温度对微好氧消化处理高含固厌氧消化污泥的影响

采用微好氧消化对高含固厌氧消化污泥进行后处理,考察了在常温、中温及高温条件下反应器的运行性能以及污泥植物毒性的改善。结果表明:在污泥停留时间为8 d,供气量为2.4 L/min的微氧条件下,高含固厌氧消化污泥VS进一步降解,比耗氧速率降低,挥发性脂肪酸及氨氮等小分子物质浓度显著降低,污泥趋于更加稳定的状态。随着处理温度的提高,污泥VS、比耗氧速率和总氨氮呈逐渐下降趋势。种子发芽实验表明:经微好氧消化处理后,污泥对向日葵、矢车菊、牵牛花等种子发芽的抑制作用均逐渐下降,说明微好氧消化有利于改善高含固厌氧消化污泥的植物毒性。而且随着处理温度的增加,处理后污泥的植物毒性呈增加趋势,这可能与挥发性脂肪酸含量的增加有重要关系。总体看来,与常温和高温条件相比,中温微好氧消化是改善高含固厌氧消化污泥土地利用性能更为可行的工艺。     

死菌DNA对厌氧消化污泥中抗生素抗性基因及微生物群落分析的干扰

为评估死菌DNA对厌氧消化污泥抗生素抗性基因(ARGs)和微生物群落分析的潜在干扰,本研究对3种不同类型厌氧消化污泥进行叠氮溴化丙锭(PMA)处理,比较在PMA屏蔽死菌DNA PCR扩增情况下污泥ARGs和微生物群落分析结果与未经PMA处理情况下的差异.结果表明,经PMA处理后,剩余污泥自厌氧消化样品和高含固厌氧消化污泥样品中的ARGs丰度分别下降了41%～86%和74%～98%;污泥水解液厌氧消化15 d后的污泥样品中ARGs下降幅度相对较小,但降幅最高也达到34%.PMA处理对3个来源不同的厌氧消化污泥微生物群落组成分析结果呈现不同程度的影响,对高含固厌氧消化污泥的微生物群落结构分析影响最为显著.在经PMA处理与未经PMA处理两种情况下,厌氧消化污泥ARGs与微生物群落组成相关性分析的结果也截然不同.研究证明了死菌DNA对厌氧消化污泥ARGs和微生物群落分析的潜在干扰,采用PMA预处理能够更准确地反映厌氧消化污泥中的微生物群落及菌体携带ARGs的特征.     

零价铁对厌氧消化过程中氨氮抑制解除的影响

氨氮抑制是影响高含固有机固体废弃物厌氧消化产甲烷效率的重要因素.本研究通过实验室批量实验,考察了微米级零价铁对剩余污泥、热水解污泥厌氧消化的影响以及对高氨氮抑制解除的影响.结果表明,投加4 g·L~(-1)和10 g·L~(-1)零价铁对剩余污泥、热水解污泥厌氧消化过程中的产甲烷速率、迟滞时间和产甲烷潜势等动力学特征均未有影响.但是,在高氨氮抑制的厌氧消化过程中, 4 g·L~(-1)和10 g·L~(-1)的零价铁投加可使厌氧消化受氨氮抑制的产甲烷迟滞时间由对照组的18.61 d分别缩短为17.22 d和16.18 d,最大产甲烷速率(以VS计)由对照组的6.34 mL·(d·g)~(-1)提升为7.84 mL·(d·g)~(-1)和7.39 mL·(d·g)~(-1).零价铁并未通过化学反应对厌氧消化的pH缓冲体系产生直接影响,而是使氨氮抑制后的产甲烷优势古菌Methanosarcina的相对丰度(27 d)由对照组的30.71%提升到53.50%和60.30%.本研究证明了零价铁并不能提升污泥产甲烷潜势,而只是在受抑制影响的厌氧消化过程中,刺激产甲烷微生物的代谢活性,强化如氨氮抑制影响的快速解除.     

厌氧氨氧化污泥中氨氧化的潜在电子受体

通过接种亚硝酸盐型厌氧氨氧化污泥,投加潜在电子受体(亚硝酸盐、Fe~(3+)和硫酸盐)研究了厌氧条件下氨氮氧化的潜在电子受体.结果表明,亚硝酸盐是厌氧氨氧化最适合的电子受体,能够与氨氮在短暂的时间内完全反应;在亚硝酸盐缺乏的情况下,厌氧氨氧化污泥中微生物利用自身细胞有机物将产物硝酸盐转化为亚硝酸盐参与氨氮转化;Fe~(3+)与硫酸盐在氨氮氧化后期出现转化,但是直接还是间接参与还需进一步研究.厌氧氨氧化污泥对氨氮产生过量氧化之前必须以亚硝酸盐为电子受体进行微生物活性激活,并且好氧氨氧化菌和亚硝化菌出现增长,推测微生物产生了H_2O_2.该现象并不可长久持续.虽然其氧化速率较慢,但是过量氧化现象较为明显.因此厌氧氨氧化污泥中肯定存在氨氮过量氧化的现象.厌氧氨氧化污泥对电子的利用顺序是亚硝酸盐、硝酸盐、Fe~(3+)和硫酸盐.     

厌氧铁氨氧化处理模拟垃圾渗滤液的影响因素研究

厌氧条件下,微生物将NH~+_4-N氧化和Fe~(3+)还原的反应称为厌氧铁氨氧化(Feammox).试验以处理垃圾渗滤液的厌氧氨氧化污泥(ANAMMOX)为接种污泥驯化Feammox污泥,研究了不同NH~+_4-N及Fe~(3+)浓度对Feammox系统的影响,并采用扫描电镜(SEM)分析了Feammox系统不同运行阶段的污泥形态特征.结果表明:在厌氧序批式反应器中,在常温条件下控制进水NH~+_4-N浓度为50 mg·L~(-1)、pH在7.4～7.6之间,经过88 d厌氧富集培养后NH~+_4-N最大转化率达到52.73%,最大转化量为28.37 mg·L~(-1),出水Fe~(2+)浓度随着运行时间的增加逐渐增加,最高浓度为2.87 mg·L~(-1).高浓度NH~+_4-N(400 mg·L~(-1))和Fe~(3+)(500 mg·L~(-1))条件下,氨氮转化量分别达到了40.69 mg·L~(-1)和29.23 mg·L~(-1),说明高进水基质条件下仍然有Feammox反应发生.低浓度NH~+_4-N(100 mg·L~(-1))和Fe~(3+)(50 mg·L~(-1))条件下,NH~+_4-N转化量与Fe~(2+)生成量的线性关系较强,R~2分别为0.86544和0.86034.通过SEM分析可得,Feammox污泥表面附着有不规则矿物,这些矿物沉积在微生物细胞表面阻碍传质,从而降低微生物代谢效率.     

热水解时间对污泥厌氧消化系统微生物群落结构影响分析

为评估热水解时间对北京市大兴区某污水处理厂污泥厌氧消化系统微生物群落结构的影响,利用Illumina MiSeq高通量测序方法,分析了不同热水解时间（15、30和45 min）对初沉污泥和剩余活性污泥厌氧消化系统中微生物群落结构及其多样性的影响因素.结果表明,消化污泥优势类群主要分布在厚壁菌门（Firmicutes）、阴沟单胞菌门（Cloacimonadota）、绿弯菌门（Chloroflexi）和同力菌门（Synergistota）,相对丰度之和超过60%,相对丰度最高菌属为W5,占比为20.8%~54.5%,表现为少数优势物种的高丰度特征.热水解污泥厌氧消化过程中,高挥发性脂肪酸和氨氮浓度导致嗜乙酸产甲烷菌相对丰度减少,嗜氢产甲烷途径多于嗜乙酸产甲烷途径.环境因子关联分析结果显示,消化进泥可溶蛋白质、消化进泥pH值、消化出泥氨氮和热水解时间是影响微生物群落结构的4个主要环境因子,其中消化出泥氨氮对产甲烷菌属的影响最大,呈负相关关系.热水解时间与Chao指数和Shannon指数均呈负相关,较长热水解时间不利于提高厌氧消化过程微生物菌群丰富度和多样性.     

应用高固体浓度厌氧消化工艺转化污泥产沼气研究

应用高固体浓度厌氧消化工艺在中温(35±1)℃条件下,考察了进料总固体(TS)含量为17%的污泥在5 L反应器中批式厌氧消化产沼气的发酵过程,并探讨了高固体浓度厌氧消化工艺转化污泥产沼气的可行性.结果表明,沼气和CH4的累积产量在整个厌氧消化期间(73 d)经历产气高峰、相对稳定和结束3个阶段,累积产气量分别达121....     

高含固污泥厌氧消化中Fe/S及pH对原位抑硫效率影响及其交互作用

以城市污水处理厂高含固污泥为对象,分别进行了连续厌氧消化抑硫试验和消化污泥Fe(Ⅲ)投加抑硫试验,探讨不同Fe/S(摩尔比)对污泥厌氧消化中溶解态硫化物去除效率的影响以及Fe(Ⅲ)与pH的交互作用.结果表明,热水解污泥厌氧消化采用原位抑硫技术,在Fe/S(摩尔比)为7.75时沼气中H_2S含量可由170.4×10~(-6)降至14.09×10~(-6),无需进行后续处理;当pH为7.00~7.50、Fe/S为1~11时,pH为原位抑硫主要显著影响因子,提高消化池pH有利于降低Fe(Ⅲ)投加量;高含固污泥厌氧消化沼气满足H_2S利用标准时,所需最低Fe/S为7.0;当消化池pH低于7.30时,将无法通过调节Fe/S实现H_2S浓度达标排放.     

高温厌氧消化中底物浓度对病原指示微生物杀灭的影响

剩余污泥中含有大量病原微生物,土地利用之前必须进行适当的处理,降低病原微生物的数量,以降低环境风险.通过研究在不同的底物浓度条件下,剩余污泥高温厌氧消化(55℃)过程对病原指示微生物的杀灭效果,分析厌氧消化前后污泥中病原指示微生物数量变化的原因.结果表明,随着底物浓度的增加,VFAs浓度和累积产甲烷量增加.在底物浓度为28~84 g·L-1、温度为55℃、持续28 d的高温厌氧消化过程中,上清液中总大肠杆菌下降2.0~3.0个数量级、粪大肠杆菌下降1.8~3.3个数量级;消化后污泥中总大肠杆菌和粪大肠杆菌杀灭率均达到99%以上;且上清液中和消化污泥中均未检测到沙门氏菌的存在.在研究底物浓度范围内,当底物浓度大于45 g·L-1时,消化液和污泥中总大肠杆菌和粪大肠杆菌的杀灭效果下降.     

低温短时水热预处理混合及初沉污泥的高温厌氧消化特性研究

以低温短时(90℃、30 min)水热预处理后的混合及初沉污泥为研究对象,分别进行了高温((55±1)℃)厌氧消化连续性试验.研究了该预处理条件下这两类污泥在水力停留时间(HRT)为20 d时的产气量、有机物分解率及物料平衡等,探讨了低温短时水热预处理对提高污泥厌氧消化性能的效果.结果表明:TS约为35 g·L-1的预处理混合污泥与初沉污泥经高温厌氧消化后,投加单位VS的产气量分别为(343.00±9.86)m L·g-1和(365.00±7.61)m L·g-1,VS去除率分别为38.9%和45.8%.COD物料平衡计算结果表明,混合和初沉污泥中分别有33.6%和43.9%的固体有机物被分解转化,生物气中CH4含量均在70%左右.     

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.     

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.     

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.     

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.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.