| 摘要 |
<p>Sludges, especially sewage sludges, are treated to stabilise them by biological digestion (21) and/or to remove heavy metals (19, 23) by using a sulphur compound cycle in which sulphate is reduced to hydrogen sulphide which is then re-oxidised (36, 40) to sulphate for return to the process. The sulphate reduction is effected during digestion (21) of the sludge and the sulphate from re-oxidation (usually sulphuric acid) is either cycled to the digestion of more sludge, or used to leach heavy metals (14) and subsequently recovered upon their precipitation as sulphides (23). Instead of sulphate, other sulphur species can be used provided they are more oxidised than hydrogen sulphide. <IMAGE></p> |
