Abstract: The present invention is a dual-stage, gravity continuously-backwashed filtering system for filtering contaminants from wastewater. This filtering system has a first sand-filter unit that is loaded with wastewater influent. The filtering sytem has injection points for coagulation chemicals and disinfection chemicals. The first sand-filter unit is connected in series to a second sand-filter unit of similar design. The first sand-filter unit is made up of large-grained sand, the second sand-filter unit fine-grained sand. The second sand-filter unit receives its influent from the effluent weir of the first sand-filter unit. The reject water from the second filter unit is re-introduced into the influent that is fed to the first filter unit. The reject matter from the first filter unit is passed to waste.