The incoming waste stream is equally split and enters the top of the filter vessels. As the wastewater travels downward through the filter media, the solids become trapped in the media bed while the water passes through. The clean effluent exits through an outlet header for further treatment or discharge. As the solids build on the media, the pressure of inside the filter builds. At a certain pressure, the media has reached a loading capacity and needs to be back washed. The backwash mode reverses the flow of the water through one filter at a time. The water enters the bottom of the vessel which expands the filter media and releases the captured solids. Once all the vessels are back washed, the filter is back to its original filtration capacity.