传统活性污泥法处理城市污水过程中重金属的变化研究

Study on the variation of heavy metals in the traditional municipal activated sludge wastewater treatment process

研究了污水处理厂传统活性污泥工艺不同处理工段污水和污泥中Cu、Zn、Pb、Cd、Hg和As含量变化及其在污水中的形态分布特征,进一步了解重金属在不同处理工段的去除情况。整个工艺流程污水中Hg的去除率最大,平均达76.4%,Pb的去除率最小,平均为29.7%。不同处理工段各重金属去除率差异较大,从进水到初沉池出水Zn去除率最大,平均达55.4%,其次为Hg和Cu,平均去除率分别为40.0%与34.2%;由初沉池出水到二沉池出水Cd、Hg和Cu平均去除率达36.1%～38.5%。进水、初沉池出水和二沉池出水中颗粒态Zn占其总量的比例(以质量分数计,下同)均在98.1%以上,颗粒态Hg占其总量的比例由84.1%降低到39.7%,颗粒态As占其总量的比例由11.7%上升至56.5%。初沉池污泥、曝气池活性污泥和脱水消化污泥中Zn含量最高,初沉池污泥中Cd含量最低,曝气池活性污泥和脱水消化污泥中As含量最低。脱水消化污泥中Zn、Cu、Pb和Cd含量高于初沉池污泥和曝气池活性污泥,Hg和As含量低于初沉池污泥而高于曝气池活性污泥。大部分Zn和Pb在初沉池中被除去,大部分Cd在二沉池中被除去,Hg和Cu在初沉池与二沉池中的去除效果相当。

Based on field investigations and plant process analysis, a study of the Cu, Zn, Pb, Cd, Hg and As changes, removals, distribution and characteristics in different stages of the activated Sludge wastewater treatment process. The results showed the decrease of heavy metal concentration in water varied with metals. The highest percentage of decrease was Hg was 76.4%, and the lowest was Pb content was 29.7%. The decreased concentration also varied with different treatment stages. Zn concentration in the sewage was reduced by 55.4% from the influent to the effluent of the primary sedimentation tank, followed by Hg and Cu, which was 40.0% and 34.2%, respectively. Cd, Hg and Cu in sewage reduced by 36.1%-38.5% from the effluent of the primary sedimentation tank to the effluent of the secondary sedimentation tank. The particulate form was dominant for Zn, with more than 98.1%. Hg in the particulate form reduced from 84. 1% to 39. 7%, while As in the particulate form increased from 11. 7% to 56. 5%. Changes of Cu, Pb and Cd were not obvious. The contents of Zn variation in sludge of primary sedimentation tank, in activated sludge and in the digested sludge were highest overall. The content of Cd in sludge of the primary sedimentation tank was the lowest. Also, the As contents in activated sludge and in the digested sludge were the lowest content. Compared with the contents of metals in sludge of the primary sedimentation tank and activated sludge, the per centage of Zn, Cu, Pb and Cd of in the digested sludge increased, while the contents of Hg and As decreased. Most Zn and Pb were deposited in the primary sedimentation tank. Most Cd was deposited in the secondary sedimentation tank. The amount of Hg and Cu removal were comparable between primary sedimentation tank and secondary sedimentation tank.