During a storm, rainwater runoff from impervious surfaces is gathered in a splitter box or diversion chamber to separate “first flush” flows. This chamber is adjacent to a primary sedimentation chamber which is generally sized to accommodate the full “first flush” volume. The filter cartridges are located within a filtration chamber down grade from the primary sedimentation chamber. In the wall separating these two chambers is connecting pipe that houses a non-fouling, polybutylene bladder valve. Solar and battery powered electronic controls inflate and deflate the bladder valve which acts to isolate and control when sedimentation, separation and filtration commence. Once the water is filtered, it is then discharged back into the environment.