腐朽木为填料的反硝化滤池特性研究

针对城市污水处理厂二级出水低碳氮比的水质特点,该文通过腐朽木的释碳静态实验和反硝化滤池动态实验,研究了腐朽木的碳源释放规律,对腐朽木释碳组份进行了GC/MS分析,同时以人工模拟配制低碳氮比废水作为反硝化滤池实验的进水,从TN、NO_3~--N的去除效果和COD、NO_2~--N、NH_3-N的变化规律,分析和研究腐朽木作为填料在不同水力停留时间(HRT)下反硝化滤池的脱氮性能和运行效果。结果表明,腐朽木可有效地释放碳源物质,腐朽木释碳组份主要为(Z)-9-Octadecenamide,其分子式为C18H35NO;反硝化滤池在初始阶段HRT为12 h时,脱氮效果最佳,TN、NO3--N去除率最高分别可达到94.41%、97.13%,此时腐朽木作为外加缓释碳源填料显著提高了滤池脱氮效果。     

以PHBV为碳源和生物膜载体的生物反硝化研究

采用了一种可生物降解聚合物(BDP)聚羟基丁酸戊酸酯(PHBV)作为碳源和生物膜载体去除水体中的硝酸盐.结果表明:以PHBV为碳源和载体的反硝化系统启动时间短,硝酸盐氮(NO3--N)去除率高于93%;水力停留时间(HRT)对反硝化效果影响显著,但反硝化系统对进水硝酸盐氮负荷具有较好的抗冲击能力;出水DOC(溶解性有机碳)浓度低于27.5mg/L,表明PHBV具有一定的控释碳源的能力;反应器不同高度脱氮效果差异显著,反应器中层(10-15cm) 处获得最大NO3--N去除率.     

以麦秆作为好氧反硝化碳源的研究

采用室内试验装置,研究以麦秆为碳源和反应介质的生物反应器在好氧条件下去除地下水中硝酸盐的影响因素和效果。结果表明,以麦秆为碳源的反应器启动快,反硝化反应受温度及水力停留时间影响大。28℃时N的去除量约33℃的3倍。当室温为(27±1)℃,进水硝酸盐氮浓度为50mg/L、水力停留时间56.85h时,反应器对氮的去除率在94.64%以上;当水力停留时间为12h时,氮去除率<50%。同时反硝化反应受pH值和进水NO3--N浓度的影响。当pH值为6.7时,N的去除率最高,达90%以上。反硝化速率与NO3--N浓度显著呈线性关系。     

以稻草为碳源和生物膜载体去除水中的硝酸盐

采用室内试验装置,研究了以农业废弃物稻草为反硝化碳源和反应介质的生物反应器对于污水中硝酸盐的去除效果及其影响因素.结果表明,以稻草为反硝化碳源和生物膜载体的反应器启动时间短,对污水中硝酸盐氮的去除效果好,且试验过程中未发现亚硝酸盐累积;进水硝酸盐浓度对装置的处理效果有一定影响,浓度过高会导致硝酸盐的去除率下降;装置对进水DO和ｐH变化有一定抗性,DO在1.0～3.5 mg/L,pH在6.5～8.5之间变化时,反应器硝酸盐的去除率变化很小,缓冲能力较强;反应器稳定性强,装置运行84 ｄ后,出水硝酸盐开始升高,硝酸盐去除率逐步降低,但去除率仍在50%以上.     

锯末+乙醇作为混合碳源去除地下水中硝酸盐的影响因素研究

本试验采用室内试验装置,研究了 pH、温度、硝酸盐浓度对锯末+乙醇作为混合碳源去除地下水中硝酸盐的影响结果表明,pH值在5～10内变化时对锯末+乙醇混合碳源体系的硝酸盐去除率影响较大,pH ＞7时的硝酸盐去除率明显高于pH ＜7时的去除率;并且随着pH值的增加,亚硝酸盐的积累量越多,锯末+乙醇混合碳源体系最佳的pH值范围是7～8.锯末+乙醇混合碳源体系受温度的影响较大,温度为8.5、15℃时的反硝化速率显著低于25℃时的速率,25℃时的反硝化速率分别是8.5、15℃时的3倍和1.5倍,锯末+乙醇混合碳源体系适宜的温度范围为25 ～35℃进水硝酸盐浓度也会影响锯末+乙醇混合碳源体系的反硝化效果,硝酸盐氮浓度在67.8 ～113 mg·L-1范围内变化时,反应体系的硝酸盐去除效果较好反应初期,硝酸盐浓度越大混合碳源体系的反硝化速率就越低,可能较大的硝酸盐负荷对反硝化细菌产生毒害作用而不利于硝酸盐的去除.     

固相反硝化反应器对含盐水体脱氮效率的预测模型

以聚丁二酸丁二醇酯(PBS)颗粒作为反硝化固体碳源和生物膜载体的填料床反应器处理含盐水体的脱氮效果表明,在温度在(29±1)℃的条件下,反应器对含盐水体中NO3--N具有良好的反硝化性能.以NO3--N去除率为响应值,利用响应曲面法考察进水硝酸盐浓度和水力停留时间对脱氮效率的影响.因素分析表明,进水NO3--N和HRT...     

生物反硝化去除地下水中硝酸盐的混合碳源研究

选取麦秸、锯末、乙醇为碳源,比较了这3种物质单独或两两组合作为碳源的情况下,生物反硝化去除模拟地下水中硝酸盐的效果.结果表明,以麦秸为碳源的反应体系具有较好的反硝化效果,但反应器出水具有颜色和异味;锯末+乙醇作为混合碳源的反应体系比单独添加锯末或乙醇反应体系的脱氮效果好;碳氮比(C/N)为40的混合碳源用量有利于硝酸盐...     

碳源对反硝化过程中一氧化二氮释放的影响

碳源种类及其浓度影响污水处理反硝化过程中一氧化二氮(N2O)的释放。以往关于碳源对反硝化过程中N2O释放特性的研究多采用单一碳源驯化活性污泥,采用混合碳源条件驯化的研究尚少。利用序批式反应器,以蔗糖和乙酸钠为混合碳源驯化反硝化菌。采用批处理试验研究了不同碳源(乙酸钠、葡萄糖和两者混合)在不同碳氮比(COD/N)条件下,利用硝酸盐氮(NO3--N)或亚硝酸盐氮(NO2--N)进行反硝化时N2O的释放。以NO2--N为电子受体进行反硝化时,N2O释放量远大于以NO3--N为电子受体进行反硝化时的释放量。碳源种类影响N2O释放,其释放比从低到高依次为乙酸钠、混合碳源和葡萄糖。以乙酸钠为碳源且当COD/N较低时,由于NO2--N积累和内源反硝化,导致较多N2O的释放,而在碳源相对充足情况下释放量较少。以葡萄糖为碳源时,由于反硝化速率较低,N2O释放量大于利用乙酸钠时的释放量,同时释放量随COD/N比的增加而增加。在混合碳源条件下,反硝化菌优先利用乙酸钠进行反硝化,N2O释放量随COD/N比的增加而降低。     

连续砂滤池在低水温条件下的反硝化脱氮效果

研究在低水温条件下连续砂滤池的反硝化脱氮效果及其主要影响因素,寻找最佳的甲醇碳源投加比。运行结果表明:当水温降低至11.7℃时,在连续砂滤池里反硝化菌培养时间为24 d;反硝化脱氮稳定运行后,砂滤池的滤速为4 m/h时反硝化去除总氮量超过15 mg/L,容积负荷达0.6 kg/(m3·d),最佳甲醇碳源投加比为2.8~3.2,出水COD、SS浓度均可达到一级A排放标准;影响连续砂滤池反硝化脱氮效果的主要因素为进水水温、硝酸盐浓度、溶解氧浓度、上升水力流速和甲醇投加比。     

NO3--N负荷对树皮填料人工湿地早期反硝化及释碳速率的影响

为了将污水厂尾水作为再生水进行利用,常常需要对尾水进行深度脱氮,针对尾水的水质特征,在深度脱氮时常常需投加碳源.试验采用树皮作为填料,兼作脱氮的缓释碳源,进行树皮填料人工湿地深度脱氮模型试验,研究进水NO_3~--N负荷对反硝化和树皮释放碳源的影响.结果表明,树皮填料人工湿地可稳定脱氮;反硝化速率遵循Monod关系式,随进水NO_3~--N负荷增大而递增,饱和常数KS=19.10 mg·L~(-1);硝氮去除率随进水NO_3~--N负荷增大而减小;在树皮填料人工湿地运行早期,树皮释碳总量、树皮释碳速率随进水NO_3~--N负荷增大而递增,与进水NO_3~--N均呈线性正相关;树皮静态释碳速率为0.2 mg·(g·d)-1,与腐朽木等中空松散的植物碳源相比,碳源缓释性能较好,释碳周期较长,是良好的缓释碳源.     

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.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

Intraspecific differences in effects of co-contamination of cadmium and

A hydroponic experiment was carried out to study intraspecific differences in the effects of different concentrations of cadmium (Cd)(0-10 mg/L) and arsenate (As(V)) (0-8 mg/L) on the growth parameters and accumulation of Cd and As in six wheat varieties Jing-9428, Duokang-1, Jingdong-11, Jing-411, Jingdong-8 and Zhongmai-8. The endpoints of wheat seedlings, including seed germination,biomass, root length and shoot height, decreased with increasing the Cd and As concentrations. Significant differences in seed germination, biomass, root length, shoot height and the accumulation of Cd and As were observed between the treatments and among the varieties (p ＜ 0.05). The lethal dosage 50% were about 20, 80, 60, 60, 80 and 20 mg As/L for Jing-9428, Duokang-1, Jingdong-11,Jing-411, Jingdong-8 and Zhongmai-8, respectively, and the corresponding values for Cd were about 30, 80, 20, 40, 60 and 10 mg Cd/L, respectively. Among the six varieties, Duokang-1 was found to be the most resistant to Cd and As toxicity, and Zhongmai-8 was the most sensitive to Cd and As co-contamination. The resistance of the six varieties was found dependant on the seedling uptake of Cd and As. Duokang-1 was the most suitable for cultivation in Cd and As co-contaminated soils.     

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.