曝气生物滤池进水COD浓度对NH_3-H去除率影响

为探讨曝气生物滤池进水COD浓度对NH3-H去除效果的影响,选取污水厂现场进行实地研究。将反应器进水COD浓度划分为5个水平:70~90 mg/L、90~110 mg/L、110~130 mg/L、130~150 mg/L、>150 mg/L,测定上述各个水平下的NH3-N去除率并进行反正弦转换后,做单因素方差分析。结果表明,在一定的水力负荷条件下,进水COD浓度与NH3-H的去除率密切相关,当进水ρ(COD)<90 mg/L和>150 mg/L时,NH3-H去除率较低;而当进水ρ(COD)为90~110 mg/L时,NH3-H去除率较高。     

BAF去除氨氮关键影响因素研究

为探讨曝气生物滤池去除氨氮的关键因素,选取沈阳仙女河污水处理厂(40万t/d)现场进行实地研究。通过测定不同条件下(pH、进水COD浓度、溶解氧、温度、水力负荷)的氨氮去除率,并进行主成分分析结果显示,影响BAF工艺脱氮的关键因素是温度、溶解氧和水力负荷。当温度在14~30℃之间时,氨氮的去除率一直维持较高,当温度低于14℃时,氨氮的去除率较低;随着溶解氧浓度的增大,氨氮的去除率也随之升高,当溶解氧增加到5.6 mg/L时,氨氮的去除率达到80%~90%,接近饱和状态;在水力负荷为3.08~4.15 m3/(m.2h)之间时,氨氮的去除率上升,超过该值,则氨氮去除率下降。     

序批式曝气生物滤池处理生活污水的中试研究

报道了沸石为填料的序批式曝气生物滤池处理生活污水的中试实验,研究了曝气时间、曝气量和生活污水浓度对处理效果的影响。结果表明,沸石作曝气生物滤池的填料效果较好。曝气2h后,即可达到很好的去除效果,污水进水COD和BOD5浓度分别为300～800mg/L和170～400mg/L时,去除率分别达到90%～70%和90%～88%。进水COD浓度分别为312.6mg/L和530.6mg/L,曝气量0.6m3/h,处理2h后出水COD浓度分别为30.63mg/L和103.92mg/L,去除率>90%,出水达到污水处理二级排放标准。因此,以沸石为填料的序批式曝气生物滤池是一种高效、低耗、具有较好应用前景的单体生活污水处理设备。     

再生水工艺中曝气生物滤池的特性研究

对再生水工艺中曝气生物滤池(BAF)的运行特性进行了试验研究,结果表明:BAF对浊度的平均去除率为72%,出水浊度稳定在5NTU以下;COD最佳水力负荷为7 m/h,最佳容积负荷为5.89 kg/(m3.d);NH4+-N最佳水力负荷为5.0 m/h;水力冲击负荷对硝化菌的影响较小,而对异养碳化菌影响较大。     

反硝化生物滤池稳定运行的影响因素研究

以高浓度硝氮废水为研究对象,考察反硝化生物滤池(DNBF)的启动情况以及稳定运行时饥饿时间、水力停留时间(HRT)和进水负荷对硝氮去除率的影响。结果表明:经过36 d的启动驯化后,DNBF对浓度为100 mg/L的硝氮去除率达90%以上;饥饿10 d后,DNBF重新启动13 d后可恢复到饥饿前的脱氮水平;进水硝氮浓度150 mg/L时,HRT从2 h增加到6 h后,硝氮去除率从48.8%升高到79.9%;而当进水负荷从0.59 kg/(m3·d)增加到3.28 kg/(m3·d)时,去除率基本稳定在81.4%。     

曝气生物滤池中COD去除影响因素试验分析

以上向流曝气生物滤池为研究对象,对COD的去除效果及影响因素进行了探讨.试验结果表明:上向流曝气生物滤池对COD去除效果具有一定的抗冲击负荷能力,在进水COD质量浓度均值为68.3mgL时,出水氨氮质量浓度均值为26.1 mg/L,去除率为61.8%,去除效果稳定.不同操作条件对COD去除效果的影响为:曝气生物滤池只需较低的曝气量,在V(气):V(水)=5:1的情况下即可获得对有机物较高的去除效率;曝气生物滤池时有机物的降解主要发生在进水端0～60cm范围内;水力负荷在0.5～1.5 m3/(m2·h)的变化范围内.反应器对有机物去除能力基本不受影响;水力负荷和进水COD等2种途径带来的COD容积负荷变化对其去除率没有明显的区别,并且有很强的抗冲击负荷的能力.     

高负荷生物滤池处理城市污水研究进展

高负荷生物滤池中试研究在城市污水处理厂内进行,进水BOD5为 118mg L。水力负荷在 10～ 2 6m3/m2 ·d的范围内对去除率有着十分显著的影响。在水力负荷HL =10m3/m2 ·d的操作条件下,该反应器对BOD5的去除率平均达到 80 %。通过实验观察发现,基于水力负荷的设计方程可以很好的反映BOD5的浓度     

生物活性炭滤池修复地表水的研究

采用自行设计的生物滤池反应器去除地表水中的氮,考察了HRT、水力负荷和氨氮负荷对生物滤池出水水质的影响。结果表明:系统TN去除率随水力负荷的增加而下降,氨氮去除率无明显变化,水力负荷小于1.2 m3/(m2·d),TN去除率达到54%以上;在进水氨氮质量浓度为14.52~17.44 mg/L条件下,HRT为10 h时,生物滤池对氮去除效果较好;当HRT为6 h,进水氨氮负荷增加到0.048 kg/(m3·d)以上,氨氮和TN平均去除率分别为96%和31%。     

曝气生物活性炭滤池深度处理垃圾渗滤液的效能研究

为了考察曝气生物活性炭滤池(BACF)深度处理垃圾渗滤液的效能,研究了填料填充度、曝气位置、气水比、水力停留时间和p H等影响因素对滤池去除有机物、氨氮和总氮的影响。结果表明,最佳的工艺运行条件为:填料填充度为80%,底部曝气,气水比为3:1,水力停留时间为8 h,p H为7~8。在最佳工艺条件下运行反应器,COD、氨氮和TN平均去除率分别达到85%、90%和57%,出水可达到实验设定水质要求。BACF具有较强的抗有机负荷能力,进水COD浓度在323至3 000 mg/L之间时,COD去除率稳定在80%。反应器受氨氮冲击负荷影响较大,氨氮进水浓度低于90mg/L时,出水可达到要求。     

粉煤灰基质滤料生物过滤处理生活污水研究

将粉煤灰基质滤料用于曝气生物滤池,该滤料具有较高的比表面积和孔隙率,吸附性能良好,挂膜后生物相丰富。对于中等浓度的生活污水,当水力负荷和COD有机物负荷分别控制在1.53 m3/(m2.h)、3.68 kg/(m3.d)以下时,该曝气生物滤池COD和NH3-N去除率能稳定在85%以上,出水COD和NH3-N达到排放标准要求。该曝气生物滤池对进水水质水量的变动具有较强的抗冲击负荷能力。     

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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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.     

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.     

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.     

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.     

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.