Abstract: The invention relates to a method and a system for controlling a membrane separation unit of an aqueous liquid effluent treatment plant comprising a system for injecting at least one chemical compound into the effluent to be treated. The method and the system allow regulating at least one parameter selected from an amount of chemical compound(s) to be added and a conversion rate in order to avoid clogging and/or precipitation of ionic species in the retentate. This regulation uses optimum setpoint values determined according to one or more parameter(s) characteristic of the retentate and not of the water to be treated. Thus, an accurate regulation of the amount of chemical compound(s) to be added and/or of the conversion rate of the membrane separation unit at an optimum value allowing at the same time avoiding clogging and/or precipitation of the species likely to precipitate and minimising the operating costs is achieved.

Abstract: The invention relates to an expanding device for combining a liquid species and a particulate solid species, which includes a vessel 200 in which a stirrer 800 having paddles that rotate about a shaft 810 is arranged, the stirrer being optionally provided with a flow guide tube 210, wherein the vessel 200 also includes a static obstacle 830 that is generally centred around said shaft and aligned with the stirrer, characterised in that the static obstacle 830 has, in a plane passing through the shaft, an outer transverse dimension that increases as it moves away from the stirrer 800 parallel to said shaft 810, having a constant or increasing slope relative to said shaft.