Removal of hydrogen sulphide from wastewater and waste gases by biologicalconversion to elemental sulphur - Colloidal and interfacial aspects of biologically produced sulphur particles

The biological oxidation of hydrogen sulphide by aerobic Thiobacillus-like bacteria has been described. The hydrogen sulphide is oxidised into sulphur particles which are in the submicron range. The colloidal properties of th ese sulphur particles are compared with those of a standard LaMer sulphur s ol. The biologically produced sulphur particles are composed of a core of e lemental sulphur covered by a layer of natural charged polymers, presumably proteins. The polymer layer renders the particles hydrophilic. Colloidal s tability can be attributed mainly to steric repulsion. Although the electro kinetic charge is always negative with varying pH, the point of zero charge is found at pH 5.8. This indicates that the polymeric molecules are orient ed with their negative charges to the bulk solution. An expanded-bed reacto r was developed in order to stimulate the aggregation of the sulphur partic les into large, well-settleable sulphur flocs with a diameter of about 3 mm . (C) 1999 Elsevier Science B.V. All rights reserved.