for sifting soil in gardens, recovering buried articles and for other similar purposes where aggregate materials are to picked up and filtered to separate larger particles from smaller sized granules and powders. The device comprises essentially a "Y" shaped frame with the single end extended as a handle and with the forked end forming a triangular container open at the top with two sides similar, a straight, approximately flat blade supported at each end by the ends of the frame, the blade being the third side of the container, and a bottom planar surface perforated to allow the passage of materials. The tool can be made in different sizes and with different kinds of perforated surfaces, depending upon the purpose and size of particles to be retained.

Abstract: Apparatus and method for periodic backwashing and inoculating with anaerobic denitrifying bacteria a columnar filter bed in a waste water treatment system. A minor portion of backwash water containing a substantial quantity of denitrifying bacteria is retained for return to the filter bed media by gravity flow after completion of the backwash cycle. The apparatus and method have particular utility in an activated sludge sewage treatment system the effluent from which contains nitrates (converted from organic nitrogen and ammonia) and suspended solids which are removed in a filter bed comprising several discrete layers of filter sand of different particle sizes supported on coarse gravel.