This work is a continuation of the study of a commercial size microstrainer, with chlorination and/or ozonation, treating combined sewer overflows. The original work covered 26 storms during the period 1/69 to 9/69 from an 11.2 acre residential drainage area in Philadelphia, Pa. A Crane-Glenfield microstrainer was used. The flow rate through the microstrainer was controlled at a variable rate proportional to the storm overflow rate. The present work was conducted to confirm the performance of the Microstraining unit and disinfection at high rate under more closely controlled conditions. The same facility was used. The disinfection procedure used in the second phase was developed to confirm the economically attractive high rate chlorination work of the first phase.