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。     

PCDD/F, PAH and heavy metals in the sewage sludge from six wastewater treatment plants in Beijing, China

In order to better understand land application of sewage sludge, the characterization of heavy metals, PCDD/F and PAHs in sewage sludge was investigated from six different wastewater treatment plants (WWTP) in Beijing City, China. It was found that the total concentrations of Zn in Wujiacun (WJC) sewage sludge, and Cd and Hg in sewage sludge generated from all of the six different places are higher than Chinese regulation limit of pollutants for sludge to be used for agriculture (GB18918-2002). The levels of 16 PAHs that have been categorized as priority pollutants by US EPA in the sewage sludge samples varied from 2467 to 25923 microg/kg (dry weight), the highest values of 25923 microg/kg being found in WJC WWTP. The concentrations of Benzo[a]pyrene were as high as 6.1mg/kg dry weight in WJC sewage sludge, exceeding the maximum permitted content by GB18918-2002. Individual PAH content varies considerably with sewage samples. The ratios of anthracene to anthracene plus phenanthrene (An/178), benz[a]anthracene to benz[a]anthracene plus chrysene (BaA/228), indene[1,2,3-cd]pyrene to indene[1,2,3-cd]pyrene plus benzo[g,h,i]perylene (In/In+BP), and fluoranthene to fluoranthene plus pyrene (Fl/Fl+Py) suggest that petroleum and combustion of fossil fuel were the dominant contributions for the PAHs in sewage sludge. The concentrations of total PCDD/F in the sewage sludge ranged from 330 to 4245 pg/g d.w. The toxicity equivalent concentrations is between 3.47-88.24 pg I-TEQ according to NATO/CCMS, which is below Chinese legislation limit value proposed for land application. The PCDD/F congener/homologue profiles found in the Beijing samples indicated that the high chlorinated PCDD/F contamination might originate mainly from PCP-related source and depositional sources while the low chlorinated PCDD/F homologues could be originating from incineration or coal combustion. The major source of PCDD/Fs in Beijing sludge is still unclear.     

Occurrence of polycyclic aromatic hydrocarbons in sewage sludge and their contribution to its toxicity in the toxalert 100 bioassay.

The contribution of polycyclic aromatic hydrocarbons (PAH) present in sewage sludge samples to toxicity was investigated. Chemical analysis using gas chromatography mass spectrometry (GC-MS) and the ToxAlert 100 bioassay, based on the inhibition to Vibrio fischeri, were applied to sludge extracts after purification by column chromatography. The levels of the 16 US EPA PAH analyzed in the sewage sludge samples varied from 17 to 2,030 microg kg(-1). In all samples examined phenanthrene was the most prominent compound. The toxicity data obtained by ToxAlert 100 can be explained by the levels and composition of the different PAH in sewage sludge samples. The present approach can contribute to evaluate the toxicity of sewage sludge.     

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。     

From agricultural use of sewage sludge to nutrient extraction: A soil science outlook

The composition of municipal wastewater and sewage sludge reflects the use and proliferation of elements and contaminants within society. In Sweden, official statistics show that concentrations of toxic metals in municipal sewage sludge have steadily decreased, by up to 90 %, since the 1970s, due to environmental programmes and statutory limits on metals in sludge and soil. Results from long-term field experiments show that reduced metal pollution during repeated sewage sludge application has reversed negative trends in soil biology. Despite this Swedish success story, organic waste recycling from Swedish towns and cities to arable land is still limited to only about 20 % of the total amount produced. Resistance among industries and consumers to products grown on land treated with sewage sludge may not always be scientifically grounded; however, there are rational obstacles to application of sewage sludge to land based on its inherent properties rather than its content of pollutants. We argue that application of urban organic wastes to soil is an efficient form of recycling for small municipalities, but that organic waste treatment from large cities requires other solutions. The large volumes of sewage sludge collected in towns and cities are not equitably distributed back to arable land because of the following: (i) The high water and low nutrient content in sewage sludge make long-distance transportation too expensive; and (ii) the low plant availability of nutrients in sewage sludge results in small yield increases even after many years of repeated sludge addition. Therefore, nutrient extraction from urban wastes instead of direct organic waste recycling is a possible way forward. The trend for increased combustion of urban wastes will make ash a key waste type in future. Combustion not only concentrates the nutrients in the ash but also leads to metal enrichment; hence, direct application of the ash to land is most often not possible. However, inorganic fertiliser (e.g. mono-ammonium phosphate fertiliser, MAP) can be produced from metal-contaminated sewage sludge ash in a process whereby the metals are removed. We argue that the view on organic waste recycling needs to be diversified in order to improve the urban–rural nutrient cycle, since only recycling urban organic wastes directly is not a viable option to close the urban–rural nutrient cycle. Recovery and recycling of nutrients from organic wastes are a possible solution. When organic waste recycling is complemented by nutrient extraction, some nutrient loops within society can be closed, enabling more sustainable agricultural production in future.     

Concentrations and specific loads of UV filters in sewage sludge originating from a monitoring network in Switzerland

Many substances related to human activities end up in wastewater and accumulate in sewage sludge. The present study focuses on the analysis of widely used UV filters 3-(4-methylbenzylidene) camphor (4-MBC), octyl-methoxycinnamate (OMC), octocrylene (OC) and octyl-triazone (OT) in sewage sludge originating from a monitoring network in Switzerland. Mean concentrations in stabilised sludge from 14 wastewater treatment plants were 1780, 110, 4840 and 5510 microg/kg dry matter for 4-MBC, OMC, OC and OT, respectively. Specific loads in sewage sludge show that UV filters originate mainly from private households, but surface runoff and industries may be considered as additional sources. This indicates that besides use for sunscreens and cosmetics UV filters might occur in plastics and other materials and be released to the environment by volatilization or leaching. Differences between the modeled per capita loads of UV filters in sewage sludge and the observed specific loads in sewage sludge are probably due to erroneous figures of production volumes, degradation and sorption during wastewater treatment as well as degradation processes during transport in the sewer or sludge treatment. Thus, further research is needed to elucidate the fate of UV filters after application and release into the environment. Other compounds used as UV filters should be included in future studies.     

城市下水污泥焚烧过程中二次污染物排放特性的试验研究

在0.15 MWt循环流化床燃烧试验台上进行了城市下水污泥与煤的混烧试验,分析了烟气中的二次污染物排放特性.分析结果表明,利用循环流化床焚烧城市下水污泥时,添加辅助燃料(如煤)及改变焚烧条件,不仅可以达到稳定燃烧的目的,而且有利于抑制焚烧中二次污染物(如CO及二恶英等有机污染物)的生成.分析了焚烧污泥污染物的排放特性,为采用焚烧方式处理城市下水污泥提供了基础性试验数据.     

A study of the influence of sewage sludge fertilization on the concentrations of PCDD/F and PCB in soil and milk

The influence of the agricultural use of sewage sludge on the concentrations of PCBs and PCDD/Fs in soil, feed and milk was investigated on four dairy farms. Evidence of contaminant accumulation in the soil was found on both farms that fertilized with sewage sludge. The concentrations in feed and milk from one of these farms were similar to the concentrations in the matched control, while the concentrations in the samples from the second sludge user were elevated. The study demonstrates that the agricultural use of sewage sludge does under some conditions lead to higher levels of PCBs and PCDD/Fs in food products.     

城市下水污泥焚烧过程中二次污染物排放特性的试验研究

在0．15MWt循环流化床燃烧试验台上进行了城市下水污泥与煤的混烧试验，分析了烟气中的二次污染物排放特性。分析结果表明，利用循环流化床焚烧城市下水污泥时，添加辅助燃料（如煤）及改变焚烧条件，不仅可以达到稳定燃烧的目的，而且有利于抑制焚烧中二次污染物（如CO及二恶英等有机污染物）的生成。分析了焚烧污泥污染物的排放特性。为采用焚烧方式处理城市下水污泥提供了基础性试验数据。     

Cumulative and Residual Effects of Repeated Sewage Sludge Applications: Forage Productivity and Soil Quality Implications in South Florida,USA (9 pp)

Background, Aim and Scope The cow-calf (Bos taurus) industry in subtropical United States and other parts of the world depends almost totally on grazed pastures. Establishment of complete, uniform stand of bahiagrass (BG) in a short time period is important economically. Failure to obtain a good BG stand early means increased encroachment of weeds and the loss of not only the initial investment costs, but production and its cash value. Forage production often requires significant inputs of lime, N fertilizer, and less frequently of P and K fertilizers. Domestic sewage sludge or biosolids, composted urban plant debris, waste lime, phosphogypsum, and dredged materials are examples of materials that can be used for fertilizing and liming pastures. Perennial grass can be a good choice for repeated applications of sewage sludge. Although sewage sludge supply some essential plant nutrients and provide soil property-enhancing organic matter, land-application programs still generate some concerns because of possible health and environmental risks involved. The objectives of this study were to evaluate the cumulative and residual effects of repeated applications of sewage sludge on (i) bahiagrass (BG, Paspalum notatum Flügge) production over years with (1997–2000) and without (2001–2002) sewage sludge applications during a 5-yr period, and (ii) on nutrients status of soil that received annual application of sewage sludge from 1997 to 2000 compared with test values of soils in 2002 (with no sewage sludge application) in South Florida.Methods The field experiment was conducted at the University of Florida Agricultural Research and Education Center, Ona, FL (27o26’N, 82o55’W) on a Pomona fine sandy soil. With the exception of the control, BG plots received annual sewage sludge and chemical fertilizers applications to supply 90 or 180 kg total N ha–1 yr–1 from 1997 to 2000. Land application of sewage sludge and fertilizer ceased in 2001 season. In early April 1998, 1999, and 2000, plots were mowed to 5-cm stubble and treated with the respective N source amendments. The experimental design was three randomized complete blocks with nine N-source treatments: ammonium nitrate (AMN), slurry biosolids of pH 7 (SBS7), slurry biosolids of pH 11 (SBS11), lime-stabilized cake biosolids (CBS), each applied to supply 90 or 180 kg N ha–1, and a nonfertilized control (Control). Application rates of sewage sludge were calculated based on the concentration of total solids in materials as determined by the American Public Health Association SM 2540G method and N in solids. The actual amount of sewage sludge applications was based on the amount required to supply 90 and 180 kg N ha–1. Sewage sludge materials were weighed in buckets and uniformly applied to respective BG plots. Soil samples were collected in June 1997, June 1999, and in June 2002 from 27 treatment plots. In 1997 and 1999, soil samples were collected using a steel bucket type auger from the 0- to 20-, 20- to 40-, 40- to 60-, and 60- to 100-cm soil depths. Forage was harvested on 139, 203, 257, and 307 day of year (DOY) in 1998; 125, 202, 257, and 286 DOY in 1999; 179, 209, 270, and 301 DOY in 2000; and on 156 and 230 DOY in 2002 (no sewage sludge applications) to determine the residual effect of applied sewage sludge following repeated application. Forage yield and soils data were analyzed using analysis of variance (PROC ANOVA) procedures with year and treatment as the main plot and sub-plot, respectively. As a result of significant year effects on forage yield, data were reanalyzed annually (i.e., 1998, 1999, 2000, and 2002).Results and Discussion All sewage sludges used in this study were of class B in terms of USEPA’s pathogens and pollutant concentration limit. Pathogen and chemical composition of the class B sewage sludge that were used in the study were all in compliance with the USEPA guidelines. The liquid sludge (SBS11) had the lowest fecal coliform counts (0.2 x 106 CFU kg–1) while the cake sewage sludge (CBS) had the greatest coliform counts of 178 x 106 CFU kg–1. The fecal coliform counts for SBS7 was about 33 x 106 CFU kg–1. Average soil test values in June 2002 exhibited: i) decrease in TIN (NO3-N + NH4-N), TP, K, Ca, Mg, Mn, and Fe; and ii) slight increase in Zn and Cu when compared with the June 1997 soil test results. The overall decrease in soil test values in 2002 might be associated with nutrient cycling and plant consumption. Although the average BG forage yield in 2002 (2.3 ± 0.7 Mg ha–1) was slightly lower than in 2000 (3.5 ± 1.2 Mg ha–1), yield differences in 2002 between the control (1.2 + 0.2 Mg ha–1) and treated plots (2.3 ± 0.5 Mg ha–1 to 3.3 ± 0.6 Mg ha–1) were indicative of a positive residual effect of applied sewage sludge. This study has shown that excessive build up of plant nutrients may not occur in beef cattle pastures that repeatedly received sewage sludge while favoring long-term increased forage yield of BG. All sources of N (sewage sludge and AMN) gave better forage production than the unfertilized control during years with sewage sludge application (1997–2000) and also during years with no sewage sludge application (2001–2002). The favorable residual effects of applied sewage sludge in 2002 may have had received additional boost from the amount of rainfall in the area.Conclusions Repeated applications of sewage sludge indicate no harmful effects on soil quality and forage quality. Our results support our hypothesis that repeated land application of sewage sludge to supply 90 and 180 kg N ha–1 would not increase soil sorption for nutrients and trace metals. Results have indicated that the concentrations of soil TIN and TP declined by almost 50% in plots with different nitrogen sources from June 1997 to June 2002 suggesting that enrichment of nitrogen and phosphorus is insignificant. The concentrations of soil nitrogen and phosphorus in 2002 following repeated application of sewage sludge were far below the contamination risk in the environment. The residual effect of these sewage sludge over the long term can be especially significant in many areas of Florida where only 50% of the 1 million ha of BG pastures are given inorganic nitrogen yearly.Recommendation and Outlook Successive land application of sewage sludge for at least three years followed by no sewage sludge application for at least two years may well be a good practice economically because it will boost and/or maintain sustainable forage productivity and at the same time minimize probable accumulation of nutrients, especially trace metals. Consecutive applications of sewage sludge may result in build up of some trace metals in some other states with initial high metallic content, but in this study, no detrimental effects on soil chemical properties were detected. The possibilities for economically sound application strategies are encouraging, but more and additional research is required to find optimal timing and rates that minimizes negative impacts on soil quality in particular or the environment in general. For proper utilization of sewage sludge, knowledge of the sewage sludges’ composition, the crop receiving it, are absolutely crucial, so that satisfactory types and rates are applied in an environmentally safe manner. There is still much to be learned from this study and this investigation needs to continue to determine whether the agricultural and ecological objectives are satisfied over the longer term.     

Optimising the preparation of activated carbon from digested sewage sludge and coconut husk.

Preparation of activated carbon from sewage sludge is a promising way to dispose of sewage sludge as well as to produce a low-cost adsorbent for pollutant removal. This research work aimed to optimise the condition for activated carbon preparation from anaerobically digested sewage sludge with the additive coconut husk. The sewage sludge sample was mixed with the additive coconut husk. The preparation condition variables investigated involved the concentration of the ZnCl2 solutions, heating temperature, dwell time and heating rate in pyrolysis and the mixing ratio of coconut husk to sewage sludge. Surface area, pore size distribution, aqueous phenol adsorption capacity and the production yield of the final products were determined and compared. Experimental results revealed that low concentrations of ZnCl2 solution tended to improve the microporosity of the final product. Heating temperature had a considerable impact on the surface area, pore size distribution and phenol adsorption capacity of the final products, whereas dwell time and heating rate performed comparatively insignificantly. The effect of increasing the mixing ratio of coconut husk to sewage sludge was principally to increase the microporosity of the final products. The activated carbon with the highest BET surface area was produced with the activation of 5 M ZnCl2 solution and, thereafter, pyrolysis at a heating temperature of 500 degrees C for 2 h with a heating rate of 10 degrees C/min. The mixing ratio of 1:4 in terms of coconut husk to sewage sludge based on their dried weights was found to be most cost effective.     

Di-(2-ethylhexyl)phthalate in sewage sludge and post-treated sludge: quantitative determination by HRGC-MS and mass spectral characterization

DEHP was quantified into sewage sludge, thermally dried sludge and compost samples from different areas of Catalonia (North East Spain) using high-resolution gas chromatography (HRGC) coupled to a mass spectrometry (MS). The aim of the work was to determine the evolution of this ubiquitous environmental contaminant along some post-treatment sludge processes, such as composting and thermally drying. DEHP concentration detected in some sludges are above the maximum limit suggested by the EC (100 ppm d.m.) for agricultural use. However, the composting and thermally drying reduce the amount of DEHP in sewage sludge to acceptable level for safe land application. The study was completed with the characterization and long-term observation of DEHP in sewage sludge, composted sludge and thermally dried sludge mixed with two types of soils. In all cases, the percentage of DEHP degraded was higher than 50% after 9 months of incubation.     

Persistence of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge-amended soil

The application of sewage sludge as a fertilizer is a common method used to improve soil properties. However, sewage sludge may contain various organic pollutants including polycyclic aromatic hydrocarbons. In the present study, the persistence of PAHs in soils fertilized with different sewage sludge doses was compared in relation to the sewage sludge dose applied (30, 75, 150, 300 and 600 Mgha(-1)) and the content of the polycyclic aromatic hydrocarbons in them. The experiment was carried out in two blocks of experimental plots divided according to the type of plants grown: field plants and perennial-willow. Sewage sludge addition to soils resulted in an increase in the content of polycyclic aromatic hydrocarbons in these soils. This increase was proportional to the quantity of sewage sludge applied. The results obtained showed that during a 42/54-month period, more than half of the individual PAHs introduced into the soil with sewage sludge were degraded. The scope of dissipation depended on the sewage sludge dose and the use to which the area was put. In the experiment with the willow only in the case of the highest sludge dose was a decrease in the PAH content above 50% noted; whereas in the case of the experiment with the field plants, it was higher by 50% for all sewage sludge doses. In experiment with field plants the highest scope of individual PAH disappearance was observed in the soil with the sewage sludge dose amounting to 300 Mgha(-1). In experiment with willow a relatively high dissipation of individual PAHs (>50%) was found in the treatment with the highest sludge dose (600 Mgha(-1)). A wider PAH dissipation range in the experiment with field plants was conditioned by the more favourable conditions created as a result of the breeding treatments applied. Agrotechnical treatments clearly increased the disappearance of the PAHs in those soils fertilized with the lowest sewage sludge doses (30 and 75 Mgha(-1)). The results obtained showed that the preferred method of treating a light soil fertilised with sewage sludges should be a one-year system, with a sludge application of 75 Mgha(-1).     

城市污泥与煤混合热解特性及动力学分析

为了污泥与煤混合热解的实验研究及工程化应用提供初步的数据及理论支持,利用热重分析仪讨论了污泥与煤混合热解的主要影响因素(加热速率、热解终温及混合比例)以及动力学参数。结果表明:加热速率对污泥热解影响较小;混合物热解终温与煤的热解终温基本一致;煤在污泥(干基)中的添加比例小于50%有利于挥发分的产出;通过热解特性及动力学参数分析,得出混合物比单一物料更易分解,且两者存在一定的协同效应;建立了污泥与煤不同混合比例在有机质主要热解区间内的经验动力学方程,经具体混合比例验证,经验动力学方程推导出的动力学参数及TG曲线与实际实验结果吻合较好。     

不同改性剂改善污泥土工性质的比较研究

选择了泥土、矿化垃圾、粉煤灰和建筑垃圾4种改性剂改性城市污水处理厂污泥(以下简称污泥)。结果表明:(1)随着4种改性剂与污泥的混合比增大,混合物含水率降低。(2)当混合比为0.7(质量比)时,各种混合物的抗压强度都达到50kPa的填埋要求;当混合比为0.3～1.0时,混合物的抗压强度随着混合比的增大呈指数形式增大;比较4种改性剂对抗压强度的增大能力,粉煤灰最强,建筑垃圾次之,泥土和矿化垃圾较弱。(3)在50kPa预压力下,混合物要达到不小于25kPa的抗剪强度,泥土与污泥最小混合比为1.0,矿化垃圾与污泥最小混合比为1.0,粉煤灰与污泥最小混合比为0.7,建筑垃圾与污泥最小混合比为0.7。(4)除加泥土的混合物外,混合物压缩系数随着混合比的增大呈总体下降趋势。(5)粉煤灰除臭效果最好,矿化垃圾次之,建筑垃圾较差,泥土最差。     

城市污水污泥固结体重金属浸出毒性及路用性能研究

城市污水污泥的重金属离子Pb、Zn超过国家固体废弃物排放最高允许值,属于危险废物。污水污泥的最佳出路是无害化处理,资源化利用,产业化发展。研究了以上海市污水污泥为原料,加入一定比例的固化剂和矿物掺合料使之固结,经养护满足路用强度性能,测试其固结体重金属离子浸出质量浓度亦满足国家固体废弃物排放标准,即污泥中的重金属离子得到有效的束缚和稳定固化,既解决了环境问题,又为污泥产业化发展开辟了新的途径。     

Organic Contaminants from Sewage Sludge Applied to Agricultural Soils. False Alarm Regarding Possible Problems for Food Safety? (8 pp)

Goal, Scope and Background Sewage sludge produced in wastewater treatment contains large amounts of organic matter and nutrients and could, therefore, be suitable as fertiliser. However, with the sludge, besides heavy metals and pathogenic bacteria, a variety of organic contaminants can be added to agricultural fields. Whether the organic contaminants from the sludge can have adverse effects on human health and wildlife if these compounds enter the food chain or groundwater still remains a point of controversial discussion. Main Features This paper presents an overview on the present situation in Europe and a summary of some recent results on the possible uptake of organic contaminants by crops after addition to agricultural fields by sewage sludge. Results Greenhouse experiments and field trials were performed to study the degradation and uptake of organic micro-contaminants in sludge-amended agricultural soil in crops, such as barley and carrots grown in agricultural soil amended with anaerobically-treated sewage sludge from a wastewater treatment plant, but studies hitherto have revealed no immediate risks. Common sludge contaminants such as linear alkylbenzene sulphonates (LAS), nonylphenol ethoxylates (NPE), polycyclic aromatic hydrocarbons (PAH), bis(diethylhexyl) phthalate (DEHP), showed neither accumulation in soil nor uptake in plants. Discussion It is assumed that the annual amount of sewage sludge produced in Europe will increase in the future, mainly due to larger amounts of high quality drinking water needed by an increasing population and due to increasing demands for cleaner sewage water. Application of sewage sludge to agricultural soils is sustainable and economical due to nutrient cycling and disposal of sewage sludge. However, this solution also involves risks with respect to the occurrence of organic contaminants and other potentially harmful contents such as pathogens and heavy metals present in the sludge. There have been concerns that organic contaminants may accumulate in the soil, be taken up by plants and thereby transferred to humans via the food chain. Results obtained so far revealed, however, no immediate risk of accumulation of common organic sludge contaminants in soil or uptake in plants when applying sewage sludge to agricultural soil. With very high dosages of sewage sludge, there may be a risk for accumulation of very apolar contaminants, such as DEHP, to the soil. Conclusions Any conclusions on the safe use of sewage sludge in agriculture have to be drawn carefully, as the studies performed until now have been limited. Further studies are required, and before final statements can be drawn, it is imminent to study a larger variety of common crops and the effect sewage sludge application may have on a possible accumulation of organic contaminants in the crops. Furthermore, a larger variety of organic contaminants need to be studied and special focus should be given to contaminants newly introduced into the environment. Besides investigating possible plant uptake of organic contaminants, the fate of these compounds in soil after sludge application need to be monitored too. Here, special attention has to begiven to studies on degradation and the formation of degradation products, to weathering and to leaching effects on groundwater, to the application of different crops on the same field (crop rotation), to the use of full-width tillage and strip tillage, and to long term application of sewage sludge on the soil. Recommendations and Perspectives There are environmental, political as well as economical incentives to increase the agricultural application of sludge. However, such usage should be performed with care as there are also ways in which sludge fertilisation could harm the environment and human health. Recently, a new European COST Action (859) has been established covering the field of food safety and improved food quality. Part of the Action is dealing with the application of sewage sludge in agriculture. Before any political and economical measures can be taken, the pros and cons have to be sufficiently investigated on a scientific level first. ESS-Submission Editor: Prof. Elena Maestri (elena.maestri@unipr.it)     

页岩对污泥氨气挥发的抑制作用

氨气是城市污水污泥产生的恶臭气体之一,控制或抑制其产生是资源化利用甚至处置过程中至关重要的.通过改进氨气测量方法定量分析外掺页岩对污泥氨气挥发的抑制作用和机理,实验研究了页岩掺量、陈放形式以及环境温度对污泥氨气挥发浓度的影响.结果表明,外掺页岩对污泥氨气挥发具有明显的抑制作用,随温度升高、陈放时间延长抑制效果有所减弱但仍具有明显作用;页岩对污泥氨气挥发的抑制作用主要为对氨气的吸附作用.     

Effects of sewage sludge amendment on heavy metal accumulation and consequent responses of Beta vulgaris plants

Use of sewage sludge, a biological residue produced from sewage treatment processes in agriculture is an alternative disposal technique of waste. To study the usefulness of sewage sludge amendment for palak (Beta vulgaris var. Allgreen H-1), a leafy vegetable and consequent heavy metal contamination, a pot experiment was conducted by mixing sewage sludge at 20% and 40% (w/w) amendment ratios to the agricultural soil. Soil pH decreased whereas electrical conductance, organic carbon, total N, available P and exchangeable Na, K and Ca increased in soil amended with sewage sludge in comparison to unamended soil. Sewage sludge amendment led to significant increase in Pb, Cr, Cd, Cu, Zn and Ni concentrations of soil. Cd concentration in soil was found above the Indian permissible limit in soil at both the amendment ratios.

The increased concentration of heavy metals in soil due to sewage sludge amendment led to increases in heavy metal uptake and shoot and root concentrations of Ni, Cd, Cu, Cr, Pb and Zn in plants as compared to those grown on unamended soil. Accumulation was more in roots than shoots for most of the heavy metals. Concentrations of Cd, Ni and Zn were more than the permissible limits of Indian standard in the edible portion of palak grown on different sewage sludge amendments ratios. Sewage sludge amendment in soil decreased root length, leaf area and root biomass of palak at both the amendment ratios, whereas shoot biomass and yield decreased significantly at 40% sludge amendment. Rate of photosynthesis, stomatal conductance and chlorophyll content decreased whereas lipid peroxidation, peroxidase activity and protein and proline contents, increased in plants grown in sewage sludge-amended soil as compared to those grown in unamended soil.

The study clearly shows that increase in heavy metal concentration in foliage of plants grown in sewage sludge-amended soil caused unfavorable changes in physiological and biochemical characteristics of plants leading to reductions in morphological characteristics, biomass accumulation and yield. The study concludes that sewage sludge amendment in soil for growing palak may not be a good option due to risk of contamination of Cd, Ni and Zn and also due to lowering of yield at higher mixing ratio.     

氧化亚铁硫杆菌对电动力处理城市污泥中重金属影响研究

分析了氧化亚铁硫杆菌对污泥中重金属形态及对电动力处理污泥中重金属的去除率影响.氧化亚铁硫杆菌处理后的污泥,pH值降低,部分重金属从稳定态转化为可溶态.经氧化亚铁硫杆菌预处理后的泥样和未经预处理的泥样,在同样条件下用电动力处理,处理结果为:预处理后Cd的去除率从61.85%上升到72.54%,Cu从34.26%上升到63.51%,Zn从65.06%上升到7L 22%.预处理对Cu的影响比Cd、Zn大得多.用电动力处理Cu超标污泥中重金属时,将污泥先用氧化亚铁硫杆菌预处理,可有效地提高其去除效果,处理后的污泥有利于农用.