基于污染物变化选择干化污泥处置技术

为了解我国城市污水厂污泥干化前后污泥含水率、pH值、总磷、总氮、有机质和重金属含量(Zn、Cu、Cr、Pb、Ni、As、Cd)的变化情况并据此选择合理的干化污泥处置技术,以我国某污泥干化厂三种类型的污泥样品为研究对象,并测定上述六项指标。结果表明:污泥干化后含水率降至3.72%;pH值降低至5.95和5.93;干化后干料中总氮、总磷和有机质的增加量分别为30%、2.7%和5%,而湿料的增加量分别为24.5%、10.7%和2.2%;重金属含量的变化与干化后污泥类型有关,湿料中重金属含量有所减少,而干料中重金属含量则有增有减。污泥干化厂应以湿料作为主要的干化产品。同时,对比样品中各指标的实测值与污泥标准中的控制限值可知,干料适合制砖、制水泥熟料和混合填埋,而湿料适于农用、土地改良和园林绿化。

THE SELECTION FOR DISPOSAL TECHNOLOGIES OF DRYING SLUDGE BASED ON CHANGES IN SEVERAL POLLUTANTS

Sludge water content,pH,the contents of TP,TN,organic matter and heavy metals including Zn,Cu,Cr,Pb,Ni,As and Cd before and after drying in the wastewater treatment plants were studied using the standardized determination methods of sludge to get more information for the reasonable disposal of sludge.The samples were dewatered sludge,totally dried-sludge(DP) and mixed sludge(the mixture of dried-sludge and dewatered sludge by 20∶ 1,MP).After drying,it was found that the water content of the sludge reduced to 3.72%,and the pH value reduced from 6.18 to 5.95 of DP and 5.95 of MP,respectively,while the concentrations of TN,TP and organic matter increased,from 30%,2.7% and 5% in DP to 24.5% 、10.7% and 2.2% in MP,respectively.After drying,the variation of heavy metals’concentration was related to the type of the product.Compared to dewatered sludge,the content of all kinds of heavy metals reduced in MP,while some of them increased and others decreased in DP.As a result,the sludge drying plants should make MP the main product.At the same time,according to the limit values in standards of sludge,it was found that DP were suitable for brick-making,cement clinker producing and co-landfilling,while MP were suitable for agriculture,land improvement and gardening.