厌氧消化污泥和未消化污泥在TG-MS上的热化学特性比较

利用热重-质谱联用仪对厌氧消化污泥和未消化污泥的燃烧和热解过程分别进行了研究.结果表明,2种污泥燃烧和热解过程中的热失重行为都可分为失水、有机物分解、无机物分解3个阶段.在300～350℃温度范围内,无论燃烧还是热解过程,未消化污泥有机物分解造成的热失重现象均比厌氧消化污泥明显.无机物分解阶段,厌氧消化污泥主要是碳酸盐的分解,未消化污泥主要是硫酸盐的分解.采用同步质谱仪对热解和燃烧的气态产物进行了分析,结果表明,污泥燃烧和热解过程除了产生大量的H2O和CO2外,热解过程还产生CH4、C2H6、C4H10、C7H8等有机气体以及H2.厌氧消化污泥热解时有机气体产生量小于未消化污泥.     

热分析-质谱联用分析生物垃圾热解机理

采用热分析-质谱联用技术研究了城市生活垃圾中三种生物质成分的热解过程,并采用Freeman-Carroll法定量分析了三种生物质热重动力学参数。结果表明木屑、落叶和菜叶这类生物质热解过程分为三个阶段,先是水分析出的微小失重阶段,之后是因纤维素等大分子进行交联缩聚的快速热解阶段,表现为放热效应,逸出的气体主要有H2O、CO2、C2H6/C2H4和CH4,最后是吸热脱链解聚的缓慢热解过程,逸出的小分子气体主要有CO2。     

微波热解污泥燃气释放影响因素及热解动力学分析

微波热解城市污水污泥可实现污泥资源化、减量化目标。城市污水污泥微波热解后产生大量能源气体H2和CO。运用气相色谱技术检测H2和CO的含量,研究了热解终温、污泥含水率、矿物催化剂对污泥微波热解过程中能源气体产率的影响,结合热重分析对热解过程进行了动力学分析。结果表明:随着热解终温升高,2种燃气产率均有所提高,800℃时,1 kg干污泥产生29.02 g H2以及302.72 g CO,两者体积之和占气体总体积的58%;污泥含水率越高,气体产率越高,但是达到90%含水率时,热解过程无法进行。镍基催化剂和白云石对能源气体产率均有促进作用,800℃时,镍基催化剂可使H2和CO产率提高到60%,对CxHy产率提高效果不明显;利用一级反应动力学方程对污泥热重结果进行分析,计算出热解动力学参数。     

含油污泥与污水污泥共热解特性及动力学研究

热解是危/固废处理处置的一种重要技术手段,热重及热解动力过程研究在快速提升原料热解特性认识上具有较大的参考价值。通过含油污泥、污水污泥及混合污泥热重分析发现,混合污泥和含油污泥的热解进程基本一致,污水污泥的掺入仅改变了混合污泥的热解程度。动力学分析表明,3种样品成分复杂,活化能均较低,热解初期反应强烈,随着有机组分反应逐渐热解完毕,反应级数趋于降低;通过分析3种样品各阶段活化能和频率因子发现,含油污泥和污水污泥的共热解在低温区的相互作用较弱,在高温区表现出一定的协同作用。     

城市污泥两段式催化热解制合成气研究

为了把城市污泥中温热解产生的挥发性产物转化为可直接利用的洁净可燃性气体或重要的化工原料合成气,采用两段式热解装置对城市污泥进行了催化热解实验研究,讨论了不同催化剂对城市污泥热解挥发性产物的催化裂解能力,结果表明:城市污泥在热解终温500℃,热解液产率最大,超过500℃,热解液产率减少,热解气增多,固相产率基本不变;城市污泥热解液的裂解温度需在900℃以上,产生的气体组分主要为H2、CO、CH4等小分子非冷凝性气体;Ni/分子筛复合催化剂对热解液转化为合成气的作用效果较好,合成气体(H2+CO)体积含量占气体总量的85%以上.     

生活垃圾热解产物中含氧物质的分布规律

采用热重分析、固定床实验、红外分析(FT-IR)研究了生活垃圾热解行为及产物中含氧物质的分布规律。用热重分析确定了生活垃圾主要失重区间(190~450℃),并计算此温度区间热解活化能为42.76 k J/mol。在热解终温为450~650℃条件下进行生活垃圾固定床热解实验,结果表明:随热解终温的增加,固体产物中氧分布率逐渐减小(39.2%~29.3%);热解气中氧分布率逐渐增加(22.1%~30.9%);热解液中氧分布率在40%左右。生活垃圾热解气中含氧成分主要是CO和CO2,在温度为450~650℃时,CO含量明显高于CO2,而CO2的释放速率则大于CO;固体产物中含氧官能团主要有—OH和C—O,其中峰面积比例顺序为C—O>—OH;热解液中含氧官能团主要有—OH、C O和C—O,其峰面积的比例顺序为—OH>C—O>C O。     

含厨余垃圾的混合污水污泥热解性能及逸出气体分析

为解决厨余垃圾进入市政管网导致的污泥处理问题,利用厨余垃圾制备初沉污泥(PS),与污水处理的残余污泥(RS)混合制备了不同厨余垃圾比例的混合污水污泥(MSS)。采用TG-FTIR评估了含厨余垃圾的混合污水污泥的热解性能及逸出气体特性。质量损失可分为3个阶段:初步脱水阶段、主要分解阶段及连续轻微分解阶段。PS含量的增加导致反应速率提高和热解特性参数CPI增加,反应时间缩短,从而提高了污水污泥的热解性能。不同温度下PS和RS之间的相互作用存在差异,低温区(<300℃)基本不存在相互作用,中温区(300~550℃)为相互促进,高温区(550~850℃)为相互抑制。FTIR主要检测出CH₄、CO₂、H₂O、CO、CO、SO₂ 6种气态产物及官能团,表明CO₂是主要的气态产物,且随着PS含量的增加,逸出气体及官能团的产生均增加。相互作用不仅体现在质量损失过程中,也体现在产物演化过程中,PS50RS50呈现最明显的相互促进效果,可认为是最适合的比例。随着温度增加,产物普遍在500~600℃内达到最大值,可认为是最佳的热解温度。     

HCl气体对污泥热解产物性质影响的试验研究

为研究污泥热解中同步提升热解产气品质和制取低重金属含量半焦吸附剂,文章分别在800℃和900℃下进行干化后污泥的快速热解实验,对比研究了通入HC(l0.1%体积分数)气体对热解气体产物组分、半焦中重金属含量及制取半焦吸附性能的影响。研究表明热解过程中通入HCl可在提高热解气组分中H2、CO含量的同时提高重金属去除率、降低热解半焦中重金属残余量,增大热解半焦比表面积、提高其吸附性能,但对于半焦吸附性能的影响程度要小于对热解产气及重金属残余量的影响。900℃通入HCl时H2和CO含量均最高分别达到35.01%和30.68%,同时半焦中重金属浓度最低,且同时具有最大比表面积、最高吸附性能,对Pb2+最大吸附量为19.2 mg/g。     

模拟医疗废物在管式电阻炉上的热解特性研究

在管式电阻炉上对由聚丙烯、面巾纸、纱布、医用脱脂棉、一次性口罩、医用乳胶手套等按一定比例组成的模拟医疗废物在氮气气氛进行了热解研究。重点探讨了10K／min，20K／min，30K／min和40K／min等不同升温速率对热解产物分布、产气特性和热解过程的影响。结果表明，随着温度升高，模拟废物的热解产生气体的主要成分逐渐由CO2和CO转变为C3H6、CH4、C2H6、C2H4和C3H8。同时，热解处理对模拟废物的减量化效果比较明显，固体残留率仅为5．61％～7．02％。而且，加热速率对模拟医疗废物热解过程的影响较大。     

活化温度对SCAC制备过程中副产物生成规律的影响

文章研究了污泥-玉米芯活性炭(SCAC)制备过程中,活化温度对副产物(热解气和热解油)生成规律的影响。热解气和热解油分别采用气相色谱仪和气质联用仪进行分析检测。试验结果表明,随着活化温度的升高,SCAC的产量逐渐降低,热解气与热解油的产量则随之增多。不同温度条件下,热解气的主要成分均为H2和CO2,热解气中H2所占的体积百分数随着活化温度的升高而增加,而CO2则相应降低。此外,热解气中CH4的含量也会随着活化温度的上升而略有提高,说明较高的活化温度更有利于热解气的资源利用。热解油组分较为复杂,每个温度条件下的液态产物都包括上百种化合物,可分为烷烃,烯烃,苯类,酚类,腈类,杂环化合物,多环芳烃,有机酸,酰胺,酯类,甾体,醇,酮以及其他类共14大类型,其中以有机酸、腈类和甾体类有机物含量居多。随着活化温度的升高,有机酸和多环芳烃的含量有所增加,而酚类化合物的含量则有所降低;当活化温度升高至650℃以上时,甾体类有机物含量明显降低。     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.