Abstract: This invention relates to a novel low operating head polishing sand filter comprising: (a) a plural-layer media bed comprising small, medium and large crushed quartzite; (b) an untreated water inlet system; (c) an underdrain system; (d) a filtered water collection and outlet system; and (e) a backwash water inlet, collection and siphon outlet system.

Abstract: This invention relates to a novel intermittent slow sand filter and a method of using the intermittent filter. More particularly, this invention pertains to a novel slow sand filter which remains effective, even when intermittently operated, and which can be periodically cleaned without disturbing the action of the intermittent filter.

Abstract: An intermittently operating slow sand filter uses the damming of water in a raised pipe to provide a constant level of water in a slow sand filter container. The container includes a water inlet and outlet, and is partially filled with sand or other filter material. A pipe from the water outlet in the slow sand filter is raised upward to the desired level of water over the sand before descending to a water reservoir. Water backs up in the pipe and the container to the desired level above the top of the sand, even when the flow of water is intermittent. The schmutzdeuke forms at the top of the filter medium. The water level in such a manually operated slow sand filter, using fine quartz sand as the filter medium, and at ambient temperatures (about 21.degree. C.) is maintained above about 1 cm above the top of the filter medium and below about 8 cm above the top of the slow sand filter.