I suggest to edit the client.cfg file found inside the "cfg folder" located in the main root of the game and edit the following lines (Could use notepad,etc... I prefer Wordpad since it organized and easier to find)
save the file once this is done. This will allow SweetFX to manage all the effect.
Download SweetFX with configurator included here:
use the configurator to install SweetFX into the games root, once you've installed the mod use the "save/load configuration" tab and either search for the preset or drag into the preset list on the left. Select the preset click on "load" tab and done. DO NOT LAUNCH GAME USING THE CONFIGURATOR!!! Use steam instead; if you got everything installed properly you will be able to turn on/off the mod by clicking "ScrollLock" key on the keyboard.