Biodegradation of nicosulfuron by the bacterium Serratia marcescens N80

By enrichment culturing of the sludge collected from the industrial wastewater treatment pond, we isolated a highly efficient nicosulfuron degrading bacterium Serratia marcescens N80. In liquid medium, Serratia marcescens N80 grows using nicosulfuron as the sole nitrogen source, and the optimal temperature, pH values, and inoculation for degradation are 30–35°C, 6.0–7.0, and 3.0% (v/v), respectively. With the initial concentration of 10 mg L^?1, the degradation rate is 93.6% in 96 hours; as the initial concentrations are higher than 10 mg L^?1, the biodegradation rates decrease as the nicosulfuron concentrations increase; when the concentration is 400 mg L^?1, the degradation rate is only 53.1%. Degradation follows the pesticide degradation kinetic equation at concentrations between 5 mg L^?1 and 50 mg L^?1. Identification of the metabolites by the liquid chromatography/mass spectrometry (LC/MS) indicates that the degradation of nicosulfuron is achieved by breaking the sulfonylurea bridge. The strain N80 also degraded some other sulfonylurea herbicides, including ethametsulfuron, tribenuron-methyl, metsulfuron-methyl, chlorimuron-ethyl,and rimsulfuron.     

Biodegradation of Chlorimuron-ethyl by the Bacterium Klebsiella jilinsis 2N3

Enrichment culturing of sludge taken from an industrial wastewater treatment pond led to the identification of a bacterium (Klebsiella jilinsis H. Zhang) that degrades chlorimuron-ethyl with high efficiency. Klebsiella jilinsis strain 2N3 grows with chlorimuron-ethyl as the sole nitrogen source at the optimal temperature range of 30–35°C and pH values between 6.0–7.0. In liquid medium, the degradation activity was further induced by chlorimuron-ethyl. Degradation rates followed the pesticide degradation kinetic equation at concentrations between 20 and 200 mg L^?1. Using initial concentrations of 20 and 100 mg L^?1, the degradation rates of chlorimuron-ethyl were 83.5 % and 92.5 % in 12 hours, respectively. At an initial concentration higher than 200 mg L^?1, the degradation rate decreased slightly as the concentration increased. The 2N3 strain also degraded the sulfonylurea herbicides ethametsulfuron, metsulfuron-methyl, nicosulfuron, rimsulfuron, and tribenuron-methyl. This study provides scientific evidence and support for the application of K. jilinsis in bioremediation to reduce environmental pollution.     

Biodegradation of triazine herbicide metribuzin by the strain Bacillus sp. N1

By enrichment culturing of soil contaminated with metribuzin, a highly efficient metribuzin degrading bacterium, Bacillus sp. N1, was isolated. This strain grows using metribuzin at 5.0% (v/v) as the sole nitrogen source in a liquid medium. Optimal metribuzin degradation occurred at a temperature of 30ºC and at pH 7.0. With an initial concentration of 20 mg L^?1, the degradation rate was 73.5% in 120 h. If the initial concentrations were higher than 50 mg L^?1, the biodegradation rates decreased as the metribuzin concentrations increased. When the concentration was 100 mg L^?1, the degradation rate was only 45%. Degradation followed the pesticide degradation kinetic equation at initial concentrations between 5 mg L^?1 and 50 mg L^?1. When the metribuzin contaminated soil was mixed with strain N1 (with the concentration of metribuzin being 20 mg L^?1 and the inoculation rate of 10¹¹ g^?1 dry soil), the degradation rate of the metribuzin was 66.4% in 30 days, while the degradation rate of metribuzin was only 19.4% in the control soil without the strain N1. These results indicate that the strain N1 can significantly increase the degradation rate of metribuzin in contaminated soil.     

Expression and functional analysis of three nicosulfuron-degrading enzymes from Bacillus subtilis YB1

To investigate the degradation activity of the manganese ABC transporter, vegetative catalase 1 and acetoin dehydrogenase E1 from Bacillus subtilis YB1, the proteins were prokaryotically expressed and purified. Assay results showed that the three enzymes were able to degrade nicosulfuron (2- (4,6-dimethoxypyrimidine-2-pyrimidinylcarbamoylaminosulfonyl) -N,N-dimethylnicotinamide), with vegetative catalase 1 exhibiting the highest activity. To further examine the degradation pathway, the degradation products of the three enzymes and the YB1 strain were detected by liquid chromatography-mass spectrometry(LC-MS). The nicosulfuron degradation products of the three enzymes were consistent with those of the YB1 strain, indicating the presence of two pathways: one due to cleavage of sulfonylurea bridges and ring-opening of 1-(4,6-dimethoxy-pyrimidin-2-yl)-3-(2-methyliminomethanesulfonyl-acetyl)-ureaas the pyrimidine ring, yielding the product; and the another due to cleavage of a sulfonylurea bridge, yielding 4,6-dihydroxy pyrimidine (111 m/z), 2-ylamine ?4,6-dimethoxy pyrimidine and ((4-(dimethycarbamoyl)pyridine-2-yl)sulfonyl)carbamic acid as products, which were further degraded to 4,6-dihydroxy pyrimidine and N,N-dimethyl-2-sulfamoyl-isonicotinamide. The above results reveal a major contribution of extracellular enzymes to the degradation of nicosulfuron by the YB1 strain. Our data help in elucidation of the mechanism of nicosulfuron bio-degradation and may facilitate the construction of engineered strains.     

耐盐性毒死蜱降解混合菌的构建及其降解特性

为明确蜡状芽孢杆菌(Bacillus cereus)混合菌株对毒死蜱的降解效果,采用正交实验的方法构建混合菌。以混合菌对毒死蜱的降解率和菌株的生长量为依据,利用单一因素实验考察了不同因素对混合菌降解毒死蜱的影响。结果表明:构建的混合菌中三菌株的体积比为1∶1∶3。在含80 mg/L毒死蜱的反应体系中,最适接菌量为8%(V/V),最适pH为7。在实验浓度下,混合菌对毒死蜱的降解符合一级动力学方程。混合菌对盐分有较高的耐受度,当反应液中氯化钠浓度在20～100 g/L之间时,混合菌对80 mg/L毒死蜱的降解率最高达61%。     

Kinetics of low frequency sonodegradation of linear alkylbenzene sulfonate solutions

The decomposition of sodium dodecylbenzene sulfonate (SDBS) in water by means of ultrasound irradiation at 20kHz was investigated. Experiments were conducted at surfactant concentrations of 175, 260 and 350 mg l(-1), liquid volumes of 120, 170 and 220 ml, temperatures of 20, 30 and 45 degrees C and applied power of 40, 80 and 125 W. The extent of degradation was followed monitoring substrate and organic carbon concentrations, while hydrogen peroxide concentration was also measured; the latter is a product of water sonolysis due to hydroxyl radical recombination. 80% SDBS conversion was achieved after 120 min of sonication at 125 W and 30 degrees C; nonetheless, SDBS and its degradation intermediates proved difficult to oxidise as only about 20-25% of the initial carbon content was transformed to carbon dioxide. At the initial stages of the reaction, degradation rate appears to be only weakly dependent on the substrate concentration with the rate increasing from 3.1 to 4 mg l(-1)min(-1) with increasing concentration from 175 to 350 mg l(-1). Degradation appears to occur at the bubble-liquid interface through hydroxyl radical-mediated reactions whose role was established by performing experiments in the presence of radical scavengers, namely potassium bromide and sodium benzoate. Degradation rates increased with increasing power and decreasing temperature and volume.     

高盐条件下硝基苯降解菌的分离及降解特性

在高盐条件下,从某制药厂曝气池的活性污泥中分离、筛选得到6株硝基苯高效降解菌,其中菌株N18在高盐条件下对硝基苯降解效率最高.经形态特征和生理生化特征分析,初步鉴定N18属于棒状杆菌属(Corynebacterium sp.).硝基苯降解试验表明,菌株最佳培养条件为30℃、培养基pH 7、摇床转速150 r/min.最佳培养条件下,当硝基苯初始质量浓度低于150 mg/L时,菌株培养72 h后硝基苯降解率达75％以上.当盐度为1％～3％时,盐度对硝基苯降解率的影响不明显,当盐度为10％时菌株生长微弱,因此N18属于中度耐盐细菌.     

废水营养比对固定化藻菌去除污染物的影响及动力学研究

海藻酸钙作载体的固定化藻菌小球,经壳聚糖覆膜后,用于模拟废水的处理。通过研究废水初始氨氮浓度及碳氮比对固定化藻菌小球处理效果的影响,发现初始氨氮浓度为50 mg/L时,氨氮的去除率达最高值74.4%;碳氮比为35∶1时,COD去除率达最高值77.7%。系统最佳氮磷比与碳氮比分别为5∶1和35∶1。固定化藻菌降解有机物的动力学过程为一级不可逆生化反应过程,其降解速率常数约为0.099 h-1。     

纳米铁-真养产碱杆菌柱实验去除硝酸盐

建立柱实验装置,探讨了反应柱中填加介质、硝酸盐的初始浓度及不同过水流速时硝酸盐的去除效果及产物的生成情况。4种不同材料,纳米铁、真养产碱杆菌、纳米铁与真养产碱杆菌简单混合体、纳米铁与真养产碱杆菌驯化培养5 d的复合体,分别与初始浓度为65 mg/L硝酸盐溶液反应。结果表明,经培养5 d的纳米铁-真养产碱杆菌复合体对硝酸盐的去除效果最佳,去除率可达到75%,且氨氮的生成量仅为2.99 mg/L;硝酸盐初始浓度分别为32、65和95 mg/L时,32mg/L的体系中硝酸盐的降解效果最好,去除率达78.9%且亚硝酸盐及氨氮的生成量分别为2.34 mg/L和2.89 mg/L,均低于另外2组;溶液流速为6.0 cm/h时,经驯化培养的纳米铁-真养产碱杆菌对硝酸盐的去除率达77%,当控制流速降至2.4cm/h时,亚硝酸盐氮的生成量降至0.34 mg/L。     

反应气耦合等离子体降解沙林模拟剂

采用水蒸气、氨气、过氧化氢气雾和臭氧4种气体对沙林模拟剂氟磷酸二异丙酯(DFP)进行降解研究,发现臭氧对DFP具有较好的降解作用,在流量200 L/h,DFP初始浓度50 mg/m3时,降解率最高可达56.1%。对高浓度DFP(大于80 mg/m3)进行降解研究时,等离子体单独作用最高降解率为89%,而添加臭氧后的降解率都在95%以上。计算得到臭氧作用的能量利用率为0.05 mg/(W·h),等离子体的能量利用率为0.55 mg/(W·h),而添加臭氧后的等离子体能量利用率为0.68 mg/(W·h)明显高于臭氧和等离子体能量利用率之和,因此对高浓度DFP进行处理时,臭氧与等离子体存在耦合作用。对等离子体和臭氧耦合等离子体降解DFP反应进行了产物分析,发现主要的降解产物基本一致,但是臭氧的存在能使降解更加彻底。     

芘高效降解菌ZQ_5的培养条件及无机元素对其降解效率的影响

以从我国最大的石油污水灌区之一——沈抚灌区污染土壤分离到的以芘为惟一碳源、能源生长的高效降解菌株ZQ5为实验材料,通过对菌株ZQ5培养条件的优化,以及采用摇瓶振荡培养方法测定菌株ZQ5对不同浓度芘的降解率,表明：菌株ZQ5在30℃振荡培养16 d后对150 mg/L芘的降解率为90.31%。通过模拟稻田施用N、P和K肥等的土壤环境,探索了无机营养元素对降解菌ZQ5降解能力的影响,发现土壤中混合加入N、P和K无机营养元素的降解率能达到82%以上,比单加某种营养元素对降解菌ZQ5的降解效果好。本研究结果可以指导稻田PAHs的原位生物修复。     

活性炭负载Fe^3＋催化H2O2氧化邻苯二甲酸二甲酯

将Fe3＋负载在活性炭上制得载铁催化剂Fe/AC,并研究了该催化剂对邻苯二甲酸二甲酯（DMP）的催化降解性能。通过正交实验和单因素实验,探讨了催化剂投加量、H2O2投加量、溶液pH值和反应温度对水中DMP降解率的影响,同时对DMP矿化度进行了分析。实验结果表明,制得的载铁催化剂具有较高的催化活性;降解效果的影响顺序是反应温度〉催化剂投加量〉H2O2投加量〉溶液pH值;在反应温度为80℃、催化剂投加量为4 g/L、H2O2投加量为20 mL/L和溶液pH值为3的条件下反应120 min后,质量浓度为10 mg/L的DMP降解率最高可达97.73%;在优化的实验条件下反应150 min,DMP矿化度可达62.73%;催化剂反复使用5次仍具有较好的催化活性,DMP降解率仍可达到77%以上;反应过程中溶液Fe3＋浓度的变化维持在1.07 mg/L左右,且可推测催化降解DMP主要是由非均相和均相催化氧化反应共同作用的。     

共代谢基质对芽孢杆菌Y-4降解异喹啉的影响

以吡啶，葡萄糖和邻苯二甲酸作为共代谢基质，研究了它们对芽孢杆菌Y_4降解异喹啉的影响。实验结果表明各降解过程均遵循二级反应动力学方程：-dS／dt=K2S2＋K1S＋K0。吡啶的加入会抑制异喹啉的降解，并且吡啶的浓度越高，抑制作用越明显。反应体系中葡萄糖的浓度为100-800mg／L时，葡萄糖的加入会促进异喹啉的降解，且葡萄糖浓度越大，异喹啉降解速率P越大，当葡萄糖的浓度为800mg／L时，其降解率速率P可由未加葡萄糖的0．1924h。上升为0．2255h-1。适宜浓度的邻苯二甲酸会对异喹啉的降解产生促进作用，邻苯二甲酸的浓度为50mg／L时，异喹啉的降解速率可由原来的0．1924h-1增加到0．2145h-1，邻苯二甲酸浓度过高反而会抑制异喹啉的降解。     

潜流人工湿地-生物接触氧化处理低温低浓度生活污水

在低温低浓度生活污水的实验研究中，回流比和气水比是影响潜流人工湿地一生物接触氧化组合工艺污染物去除效果的重要因素，推荐回流比R=1．0，气水比为4：1，在该工况下，进水COD浓度在170．8～221．3mg／L时，平均去除率可达90％；进水NH3-N浓度在17．3～25．9mg／L，平均去除率45％～65％；进水TN浓度在25．1～38．49mg／L时，平均去除率45％～65％；进水TP浓度在2．2～3．1mg／L时，平均去除率65％～80％。污染物沿程浓度分析结果表明，该组合工艺可以在低温季节通过曝气促进氨氮硝化，大幅提高NH3-N和TN去除率，同时可以充分发挥复合潜流湿地功能。     

一株高效硝化菌的鉴定及其特性

本研究通过测定菌株ABT01在不同初始氮浓度、pH、C/N、温度和溶氧条件下对氨氮的去除效果,获得该菌株的最佳应用条件。实验结果表明,当初始氨氮浓度低于40 mg/L时,该菌株的氨氮去除率高达85%以上。该菌株最适脱氨氮条件均为：pH 5.0-7.0、C/N=5、35℃、摇床转速150 r/min（溶解氧5.1 mg/L）,氨氮去除率最高达96.8%。同时该菌株经16S rDNA测序、细胞壁脂肪酸组成等鉴定方法,确定ABT01为枯草芽孢杆菌（Bacillus subtilis）。研究表明,枯草芽孢杆菌ABT01具有较好的氨氮去除能力,对水产养殖水质调控有潜在的应用价值。     

Degradation of diuron in aqueous solution by ozonation

Degradation of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] in aqueous solution and the proposed degradation mechanism of diuron by ozonation were investigated. The factors that affect the degradation efficiency of diuron were examined. The generated inorganic ions and organic acids during the ozonation process were detected. Total organic carbon removal rate and the amount of the released Cl(-) increased with increasing ozonation time, but only 80.0% of the maximum theoretical concentration of Cl(-) at total mineralization was detected when initial diuron concentration was 13.8 mg L(-1). For N species, the final concentrations of NO3(-) and NH4+ after 60 min of reaction time were 0.28 and 0.19 mg L(-1), respectively. The generated acetic acid, formic acid and oxalic acid were detected during the reaction process. The main degradation pathway of diuron by ozonation involved a series of dechlorination-hydroxylation, dealkylation and oxidative opening of the aromatic ring processes, leading to small organic species and inorganic species. The degradation efficiency of diuron increased with decreasing initial diuron concentration. Higher pH value, more ozone dosage, additive Na2CO3, additive NaHCO3 and additive H2O2 were all advantageous to improve the degradation efficiency of diuron.     

三维过电位电解处理罗丹明B废水

选用钛基RuO2-TiO2涂层电极作为三维过电位电解装置的阳极，紫铜作为阴极，活性炭作为第三极，研究了三维过电位电解处理罗丹明B废水的效果，并考察了外加电压、电解时间、初始浓度、pH值和搅拌方式等因素对其处理效果的影响。实验结果表明，外加电压、电解时间和初始浓度等因素均对罗丹明B的降解效果有影响，而pH值、搅拌方式等对罗丹明B的降解效果基本没有影响。与二维电解的对比研究表明，在罗丹明B溶液初始浓度为20mg／L，电解时间为1h，电解电压为20V时，采用二维电解的降解率为20％左右，而三维过电位电解的降解率接近80％。最终产物分析结果显示，经过处理的罗丹明B苯环开环变成直链烃类物质，或者饱和环状有机物，不再具有生物毒性，适合后续的生化处理。     

曝气量对悬浮系统单级自养脱氮性能的影响

通过连续实验和间歇实验研究了不同曝气量对SBR系统自养脱氮性能的影响。连续实验表明,在进水氨氮浓度为155～185 mg/L时,曝气量分别为20、28、36和44 L/h时,TN去除率分别为80%、82%、80%和77%;增大和减小曝气量均会降低系统的脱氮效率。间歇实验表明,随着曝气量的增加,氨氮的降解速率有所升高,20、28、36和44 L/h曝气条件下氨氮的降解速率分别为7.23、7.25、7.86和7.95 mg/(g MLVSS.h);在降解的过程中DO浓度一直维持在较低的水平(<0.5 mg/L),pH值则呈先升高后降低的趋势;氨氮降解结束时,pH值和DO浓度同时升高。结果表明,改变曝气量会影响单级自养脱氮反应的进程,但对降解过程DO浓度值变化不大;DO浓度和pH值变化对氨降解结束具有指示作用。     

介质阻挡放电氧化降解木质素磺酸钠的动力学研究

为了有效地处理难生物降解的造纸废水，采用气相介质阻挡放电产生氧化性物质，对木质素磺酸钠进行了氧化降解研究。在不同操作条件下，对其降解动力学及矿化程度进行了研究。结果表明，介质阻挡放电能有效地降解木质素磺酸钠，其氧化降解反应遵循准一级动力学反应。当峰值电压为20 kV，被水蒸气饱和的空气为气源，流量为7 L/min时，氧化处理60 min后，木质素磺酸钠降解率达到70％。其速率常数K随峰值电压、气源、气体流量和木质素磺酸钠的初始浓度的变化而不同。气体流量越大，木质素磺酸钠的初始浓度越低，速率常数K越大，降解效果越好。随着处理时间的增加，氧化性物质能将部分木质素磺酸钠矿化使溶液TOC降低，当被水蒸气饱和的空气作为气源时，氧化处理120min，21.38%的TOC被去除。     

Alcaligenes sp.YF11菌对杀灭菊酯的降解机理

测定了降解菌Alcaligenessp.YF11对不同浓度杀灭菊酯的降解及其降解途径。在纯培养系统中,Alcaligenessp.YF11对100mg／L的杀灭菊酯的降解符合零级动力学特征,其降解速率为2．1mg／L·h;50mg／L的杀灭菊酯在24h的降解率为87.5％;10mg／L的杀灭菊酯10h的降解率为71．0％。Alcaligenesso．YF11对杀灭菊酯的降解为矿化作用。