METHOD AND APPARATUS FOR BIOLOGICAL TREATMENT OF SPENT CAUSTIC

摘要

The invention provides a method and apparatus for biologically treating a spent caustic to provide a treated spent caustic, said method comprising the steps of : (a) passing a spent caustic stream (25) comprising water, alkali metal hydroxide and sulphide to a first bioreactor (30); (b) biologically oxidising sulphide in the first bioreactor (30) with sulphide-oxidising bacteria to form sulphur (S0) and sulphate to provide a partially oxidised spent caustic comprising sulphur (S0) and sulphate; (c) passing the partially oxidised spent caustic to a second bioreactor (40) where at least a portion of the partially oxidised spent caustic is further oxidised with sulphide-oxidising bacteria to generate sulphate from sulphur (S0) to provide a treated spent caustic comprising sulphate.