流量分配对短程生物脱氮过程中N2O产生的影响

利用SBR反应器,通过在线pH曲线控制好氧-缺氧反应时间,成功实现了短程生物脱氮,并考察了分段进水条件下流量分配对SBR反应器运行性能及N2O产量的影响.结果表明,与原水分2次在不同阶段等量加入反应器的二段进水方式相比,原水分3次等量进入反应器的三段进水方式能够有效降低脱氮过程中外碳源投加量和氧化亚氮产量;氧化亚氮主要产生于硝化过程,反硝化过程能够将硝化阶段积累的N2O还原至N2.2次、3次等量进水条件下,生物短程脱氮过程中乙醇投加量分别为0.8和0.6 mL,N2O释放量分别为8.86和5.05 mg·L-1(以N计).硝化过程中NO-2-N的积累是导致系统N2O产生的主要原因.     

SBR法对焦化废水生物脱氮研究

采用SBR工艺对焦化废水的有机物降解和生物脱氮进行了研究。试验结果表明。焦化废水的生物脱氮是以短程硝化／反硝化的途径存在的，而且在好氧阶段存在同时硝化／反硝化（sND）过程。好氧阶段的反硝化效率约占整个反应周期脱氮效率的37．0％。SBR反应器对NH3-N的去除效率在95．8％-99．2％．CODCr的去除效率在85．3％～92．6％。由于出水中NO2-N的积累。NO2—N对CODCr浓度贡献值得关注。     

pH调控反硝化除磷过程PAOs-GAOs竞争及N2O释放特性

该文以厌氧/缺氧/好氧方式(An/A/O)运行序批式生物反应器(SBR),采用NO_3~-驯化缺氧反硝化聚磷菌,利用pH值调控An/A/O-SBR内各菌群间的竞争优势,通过考察脱氮除磷过程的化学计量学参数变化,确定了不同pH下SBR内聚磷菌-聚糖菌(PAOs-GAOs)间竞争关系及N_2O释放特性。结果表明,An/A/O-SBR内存在PAOs和GAOs对碳源的竞争,高pH有利于反硝化聚磷菌增殖、提升SBR内同步脱氮除磷效率并降低N_2O产率。pH由6.5增至8.0,PAOs转化外碳源比例由24.1%增至55.6%。pH=8.0,SBR内脱氮和除磷效率均达90%以上,平均N_2O产率为2.8%。不同pH值下,An/A/O-SBR内厌氧阶段ΔGly/ΔPHA、ΔGly/CODin、PRA/CODin以及缺氧阶段PUA/NaRA、ΔGly/ΔPHA均表现出PAOs-GAOs共存特性,微碱性条件促进SBR内微生物趋向富集反硝化聚磷菌的生化反应动力学。pH=6.5,N_2O产率达11.2%。低pH值耦合高NO_2~-形成高浓度游离亚硝酸,对反硝化聚磷菌的毒性及对亚硝态氮还原酶、氧化亚氮还原酶的活性抑制作用,是导致低pH值下SBR脱氮除磷性能降低和N_2O产率增加的重要因素,以N_2O作为终产物的GAOs反硝化比例增加,加剧了低pH条件下N_2O释放。     

酒精废水消化液生物硝化和脱氮试验

酒精糟液厌氧消化液CODCr浓度为3500～4300mgL,BOD5浓度为1500～2100mgL,TN浓度为400～700mgL,NH3N浓度为300～600mgL。采用SBR反应器对该消化液进行生物脱氮试验,对反应器的有机负荷、氨氮负荷、脱氮效果、脱氮过程中氮形态的变化以及碳源提供等进行了研究分析。试验结果表明,当消化液碳源充足,SBR充水比λ=0.35,缺氧时间3h以及BOD5污泥负荷0.26～0.32kgkg·d条件下,SBR处理出水CODCr598～632mgL,BOD560～100mgL,氨氮6～9mgL,总氮200～216mgL,总氮去除率为60%左右。该处理系统中缺氧段反应时间仅为3h,却承担70%～75%的CODCr总去除负荷,显著提高了该系统的有机负荷和氨氮负荷。在消化液碳源不足的条件下,可投加乙酸钠作为生物脱氮的外碳源,投加量宜为500mgL。     

好氧反硝化SBR工艺启动研究

该文以人工模拟的高C/N比(10)废水为处理对象,利用缺氧/好氧交替和高曝气的运行方式,以城市生活污水处理厂污泥作为接种污泥,研究了好氧反硝化序批式活性污泥反应器(SBR反应器)的启动过程。结果表明:在SBR反应器启动45 d后,出现明显的好氧反硝化过程;继续培养25 d,好氧反硝化SBR反应器的脱氮效率达到稳定。当反应器污泥负荷为0.11 kg COD/(kg MLSS·d)时,好氧反硝化SBR反应器对COD、总氮和氨氮的去除效率分别为(94.97%±0.53%)、(90.37%±5.89%)和(99.18%±0.34%)。城市生活污水处理厂污泥可用于好氧反硝化生物脱氮工艺的启动,缺氧/好氧交替和高曝气的方式可以加速好氧反硝化工艺的启动。     

两段SBR法去除有机物及短程硝化反硝化

采用两段SBR法处理有机物和氨氮含量较高的化工废水.一段反应器(SBR1)的反应过程处于好氧状态,主要去除大部分有机物;二段反应器(SBR2)先好氧,去除剩余有机物和硝化反应,并且控制硝化反应进程至亚硝酸型硝化结束.然后缺氧反硝化,反硝化以原水作为碳源.试验结果表明:两段SBR法可以增加二段污泥中硝化菌的含量,使具有不同作用的2大类微生物群体分别在各自的反应器内生存.在进一步降低出水COD的同时,避免高有机负荷对硝化反应的冲击,使碳氮比(C/N)不再成为脱氮系统的影响因素.因此,与单一SBR法相比,两段SBR法不仅提高处理效率,还能节约能耗及外加碳源的费用.     

低C/N比条件下高效生物脱氮策略分析

针对低C/N比污水传统生物脱氮碳源不足、脱氮效率不高,提出从充分利用碳源和减少生物脱氮碳源需求量两个方面,来实现高效生物脱氮.在充分利用碳源方面,介绍了好氧缺氧分段进水工艺、脉冲式SBR工艺等改进型生物脱氮工艺;在减少生物脱氮碳源需求量方面,介绍了短程硝化反硝化、厌氧氨氧化、完全自养脱氮等新型生物脱氮技术.并对这些技术和工艺的原理、优势、存在的问题以及应用情况进行了简要的分析.     

前置反硝化脱氮系统外加碳源在线控制基础

以低碳氮比(C/N)生活污水为研究对象,对连续流前置反硝化生物脱氮系统外加碳源的控制方法进行了研究,从而能使出水硝酸盐和亚硝酸盐(NO_x-N)的浓度在满足出水水质标准的情况下,尽可能减少外加碳源的投加量.试验结果表明:总回流比大于2碳源不足时,增加总回流比并不能提高脱氮效率;总回流比一定,缺氧区出水NO_x^--N的浓度达到2mg/L左右时,即使碳源投加量成倍增加,TN的去除率提高不多.在对总回流比与投加碳源量的相互关系分析的基础上提出了外加碳源量的控制方案:通过使缺氧区出水NO_x^--N浓度维持在2mg/L左右来控制外加碳源的投加量,总回流比由进水TN及出水NO_x^--N浓度的标准值来确定.该控制方案既容易判断碳源投加的最佳点又能节省碳源的投加量,易于在污水处理实践中实现.     

低DO硝化耦合内碳源反硝化脱氮处理生活污水

为了进一步合理利用碳源,降低曝气能耗,有效解决低C/N生活污水的脱氮问题,采用2个串联的SBR在无外加碳源的条件下处理低C/N实际生活污水,分别启动内碳源反硝化反应器（ED-SBR）和低DO硝化反应器（LDON-SBR）,并按照厌氧（ED-SBR）-好氧（LDON-SBR）-缺氧（ED-SBR）的方式运行,综合考察各反应器处理性能,并探讨低DO硝化耦合内碳源反硝化工艺脱氮的可行性.结果表明：LDON-SBR反应器在DO浓度为0.3~0.5mg/L的条件下能够成功实现90%以上的硝化并稳定维持,同时反应器存在明显的同步硝化反硝化（SND）现象,SND率可达29.6%;ED-SBR反应器在厌氧阶段能够将进水中的有机物转化为内碳源并储存,在缺氧阶段能够进行内源反硝化,使NO₃^--N平均浓度从27.3mg/L降低至3.9mg/L,NO₃^--N平均去除率为86.5%;系统整体COD去除率为80%左右.     

生物脱氮系统中无厌氧释磷的生物除磷工艺

采用2个工作容积为6L的SBR反应器(1#和2#)分别进行人工废水的脱氮试验研究,其中1#进水是以醋酸钠为碳源,2#以淀粉为碳源,2个反应器进水的COD、氨氮、磷酸盐和硝氮浓度一致.2个反应器均按缺氧76min-好氧294min交替的模式运行·在COD/NO-3N比为8.76:1(400 mg·L-1:45.67 mg·L-1)和15.03:1(400 mg·L-1:26.61 mg·L-1)2种水质条件下.考察了2个反应器对COD、氮和磷的脱除情况.结果表明.2种碳氮比下,1#反应器为传统的硝化.反硝化生物脱氮.对硝酸盐和COD具有较好的脱除效果,对磷基本不能去除;2#反应器在缺氧段发生反硝化脱氮作用,在好氧时段发生硝化作用,同时伴有明显的磷去除.这种现象稳定持续,致使反应器中污泥浓度明显增加.结合pH、DO等环境因素的分析,判定这是一种新型的非传统生物除磷现象.     

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.     

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.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

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.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

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.