In one embodiment, a method includes gasifying a fuel source using a first oxygen stream supplied from an air separation unit (ASU), discharging a gasifier blowdown from a gasification and scrubbing system configured to gasify the fuel source, generating a grey water from the gasifier blowdown, and biologically treating the grey water in a reactor using a second oxygen stream supplied by the ASU.

A separator for salts contained in a solution which is brought under supercritical conditions, with at least one salt filter which can retain therein salts initially contained in the solution and which are precipitated, including those in the form of micro- or nanoparticles. The operation of the salt separator makes it possible, if necessary, to heat the solution for conversion to a temperature ensuring the precipitation of the salts and their retention within suitable filters and then to separate the solution for conversion into a salt-depleted stream which is discharged from the separator and directed to a conversion reactor, in particular a gasification reactor, and, if appropriate, into a stream loaded with salts to be extracted in the form of a brin.