微污染水源中溶解性有机氮组成规律及其水处理特性

以上海市黄浦江和青草沙长江原水为对象,研究了两大水源水中溶解性有机氮(DON)的含量变化、分子组成特征及其在常规净水工艺中的去除效果,并对DON与常规水处理指标间的相关性进行了分析.结果表明:两种原水以DOC、DON和UV254表征的有机物含量均以小分子量(5kDa)和亲水性有机物为主;微污染黄浦江原水中同时存在外源性及内源性污染,而青草沙长江原水中内源性污染占主导地位;饮用水常规净水处理工艺对黄浦江原水中DON的去除率为40%,优于长江原水DON的去除率16.7%;黄浦江和长江原水DON浓度与DOC和UV254相关性良好,其相关系数分别为0.59,0.52和0.74,0.51;鉴于常规处理对DON去除效果有限,而DON是导致强三致特性含氮消毒副产物(N-DBPs)的总前体物,因此水厂应通过强化常规、深度处理等手段改善DON在净水工艺中的去除效果.     

微污染水源中溶解性有机氮组成规律及其水处理特性

以上海市黄浦江和青草沙长江原水为对象,研究了两大水源水中溶解性有机氮(DON)的含量变化、分子组成特征及其在常规净水工艺中的去除效果,并对DON与常规水处理指标间的相关性进行了分析.结果表明:两种原水以DOC、DON和UV254表征的有机物含量均以小分子量(<5kDa)和亲水性有机物为主;微污染黄浦江原水中同时存在外源性及内源性污染,而青草沙长江原水中内源性污染占主导地位;饮用水常规净水处理工艺对黄浦江原水中DON的去除率为40%,优于长江原水DON的去除率16.7%;黄浦江和长江原水DON浓度与DOC和UV254相关性良好,其相关系数分别为0.59,0.52和0.74,0.51;鉴于常规处理对DON去除效果有限,而DON是导致强三致特性含氮消毒副产物(N-DBPs)的总前体物,因此水厂应通过强化常规、深度处理等手段改善DON在净水工艺中的去除效果.     

不同氧化剂降低膜污染效果的研究

采用不同的氧化剂预处理黄浦江原水后进行微滤膜(MF)膜过滤试验,考察预氧化对有机物的去除作用,及其对MF膜过滤特性的影响.结果表明,3种不同氧化剂对有机物的去除效果存在较大差别.臭氧投量在0.5~3.0mg/L范围内,臭氧对DOC和UV254的去除率最高分别为10%和71%;而氯和高锰酸钾对有机物的去除效果则较差.臭氧可将大分子有机物转变成小分子有机物,将大部分疏水性有机物氧化成亲水性有机物.这种有机物组成结构的改变对膜过滤特性产生影响,明显降低了膜污染,膜污染下降率最高可达到22.7%.氯和高锰酸钾的氧化性相对较弱,仅能去除少部分疏水性有机物,对膜污染有较小减缓作用,膜污染下降率最高分别为9%和8.5%.     

强化混凝去除黄浦江水有机物的试验研究

强化混凝去除有机物的效果与水源的分子量分布特性有着密切的关系.由于黄浦江水中低分子量的溶解性有机物占多数,因此,强化混凝处理有机物效果有限.对于＜1k分子量区间的有机物.增加混凝剂投量可有效去除紫外吸光值(UV254),但去除溶解性有机碳(DOC)的效果很差.尽管增加混凝剂投量和降低pH都能有效地去除有机物,但决定强化混凝效果的主要因素是pH,去除黄浦江水有机物的最佳pH范围为6～5.     

城市污水二级出水有机物分子量分布和亲疏水特性对纳滤膜污染的影响

分别采用分子量分级膜和XAD-8树脂,研究了污水厂二级出水中有机物分子量分布特征及不同分子量分布区间亲疏水有机物的相对含量,考察了分子量分布及亲疏水特性对纳滤膜透水性能的影响.结果表明,二级出水有机物中,小分子亲水性有机物含量最高,小于2k的有机物占总有机物含量的45.61%,其中亲水性物质占28.07%,疏水性物质占17.54%;不同特征的原水分别经纳滤膜过滤,分子量分布对膜污染影响较大,分子量小于30k时,分子量区间越小,比通量衰减越快,分子量大于30k时,分子量区间越大,比通量衰减越快,且分子量较小的有机物通量衰减程度大于分子量较大有机物;在分子量分布相同区间内,亲水性有机物的比通量衰减较慢,说明相同分子量时,膜对亲水性物质的截留率较低,而疏水性物质是引起膜通量衰减的主要原因.     

不同组分的有机物对膜过滤通量下降的影响

采用DAX-8、XAD-4、IRA-958型树脂将自来水中有机物分离成强疏水性、弱疏水性、极性亲水性、中性亲水性有机物,以聚偏氟乙烯、聚醚砜、醋酸纤维3种材质的膜对各组分水样进行膜过滤试验,研究不同组分的有机物对膜过滤通量的影响.结果表明,过滤原水时,PES膜、PVDF膜和CA膜的通量分别比初始通量下降了67%、 59%和19%,表明疏水性越强的膜,越容易造成污染.就各种组分对通量的影响而言,过滤中性亲水性组分的通量下降为初始通量的41%～75%,而弱疏水性组分为6%～33%,表明中性亲水性组分对膜过滤通量的影响最大.3种膜中,CA膜对中性亲水性组分的截留率最高,达14.69%,但通量下降程度却最小,说明膜通量下降的程度并不与有机物截留总量正相关.对膜污染机制进行探讨后发现,对于截留分子量较大的超滤或微滤膜,相对分子质量>3×10⁴的中性亲水性组分通过堵塞膜孔内部,从而造成严重的膜污染;而对于截留分子量较小的超滤膜,中性亲水性组分由于无法进入膜孔,主要在膜表面形成滤饼层,从而对膜通量的影响较小.     

混凝和活性炭吸附去除微污染水源水中DON的研究

溶解性有机氮(dissolved organic nitrogen,DON)作为饮用水中新兴氮消毒副产物(nitrogenous disinfection by-products,N-DBPs)的前体物逐渐受到国内外学者的关注.为探讨混凝和活性炭吸附对微污染水源水中DON的去除机制,首先测定原水中DON、溶解性有机炭(dissolved organic carbon,DOC)、NH4+-N、UV254、pH和溶解氧(dissolved oxygen,DO)等指标和DON、DOC分子量分布;接着通过混凝和活性炭吸附试验来考察原水中DON、DOC和UV254变化,并应用三维荧光光谱对原水中DON变化进行表征.结果表明,微污染水源水中DON、DOC和UV254分别为1.28 mg.L-1、8.56 mg.L-1和0.16 cm-1,DOC与DON比值(DOC/DON)为6.69 mg.mg-1,SUVA为1.87 m-1.(mg.L-1)-1;小分子量(<6 000)DON占较高比例约为68%,大分子量(>20 000)DON占的比例为22%;当混凝剂投加量为10 mg.L-1,DON的去除率大约为20%,DOC和UV254去除率约26%、70%;当活性炭投加量为1.0 g,DON、DOC和UV254的去除率大约为60%、35%、100%;混凝和活性炭吸附组合试验时,对DON、DOC的去除率大约为82%和64%;三维荧光光谱证实,原水中DON变化与3个主要峰有关,分别代表物质为色氨酸类蛋白质、芳香族类蛋白质和富里酸类物质.     

东江水源水中有机物分子量分布特征研究

采用超滤膜法考察了东江水源水中有机物分子量分布特点,研究了东江泄洪和不泄洪水源水中有机物分子量分布的变化特征。结果表明,东江水源水在不泄洪期间水源水中的溶解性有机物主要为小分子量的有机物。而在泄洪期间,东江水源水中溶解性有机物主要为大分子量的有机物。UV254的分布和有机物分子量分布一致,DOC与UV254具有良好的相关性。泄洪期间水源水中SUVA值小于3,水体中有机物很难通过常规混凝工艺去除,此结果与水厂的实际运行情况相吻合。     

亲水聚合物改性微滤膜在膜生物反应器中的膜污染研究

采用经过聚合多巴胺和氨基聚乙二醇(mPEG-NH_2)表面改性的PVDF微滤膜,通过浸没在膜生物反应器(MBR)中验证改性微滤膜的抗污染性能.同时,采用多种分析手段对改性膜进行表征,包括膜表面微观形貌、润湿性、粗糙度和表面官能团等.实验同时考察了改性膜在MBR中运行的水通量衰减、污染膜的阻力分布,以及对膜面污染物的胞外多聚物组分的影响.结果发现,所采用的膜改性方法明显改善了膜表面的亲水性.短期过滤实验结果表明,多巴胺涂覆膜的稳定通量比原膜高47%,PEG改性膜则在水通量方面有进一步提高;在长期恒通量过滤阶段,多巴胺涂覆膜和PEG接枝膜的比膜通量分别比原膜高37%和88%.实验还发现,改性膜表面滤饼层中蛋白质和多糖含量均低于原膜.     

UV/H2 O2法对印染废水生化出水中不同种类有机物的去除效果

采用UV/H2O2高级氧化法对印染废水生化出水的处理进行研究,探讨了不同反应时间、H2O2投加量、反应初始pH值等因素对UV254,ADMI7.6、DOC和COD去除效果的影响.结果表明,以UV254、ADMI7.6、DOC和COD的去除率为筛选依据,确定出最佳参数组合为:反应初始pH值为原水pH 7.4～8.1,H2O2投加量为4.5 mmol.L-1,紫外光照射时间为50 min,在最佳处理条件下,UV254、ADMI7.6、DOC和COD的去除率分别达到77%、94%、40%和69%.通过XAD-8/XAD-4吸附树脂联用技术将印染废水生化出水中溶解性有机物分为疏水酸、非酸疏水物质、弱疏水物质及亲水物质4类有机物,研究了UV/H2O2氧化工艺对生化出水中各种有机物及色度的去除效果.实验结果表明,对于该印染废水的生化出水,疏水性物质是引起色度的主要物质,所占比例以ADMI7.6表征时为92%,其中以非酸疏水物质的贡献最大,达到53%.UV/H2O2高级氧化法处理此水样中的弱疏水性有机物、疏水酸和非酸疏水物质均有较好的处理效果,对亲水性有机物的处理效果较差.实验表明,相对分子质量>10 000的大分子有机物对DOC和ADMI7.6的去除贡献较大,对UV254的去除贡献接近一半.     

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.