可控湿法氧化聚沉工艺对城市污泥中重金属的稳定化影响

Effects of wet oxidation and coagulation on the stabilization of heavy metals in municipal sludges

采集了长沙市污水厂的剩余污泥(S1)和湿法氧化聚沉工艺处理的深度脱水污泥(S2),对比分析了处理前后污泥的形貌变化及重金属Zn、Cu、Pb、Cd、Hg和As的形态分布,初步探讨了重金属稳定化机理,对脱水污泥中重金属Zn、Cu、Pb、Cd、Hg和As进行了稳定性评估.结果表明,脱水污泥中重金属的总量均低于我国污泥农用标准中的酸性限值,符合B级污泥泥质要求.处理后,污泥中Zn、Cu、Pb、Cd、Hg和As主要以硫化物有机结合态和残渣态(稳定态)存在,不稳定态在不同程度上向稳定态发生了转变,Cu、Hg的增幅最大,达21.1%.S2中重金属的生物可利用性较S1都有显著的降低,平均降幅达73.1%,S2中重金属的生物可利用性顺序为:Zn>Pb>Cu>Cd>As>Hg.污泥经过湿法氧化聚沉工艺处理后,污泥中重金属Zn、Cu、Pb、Cd、Hg和As得到了明显的稳定化,为污泥后续资源化、安全化提供了科学依据.

Excess activated sludge（S1） and mechanically dewatered sludge（S2） were collected from the municipal wastewater treatment plant of Changsha.The morphology change and chemical fractions of heavy metals（Zn,Cu,Pb,Cd,Hg,As） in sewage dewatered sludge were analyzed.And the stabilization mechanism of heavy metals was discussed by comparison with the excess activated sludge.The results showed that the total amount of the heavy metals in the dewatered sludge was less than the acidity limit value in the pollutant control standards for the agricultural sludge,and accorded with the grade B of the sludge shale requirements.Zn,Cu,Pb,Cd,Hg,As mostly existed in the residue form.Unstable state of these heavy metals were converted into stable state to varying degrees after treatment.In particular,increase of Cu,Hg was the largest.The bioavailability of these heavy metals in S2 were significantly lower than in S1.Meanwhile,the reduction of bioavailability was evident.The bioavailability of the heavy metals in S2 was in the order of Zn〉Pb〉Cu〉Cd〉As〉Hg.The heavy metals（Zn,Cu,Pb,Cd,Hg,As） were stabilized evidently by the technique of wet oxidation and coagulation.The results may provide a scientific basis for safe disposal of the sludge.