The report highlights various types of SBRs, design considerations and procedures, equipment required, and experiences gained from practical applications. This report will help both designers and operators of SBRs understand how to use this technology successfully. The focus is on the application of fill-and-draw, variable volume, periodically operated, unsteady-state principles to activated sludge systems.  Research findings are presented, from both the laboratory and pilot and full scale SBRs. Also included is a description of trends for technological developments and a discussion of open questions regarding research, development, application, and operation.  Contents Introduction                          Fundamentals of Periodic Processes                          General Overview of SBR Applications                          Design of Activated Sludge SBR Plants                          Equipment and Instrumentation                          Practical Experiences                          Evaluation of SBR Facilities in Australia                           Evaluation of SBR Facilities in the USA and Canada                           Evaluation of SBR Facilities in Germany                           Evaluation of SBR Facilities in France                           Evaluation of SBR facilities in Japan   Scientific and Technical Report No. 10