TECHNOLOGY FOCUS - ENVIRONMENT - Preferred Process : The adapted bacteria are used at pH 7-8.5 and are active at 21-37 degrees Centigrade. A claimed 3-stage process comprises:(i) adding the contaminated material to a rotting slurry containing the bacteria or other microorganisms to adapt the bacteria to the degradation of organometallic compounds;(ii) adding contaminated material; and then(iii) progressing the degradation in a 'starvation' stage without addition of contaminated material.Stage (i) is for 30-40 days and ends when biogas production is the same as the value for the rotted slurry without added bacteria. Stage (ii) is for 5-15 days and ends when the organic non-metallic impurities disappear. Stage (iii) is for 25-35 days and ends when the required degree of degradation of the organometallics is achieved.    TECHNOLOGY FOCUS - BIOLOGY - Preferred Process : The adapted bacteria are used at pH 7-8.5 and are active at 21-37 degrees Centigrade. A claimed 3-stage process comprises:(i) adding the contaminated material to a rotting slurry containing the bacteria or other microorganisms to adapt the bacteria to the degradation of organometallic compounds;(ii) adding contaminated material; and then(iii) progressing the degradation in a 'starvation' stage without addition of contaminated material.Stage (i) is for 30-40 days and ends when biogas production is the same as the value for the rotted slurry without added bacteria. Stage (ii) is for 5-15 days and ends when the organic non-metallic impurities disappear. Stage (iii) is for 25-35 days and ends when the required degree of degradation of the organometallics is achieved. EXAMPLE - Laboratory tests were carried out on sediment from the new fishing harbor at Cuxhaven, the sediment treated initially containing 450 mug tributyltin (TBT)/kg and the progress of the treatment being shown in the graph below. In the adaption phase (stage (i)) a rotted slurry was added to the sediment starting with 66 g and averaging 500 g per 1450 g organic substances content, this phase lasting 24 days. In the second (degradation) phase there is a steep increase in gas production and in the third phase (i.e. 'starvation' phase) there was no addition of further material. A decrease of some 70 % in the concentration of organotin compounds was achieved in the third phase and the organics content was reduced from 30 % to 7.1%.