游离氨对硝化菌活性的抑制及可逆性影响

为考察游离氨(FA)对硝化菌(氨氧化菌AOB和亚硝酸盐氧化菌NOB)活性的抑制影响,采用SBR反应器,基于FA与过程控制协同作用在实现短程硝化的基础上,考察了不同FA浓度(1.0,5.3,16.6,13.4,9.9,5.2,1.0mg/L)梯度下,FA对AOB和NOB活性的抑制作用及可逆性.结果表明,当FA浓度达到13.4mg/L时,系统内亚硝态氮积累率(NiAR)逐渐增加,硝态氮积累率(NaAR)逐渐减小,且NiAR/ NaAR>1时,系统实现了稳定短程硝化.在此FA浓度条件下,FA对AOB和NOB活性均产生一定的抑制作用,但相对于AOB,NOB对FA的抑制作用更加敏感.当AOB活性被短暂抑制后,其活性又迅速恢复;而NOB活性被完全抑制.此后当FA浓度又逐渐降至1.0mg/L时,AOB活性始终维持较高水平,而NOB活性尚未恢复.也即是说,在本试验控制的FA浓度条件下,FA对AOB活性的抑制作用是可逆的,而对NOB活性的抑制作用不可逆.     

高浓度游离氨冲击负荷对生物硝化的影响机制

工业废水厂或含工业废水较多的城市污水处理厂,在运行过程中可能会意外受到高浓度氨氮废水急性冲击负荷的影响,造成生物硝化反应受到抑制,出水不能稳定达标.为了指导实际污水处理厂应对游离氨(FA)急性冲击负荷造成的出水不达标问题,本文探究高浓度氨氮废水对污水生物硝化系统的影响机制.本文利用序批式活性污泥反应器(SBR)处理模拟高氨氮废水,通过监测氨氮最大比降解速率、硝酸盐氮最大比生成速率、亚硝化和硝化比耗氧速率,硝化菌丰度等指标,研究高浓度氨氮废水中FA对硝化菌活性的影响规律.结果表明,FA在低浓度范围内,增加FA急性负荷能够促进硝化活性,而当FA急性冲击负荷大于一定值时,会对硝化作用造成抑制;FA浓度越大,受到抑制的硝化生物活性所需要的恢复周期越长.利用荧光原位杂交分析技术,发现当进水FA浓度(以N计)从3.6 mg·L~(-1)升高到8.1 mg·L~(-1)时,氨氧化菌(AOB)和亚硝酸盐氧化菌(NOB)菌群数量都略微升高,而当FA浓度大于8.1 mg·L~(-1)时,AOB和NOB菌群数量明显下降.FA对AOB和NOB菌群的临界抑制浓度分别为8.1 mg·L~(-1)和6.6 mg·L~(-1),NOB相对于AOB菌群更敏感.     

游离氨和游离亚硝酸对亚硝态氮氧化菌活性的影响

高浓度游离氨(FA)或游离亚硝酸(FNA)条件下硝化过程常出现亚硝态氮积累,FA、FNA对亚硝态氮氧化菌(NOB)的影响并不清楚.首先用高浓度亚硝态氮污水富集培养NOB,对富含NOB的污泥进行荧光原位杂交技术(FISH)分析表明,Nitrobacter占细菌总数比例为(71±5)%.用此污泥考察不同FA、FNA浓度对NOB活性的影响.结果表明,NOB的活性随着FA浓度的增大逐渐减小,当FA浓度在10mgNH3-N/L左右时,NOB的活性仅为FA为0时的50%.低浓度的FNA(FNA < 0.03mg HNO2-N/L)对NOB活性具有促进作用;当FNA3 0.2mg/L时,NOB的活性被完全抑制.采用Aiba模型计算得到FNA对NOB的抑制常数KI,FNA,NOB为0.0968mg/L. FNA在0.0968mg/L左右时NOB活性仅为FNA为0.003mg/L时的50%.     

高氨氮味精废水的亚硝化/反亚硝化脱氮研究

两段SBR法处理经稀释的味精废水有良好的有机质降解和脱氮效果，整个生物处理过程可分为碳氧化阶段和三个亚硝化／反亚硝化阶段，碳氧化阶段主要是有机质的降解和曝气吹脱除氮，随后通过亚硝化／反亚硝化反应实现生物脱氮和有机特的降解。SBRⅠ碳氧化阶段废水中有机质浓度较高，在降解过程中消耗废水中的溶解氧，竞争性抑制了亚硝化反应的发生，而亚硝化反应的形成是由于游离氨（FA）对硝酸细菌的抑制而形成的。     

固定化氨氧化细菌短程硝化稳定性研究

以高分子聚合物为载体,采用细胞增殖技术固定氨氧化细菌,研究了氨氮负荷、HRT、初始游离氨(FA)和有机物等因素对短程硝化过程稳定性的影响.实验结果表明,当进水氨氮负荷分别为100、150和200 mg/L时,出水氨氮浓度均小于10 mg/L;当进水氨氮浓度为25.8、51.1和93.3 mg/L时,分别经历3、6、12 h后,出水氨氮浓度低,亚硝化效果好,可以根据进水氨氮浓度的变化,适当地凋整系统水力停留时间(HRT)并优化系统的运行;当游离氨(FA)浓度>9 mg/L时,对氨氧化细菌会产生抑制;低分子有机物的存在对氨氧化细菌的活性具有一定的促进作用,有机物浓度对亚硝化率基本不产生影响,实验过程中在有机物存在的条件下.发生了短程硝化反硝化反应.使得系统总氮减少.     

CANNED工艺细菌种群结构变化的FISH研究

采用电镜观察和荧光原位杂交技术（FISH）,对亚硝化/电化学生物反硝化全自养脱氮（CANNED）工艺在不同游离氨（FA）质量浓度下反应器内细菌形态和种群结构进行了研究. 结果表明:在亚硝化段,ρ（FA）为0.5 mg/L时,氨氧化菌（AOB）和亚硝酸盐氧化菌（NOB）分别占总菌数的0.9%和2.8%;ρ（FA）为12.4～48.6 mg/L时,AOB和NOB分别占33.6%～47.4%和1.0%～2.9%,能够实现短程硝化. 在电化学生物反硝化段,当ρ（FA）为0.5～12.4 mg/L时,脱氮硫杆菌、厌氧氨氧化菌和真细菌分别占总菌数的7.2%～15.3%,7.2%～10.3%和9.1%～14.3%;当ρ（FA）增加到48.6 mg/L时,上述3种细菌所占比例分别增加到总菌数的34.5%,44.2%和60.8%,表明随着ρ（FA）的增加,提高ρ（FA）有利于上述3种菌的生长,与SEM结果一致.      

羟胺抑制协同pH调控对人工快渗系统短程硝化的影响

针对人工快渗系统(CRI)总氮去除率低的问题,研究了羟胺抑制协同pH调控对人工快渗系统实现由全程硝化向短程硝化转化的可行性,探讨了其对系统内氮素污染物迁移转化和硝化功能菌空间分布及活性的影响.结果表明,0.5 mmol·L~(-1)羟胺连续添加13 d后可实现CRI系统短程硝化的快速启动,氨氮去除率、亚硝氮积累率分别为91.1%、77.9%,经16 d不添加羟胺运行后氨氮去除率、亚硝氮积累率分别降低3.9%、9.8%,此时调控进水pH至8.4,氨氮去除率和亚硝氮积累率均超过90%,CRI系统短程硝化效果显著且稳定性较高.羟胺对硝化菌具有选择性抑制,对AOB和NOB产生明显抑制的浓度分别为0.7、0.5 mmol·L~(-1),羟胺浓度为1.0 mmol·L~(-1)时AOB和NOB活性均被严重抑制且解抑较难;pH调控对短程硝化的影响主要与游离氨(FA)的抑制作用有关,对AOB和NOB产生明显抑制的FA浓度分别为26.5、5.6 mg·L~(-1),NOB比AOB对FA的敏感性更高.     

控制ORP实现连续流反应器部分亚硝化稳定运行

利用ORP在线监控设备,研究了控制ORP值实现连续流部分亚硝化反应器稳定运行的可行性,并使出水水质满足厌氧氨氧化需求.结果表明,在亚硝氮与氨氮比值、温度和pH值恒定的条件下,反应器内ORP值波动主要由于DO浓度波动引起.在稳定的亚硝化系统中,当ORP值大于250mV左右时,反应器出水亚硝氮与氨氮比值大于2.1;当ORP值控制在150mV左右时,反应器出水亚硝氮与氨氮比值稳定在1.2~1.3之间.ORP值控制在120mV时,反应器出水亚硝氮与氨氮浓度比值为0.9~1.06.将ORP值控制在150mV时,随着进水氨氮浓度由300mg/L提高至813mg/L,反应器出水亚硝氮与氨氮比值基本维持在1.1~1.3之间.但随之增加的游离氨浓度易导致亚硝化菌活性抑制.因此,在低氧环境下ORP作为连续流部分亚硝化反应器亚硝化程度的控制指标,其灵敏度和精度明显优于DO监测设备.     

厌氧氨氧化耦合反硝化快速启动CANON工艺

在SBR反应器中.先采用低基质浓度配水启动稳定的厌氧氨氧化耦合反硝化(SAD),之后在低曝气条件下以模拟生活污水富集氨氧化细菌(AOB),启动CANON工艺.基于对反应器内脱氮性能和不同阶段功能菌动力学活性的分析,系统阐述了影响CANON工艺启动与稳定运行的影响因素.结果表明此启动方式不仅缩短了亚硝化启动时间,同时缩短了ANAMMOX菌对有机环境的适应时间,经过60d成功启动了CANON工艺并应用于处理生活污水,反应器ANR超过了93%.反应器较短的周期(4h),使得ANAMMOX菌和异养菌反硝化菌活性始终保持在合理范围内,μNH_4~+-N/μCOD比值始终大于1.0.异养反硝化菌对COD的降解反应,使反应器内pH值提高,同时反应周期间初期和末期游离氨(FA)始终处于对NOB的抑制水平,也是实现稳定亚硝化的重要原因.     

两种不同抑制策略下部分亚硝化系统运行特性比较

为研究如何控制部分亚硝化系统的稳定性,在高氨氮负荷[1 kg·(m~3·d)~(-1)]和不同的双重抑制策略下启动并连续运行两个序批式反应器(sequencing batch reactors,SBRs).结果表明在温度35℃±1℃,进水氨氮负荷为1 kg·(m~3·d)~(-1)的条件下,FA和DO的双重抑制和FNA和DO的双重抑制均可成功实现高氨氮废水稳定的部分亚硝化,出水NO-2-N/NH+4-N接近1,NO-3-N浓度接近于零,满足ANAMMOX反应的进水基质要求.R1反应器在DO和FA的控制策略下,亚硝氮氧化速率从28.16mg·(g·h)~(-1)减小到0.3 mg·(g·h)~(-1)(以NO-2-N计,下同),而氨氧化速率减小43.60%,最终稳定在20 mg·(g·h)~(-1)(以NH+4-N计,下同)左右.R2反应器在DO和FNA的控制策略下,亚硝氮氧化速率从12.37 mg·(g·h)~(-1)降至0.02 mg·(g·h)~(-1),而氨氧化速率仍维持在较高水平[45 mg·(g·h)~(-1)].DO和FNA双重抑制的系统与DO和高FA双重抑制的系统相比,具有富集时间短,AOB活性高,运行稳定性强等优点,更适用于启动部分亚硝化系统及维持系统稳定性.     

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.     

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.     

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.     

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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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.     

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.     

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.     

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.