污水污泥中重金属污染物的溶出过程研究

污水污泥中污染物尤其是重金属的水体浸出作为重要的二次污染途径备受关注。为了探讨污水污泥中重金属的溶出规律,对上海7个污水处理厂的污水污泥进行了重金属总量分析,并采用水平振荡法对上述污水污泥中重金属进行了溶出动力学研究。结果表明,污水污泥中Cu、Cr和Zn的含量均较高,之后依次是Pb、As、Cd和Hg;污水污泥中重金属溶出动力学过程分为快速反应和慢速反应两个过程,可以用Elovich方程进行模拟;污水污泥中各重金属的溶出负荷差异较大,Cu、Cr和Zn的溶出负荷较大,其他较小,但各重金属相对于污水污泥中重金属总量的溶出百分比差异不大,基本处于10%以下。     

污泥热干化过程中重金属Pb、Cu、Zn的形态转化及稳定特性

基于不同干化工艺条件下,对城市脱水污泥在不同的温度下进行干化预处理研究,对干化后污泥中重金属的量及不同形态进行定量分析,研究污泥干化过程前后影响污泥中重金属含量及形态变化的条件因子。结果表明,污泥中不同重金属的含量差异较大,在不同工艺温度干化作用下,不同重金属形态含量发生了明显的变化,且不同重金属在干化过程中各形态含量变化差异较大。污泥在高温干化作用下,可使一部分重金属的交换态、可还原态和可氧化态向残渣态转化。高温对污泥中重金属形态有较好的稳定作用。研究结果对城市污泥热处理过程中重金属的污染迁移及控制有重要指导意义。     

城市污水处理厂的污泥农用对土壤的重金属影响

污泥农用是城市污水处理厂污泥资源化利用的有效途径，但污泥中的重金属元素含量高，可能成为环境中的一种安全隐患。重金属对环境的危害不仅与其总量有关，更大程度上由其形态分布所决定。实验研究了污泥农用所引入的重金属对土壤重金属总量及其形态的影响，研究结果表明，污泥农用虽然明显增加了土壤中的重金属总量，但重金属在土壤中的活性却受到了抑制，从而降低了重金属通过食物链危害人类健康的风险。     

污泥淋溶器的改进对重金属淋溶行为的影响

为增强污泥淋溶器固定污泥重金属的效果,降低其淋滤液中重金属含量从而更加安全地农业利用,在前期研究基础上对污泥淋溶器进行了改进,实验不同高度开孔和在污泥中间垂直放置黑网两个改进措施。研究表明,距淋溶器底部2 cm处开孔,污泥淋滤液的Cd和Cu总量显著低于底部开孔(原始污泥淋溶器)。淋溶器底部2 cm形成厌(缺)氧层使得下层硫化物态Zn、Cd和Cu含量显著高于孔的上层,提高了污泥重金属的生物稳定性。添加中间黑网可显著降低污泥淋滤液Cu总量。上述污泥淋溶器的两个改进措施均可有效固定污泥中某些重金属,减小污泥淋滤液重金属累计总量,促进污泥淋滤液更安全农用。     

污泥耐受性草本植物的筛选及其对重金属Cu、Zn的富集

为探索植物修复污泥中重金属污染的可行性,配制不同污泥含量的介质土开展盆栽实验,对从河南、云南和上海等地收集的抗逆性强的19种草本植物进行污泥适应性筛选；研究了植物对污泥的生理响应及其对重金属Cu、Zn的吸收和分布.结果表明,上海市浦东新区白龙港污水处理厂污泥农用是可行的,农用时污泥比例应控制在60％以下；筛选出三叶鬼针草、稗子、荆芥和金叶马兰4种污泥耐受性植物；三叶鬼针草具有修复重金属Cu、Zn污染土壤的潜力；稗子具有修复重金属Zn污染土壤的能力；金叶马兰具有修复重金属Cu、Zn污染土壤的能力.     

Fenton氧化联合人工湿地处理污泥中的重金属

针对单独应用Fenton氧化技术处理污泥的不足以及人工湿地在处理污水污泥方面的优势,以污水处理厂污泥浓缩池中含重金属污泥为对象,研究其依次经过Fenton氧化和人工湿地处理后重金属的去除效果及形态变化,以及污泥pH、TN和TP的变化情况。结果表明,Fenton氧化提高了污泥重金属的生物有效性,并促进了人工湿地对重金属的去除。Fenton氧化污泥经人工湿地处理后,Cu、Zn、Ni和Mn的去除率分别为67.2%、79.7%、37.0%和17.0%,与对照相比重金属的平均去除率提高了27.5%。经人工湿地处理后Fenton氧化污泥和原污泥重金属的生物有效性均降低。Fenton氧化污泥pH为4.4~4.6,经人工湿地处理后为6.2~7.1。人工湿地对Fenton氧化污泥和原污泥中TN的影响较小,而对TP表现出较高的去除率,2系统TP的去除率分别为51.1%和45.5%。     

污泥施入黄土后重金属Cu、Zn、Cd的淋滤迁移

污泥土地利用是目前国内外污泥处置的主要方式和鼓励方向,在中国西北黄土地区更有前景和意义.污泥富含有机质和营养元素可弥补黄土的贫瘠缺陷,改善黄土肥力、增加植物产量.污泥施入黄土后,灌溉水对污泥重金属的淋滤迁移和污染风险是值得研究的课题之一.研究旨在了解重金属Cu、Zn、Cd在黄土层中的淋滤迁移特征,为黄土地区污泥的土地利用及重金属污染控制提供实验依据.实验选择污泥中含量或毒性大的Cu、Zn、Cd 3种重金属作为研究对象,通过室内模拟土柱对表层堆肥污泥中2种源强的重金属进行1年灌溉用水量的淋滤对比实验,测定淋滤前后土柱中和渗出液的Cu、Zn、Cd总量、有机质及pH值,以期分析重金属在黄土中的淋滤、迁移特征.结果表明,淋滤作用可使堆肥污泥Cu、Zn、Cd发生少量迁移并富集于土柱中、上部,大部分或绝大部分重金属仍滞留于耕作层(0～20 cm);淋滤使堆肥污泥Cd与Cu向下迁移约30 cm,Zn向下迁移约20 cm;渗出液呈弱碱性,其中Cu、Zn、Cd 3种重金属的浓度较入渗水均有增多,但随渗出液从黄土柱中溶出的重金属量极少.实验表明,耕作层重金属源强对Cu、Zn、Cd在土柱剖面中的淋滤、迁移和滞留作用以及溶出量均有不同程度的影响,堆肥污泥土地利用可以明显改善黄土肥力,灌溉对耕作层污泥有机质的淋滤损失量较小.并得出,堆肥污泥在黄土地区的土地利用是可行的.     

添加不同钝化剂降低污泥堆肥的植物毒性研究

高温堆肥后污泥的土地利用可充分发挥资源化、无害化的优势，污泥土地利用防止重金属污染一直是污泥施用中最重要的问题。通过测验发芽率指数这一代表植物毒性的指标证明，通过在污泥堆肥中加入粉煤灰、磷矿粉和草炭等不同的改性剂或重金属钝化剂可大大降低堆肥的植物毒性，从而降低污泥中重金属的可利用性。     

堆肥污泥重金属在黄土中的淋滤特征

堆肥污泥中所含重金属是污泥堆肥土地利用最大的障碍,实验选用北方贫瘠的黄土作为供试样品,通过室内土柱淋滤实验,对堆肥污泥重金属在黄土中的淋滤特征进行了研究。结果显示,在0～40 cm的浅层淋滤层,各种重金属在黄土中的纵向迁移能力为:Pb>Zn>Ni>Cu,而在50～55 cm的深层淋滤层,Cd在黄土中的迁移能力相对其他4种重金属是比较强的;各种重金属在50～60 cm深层淋滤层中会出现二次富集,出现明显富集层。研究揭示了堆肥污泥重金属在黄土中的迁移特征,为有效控制和消除堆肥污泥土地利用中重金属的污染研究提供了理论依据。     

北京城市污水处理厂污泥中重金属污染状况及潜在生态风险分析

2011—2017年对北京城市中心区8家污水处理厂污泥中8种重金属(Cd、Cr、Cu、Zn、Pb、As、Hg、Ni)开展了持续监测,分析其重金属污染状况、年际及季节变化特征,并应用内梅罗指数法评估污泥在土地利用过程中重金属的潜在生态风险。结果表明:污泥重金属含量为ZnCuCrPbAsNiHgCd,除Hg外,其他重金属含量均低于全国平均水平;四季重金属总量中位值较接近,夏季稍高;Ni、Cd、Hg各年年均值变异系数最大,分别为43%、36%、23%,其他金属变异系数为5%～13%;56%的Hg检测结果超过了《城镇污水处理厂污泥处置农用泥质》(CJ/T 309—2009)中A级污泥限值,且8家污水处理厂均有超标记录;内梅罗指数显示Hg、Zn、Cd、Cu达到重度污染级别,污泥施用于土壤存在较严重的潜在生态风险。因此,污泥用于土壤环境前,需降低其重金属含量。     

还原焙烧电镀污泥中的金属形态和浸出性

分别以煤粉和稻杆为还原剂对电镀污泥进行还原焙烧，并通过酸浸回收焙烧渣中的金属。研究了焙烧温度、焙烧时间和还原剂投加量对目标金属Cu浸出率的影响以及主要杂质金属的浸出性，并采用BCR逐级提取法分析了焙烧前后污泥中的金属形态分布。结果表明，当在电镀污泥中投加30％的煤粉在600℃下焙烧1h后Cu的浸出率达到97．78％，当投加50％的稻杆时浸出率为89．47％，而氧化焙烧后浸出率仅为37．71％；并且还原焙烧渣中多数杂质金属的浸出率较低，从而可以实现Cu与杂质金属的初步分离。氧化焙烧容易导致金属从易浸出的非残渣态向难浸出的残渣态转化，而还原焙烧则能抑制这种转化过程，金属形态是决定其浸出性的重要因素。     

电镀污泥的热处理特性以及对金属回收的影响

焙烧-酸浸法可有效回收电镀污泥中的有价金属,而污泥的热处理特性是决定能否采用焙烧预处理的重要因素。研究了氧化焙烧和还原焙烧对污泥成分和金属浸出性的影响,并对焙烧前后的污泥进行了金属形态分析和X射线衍射(XRD)分析。结果表明,焙烧预处理实现了污泥减量和金属富集;ES1经氧化焙烧后金属浸出率接近原泥,Cu的浸出率达99%;ES2的还原焙烧效果优于氧化焙烧,特别是Cu的浸出率超过97%,XRD分析发现,还原焙烧过程中金属Cu被还原为铁铜合金;2种焙烧均造成了ES3中目标金属Ni的浸出率的降低;金属浸出性的下降与残渣态的形成有关。     

调理剂对堆肥产品重金属生物有效性的影响

城市污泥中重金属含量及其生物有效性是限制污泥农用的主要因素,因此,研究污泥堆肥化处理过程中重金属生物有效性,对污泥的农用具有重要意义。实验以城市污泥为原料,以菌菇渣和秸秆为调理剂,设置4个处理:A(污泥∶菌菇渣∶秸秆=1∶0.4∶0.025)、B(污泥∶菌菇渣∶秸秆=1∶0.3∶0.025)、C(污泥∶秸秆=1∶0.12)和D(污泥∶秸秆=1∶0.09),进行好氧堆肥实验,采用BCR顺序提取法测定各种形态的重金属,研究堆肥前后重金属形态的变化规律。结果表明,城市污泥中Cu、Ni、Pb和Cr主要以可氧化态及残渣态存在,生物有效性较低,而Zn和Cd主要以酸溶态和可还原态存在,生物有效性较高;堆肥过程显著降低了Cu、Zn、Ni和Pb的生物有效性,并改变了Cu、Zn、Ni、Pb、Cr和Cd的形态分布,使污泥中的Cu、Zn、Ni、Pb和Cd向着更稳定的可氧化态或残渣态转变;污泥经过堆肥处理后,Cu、Zn和Ni 3种重金属生物有效性关系为:ABCD,与其他处理相比,处理A残渣态的Pb和Cr增加比例较多,综合来看,处理A对重金属生物有效性的降低最为明显,重金属钝化效果最佳。     

Metal mobility at an old, heavily loaded sludge application site

This study was undertaken to determine the present distribution and mobility of sludge-applied metals at an old land application site. Trace metals concentrations were determined for soils (using 4 M HNO3 extracts), soil leachates (collected with passive wick lysimeters over a 2.5-year period), and plant tissue from a field site which received a heavy loading of wastewater sludge in 1978 and an adjacent control plot. Blue dye was used to indicate preferential percolate flowpaths in the sludge plot soil for sampling and comparison with bulk soil metals concentrations. After nearly 20 years, metals in the sludge plot leachate were found at significantly greater concentrations than in the control plot, exceeding drinking water standards for Cd, Ni, Zn, and B. Annual metals fluxes were only a fraction of the current soil metal contents, and do not account for the apparent substantial past metals losses determined in a related study. Elevated Cd, Cu, and Ni levels were found in grass growing on the sludge plot. Despite heavy loadings, fine soil texture (silty clay loam) and evidence of past and ongoing metals leaching, examination of the bulk subsoil indicated no statistically significant increases in metals concentrations (even in a calcareous subsoil horizon with elevated pH) when comparing pooled sludge plot soil profiles with controls. Sampling of dyed preferential flow paths in the sludge plot detected only slight increases in several metals. Preferential flow and metal complexation with soluble organics apparently allow leaching without easily detectable readsorption in the subsoil. The lack of significant metal deposition in subsoil may not be reliable evidence for immobility of sludge-applied metals.     

Implications of rhizospheric heavy metals and nutrients for the growth of alfalfa in sludge amended soil

Rhizospheric distribution of nutrients and heavy metals in sludge amended soil was investigated using the rhizobag technique to give an indication of the release of metals from wastewater sludge. DTPA-extractable Zn, Cd, Ni and Mn, and available P, K and NH4+-N in the rhizosphere were markedly depleted when soil was amended with sludge. There was no conspicuous depletion or accumulation of DTPA-extractable Cu in the rhizosphere when the soil was amended with sewage sludge but DTPA-extractable Fe accumulated in the rhizosphere when the soil was amended with increasing amounts of sludge. The pH value in the rhizosphere increased with distance from the roots when soil was amended with larger amounts of sludge. The exchangeable fraction of Cu in the rhizosphere was depleted whether or not the soil was treated with sludge. Carbonate, oxide, organic and residual fractions of Cu and Zn were depleted in the rhizosphere at a distance of 0-2 mm from the roots when soil was amended with 50% sludge. Application of sewage sludge had a positive effect on alfalfa growth. With an increase in sludge amounts, the concentrations of Fe, Cu and Zn in alfalfa shoots did not change. Soil amendments with less than 25% sludge did not increase the availability or mobility of heavy metals. The depletion in rhizospheric DTPA-extractable Zn, Cd and Ni indicates that with the sole exception of Cu, release of metals from sludge amended soil was very limited.     

Occurrence and fate of heavy metals in the wastewater treatment process

The occurrence and the fate of heavy metals (Cd, Pb, Mn, Cu, Zn, Fe and Ni) during the wastewater treatment process were investigated in the wastewater treatment plant (WTP) of the city of Thessaloniki, northern Greece, operating in the activated sludge mode. For this purpose, wastewater and sludge samples were collected from six different points of the plant, namely, the influent (raw wastewater, RW), the effluent of the primary sedimentation tank (primary sedimentation effluent, PSE), the effluent of the secondary sedimentation tank (secondary sedimentation effluent, SSE), sludge from the primary sedimentation tank (primary sludge, PS), activated sludge from the recirculation stream (activated sludge, AS), and the digested/dewatered sludge (final sludge, FS).

The distribution of metals between the aqueous and the solid phase of wastewater was investigated. Good exponential correlation was found between the metal partition coefficient, logK_p, and the suspended solids concentration. The mass balance of heavy metals in the primary, secondary and the whole treatment process showed good closures for all metal species. The relative distribution of individual heavy metals in the treated effluent and the sludge streams indicated that Mn and Cu are primarily (>70%) accumulated in the sludge, while 47–63% of Cd, Cr, Pb, Fe, Ni and Zn remain in the treated effluent.     

Electrokinetic enhancement removal of heavy metals from industrial wastewater sludge

An enhanced electrokinetic process for removal of metals (Cr, Cu, Fe, Ni, Pb, Zn) from an industrial wastewater sludge was performed. The electrokinetic experiments were conducted under a constant potential gradient (1.25 V cm(-1)) with processing fluids of tap water (TW), sodium dodecylsulfate (SDS) and citric acid (CA) for 5 days. Results showed that metal removal efficiency of heavy metals for EK-TW, EK-SDS and EK-CA systems are 11.2-60.0%, 37.2-76.5%, and 43.4-78.0%, respectively. A highest metal removal performance was found in EK-CA system. The removal priority of investigated metals from sludge by EK process was found as: Cu > Pb > Ni > Fe > Zn > Cr. The results of sequential extraction analysis revealed that the binding forms of heavy metals with sludge after electrokinetic process were highly depend upon the processing fluid operated. It was found that the binding forms of metals with sludge were changed from the more difficult extraction type (residual and sulfate fractions) to easier extraction types (exchangeable, sorbed, and organic fraction) after treatment by electrokinetic process. Results imply that if a proper treatment technology is followed by this EK process to remove metals more effectively, this treated sludge will be more beneficial for sludge utilization afterwards. Before it was reused, the risk associated with metals of more mobile forms to the environment need to be further investigated. The cost analysis was also evaluated for the investigated electrokinetic systems.     

污泥中重金属的去除及回收试验

论述了利用离子交换技术循环使用柠檬酸去除污泥中重金属,并置换回收重金属的适宜工艺条件.经柠檬酸处理后,污泥中90%以上的重金属被去除;柠檬酸处理液中的重金属用离子交换法回收,考察了树脂种类、流速、操作方式等因素对离子交换、再生效果的影响;在适宜工艺条件下,重金属的交换率均为100%,而洗脱率均接近90%;柠檬酸及离子交换树脂循环使用,重金属也得到回收,降低了处理成本.     

测定城市生活污泥中重金属的酸消解方法研究

采用HNO3-HC1O4-HF、HNO3-HC1O4、王水-HC1O4、HNO3等不同的酸消解方法对城市生活污泥进行消解。通过对这4种消解方法进行实验比较及对Cu、Ni、Zn三种金属元素浓度的测定，发现HNO3-HC1O4是适合城市生活污泥特点的消解方法。