Weeping walls are the most common method of passive solid separation. Raw effluent in a bunker is held in beds, effluent is separated by walls which are generally constructed of wooden slats or plastic panels. Liquid will seep through the gaps in the walls, leaving the solid effluent behind in the sludge bed. Effluent solids removed from sludge beds are generally a wet semi-solid effluent product. This Farmfact highlights some of the key features of a passive solids separator, and the pros and cons of this type of system.