【作者】 孙西宁；

【导师】 张增强；

【作者基本信息】 西北农林科技大学 ， 环境工程， 2007， 硕士

【摘要】 污水污泥中含有大量的水分、丰富的有机物及N,P,K等营养元素。但同时还含有重金属及病原菌等有害物质,如果不加处理任意排放,不仅对环境造成污染,同时又是对资源的严重浪费。污泥堆肥的土地利用是污泥处置和资源化利用的最经济可行的方式,被许多国家广泛采用。污泥中的重金属含量是限制污泥土地利用的主要因素,但是人们普遍认为通过重金属总量并不能准确地判断重金属的潜在环境影响,所以,很有必要采用顺序浸提去获得重金属的生物有效性或其毒性方面恰当的信息。本研究首先跟踪测定了杨凌污水处理厂污泥中营养物质和重金属含量的季节性变化趋势,掌握了污泥中重金属随时间的变化规律。接着分别采用BCR法和Sposito法测定了污泥在堆肥过程重金属形态的变化。所得结论如下:1.污泥中含有丰富的氮、磷以及一些营养元素,污泥含有较高的有机质﹑全氮﹑全磷成分,其含量分别为361.4～529.4,20.13～35.42及3.11～7.48 g/kg;而重金属Ni、Cd、Pb、Zn、Cu、Cr和As的含量分别为22.86～38.03,0.68～5.07,29.53～76.16,297.4～313.7,124.4～200.7,43.23～255.0及6.02～15.97 mg/kg,Hg含量在此期间未被检测出.虽然重金属随着时间和季节有所变化,但与我国的污泥农用碱性标准比较,在整个的变化范围内,所有重金属元素的总量范围仍在污泥农用规定的标准内,同时也远低于USEPA503标准。可以认为生活污泥中的重金属对农用的影响较小,采取适当的处理即可将污泥农林利用。为了进一步了解重金属对环境的影响,采用单一试剂(DTPA)浸提法测定了重金属的生物有效性,得出重金属活性顺序为:Ni>Cd>Pb>Zn>Cu>As。2.在纯污泥堆肥过程中,BCR法测定结果表明:可还原态都呈下降趋势,其中Cd的下降幅度很小;除了Cd以外,其它几中重金属的残渣态含量随着堆肥天数的增加都明显升高。Sposito法测定结果表明:除了Cd以外,其它金属的易活动态均降低;所有重金属大部分都以稳定的有机结合态和残渣态形式存在,这两种形态的总量都在50%以上(Cu、Cd和Pb在80%左右),并呈增加的趋势。所以两种方法的测定结果基本一致,即都显示除Cd外,经过堆肥处理后Zn、Cu、Ni、Pb、Cr的稳定性增加。3.将污泥与锯末混合堆肥,分别用BCR法和Sposito法测定了堆肥过程中重金属形态的变化。两种测定结果一致的地方是:除了Cd外,Cu、Ni、Pb和Cr四种重金属经过堆肥化处理,易活动态含量都呈下降趋势,说明堆肥化处理使这四种金属的稳定性增加。不一致的地方是:(1)对于Zn元素,BCR法测定结果显示其有效性降低;而Sposito法的测定结果却正好是相反的。(2)对于Pb元素,虽然两种测定方法的结果都显示其有效性是降低的,但BCR法显示Pb的有效性降低幅度较大;而Sposito法显示Pb的有效性在处理前后变化很小。4.在纯污泥堆肥过程中,所有重金属总含量都呈下降趋势,大部分易活动态的重金属含量将下降。在污泥与锯末混合堆肥过程中,除了Cd以外所有重金属总含量都呈下降趋势。另外,在这两种不同原料的堆肥处理中,用BCR法测定的所有形态各重金属总和要大于用Sposito法的测定总和。由于该污泥中As的总含量本来很少,所以顺序浸提时各形态都没有检测出。更多还原

【Abstract】 Sewage sludge contains a lot of water, be rich in organic matter and N, P, K, and other nutrients. But it also contain heavy metals、pathogens and other harmful substances. It may not only pollute the environment, but also make the resources wasted, if not treated before discharge. The agricultural utilization of sludge compost is the most economical and available way for disposal and resources recovery of sludge, and it has been widely used in many countries. The major limitation of soil application of sludge compost is the total heavy metal contents and their bioavailability to the soil–plant system. However, it is widely accepted that the determination of total elements does not give an accurate estimation of the potential environmental impact. So, it is necessary to apply sequential extraction techniques to obtain suitable information about their bioavailability or toxicity.In this paper, the contents of nutrition (N, P, K as well as OM) and the heavy metals (Cd, Pb, Zn, Cu, Cr, As and Hg) of the sludge of Yangling Waste Water Treatment Plant were investigated, and the change trend of the heavy metals have been grasped. Then the change of heavy metal forms in sludge during compost process were determined by use the BCR (Community Bureau of Reference) sequential extraction procedure and the Sposito sequential extraction procedure. The conclusion was showed as follows:1. The results showed that the sludge of Yangling Waste Water Treatment Plant contended high organic matter, total nitrogen (TN) and total phosphor (TP), the contents of organic matter, total nitrogen (TN) and total pHospHor (TP) were as follows: 361.41-529.38, 20.13 -35.42, 3.11-7.48 g/kg, respectively. And the contents of Ni, Cd, Pb, Zn, Cu, Cr, As were 22.86-38.03, 0.68-5.07, 29.53-76.16, 297.4-313.7, 124.37-200.66, 43.23-255.00, 6.02-15.97 mg/kg, respectively. However, the contents of Hg in sewage sludge samples were not determined in near a year time. All the heavy metals’contents were lower than the heavy metal limits for agricultural application of China, and far below USEPA503 standard. So it is believed that the influence that agricultural utilization of sludge compost is little. It is suitable to apply it to farmland if the sludge were treated with some methods. The bioavailability of heavy metals was determined using simple (DTPA) extraction. The active order of heavy metals was as follows: Ni >Cd > Pb >Zn> Cu>As. 2. In the pure sludge compost process, the results of BCR indicated that the exchangeable fraction of heavy metals all tended to decline, the descend range of Cd is very small; the content of residual fraction tended to increase except Cd. The result of Sposito showed that the mobile fractions tended to decrease except Cd; most heavy metals existed in residual fraction and bound to organic matter, the content of these two kinds of forms are all over 50% (Cu, Cd and Pb about 80%) and tended to increase, too. So the results of the two methods all showed that the stability of Zn、Cu、Ni、Pb and Cr increased after compost except Cd.3. During the course of the sludge and sawdust mix compost, there are some same conclusion: the two methods all showed that the mobile fractions’content of Cu、Ni、Pb and Cr tended to decrease except Cd. On the other hand, the result of BCR showed that the bioavailability of Zn decrease, but the Sposito method is on the contrary; the result of the two methods indicated that the bioavailability of Pb decrease, the range was large in BCR method but very small in Sposito method.4. The content of total heavy metal by BCR is larger than that of Sposito. As was not determined in every form of the compost, the As content was very little in raw sludge.更多还原