(EP827430-A1)      Purificn. of water or soil contg. heavy metals comprises setting up conditions in the soil or water in which the microorganisms present will form hydrogen sulphide and opt. adding apathogenic, facultative anaerobics tolerant to heavy metals also, in order to form hydrogen sulphide which reacts with the heavy metals to form metal sulphides.    Nutrient or buffer salts, biologically utilisable carbon source cpds. and yeast (pref. a pre-culture with increased cell density) are added to the soil or water. The soil is covered with a surface sealing material. A carrier treated with sulphur vapour and seeded with microorganisms is added to the water.    In an example, 5 g of light brown soil contaminated with 1000 mg/kg PbCrO4 was added to an airtight vessel into which was added 4 ml of an aq. soln. contg. ca. 40 mg Na acetate, 5 mg Na ammonium hydrogen phosphate and 20 g colloidal sulphur. The vessel was sealed and left to stand for 8 weeks at room temp. during which period the soil changed to a black colour due to the formation of PbS.    ADVANTAGE -   Heavy metals present in a wide concn., temp. or pH range can be removed without the use of microorganisms which can cause illness in humans. The need to place the soil or water in a sarcophagus is eliminated.    (US5968359-A)      Purificn. of water or soil contg. heavy metals comprises setting up conditions in the soil or water in which the microorganisms present will form hydrogen sulphide and opt. adding apathogenic, facultative anaerobics tolerant to heavy metals also, in order to form hydrogen sulphide which reacts with the heavy metals to form metal sulphides.    Nutrient or buffer salts, biologically utilisable carbon source cpds. and yeast (pref. a pre-culture with increased cell density) are added to the soil or water. The soil is covered with a surface sealing material. A carrier treated with sulphur vapour and seeded with microorganisms is added to the water.    In an example, 5 g of light brown soil contaminated with 1000 mg/kg PbCrO4 was added to an airtight vessel into which was added 4 ml of an aq. soln. contg. ca. 40 mg Na acetate, 5 mg Na ammonium hydrogen phosphate and 20 g colloidal sulphur. The vessel was sealed and left to stand for 8 weeks at room temp. during which period the soil changed to a black colour due to the formation of PbS.    ADVANTAGE -   Heavy metals present in a wide concn., temp. or pH range can be removed without the use of microorganisms which can cause illness in humans. The need to place the soil or water in a sarcophagus is eliminated.    (EP827430-B1)      Purificn. of water or soil contg. heavy metals comprises setting up conditions in the soil or water in which the microorganisms present will form hydrogen sulphide and opt. adding apathogenic, facultative anaerobics tolerant to heavy metals also, in order to form hydrogen sulphide which reacts with the heavy metals to form metal sulphides.    Nutrient or buffer salts, biologically utilisable carbon source cpds. and yeast (pref. a pre-culture with increased cell density) are added to the soil or water. The soil is covered with a surface sealing material. A carrier treated with sulphur vapour and seeded with microorganisms is added to the water.    In an example, 5 g of light brown soil contaminated with 1000 mg/kg PbCrO4 was added to an airtight vessel into which was added 4 ml of an aq. soln. contg. ca. 40 mg Na acetate, 5 mg Na ammonium hydrogen phosphate and 20 g colloidal sulphur. The vessel was sealed and left to stand for 8 weeks at room temp. during which period the soil changed to a black colour due to the formation of PbS.    ADVANTAGE -   Heavy metals present in a wide concn., temp. or pH range can be removed without the use of microorganisms which can cause illness in humans. The need to place the soil or water in a sarcophagus is eliminated.