A study was conducted to determine the applicability of a swirl concentrator chamber to perform the functions of a grit separation and removal facility. The ability of the swirl flow pattern to effectively remove solids of particular sizes or specific gravities was noted during the first study. This hydraulic flow configuration was developed and adapted to effectively remove grit from either the underflow from the combined sewer overflow regulator or from domestic sanitary sewage. Hydraulic model studies were used to develop optimum design configurations. The efficiency of removing grit particles of 2.65 sg and size greater than 0.2 mm will be equal to that of conventional grit removal devices. The unit has no moving parts. Conventional grit washers and lifts can be employed. The complete report on studies carried out on a swirl grit removal model by the LaSalle Hydraulic Laboratory Ltd. is included as an appendix.

Prepared by American Public Works Association, Chicago, Ill., under project 11023 GSC (S-802219) program element 1BB034. Includes appendices. Includes bibliographical references (p. 92).

Conclusions, recommendations and overview -- The study. Grit removal, basic principles and practices ; The APWA study -- General features and design. Basic criteria of grit and porganix constituents of inflow ; Flow rate, -- Implementation -- Glossary of pertinent terms -- Appendix A. Hydraulic model study -- Appendix B. The Geiger grit chamber / (translated from the German) -- Appendix C. Scale effects on particle settlement.