蚯蚓对剩余污泥中重金属Cu、Zn的活化实验研究

以中国矿业大学南湖校区污水处理站的剩余污泥(简称污泥)为研究对象,通过培养实验,研究污泥中蚯蚓的生长情况和蚯蚓活动对污泥中重金属生物有效性的影响。实验结果表明,蚯蚓能够在一定浓度Cu、Zn的污泥中正常生长,表现出一定的重金属耐性,其耐受能力与重金属的种类、浓度、污泥的理化性质有关。蚯蚓活动能够降低污泥的pH,使之趋于中性。对不同浓度Cu处理污泥,蚯蚓活动使污泥有机质含量均有不同程度下降,其中对Cu为100 mg/kg的污泥中有机质含量影响最大;对不同浓度Zn处理污泥,蚯蚓活动使污泥有机质含量降低的幅度不大。蚯蚓活动可在一定程度上活化污泥中的重金属Cu和Zn,蚯蚓对Cu的活化效果较为明显,在污泥中添加Cu为50 mg/kg时,Cu活化率增加值最大,达到了11.14%;蚯蚓活动对Zn的活化效果不明显,Zn活化率增加值均低于1%。     

蚯蚓过腹处理对污泥中四环素降解及大量营养元素赋存的影响

针对污泥中大量抗生素残留对环境的威胁和污泥资源化利用的瓶颈等问题,采用微宇宙实验手段研究了蚯蚓过腹处理污泥过程中四环素的降解特征和污泥蚓粪中大量营养元素的赋存特征。结果表明,污泥中的四环素降解率与处理时间呈正相关关系;室温静置32 d后,污泥中9%～11%的四环素发生降解。蚯蚓过腹处理下,污泥中四环素浓度与四环素降解率呈负相关关系,随着污泥中四环素浓度的增加,四环素降解率逐渐降低,蚯蚓过腹处理32 d后,污泥中四环素的降解率提升了45%～64%。蚯蚓过腹形成的污泥蚓粪中总氮和有机质含量显著减低,而铵态氮、硝态氮、速效磷、速效钾和总钾含量以及pH和电导率均显著升高;随着污泥中四环素浓度的增加,污泥蚓粪中总氮和氨氮含量以及pH和电导率呈显著降低趋势;污泥蚓粪中铵态氮和硝态氮含量、pH和电导率与四环素降解率均呈正相关关系。蚯蚓过腹处理能够显著提升污泥中四环素的降解率及污泥蚓粪中速效氮磷钾的含量。     

赤子爱胜蚓处理污泥对其性质变化的影响

用赤子爱胜蚓(Eisenia foetida)直接处理脱水污泥,以不加蚯蚓为对照,研究了蚯蚓生物量、污泥理化性质(pH、电导、灰分、总有机碳)、营养物质(氮、磷、钾)以及重金属(铜、锌、铅、铬)的变化。结果表明:蚯蚓能很好地适应直接投加污泥的生存环境,蚯蚓平均增重0.7 g/d,产卵4.81个/d。随着时间的增加,接种蚯蚓的污泥理化性质和营养物质以及重金属含量均有显著的变化。蚯蚓处理后,污泥的pH由7.83显著降低至7.03;电导由0.46 S/m显著增至2.23 S/m;灰分从43.89%显著增至57.53%;TOC由32.32%显著降低至23.59%;污泥中的营养物质N、P、K含量显著增加,N、P、K分别提高了37.48%、19.96%和20.14%;同时蚯蚓活动显著降低了污泥中的重金属含量,降低次序为CuZnCrPb。蚯蚓处理后污泥小团粒性状明显,无臭味,不生蛆。     

芦苇和香蒲在人工湿地城市污泥处理系统中的应用

用有机玻璃材料做成模拟人工湿地,分别种植芦苇和香蒲考察2种模拟植物湿地对城市污泥干化和稳定化、污泥中营养元素和重金属去除效果,并和空白湿地对比。实验污泥取自当地污水厂二沉池,污水处理采用厌氧池加氧化沟工艺。模拟人工湿地进泥负荷为0.72 kg TS/(m2.d),进泥中TS平均含量为5.58 g/L,pH为6.80。实验期为1年,采用间歇式进泥,渗滤液月采集测样一次,湿地剩余污泥2月1次。实验结果受天气和气候影响较大,处理效果夏季好于冬季,出水水质和剩余污泥的干化及稳定效果芦苇湿地好于香蒲湿地。剩余污泥中各种重金属含量低于污泥农用标准中各重金属离子浓度要求。结果表明,人工湿地植物净化系统对城市污泥有较好的脱水和稳定化效果。     

城市污水厂混合污泥的生态稳定处理

城市污水厂初沉池和二沉池混合污泥利用由蚯蚓和微生物共同组成的人工生态系统进行稳定处理。蚯蚓生态床可集污泥浓缩、调理、脱水、稳定、处置和综合利用等多种功能于一身：(1)蚯蚓和微生物将污泥作为生长营养源，对其进行分解和吸收；(2)蚯蚓生理代谢产生的蚓粪是高效农肥和土壤改良剂；(3)在生态床中增殖的蚯蚓具有重要的饲料和药用价值。污泥物质经蚯蚓污泥稳定床处理后，可全部被生态系统吸收利用和转化，具有流程简单、管理方便、无二次污染、造价和运行费用低廉、副产物具有经济利用价值等特点，为解决污泥的最终处置问题提供了生态利用的新途径。     

微波法制备污泥活性炭研究

采用微波加热法,以污水厂剩余污泥为原料,磷酸为污泥活化剂制备污泥活性炭.微波功率、辐照时间和磷酸浓度对污泥活性炭吸附性能具有显著影响,在最佳工艺条件微波功率480 W、辐照时间315 s和磷酸浓度40%条件下制得的活性炭碘值301 mg/g,比表面积168 m2/g,污泥中重金属绝大部分被固化.与传统商品炭相比,污泥炭孔隙结构以中孔为主.利用该活性炭处理城市生活污水处理厂出水,COD去除率可达87%以上,污泥炭的吸附等温线用Langmuir等温吸附模型进行描述.     

畜禽养殖废水生物处理剩余污泥臭氧减量过程中的重金属释放

采用臭氧氧化污泥减量法对畜禽养殖废水SBR中的剩余污泥进行处理。当臭氧反应时间控制在30min时，污泥的溶解比例在30％左右（以MLSS计）。上清液中一定量的SCOD溶出可为生物处理单元提供充足的碳源，同时在上清液中，TN、TP及水相重金属浓度增加有限，臭氧氧化后的污泥液回流污水处理系统后造成的N、P处理负荷较小，重金属对污泥微生物的活性抑制风险较低。若继续延长臭氧的反应时间，上清液SCOD、TN、TP以及重金属cu、Pb的释放速率明显增加，同时上清液的C／N降低，臭氧化后的污泥液回流反而不利于生物单元的脱氮处理。综合考虑TN、TP及水相重金属浓度增加的危害性，臭氧反应时间应控制在30min，臭氧实际投加量应为123．1mg O3／gSS。     

鼠李糖脂对剩余污泥中铜和镍的去除

采用批次淋洗的方法研究了鼠李糖脂浓度、pH、淋洗时间、提取次数以及重金属形态对剩余污泥中Cu和Ni去除效果的影响。结果表明,随着鼠李糖脂浓度的增加,2种重金属的去除率增加,且鼠李糖脂在碱性条件下对Cu和Ni的去除效果较好,最高去除率可分别高达80.77%和46.74%;随着振荡时间和提取次数的增加,Cu和Ni的去除率随之增加,并明显高于去离子水的提取;对污泥重金属形态进行分析发现,鼠李糖脂能有效去除酸提取态的Cu和Ni。研究结论可为剩余污泥的资源化而产生重金属安全隐患问题提供解决的参考方案和奠定理论基础。     

畜禽养殖废水生物处理剩余污泥臭氧减量过程中的重金属释放简

采用臭氧氧化污泥减量法对畜禽养殖废水SBR中的剩余污泥进行处理。当臭氧反应时间控制在30 min时，污泥的溶解比例在30%左右（以 MLSS计）。上清液中一定量的SCOD溶出可为生物处理单元提供充足的碳源，同时在上清液中，TN、TP及水相重金属浓度增加有限，臭氧氧化后的污泥液回流污水处理系统后造成的N、P处理负荷较小，重金属对污泥微生物的活性抑制风险较低。若继续延长臭氧的反应时间，上清液SCOD、TN、TP以及重金属Cu、Pb的释放速率明显增加，同时上清液的C/N降低，臭氧化后的污泥液回流反而不利于生物单元的脱氮处理。综合考虑TN、TP及水相重金属浓度增加的危害性，臭氧反应时间应控制在30 min，臭氧实际投加量应为123.1 mg O₃/g SS。     

高温堆肥与蚯蚓堆肥对城市污泥重金属形态的影响

采用高温堆肥和蚯蚓堆肥工艺，研究了城市污泥与锯末、粉煤灰或磷矿粉按不同比例混合堆肥前后重金属（Cu、Pb、Zn、Cd和As）交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和残留态的变化。研究表明：高温堆肥和蚯蚓堆肥前后各试验污泥的重金属形态和含量呈现出不同的变化，都可以降低污泥中交换态Cu、Pb、Zn、Cd和As的含量；对于Cu和Pb，高温堆肥优于蚯蚓堆肥；对于Zn、Cd和As，蚯蚓堆肥优于高温堆肥。2种堆肥方式中，粉煤灰用量为10%的钝化效果优于20%，磷矿粉的钝化效果同粉煤灰一样。     

Earthworm contamination by PCBs and heavy metals

A comparison is made of soil and earthworm contamination by PCBs and heavy metals between a nature reserve and two sites conditioned by the addition of sewage sludge and compost.The tissues and gut content of the earthworms shows a higher PCB concentration than that of the surrounding soil and also a difference in the fingerprint of some single PCB compounds.Earthworms display a selective accumulation of cadmium and zinc in their tissues and gut content.     

Earthworm communities along a gradient of urbanization

Earthworms were studied at six sites along a gradient of urbanization and their relations with several soil abiotic factors were determined. Concentrations of heavy metals, calcium and magnesium in earthworms and in soils were measured by atomic absorption spectroscopy. Strong negative correlations were detected between earthworm density and soil concentrations of cadmium and magnesium. Earthworm biomass was negatively correlated with lead, copper and zinc, and positively correlated with the distance from the centre of the city. High concentrations of Cd and Zn (concentration factors 49 and 32) were accumulated by earthworms in contrast to those of Cu and Pb (2 and 1). Relations between worm and soil concentrations of heavy metals, Ca and Mg are discussed.     

Heavy metal concentrations in soil and earthworms in a floodplain grassland

We determined accumulated heavy metal concentrations (Cd, Pb, Cu, Zn) of earthworms in moderately contaminated floodplain soils. Both soil and mature earthworms were sampled before and after flooding and earthworm species were identified to understand species specific differences in bioconcentration. Accumulated metal concentrations in floodplain earthworms differed before and after flooding. Differences in uptake and elimination mechanisms, in food choice and living habitat of the different earthworm species and changes in speciation of the heavy metals are possible causes for this observation. Regression equations taken from literature, that relate metal accumulation by earthworms in floodplains as a function of metal concentration in soil, performed well when all species specific data were combined in an average accumulation, but did not address differences in accumulation between earthworm species.     

Bioavailability and plant accumulation of heavy metals and phosphorus in agricultural soils amended by long-term application of sewage sludge

Amendment of agricultural soils with municipal sewage sludges provides a valuable source of plant nutrients and organic matter. Nevertheless, addition of heavy metals and risks of eutrophication continue to be of concern. Metal behaviour in soils and plant uptake are dependent on the nature of the metal, sludge/soil physico-chemical properties and plant species. A pot experiment was carried out to evaluate plant production and heavy metal uptake, soil heavy metal pools and bioavailability, and soil P pools and possible leaching losses, in agricultural soils amended with sewage sludge for at least 10 years (F20) compared to non-amended soils (control). Sewage sludge application increased soil pH, N, Olsen-extractable-P, DOC and exchangeable Ca, Mg and K concentrations. Total and EDTA-extractable soil concentrations of Cu and Zn were also significantly greater in F20, and soil metal (Cu, Mn and Zn) and P fractionation altered. Compared to the control, in F20 relative amounts of acid-extractable (Mn, Zn), reducible (Mn, Zn) and oxidisable (Cu, Zn) metal fractions were greater, and a dominance of inorganic P forms was observed. Analyses of F20 soil solutions highlighted risks of PO4 and Cu leaching. However, despite the observed increases in metal bioavailability sewage sludge applications did not lead to an increase in plant shoot concentrations (in wild plants or crop species). On the contrary, depending on the plant species, Mn and Zn tissue concentrations were within the deficiency level for most plants.     

Assessing the impact of organic and inorganic amendments on the toxicity and bioavailability of a metal-contaminated soil to the earthworm Eisenia andrei

Metal-contaminated soil, from the El Arteal mining district (SE Spain), was remediated with organic (6 % compost) and inorganic amendments (8 % marble sludge) to reduce the mobility of metals and to modify its potential environmental impact. Different measures of metal bioavailability (chemical analysis; survival, growth, reproduction and bioaccumulation in the earthworm Eisenia andrei), were tested in order to evaluate the efficacy of organic and inorganic amendments as immobilizing agents in reducing metal (bio)availability in the contaminated soil. The inorganic amendment reduced water and CaCl₂-extractable concentrations of Cd, Pb, and Zn, while the organic amendment increased these concentrations compared to the untreated soil. The inorganic treatment did not significantly reduce toxicity for the earthworm E. andrei after 28 days exposure. The organic amendment however, made the metal-contaminated soil more toxic to the earthworms, with all earthworms dying in undiluted soil and completely inhibiting reproduction at concentrations higher than 25 %. This may be due to increased available metal concentrations and higher electrical conductivity in the compost-amended soil. No effects of organic and inorganic treatments on metal bioaccumulation in the earthworms were found and metal concentrations in the earthworms increased with increasing total soil concentrations.     

Effects of earthworms and effective microorganisms on the composting of sewage sludge with cassava dregs in the tropics

The present study revealed the role of earthworm-effective microorganisms (EM) in converting sewage sludge and cassava dregs into a valuable product. Sewage sludge was toxic to earthworm, therefore it was mixed with cassava dregs in 80:20 proportions (dry weight). Treatments included mixed substrate inoculated versus not inoculated with EM and treated with or without earthworms. The pH, total organic carbon, total nitrogen, and C:N ratio decreased from the initial measurements in the range of 17.43–18.46%, 25.48–33.82%, 19.60–25.37%, and 6.68–14.05% respectively; but electrical conductivity and available phosphorus increased in the range of 113.47–158.16% and 42.42–57.58%, respectively. In addition, they interactively increased total phosphorus from 19.84–63.01% and potassium from 16.41–50.78%, and decreased the polycyclic aromatic hydrocarbons content of substrate from 21.17% to 32.14% with an increase in earthworms from 51.71 to 57.69, respectively. Earthworms and EM could be used together as an efficient method for co-composting sewage sludge plus cassava dregs in the tropics. This could be expected to result in stabilization of waste, increase in nutrients, and reduction of pollutant content.

Implications: The first reports of interaction of earthworms and effective microorganisms in the treatment of sewage sludge and cassava dregs in the tropics. Co-composting was an efficient technology for treating sewage sludge and cassava dregs at the same time, in the tropics. The survival rate of the earthworms both> 95%, the highest number of cocoons (640.33) and hatchlings (4694.33) both in EW+EM (Earthworms added and EM inoculated) treatment. Earthworms and EM (Only EM inoculated) interactively increased total phosphorus and potassium content, and decreased the PAH content of substrate with increase in earthworms.     

A review of studies performed to assess metal uptake by earthworms

Earthworms perform a number of essential functions in soil; the impacts of metals on earthworms are often investigated. In this review we consider the range of earthworm species, types of soil and forms of metal for which metal uptake and accumulation have been studied, the design of these experiments and the quantitative relationships that have been derived to predict earthworm metal body burden. We conclude that there is a need for more studies on earthworm species other than Eisenia fetida in order to apply the large existing database on this earthworm to other, soil dwelling species. To aid comparisons between studies agreement is needed on standard protocols that define exposure and depuration periods and the parameters, such as soil solution composition, soil chemical and physical properties to be measured. It is recommended that more field or terrestrial model ecosystem studies using real contaminated soil rather than metal-amended artificial soils are performed.     

Residual metal concentrations in soils and leaf accumulations in tobacco a decade following farmland application of municipal sludge

The objectives of this investigation were to examine the long-term residual effects of metal loading through sewage sludge applications on the total vs. diethylene triamine pentacetic acid (DTPA) extractable metal concentrations in soil and leaf accumulations in tobacco. Maryland tobacco (Nicotiana tabacum L.), cv. 'MD 609', was grown in 1983 and 1984 at two sites in Maryland that had been amended in 1972 with dewatered, digested sewage sludge from washington, DC, at rates equal to 0, 56, 112 and 224 mg ha(-1). The metal concentrations in the sludge, in mg kg(-1) dry weight, were: 1300 Zn, 570 Cu, 280 Pb, 45 Ni and 13 Cd. Soil samples collected from the surface horizon and composite leaf samples of cured tobacco were analyzed for total Zn, Cu, Mn, Fe, Pb, Ni and Cd concentrations. The soil samples were also examined for soil pH and DTPA extractable metals. Equations were generated using polynomic and stepwise regression analyses which described the relationships between total vs. DTPA extractable soil metals, and between DTPA soil and soil pH vs. plant metal concentrations, respectively. Significant increases were observed for both total and DTPA extractable metal concentrations for all metals, with all but total Mn and Ni being significant for linear and quadratic effects regarding sludge rates. However, linear relationships were found between DTPA extractable vs. total soil concentrations for all elements except Pb and Ni which were quadratic. Significant increases in plant Zn, Cu, Mn, Ni and Cd and decreases in Fe were observed with increased sludge rates. Plant Pb levels were unaffected by sludge applied Pb. Linear relationships were observed between plant Zn and Cd and DTPA soil metal levels: however, Mn and Cu levels were described by quadratic and cubic relationship, respectively. Relationships between plant Fe and Pb and DTPA extractable concentrations were nonsignificant. Additional safeguards to protect crop contamination from heavy metals such as Cd were discussed.     

Interactions between sewage sludge-amended soil and earthworms—comparison between <Emphasis Type="Italic">Eisenia fetida</Emphasis> and <Emphasis Type="Italic">Eisenia andrei</Emphasis> composting species

Vermicomposting is an eco-friendly technology, where earthworms are introduced in the waste, inter alia sewage sludge, to cooperate with microorganisms and enhance decomposition of organic matter. The main aims of the present study was to determine the influence of two different earthworm species, Eisenia fetida and Eisenia andrei, on the changes of selected metallic trace elements content in substratum during vermicomposting process using three different sewage sludge mainly differentiated by their metal contents. Final vermicompost has shown a slight reduction in Cd, Cu, Ni, and Pb, while the Zn concentration tends to increase. Accumulation of particular heavy metals in earthworms’ bodies was assessed. Both species revealed high tendency to accumulate Cd and Zn, but not Cu, Ni, and Pb, but E. andrei has higher capabilities to accumulate some metals. Riboflavin content, which content varies depending on metal pollution in several earthworms species, was measured supravitaly in extruded coelomocytes. Riboflavin content decreased slightly during the first 6 weeks of exposure and subsequently restored till the end of the 9-week experiment. Selected agronomic parameters have also been measured in the final product (vermicompost) to assess the influence of earthworms on substratum.     

Feasibility of vermicomposting dairy biosolids using a modified system to avoid earthworm mortality

A laboratory study was conducted to examine the feasibility of vermicomposting dairy biosolids (dairy sludge), either alone or with either of the bulking agents-cereal straw or wood shavings, using the epigeic earthworm-Eisinea andrei. Earthworms added directly to these three substrates died within 48 hours. A system was developed to overcome the toxic effect of unprocessed dairy biosolids. The substrates were placed over a layer of vermicomposted sheep manure into which the earthworms were inoculated. Within two weeks, all earthworms were within the upper layer of substrate. Compared to sheep manure which is a favourable substrate for vermicomposting, the three substrates containing dairy biosolids were more effective in supporting earthworm growth and reproduction. The final products obtained after 63 days of vermicomposting had 39-53% less organic carbon than the initial substrates. Organic fractionation indicated that vermicomposting increased the stability of the materials to biological decomposition. The vermicomposts obtained from the three substrates with dairy biosolids had low heavy metal contents and electrical conductivities, and did not inhibit plant growth when compared with a commercial vermicompost in a bioassay.