A waste water treatment system for processing to accommodate the excess waste water overflowing from the sewer system comprises the parts of the screen arrangement disposed on the second portion of the container and the container with the first portion of the first and the second for receiving the waste water of the sewage system. A support structure for supporting the screen with a plurality of screen arrangement screen portion, and the support structure includes a bump is disposed higher than the screen between the screen to catch the debris carried by the waste water. The system further includes a discharge flow path that is in fluid communication with the second portion of the agent dispenser and the container for the injection agent in the waste water. If the rainfall is sufficient, the waste water flows into the container from the sewer system, there is introduced into after having passed through the screen arrangement portion discharge passage, wherein waste water after passing through the first portion of the container in a first direction, is distinct from the first direction, in a second direction and it passes through a second portion of the container. Treatment agent dispenser is operated to introduce the treating agent in order to sufficiently sterilize at least a portion of the effluent, the screen is arranged transversely with respect to the array portion in the first direction. Waste water treatment systems, sewer systems, public sewage, excellent treating agents.