不同基质中三氯乙烯的好氧代谢研究

本实验选取了苯酚、苯甲酸、苯、甲苯、氯苯等五种化合物作为活性污泥的驯化基质，以瓦呼仪作为测试手段，分析了五种基质在驯化后的活性污泥中的可降解性及三氯乙烯（TCE）在不同基质驯化后的活性污泥中的可生化性，并用计算出的12h有机物氧化率表征有机物的可生化性难易度。苯酚、苯甲酸、甲苯、苯在40mg／L时的氧化率达到最大值，分别为93．71％、64．67％、39．24％、9．15％。氯苯仅在20mg／L时可降解，氧化率为46．09％，据此推断出几种代谢基质的可降解性从易到难的顺序为：苯酚〉苯甲酸〉甲苯〉苯〉氯苯。在甲苯、苯酚、苯甲酸、氯苯驯化后的活性污泥中TCE在50μg／L时，其氧化率达到最大值，分别为54．14％、33．69％、23．91％、21．11％。在苯驯化后的活性污泥中TCE仅在10μg／L时可降解，氧化率为13．8％。据此可推断出TCE在五种代谢基质中的可生化性从高到低的顺序为：甲苯〉苯酚〉苯甲酸〉氯苯〉苯。     

不同共代谢基质下三氯乙烯的厌氧生物降解研究

使用已驯化的厌氧活性污泥,分别以纯牛奶、玉米汁和甲苯作为共代谢基质,对三氯乙烯（ TCE）的降解性能进行对比研究。结果表明：TCE是通过还原脱氯发生降解的;同质量浓度下,甲苯是最佳共代谢基质,纯牛奶和玉米汁相对较差;且在一定范围内,共代谢基质浓度越大,TCE降解效果越好;实验数据的回归结果表明,反应均符合一级动力学。     

铁还原环境下四氯乙烯的共代谢降解

用微环境批实验的方法研究了地下水中加入醋酸盐基质在铁还原环境下四氯乙烯(PCE)的共代谢降解;用接种活性污泥培养驯化后的微生物降解PCE。研究表明,在同一驯化周期中,随着驯化时间的变化,微生物量和活性呈增加的趋势,到第11天基本达到最大值;经过13天,PCE的去除率达90%以上,产生的Fe(Ⅱ)浓度为68.23 mg/L;加入PCE一天后,就有TCE的产生;在实验的第10天有少量DCEs的产生,到实验结束时,TCE的量没有下降;以地下水为基础培养液的铁还原环境,碳平衡达89.00%~100.0%。     

以醋酸为共代谢基质时四氯乙烯的生物降解初步研究

四氯乙烯（PCE）是一种广泛用于干洗和脱脂的有机溶剂,是地下水中常见的污染物.在本实验中,将某肉联厂厌氧污泥接种到土壤中,进行微生物培养.当系统中的微生物活性较高时,以醋酸为共代谢基质,进行驯化实验,当系统中的微生物适应浓度为120μg/L的PCE之后,对PCE在厌氧条件下的降解情况进行研究.研究结果表明,将厌氧污泥接种到土壤中培养的微生物,在以醋酸为共代谢基质的条件下,可以使PCE很快转化为三氯乙烯（TCE）,并可以进一步转化为二氯乙烯（DCEs）.PCE在天然地下水中的半衰期为108d,本实验PCE降解的半衰期为2.95d,反应速率常数为0.2342d^-1.     

还原态蒙脱石有氧条件产生羟自由基降解有机污染物

近期见有含二价铁矿物可活化分子氧产生羟自由基而氧化污染物的报道。本文选用土壤/沉积物中的常见组分蒙脱石(含铁约2%),研究了还原态蒙脱石在不同条件下活化分子氧降解苯酚的效果。结果表明,20g/L还原态蒙脱石(还原程度为30%)在pH=6和有氧条件下,可通过产生羟自由基使11μM苯酚的降解率在6h内持续增加至59.1%。苯酚降解率对应的最佳pH为5,当pH>6时降解率则随着p H的升高而急剧降低;苯酚降解效果还随还原态蒙脱石剂量(0~40g/L)增加而提高;苯酚初始浓度为11μM降解率最高,增加或者降低初始浓度均使降解率降低。还原态蒙脱石铁含量低,活化分子氧时其八面体边缘配位和结构内部二价铁共同起作用,而受八面体层Al、Mg等惰性组分阻碍,其结构二价铁难以向边缘位置传递电子,这与前期报道的还原态绿脱石(含铁约20%)不同。     

电化学循环井耦合氧化 -还原降解地下水中三氯乙烯

三氯乙烯（TCE）是一种地下水中常见的有机污染物,传统的地下水循环井修复技术虽然有效但耗时长,且需配套地面处理。文章研发了一种电化学循环井耦合修复体系,以期通过顺序化学氧化 -还原作用高效快速降解地下水中TCE。以地下水循环井为基础,通过抽水井中的地下水电解,原位提供O2和H2,投加Fe（Ⅱ） -EDTA络合物活化O2产生羟基自由基氧化降解TCE,进而利用钯催化剂催化剩余的H2还原降解TCE。在二维砂槽模拟含水层中评价了该体系的运行效果,含水层中初始TCE浓度为7.50 mg/L,经过13天的连续通电处理后,TCE浓度降低到1.65 mg/L,降解率达到78%。处理后Cl-浓度相应增加118.20 μmol/L,接近于TCE降解量（44.50 μmol/L）的3倍,证明TCE近乎完全脱氯。运行过程中,TCE平均降解速率由0~5 d的0.90 mg/(L·d) 降低到9~13 d的0.10 mg/(L·d),氧化降解主要发生在前期阶段,钯催化还原效率较为稳定,后期两种过程降解效率都逐渐下降,主要原因是溶解态Fe（Ⅱ）浓度减少以及钯催化剂活性降低。该耦合修复体系是基于地下水循环井技术的改进,其氧化 -还原作用机理有望实现地下水中多种不同有机污染物的降解。     

锰钾矿处理高浓度含酚废水研究

对人工合成锰钾矿氧化降解高浓度含酚废水的特性进行了研究。结果表明,体系酸度和矿物用量是影响废水处理效果的重要因素。加酸量为0.12 mol/L,矿物用量20 g/L,温度70℃,反应时间3 h时效果最佳,废水总酚含量由1269 mg/L降低至268 mg/L,同时CODCr与TOC去除率为31.2%和70.5%。经GC/MS测定,水中酚类物质为苯酚、甲基苯酚、二甲基苯酚,最佳条件下,酚类物质浓度已低至检测限以下,水中残余吲哚、长链烷烃、喹啉及其衍生物等难降解有机物。     

菱铁矿催化过氧化氢过硫酸钠修复地下水中TCE时对微生物的影响

地下水中存在着一定量的土著微生物,为了了解类芬顿氧化去除地下水中三氯乙烯(trichloroethylene, TCE)时对微生物的影响,实验利用某污水处理厂好氧段活性污泥和水的混合物作为供试微生物,选择菱铁矿催化过氧化氢过硫酸钠的氧化体系,通过监测微生物的FDA(Fluorescein Diacetate,简称FDA)活性、TCE的浓度等指标,揭示该氧化体系对微生物的影响及存在TCE时微生物与TCE的相互影响。研究结果表明,该氧化体系会导致微生物的酶活性丧失,氧化剂体积与含微生物污水体积的比值(V氧∶V污)越大,对微生物的致死率越高。当V氧∶V污=1.2∶1时,即过氧化氢和过硫酸钠的浓度分别为0.1 mol/L和0.004 2 mol/L时,致死率为50%。当存在TCE时,也会导致微生物酶活性的丧失,随着TCE浓度的增加,对微生物的致死率越高。反之,微生物存在时,对该体系修复TCE几乎没有影响。     

低温条件下高效苯酚降解菌的筛选及降解特性

在18℃的低温条件下,从不同菌源中富集、驯化、筛选得到两株高效苯酚降解菌株A4和B14,在转速为150r·min-1、温度为18℃、pH为6～9的条件下,两株菌对苯酚起始浓度为300mg/L的苯酚降解率分别为90.43%和99.02%.在中性条件下,对苯酚起始浓度小于300mg/L的苯酚降解率均保持在98%以上.经形态特征观察及生理生化实验初步鉴定,结果显示,A4为微球菌属,B14为假单胞菌属.对菌株的降解特性研究表明两株菌最适生长的pH值为6～9,A4菌株比B14菌株具有更广泛的pH适应性;菌株对苯酚的降解率随着生物投加量的增加而升高,在投菌量大于5mL·100 mL-1时,苯酚降解率接近100%;两株菌在通气状况良好的条件下,对苯酚的降解率及其生长情况明显优于缺氧条件.通过对比实验,A4菌株对外界环境的适应性明显强于B14,而后者的生长速率明显高于前者.     

电化学循环井驱动模拟含水层化学氧化降解三氯乙烯

传统原位化学氧化地下水修复技术存在氧化剂迁移距离短和利用率低等问题。本研究在双井循环模式促进传质的基础上,通过注水井中的地下水电解原位提供O₂和H₂,配合乙二胺四乙酸(ethylenediamine tetraacetic acid,EDTA)络合溶解出含水层Fe(Ⅱ),活化O₂产生羟基自由基(•OH),实现地下水三氯乙烯(TCE)的氧化降解。在填充了砂土和黏土互层的二维砂槽中,设置电流为0.2 A、流速为72 cm/d、初始TCE浓度为3 mg/L,经过9 d的连续通电处理后,TCE浓度降低到1 mg/L,降解率达到67%。通电前投加0.5 mmol/L EDTA,经过1 d水流循环后含水层中溶解态Fe(Ⅱ)浓度从02 mg/L增加到414 mg/L,黏土区域较高。通电过程中,循环井促进O₂、Fe(Ⅱ)-EDTA和TCE的有效接触与反应,使TCE氧化降解。通电初期,黏土区域Fe(Ⅱ)氧化速率、TCE降解速率较周围慢,后期差异逐渐减小。未通电时加入醋酸钠可促进Fe(Ⅲ)还原,使含水层中铁循环利用。该修复过程通过循环井提升了氧化剂迁移距离,使用源于含水层的Fe(Ⅱ)-EDTA和稳定性较好的O₂提高了氧化剂利用率,有望应用于有机污染地下水修复。     

紫外光及日光下天然金红石光催化降解苯酚的研究

研究了山西代县天然金红石在紫外光和日光照射条件下对苯酚的光催化降解性能,考察了光照时间、pH值、苯酚初始浓度以及H2O2添加量对降解过程的影响。在紫外光照射下,酸性条件(pH=3.5)利于光催化降解,中性和碱性条件下降解效率较低;当初始浓度为60mg/L时,降解速率可达1.922mg/(L.h);H2O2作为电子捕获剂可提高苯酚降解速率,最佳投加量为2mL/L。在日光条件下,天然金红石对苯酚表现出良好的降解性能,照射7h后,降解率达87.68%,仅略低于P25型TiO2(99.72%),可在14h内完全降解。根据电子探针和X射线衍射分析结果,认为天然金红石晶格中的V、Fe等杂质可能是提高其可见光响应效果和光催化活性的主要原因。     

MCPA biodegradation in an anoxic sequencing batch reactor (SBR)

This research investigated the potential for industrial-strength 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation by activated sludge microorganisms in a sequencing batch reactor (SBR) under nitrate-reducing conditions. The research was divided into four phases consisting of Phase I (a “proof-of-concept” phase); Phase II (an initial “tolerance” exploration phase); Phase III (an “effect of hydraulic retention time” phase), and Phase IV (a “limits” phase). The SBR successfully and simultaneously removed the nitrates completely and around 98 % of the MCPA up to an initial concentration of 50 mg/L MCPA in the dimethylamine salt form (DMCPA) (Phases I, II and III); however, it took approximately 28 days to observe a steady, high-level of MCPA removal. When the concentration of DMCPA was increased to 75 mg/L (Phase IV), the MCPA removal efficiency dropped to 85 %, but removal was observed only for a relatively short period of time since the biomass appeared to eventually become saturated with the herbicide, stopping conversion of DMCPA to its acid form and halting biodegradation.     

Removal of Cr(VI) and phenol coupled with the reduction of sulfate by sulfate-reducing bacteria sludge

Biological treatment of industrial wastewater containing heavy metal and organic pollutant has attracted extensive attention. In this study, Cr(VI) reduction coupled with phenol degradation was investigated by the sulfate-reducing bacteria (SRB) sludge with addition of zero-valent iron (ZVI). The results showed that the SRB wet sludge (SWS) had a good bioactivity in the reduction of Cr(VI) only when the initial concentration of Cr(VI) was below 60 mg L^?1. The addition of ZVI significantly enhanced the bioactivity and reusability of SWS, and the reduction percentage of Cr(VI) achieved 98% after SWS was successively used for seven cycles. SWS coupled with ZVI showed a high activity in phenol degradation, with more than 94% phenol being degraded in each cycle. However, in the simultaneous removal of Cr(VI) and phenol, phenol degradation was inhibited due to the toxicity of Cr(VI) to phenol degrading microbes in SWS. On the other hand, reduction of sulfate and Cr(VI) was not affected by the presence of phenol, with more than 95% of sulfate and Cr(VI) being removed at the end of the 5th cycle. This study enriches our understanding on the applications of the SRB sludge in the removal of organic and inorganic contaminants in wastewater.     

Biodegradation of Cypermethrin by Pseudomonas in a batch activated sludge process

The biodegradation of Cypermethrin (20 to 125 mg/L) in an effluent using batch activated sludge was studied. Degradation was found to occur to a great extent only in the presence of Pseudomonas (IES-Ps-1) culture. Under aerobic conditions using mechanical aerators, Cypermethrin (20 mg/L) was almost completely degraded in just over 48 h at ambient temperature. Further loading of organic compound in subsequent experiments demonstrated that IES-PS-1was capable to degrade 82 % Cypermethrin at 40 mg/L dose in approximately 48 h. When the concentration was increased to 80 mg/L, 50% degradation of this compound was observed. Over this time period the cells could utilize only 17 % of Cypermethrin when it was given 125 mg/L, respectively. These findings indicate that increased concentration of Cypermethrin has a marked effect on biodegradation performance of IES-Ps-1 with a modest increased in the duration of lag phase, but did not lead to complete inhibition or cell death. These results proved that IES-Ps-1 is responsible for Cypermethrin degradation. Such finding may be useful in designing a scale-up in situ or on-site hazardous waste bioremediation process for field application.     

Biodegradation of phenol from a synthetic aqueous system using acclimatized activated sludge

Phenol is one of the aromatic hydrocarbons. Phenol and its derivatives are highly toxic. These pollutants can be observed in the effluents of many industries. This research investigates the removal of phenol by the use of activated sludge in a batch system. The effects of influencing factors on biodegradation efficiency have been evaluated. The main factors considered in this study were the volume of acclimatized activated sludge inoculation, pH, temperature, and initial concentration of phenol. The inoculation volumes of 1, 3, and 5 mL of acclimatized activated sludge were taken into account. Different pH values of 3, 5, 7, 9, and 11 were examined. The experiments were conducted for temperatures of 25, 30, 35, and 40 °C and initial phenol concentrations of 400, 800, 1,000, and 1,500 ppm. The results show that the acclimatized activated sludge has a high capacity for the removal of phenol. From a 100-mL aqueous solution was removed 1,500 ppm of phenol after 80 h. Furthermore, maximum phenol removal was observed for an inoculation volume of 5 mL for three different phenol concentrations of 100, 400, and 800 ppm. The best pH was 7 for the biodegradation process, and the optimum temperature was 30 °C. It was further found that an increase in the phenol concentration increased its removal time. Moreover, the activated sludge could effectively remove about 99.9 % of phenol from a synthetic aqueous solution in a batch system.     

Adsorption of reactive dyes from aqueous solutions by tannery sludge developed activated carbon: Kinetic and equilibrium studies

Adsorption kinetic and equilibrium studies of two reactive dyes, namely, Reactive Red 31 and Reactive Red 2 were conducted. The equilibrium studies were conducted for various operational parameters such as initial dye concentration, pH, agitation speed, adsorbent dosage and temperature. The initial dye concentration was varied from 10 - 60 mg/L, pH from 2–11, agitation speed from 100–140 rpm, adsorbent dosage from 0.5 g to 2.5 g and temperature from 30 °C -50 °C respectively. The activated carbon of particle size 600 μm was developed from preliminary tannery sludge. The dye removal capacity of the two reactive red dyes decreased with increasing pH. The zero point charge for the sludge carbon was 9.0 and 7.0 for the two dyes, respectively. Batch kinetic data investigations on the removal of reactive dyes using tannery sludge activated carbon have been well described by the lagergren plots. It was suggested that the Pseudo second order adsorption mechanism was predominant for the sorption of the reactive dyes onto the tannery sludge based carbon. Thus, the adsorption phenomenon was suggested as a chemical process. The adsorption data fitted well with Langmuir model than the Freundlich model. The maximum adsorption capacity(q⁰) from Langmuir isotherm were found to have increased in the range of 23.15–39.37 mg/g and 47.62–55.87 mg/g for reactive dyes reactive red 31 and reactive red 2, respectively.     

Microbiological degradation of phenol using two co-aggregating bacterial strains

Phenol biodegradation in an aerobic batch reactor was investigated using mixed two co-aggregating strains (Flavobacterium sp. and Acetobacter sp.). Response surface methodology by the Box–Behnken model was used to evaluate the optimal cell growth and phenol degradation conditions. The optimum temperature, pH value and inoculum size were found to be 33 °C, 6.06 and 13 %, respectively. In the conditions, phenol degradation rate and biomass were predicted to be 96.97 % and 410.78 mg/L within the range examined, respectively. Less toxic acetaldehyde, ethanol and acetic ether were identified as main intermediate products from the degraded samples using GC–MS. Substrate inhibition was calculated from experimental biomass growth and phenol degradation parameters using the Haldane equation. Kinetic parameters derived from nonlinear regression with correlation factors (R ²) were 0.9682 for phenol degradation and 0.9594 for biomass growth, respectively. The phenol concentration to avoid substrate inhibition was 278.17 mg/L.