Abstract: Process for purifying and filtering fluids, especially water, containing suspended contaminants and using gravity separation means as well as membrane separation means, in a finishing stage, comprising the step of introducing a pulverulent reagent into the fluid stream to be treated downstream of the gravity separation and upstream of the membrane separation, wherein said pulverulent reagent is recycled from the purge of the membrane separation means to the upstream of the gravity separation means.

Abstract: A method of changing operating modes in automatic water filtering apparatus comprising inside-skin tubular membrane modules for filtering water, the possible filtering modes being: dead-end filtering; cross-flow filtering; and cross-flow filtering with continuous purging; both cross-flow filtering modes including recirculation in a loop; wherein two types of triggering are provided for filter membrane backwashes, a first one of said types being related to time periods between two backwashes, which time periods are predetermined for each mode of filtering, and a second one of said types being related to reference values of an operating parameter of the automatic apparatus, which values are predetermined for each mode of filtering; with the mode of filtering being changed after a backwash has been triggered in response to one of the reference values, with changes taking place in the following order: dead-end filtering, cross-flow filtering, cross-flow filtering with continuous purging, or vice versa.

Abstract: A method of backwashing bundles of inside-skin tubular filter membranes in modules, in which:a circuit is provided so that dead-end mode filtering takes place with the tubular membranes being fed from one end while cross-flow mode filtering takes place with the tubular membranes being fed from the other end, thereby ensuring in both cases that the major portion of the matter stopped by the membranes collects in the same relatively small zone in the bundles of membranes contained in the modules;water is drawn off from the periphery of the modules; andbackwashing is performed in two stages: a first stage in which all of the backwashing water is used for cleaning said relatively small zone and in which the recirculation loop that enables cross-flow filtering to be performed is closed; and a second stage in which the backwashing water is caused to pass through all of the membranes and all the recirculation loop.Apparatus for implementing the method is also described and is shown in FIG.