上海城镇污水厂污泥中Zn的形态及其发酵转化与淋溶风险

重金属已经成为制约污水处理厂剩余污泥农用的关键因素之一,锌(Zn)是我国城镇污水处理厂污泥中含量最高的重金属元素之一。本文以上海市2个典型城市污水处理厂的脱水污泥为研究对象,在对其Zn污染状况进行分析的基础上,系统研究了2种污泥在好氧和厌氧发酵处理过程中Zn的形态变化,以及在模拟酸雨条件下未发酵和发酵污泥中Zn的溶出情况。结果表明,污泥样品中,Zn的总量在2种污泥中均达到1 500mg/kg以上,远高于污泥农用的国家标准最高限值,环境风险较高。Zn在污泥中主要以铁锰氧化物结合态、有机结合态和残渣态存在,分别约占总Zn量的35%、16%和48%左右。经过好氧发酵后Zn的残渣态含量先降低后升高,而厌氧发酵无显著形态变化。Zn在以生活污水为主的污泥中比工业污水和生活污水混合型污泥中更易溶出,而且受到硝酸型酸雨影响比硫酸型酸雨大。

Speciation Analysis,Transformation during Fermentation and Leaching Risk of Zinc in the Sludge from the Municipal Wastewater Treatment Plant in Shanghai

The residue of heavy metals in sludge from municipal waste water treatment plant is the key barrier for application of the sludge as farming soil. Zinc is one of the most abundant heavy metals in sludge in China. Samples of the dehydrated sludge were collected from two typical municipal wastewater treatment plants in Shanghai. The total Zn content and its speciation in the samples were analyzed. Then aerobic and anaerobic fermentations were performed to explore the change of Zn speciation during the treatment. Theleaching of Zn in the sludge under the imitating acid raining was observed. The results showed that the total Zn contents in the raw sludge samples from the two plants were more than 1 500 mg/kg dry weight which is much over the National Standard limit and at a high environment risk. Zn exists in the sludge mostly by the speciation of Iron and Manganese Oxides,organic combination,and detritus with percentage 35~,16~ and 48~ of total Zn content,respectively. The detritus content increased at the beginning and decreased after the aerobic fermentation no obvious change of Zn speciation occurred after anaerobic fermentation. Zn was easier to be leached in the sludge from mainly living wastewater than from mixing of living and industrial wastewater. The nitric acid rain had more effects on the leaching of Zn in sludge than the sulfuric acid rain did.