ELUCIDATION OF REMOVAL MECHANISM OF ARSENIC FROM SEWAGE SLUDGE AND INCINERATED ASH OF SEWAGE SLUDGE AND DEVELOPMENT OF ITS REMOVAL METHOD

碱性条件对污水污泥中砷的洗脱作用大于酸性条件。污泥碱化至pH为9和11，砷的洗脱率分别超过80%和95%。用高效液相色谱-质谱法发现，在pH5、7、9和11时，从污泥中洗脱的砷的主要形式是砷酸，而在pH1时，砷的主要形式是砷酸。与砷酸和砷酸相比，一甲基larsonic酸和二甲基larsinic酸的洗脱量较小。这一结果表明，洗脱后砷的形态取决于水体系中砷的pH-EH图。结果表明，在酸性条件下，铁氧化菌和三铁的加入对砷的洗脱是有效的，因为污泥中的硫化砷被它们氧化，从而导致砷的洗脱。研究了从污泥焚烧灰中连续脱除砷的可能性。通过加入消化气脱硫过程中产生的含硫废渣和消化污泥中存活的硫氧化菌，使灰的pH值降至1以下。结果表明，在固体滞留时间为10 d、固体灰分浓度为20 gD的条件下，焚烧灰中砷可连续洗脱80%以上。S/L，废物浓度20gwt /L。

Alkaline condition eluted arsenic in the sewage sludge more than acidic one. Alkalization of sewage sludge to pH 9 and 11 eluted arsenic more than 80 and 95%, respectively. It was found that the predominant form of arsenic eluted from the sludge was arsenic acid at pH5, 7, 9 and 11 by using a HPLC-MS, whereas it was arsenious acid at pH1. The eluted amount of of monomethylarsonic and dimethylarsinic acids was small compared with those of arsenic and arsenious acids. This result indicated that the form of arsenic eluted depended on the pH-EH diagram of arsenic in an aqueous system. It was shown that the addition of iron oxidizing bacteria and ferric iron was effective for the elution of arsenic on the acidic condition since arsenic sulfide in the sludge was oxidized by them and it caused the elution of arsenic.The possibility of continuous arsenic elution from incinerated ash of sewage sludge was studied. The pH of ash dropped below 1 by adding waste containing sulfur produced from desulfurization process of digested gas and sulfur oxidizing bacteria surviving in the digested sewage sludge. It was found that more than 80% of arsenic in incinerated ash could be eluted continuously on the condition of a solid retention time of 10 days, solid concentration of ash of 20 gD.S/L and waste concentration of 20gW.T./L.