Photolytic degradation of triclosan in freshwater and seawater

A 12-days photolysis experiment of triclosan, a widely used bactericide, was performed in freshwater and seawater under a low intensity artificial white light source. Photodegradation of triclosan was observed in both the freshwater and seawater samples. Assuming a first-order reaction, half-lives of triclosan in the freshwater and seawater were approximately 8 and 4 days, respectively. 2,8-Dichlorodibenzo-p-dioxin (DCDD) was detected in both the freshwater and seawater samples after 3 days of irradiation. The photodegradation of triclosan and the production of DCDD suggest that triclosan could be less stable and DCDD might be more stable in seawater than freshwater. As a result, DCDD produced from triclosan survives for a longer time in seawater.     

Electrochemical degradation applied to the metabolites of Acid Orange 7 anaerobic biotreatment

The electrochemical oxidation of the biotic degradation products of the textile dye C.I. Acid Orange 7 (AO7) was achieved using a boron doped diamond electrode (BDD). Tests were performed with model solutions of the biotic degradation products, sulphanilic acid (SA) and 1-amino-2-naphthol (AN), and also with real effluents obtained in experiments carried out in an up-flow anaerobic sludge blanket (UASB) reactor, fed with a simulated textile effluent containing AO7, working in mesophilic or thermophilic conditions. Bulk electrolysis was studied using two different supporting electrolytes - NaCl and Na(2)SO(4). The influence of initial metabolite concentration and current density on the electrodegradation rates of the biotic products was investigated. For the UASB effluents, oxidation tests were carried out for different electrolytes and at different current densities. Samples were collected at pre-selected intervals and absorbance measurements, chemical oxygen demand (COD) and total organic carbon (TOC) tests and high performance liquid chromatography (HPLC) analysis were performed. Results have shown an almost complete elimination of the persistent pollutants and a COD removal higher than 70% for both AN and SA. For the UASB effluents, COD removals between 45% and 90% and TOC removals varying from 19% to 41% were obtained.     

Monitoring the photochemical degradation of triclosan in wastewater by UV light and sunlight using solid-phase microextraction

Photo solid-phase microextraction (photo-SPME) is applied for the first time to study the photochemical behavior of an emerging pollutant, triclosan, in real contaminated wastewater samples using a solar simulator. In this study, water samples are extracted by SPME and then, the fiber coating is irradiated for a selected time. This on-fiber procedure, so-called photo-SPME, followed by gas chromatography-mass spectrometry makes it possible to study photodegradation kinetics and the generation of byproducts. Several photoproducts were identified in the real samples including the 2,8-dichlorodibenzo-p-dioxin, dichlorophenols and a compound tentatively identified as other DCDD congener or a dichlorohydroxydibenzofuran. Accordingly, it was possible to postulate main photodegradation mechanisms. Photo-SPME demonstrated slower kinetics in wastewater than in spiked ultrapure water probably due to the presence of dissolved organic matter. This technique was extensively compared with conventional aqueous photodegradation showing high similarity. The influence of pH on the triclosan photolysis and on the triclosan-dioxin conversion was also investigated in wastewater. Photodegradation of triclosan and formation of 2,8-DCDD occurred independently of sample pH. This study represents an advance in the use of photo-SPME to understand the photochemical fate of environmental organic pollutants and demonstrates its clear advantages with real samples.     

Biological degradation of triclocarban and triclosan in a soil under aerobic and anaerobic conditions and comparison with environmental fate modelling

Triclocarban and triclosan are two antimicrobial agents widely used in many personal care products. Their biodegradation behaviour in soil was investigated by laboratory degradation experiments and environmental fate modelling. Quantitative structure-activity relationship (QSAR) analyses showed that triclocarban and triclosan had a tendency to partition into soil or sediment in the environment. Fate modelling suggests that either triclocarban or triclosan "does not degrade fast" with its primary biodegradation half-life of "weeks" and ultimate biodegradation half-life of "months". Laboratory experiments showed that triclocarban and triclosan were degraded in the aerobic soil with half-life of 108 days and 18 days, respectively. No negative effect of these two antimicrobial agents on soil microbial activity was observed in the aerobic soil samples during the experiments. But these two compounds persisted in the anaerobic soil within 70 days of the experimental period.     

Photocatalytic oxidation of triclosan

In the spring of 2003, there was an outbreak of the severe respiratory syndrome (SARS) in Hong Kong. Health concerns have thus triggered an increased and predominant use of various types of household cleansing agents such as triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol). However, it has been reported recently that triclosan could be photochemically converted to toxic 2,8-dichlorodibenzo-p-dioxin (2,8-Cl(2)DD) in the environment. It is therefore necessary to develop environmentally friendly methods for the treatment of triclosan. To this end, photocatalytic degradation of triclosan in aqueous solution was conducted using TiO(2) (Degussa P25) under irradiation of UV light (lambda < 365 nm). It was found that triclosan could be degraded by this approach. Hydrogen peroxide was added to enhance the degradation process, and the optimal initial hydrogen peroxide concentration for triclosan degradation was 0.005% (w/v). Product identification indicated that triclosan oxidation occurred at its phenol moiety and yielded quinone and hydroquinone intermediates. The formation of a dichlorophenol intermediate in triclosan degradation suggested bond-breaking of the ether linkage occurred during the process. Moreover, no chlorinated dibenzo-p-dioxin congener was detected. These findings confirm that the photocatalytic degradation of triclosan is an environmentally friendly process.     

Fenton氧化法对磺胺类抗生素的降解动力学

采用Fenton氧化法同时降解水溶液中磺胺吡啶(SPY)、磺胺二甲基嘧啶(SMZ)和磺胺甲噁唑(SMX)。系统考查了初始H2O2浓度、Fe2+浓度、pH对3种磺胺类抗生素降解性能的影响。结果表明,3种磺胺抗生素被完全降解的最佳Fenton氧化条件是:H2O2浓度为2.0 mmol/L,Fe2+浓度为0.10 mmol/L,pH为3.0~3.5,反应时间为20 min。Fenton试剂对3种磺胺类抗生素的降解符合一级反应动力学,速度常数为0.0318~0.2002 min-1。     

Mineralization and degradation of glyphosate and atrazine applied in combination in a Brazilian Oxisol

The aim of this study was to investigate the behavior of the association between atrazine and glyphosate in the soil through mineralization and degradation tests. Soil treatments consisted of the combination of a field dose of glyphosate (2.88 kg ha?1) with 0, ?, 1 and 2 times a field dose of atrazine (3.00 kg ha?1) and a field dose of atrazine with 0, ?, 1 and 2 times a field dose of glyphosate. The herbicide mineralization rates were measured after 0, 3, 7, 14, 21, 28, 35, 42, 49, 56 and 63 days of soil application, and degradation rates after 0, 7, 28 and 63 days. Although glyphosate mineralization rate was higher in the presence of 1 (one) dose of atrazine when compared with glyphosate alone, no significant differences were found when half or twice the atrazine dose was applied, meaning that differences in glyphosate mineralization rates cannot be attributed to the presence of atrazine. On the other hand, the influence of glyphosate on atrazine mineralization was evident, since increasing doses of glyphosate increased the atrazine mineralization rate and the lowest dose of glyphosate accelerated atrazine degradation.     

污水深度处理微絮凝-D型滤池工艺运行性能与经济性分析

根据昆明市第一污水处理厂深度处理微絮凝-D型滤池工艺的运行数据,评价了工艺出水水质及总磷(TP)去除效果,同时分析了混凝剂投加量及药剂费用。结果表明,微絮凝-D型滤池工艺出水TP平均浓度为0.15 mg/L,最优水平值为0.05 mg/L,95%保证值为0.37 mg/L,TP平均去除率为63.6%。出水悬浮固体(SS)浓度95%保证值为10 mg/L。混凝剂聚合氯化铝(PAC)的投加量在1.5~4 mg Al2O3/L范围波动,去除单位TP的PAC投加量平均值为16.7 mg Al2O3/mg-P,投加比为2~8 mol-Al/mol-P。当投加比超过5时,出水TP浓度可达到0.3 mg/L以下。吨水PAC成本平均值为0.017元/t。     

三氯生在碳纳米管上的吸附

药品和个人护理用品(PPCPs)已成为一个引起广泛关注的新的环境问题。采用碳纳米管（CNTs）对水溶液中的三氯生进行吸附处理,考察了碳纳米管粒径及用量、温度、pH、振荡时间等因素对三氯生去除率的影响。研究结果表明,碳纳米管能快速吸附水中的三氯生,粒径较小的碳纳米管可获得较高的三氯生去除率;低温有利于吸附反应的进行;pH在6.5～7.0时,三氯生的去除率可达97%。三氯生在碳纳米管上的吸附可以很好地用Langmuir和Freundlich吸附等温方程进行描述。     

Effects of triclosan on zebrafish early-life stages and adults

Background, aim and scope  

The biocide triclosan (TCS) is commonly used in personal care, acrylic, plastic, and textiles products. TCS has been detected in surface water in several countries, and its ecological impact is largely unknown. In this work, the toxicity of TCS in zebrafish (Danio rerio), embryos and adults was studied. Several lethal and sub-lethal endpoints were analysed in organisms exposed to TCS such as mortality, embryo development and behaviour, hatching, micronuclei and biochemical markers (cholinesterase (ChE), glutathione S-transferase (GST) and lactate dehydrogenase (LDH)).     

Removal and reductive dechlorination of triclosan by Chlorella pyrenoidosa

Triclosan that is widely used as antimicrobial agent has been detected as contaminant in various aquatic environments. In this work, removal and biodegradation of triclosan in water by using a ubiquitous green alga, Chlorella pyrenoidosa was investigated. When C. pyrenoidosa was exposed to a series concentration of triclosan from 100 to 800 ng mL⁻¹, more than 50% of triclosan was eliminated by algal uptake from the culture medium during the first 1 h exposure and reached equilibrium after the 6 h treatment. In the biodegradation experiments, a removal percentage of 77.2% was obtained after C. pyrenoidosa was cultivated with 800 ng mL⁻¹ triclosan for 96 h. A major metabolite from the reductive dechlorination of triclosan was identified by using liquid chromatography coupled with electrospray ionization-mass spectrometry. The ultrastructural morphology of algal cells grown in the presence of triclosan was observed by using transmission electron microscopy and the growth of algal cells was detected. It was found that the trilcosan treatment resulted in the disruption of the chloroplast and the release of organic material into aquatic environment, which indicated that triclosan may affect membrane metabolism.     

纳米铜及三氯生对污泥硝化作用的影响

金属纳米颗粒 (NPs) 与药品及个人护理品 (PPCPs) 的广泛使用,使其不可避免地释放至污水中,进入污水处理系统对污水生物处理产生潜在危害。由于硝化菌极易受到有毒有害物质的影响,选取纳米铜(CuNPs) 和三氯生 (TCS) 作为目标污染物,研究其对污泥硝化过程中COD去除、硝化效果、污泥理化性质等方面的影响。结果表明,目标污染物的暴露初期对硝化效果产生不同程度的抑制,TCS、CuNPs及二者复合暴露时硝化效率分别下降8.7%、34%和31.7%,但随着暴露时间的增加,硝化效率逐渐恢复至正常水平。然而尽管硝化反应结束后对NH+4-N的去除率无明显差异,但CuNPs及二者同时暴露时对硝化速率及污泥的同化作用有显著抑制,而单独的TCS无明显影响。进一步研究发现CuNPs及二者复合暴露时对污泥的表面结构有一定的破损影响,且污泥的沉淀性能变差。     

Fenton试剂氧化对硝基酚中氧化还原电位的变化规律

考察了Fenton试剂氧化对硝基苯酚(PNP)过程中氧化还原电位(ORP)的变化规律.结果表明:(1)当pH为3、H2O2投加量为3 mmol/L、Fe2+投加量为0.3 mmol/L时,废水中PNP在5.0 min时降到5 mg/L左右,去除率达95%;废水可生化性得到有效改善(BOD5/COD由最初的0.073升至...     

Kinetics of phenol degradation in an anaerobic fixed-biofilm process.

A mathematical model was developed to describe phenol degradation in an anaerobic fixed-biofilm process. The model incorporates the mechanisms of diffusive mass transport and Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A pilot-scale column reactor was used to verify the model. Batch kinetic tests were conducted independently to determine the biokinetic parameters used in the model, while shear loss and initial thickness of biofilm were assumed so that the model simulated the substrate concentration results well. The removal efficiency for phenol was approximately 98.5% at a steady-state condition. The model accurately described the effluent substrate concentrations and the sequence of biodegradation in the reactor. The model simulations are in agreement with the experimental results. The approaches presented in this paper could be used to design fullscale anaerobic fixed-biofilm reactor systems for the biodegradation of phenolic substrates.     

造纸废水生化降解工艺的应用与探讨

结合工程实例 ,讨论了生化法对麦草碱法造浆黑液及造纸综合废水处理的可行性。探讨结果表明 ,只要控制适当的理化条件、驯化优势菌种 ,微生物方法对造纸综合废水及黑液CODCr的降解具有显著的作用 ,做到达标排放是完全可能的。     

超声-Fenton高级氧化降解染料工业废水的研究

采用超声与Fenton高级氧化技术联合处理染料废水,取得了满意的效果。同时考察了初始浓度、初始pH值、超声时间、超声频率、超声功率、H2O2和FeSO4初始浓度等因素对其COD去除效果的影响,当超声波频率为45 kHz,功率为200 W,初始pH值为2.63,超声时间为150 min,H2O2浓度为60 mmol/L,FeSO4浓度为12 mmol/L时,染料废水COD去除率达到91.8%。     

UV/H2O2工艺降解典型消炎药布洛芬影响因素和降解机理

布洛芬是一种典型药物和个人护理用品（PPCPs）,大量生产和广泛使用给环境带来了一定危害。基于响应面方法,采用UV/H2O2工艺降解布洛芬（IB）,对降解过程中的影响因素（光强、H2O2投加量、初始IB浓度）进行了探讨,构建响应面模型。优化的最佳反应条件为：H2O2投加量0.10 mol·L-1、初始IB浓度5.00 mg·L-1、UV光强1 400 μW·cm-2,预测和实验IB以及反应动力学速率常数接近,说明响应面模型能够有效描述UV/H2O2降解反应过程。同时用离子阱质谱仪鉴定出IB羟基加成物、4-乙基苯酚、对异丁基苯甲酸等降解中间产物,其中IB羟基加成物的细胞毒性大于IB本身,最后提出降解机理。本研究为UV/H2O2工艺降解典型消炎药类污染物提供技术参考。     

Occurrence and toxicity of antimicrobial triclosan and by-products in the environment

Introduction and aims  

A review was undertaken on the occurrence, toxicity, and degradation of triclosan (TCS; 5-chloro-2,4-dichlorophenoxy)phenol) in the environment. TCS is a synthetic, broad-spectrum antibacterial agent incorporated in a wide variety of household and personal care products such as hand soap, toothpaste, and deodorants but also in textile fibers used in a range of other consumer products (e.g., toys, undergarments and cutting boards among other things).     

UV-Fenton光催化法深度处理紫胶漂白废水

采用UV-Fenton联合的方法处理紫胶漂白废水,单因素实验研究了H2O2用量、FeSO4用量、反应时间和初始pH值对紫胶漂白废水降解的影响,并通过数学回归模型和响应曲面法优化得到UV-Fenton深度处理紫胶漂白废水的最优条件：初始pH值5.0,H2O2用量49 g·L-1、FeSO4用量2.6 g·L-1、反应时间为4 h。经最优工艺条件深度处理后的紫胶漂白废水COD、BOD5、悬浮物、色度、总氮和总磷分别降低至48 mg·L-1、32 mg·L-1、27.3 mg·L-1、24 NTU、0.027 mg·L-1、0.021 mg·L-1,除BOD5稍高外,其余指标均达到污水综合排放一级标准。在最优条件下,以紫胶漂白废水COD值和COD去除率为指标的降解动力学模型可分别表示为：lny=0.034 98+0.001 85x+6.898×10-6x2和z=95.36-92.78×0.970 6t。由动力学方程可看出,废水COD值在反应开始的前2 h内,降低幅度接近90%,且以反应开始时最为剧烈,随着反应的进行,反应剧烈程度迅速减弱。     

Parathion degradation and its intermediate formation by Fenton process in neutral environment

The purpose of this study is to investigate parathion degradation by Fenton process in neutral environment. The initial parathion concentration for all the degradation experiments was 20 ppm. For hydrogen ion effect on Fenton degradation, the pH varied from 2 to 8 at the [H₂O₂] to [Fe²⁺] ratio of 2-2 mM, and the result showed pH 3 as the most effective environment for parathion degradation by Fenton process. Apparent degradation was also observed at pH 7. The subsequent analysis for parathion degradation was conducted at pH 7 because most environmental parathion exists in the neutral environment. Comparing the parathion degradation results at various Fenton dosages revealed that at Fe²⁺ concentrations of 0.5, 1.0 and 1.5 mM, the Fenton reagent ratio ([H₂O₂]/[Fe²⁺]) for best-removing performance were found as 4, 3, and 2, resulting in the removal efficiencies of 19%, 48% and 36%, respectively. Further increase in Fe²⁺ concentration did not cause any increase of the optimum Fenton reagent ratio for the best parathion removal. The result from LC-MS also indicated that hydroxyl radicals might attack the PS double bond, the single bonds connecting nitro-group, nitrophenol, or the single bond within ethyl groups of parathion molecules forming paraoxons, nitrophenols, nitrate/nitrite, thiophosphates, and other smaller molecules. Lastly, the parathion degradation by Fenton process at the presence of humic acids was investigated, and the results showed that the presence of 10 mg L⁻¹ of humic acids in the aqueous solution enhanced the parathion removal by Fenton process twice as much as that without the presence of humic acids.