Abstract: According to the present invention a new device is provided for preparing biocide solutions of constant concentrations. More specifically, solid biocide is dissolved, in a controlled and monitored way, to provide solutions, all having the same and constant dose of biocide per volume. The new device overcomes the main disadvantage of the existing solid-biocide feeders, namely the decrease in the biocide concentration with time due to the gradual depletion of solid biocide in the feed container.

Abstract: A method and apparatus for retrofitting existing waste water treatment facilities having at least one existing basin including installing generally vertical partitions at spaced locations in the at least one existing basin in order to divide the at least one existing basin into a plurality of treatment stage regions, installing at least one air lift in each of the plurality of treatment stage regions, loading each treatment stage regions with a quantity of floatable porous particles, supplying waste water to at least one of the plurality of treatment stage regions and allowing the waste water, but generally not the particles, to flow from at least one of the plurality of treatment stage regions to at least another of the plurality of treatment stage regions and operating the at least one air lift in each of the plurality of treatment stage regions to provide aerobic waste water flow therein in operative engagement with the floatable porous particles.