Removal of 17β-estradiol in laccase catalyzed treatment processes

The removal of 17β-estradiol （E2） in laccase catalyzed oxidative coupling processes was systematically studied in this work. We focused on the influence of pH and natural organic matter （NOM） on the performance of the enzymatic treatment processes. It was found that the optimal pH for E2 removal was between 4 and 6. The removal of E2 was slightly inhibited in the presence of NOM. Enzymatic transformation of E2 was second-order in kinetics with first-order to both the concentrations of the enzyme and contaminant. Mass spectrum （MS） analysis suggested that coupling products were formed through radical-radical coupling mechanism. The results of this study demonstrated that laccase catalyzed oxidative coupling process could potentially serve as a treatment strategy to control steroid estrogens.     

Feasibility of bubble surface modification for natural organic matter removal from river water using dissolved air flotation

A novel, functionalized bubble surface can be obtained in dissolved air flotation (DAF) by dosing chemicals in the saturator. In this study, different cationic chemicals were used as bubble surface modifiers, and their effects on natural organic matter (NOM) removal from river water were investigated. NOM in the samples was fractionated based on molecular weight and hydrophobicity. The disinfection byproduct formation potentials of each fraction and their removal efficiencies were also evaluated. The results showed that chitosan was the most promising bubble modifier compared with a surfactant and a synthetic polymer. Tiny bubbles in the DAF pump system facilitated the adsorption of chitosan onto microbubble surfaces. The hydrophobic NOM fraction was preferentially removed by chitosan-modified bubbles. Decreasing the recycle water pH from 7.0 to 5.5 improved the removal of hydrophilic NOM with low molecular weight. Likewise, hydrophilic organic compounds gave high dihaloacetic acid yields in raw water. An enhanced reduction of haloacetic acid precursors was obtained with recycle water at pH values of 5.5 and 4.0. The experimental results indicate that NOM fractions may interact with bubbles through different mechanisms. Positive bubble modification provides an alternative approach for DAF to enhance NOM removal.

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Controlling various contaminants in wastewater effluent through membranes and engineered wetland

For effective wastewater reclamation and water recovery, the treatment of natural and effluent organic matters (NOM and EfOM), toxic anions, and micropollutants was considered in this work. Two different NOM (humic acid of the Suwannee River, and NOM of US and Youngsan River, Korea), and one EfOM from the Damyang wastewater treatment plant, Korea, were selected for investigating the removal efficiencies of tight nanofiltration (NF) and ultrafiltration (UF) membranes with different properties. Nitrate, bromate, and perchlorate were selected as target toxic anions due to their well known high toxicities. Tri-(2-chloroethyl)-phosphate (TCEP), oxybenzone, and caffeine, due to their different K _ow and pK _a values, were selected as target micropollutants. As expected, the NF membranes provided high removal efficiencies in terms of all the tested contaminants, and the UF membrane provided fairly high removal efficiencies for anions (except for nitrate) and the relatively hydrophobic micropollutant, oxybenzon. Through the wetlands, nitrate was successfully removed. Therefore, a fair process of combining membranes with an engineered wetland could be proposed for sustainable wastewater reclamation and optimum control of contaminats.     

Mechanisms for simultaneous ozonation of sulfamethoxazole and natural organic matters in secondary effluent from sewage treatment plant

• SMX was mainly degraded by hydrolysis, isoxazole oxidation and double-bond addition. • Isoxazole oxidation and bond addition products were formed by direct ozonation. • Hydroxylated products were produced by indirect oxidation. • NOM mainly affected the degradation of SMX by consuming ^•OH rather than O₃. • Inhibitory effect of NOM on SMX removal was related to the components’ aromaticity. Sulfamethoxazole (SMX) is commonly detected in wastewater and cannot be completely decomposed during conventional treatment processes. Ozone (O₃) is often used in water treatment. This study explored the influence of natural organic matters (NOM) in secondary effluent of a sewage treatment plant on the ozonation pathways of SMX. The changes in NOM components during ozonation were also analyzed. SMX was primarily degraded by hydrolysis, isoxazole-ring opening, and double-bond addition, whereas hydroxylation was not the principal route given the low maximum abundances of the hydroxylated products, with m/z of 269 and 287. The hydroxylation process occurred mainly through indirect oxidation because the maximum abundances of the products reduced by about 70% after the radical quencher was added, whereas isoxazole-ring opening and double-bond addition processes mainly depended on direct oxidation, which was unaffected by the quencher. NOM mainly affected the degradation of micropollutants by consuming ^•OH rather than O₃ molecules, resulting in the 63%–85% decrease in indirect oxidation products. The NOM in the effluent were also degraded simultaneously during ozonation, and the components with larger aromaticity were more likely degraded through direct oxidation. The dependences of the three main components of NOM in the effluent on indirect oxidation followed the sequence: humic-like substances>fluvic-like substances>protein-like substances. This study reveals the ozonation mechanism of SMX in secondary effluent and provides a theoretical basis for the control of SMX and its degradation products in actual water treatment.     

二氧化锰体系中环丙沙星的氧化转化研究

为了更全面的了解环丙沙星在自然界中的环境化学行为,采用批处理实验方法研究了环丙沙星在二氧化锰作用下的氧化转化过程,并讨论了溶液的pH对反应的影响。结果表明,在无二氧化锰的条件下,环丙沙星的质量浓度在1周内检测没有明显的变化。在二氧化锰存在的条件下,环丙沙星对二氧化锰的氧化作用具有较强的反应感受性。pH一定的条件下,当环丙沙星相对过量时,环丙沙星去除率随自身质量浓度的增大而减小,随二氧化锰质量浓度的增大而增大。此外,随着溶液pH值由3.5升至5.9时,环丙沙星的去除率显著上升。     

Removal of methylene blue by coupling black carbon adsorption with TiO2 photodegradation

In this study, the removal of methylene blue (MB) by the coupling of black carbon (BC) and TiO₂ was investigated. The effects of different parameters such as catalyst dose, sorbent, initial concentrations of dye, pH of the solutions, recycles on discoloration, and chemical oxidation demand (COD) reduction of MB were monitored to optimize the reaction conditions. The discoloration and COD conversation rate of MB obtained by the coupling process were 100% after 90?min irradiation. The synergistic effect of MB-adsorption on BC followed by degradation through TiO₂ photocatalysis was proved by FT–IR spectrophotometer. The BC as by-product of natural materials is a promising adsorbent for waste water treatment.     

Occurance and control of manganese in a large scale water treatment plant

The continuous variations of dissolved oxygen (DO), manganese (Mn), pH, and their effect on manganese removal by different water treatment processes are investigated. The results show that the declined DO concentration and pH value in the bottom of reservoir results in the increasing release of Mn from sediment to source water. Manganese concentration increased from 0.1 to 0.4 mg·L^-1 under the condition that DO concentration decreased from 12.0 to 2.0 mg·L^-1 in raw water. The different water treatment processes exhibited different efficiency on manganese removal. The processes with recycling of the suspended sludge, low elevation velocity in settling tank and slow filter rate, will benefit the manganese removal. During a high release of manganese in raw water, traditional coagulation-sedimentation and filtration could not completely remove Mn, although granular activated carbon filtration (GAC) had been applied. At that case, preoxidation with chlorine or potassium permanganate (KMnO₄) was necessary to address the high manganese concentration.     

二氧化锰体系中环丙沙星的氧化转化研究

为了更全面的了解环丙沙星在自然界中的环境化学行为,采用批处理实验方法研究了环丙沙星在二氧化锰作用下的氧化转化过程,并讨论了溶液的pH对反应的影响。结果表明,在无二氧化锰的条件下,环丙沙星的质量浓度在1周内检测没有明显的变化。在二氧化锰存在的条件下,环丙沙星对二氧化锰的氧化作用具有较强的反应感受性。pH一定的条件下,当环丙沙星相对过量时,环丙沙星去除率随自身质量浓度的增大而减小,随二氧化锰质量浓度的增大而增大。此外,随着溶液pH值由3.5升至5.9时,环丙沙星的去除率显著上升。     

Enhanced production of laccase by Coriolus hirsutus using molasses distillery wastewater

The effect of physical parameters of cultivation (load volume, temperature, pH, agitation, inoculum size, and incubation period) in the production of laccase by wood-rotting basidiomycete Coriolus hirsutus were studied using diluted molasses distillery wastewater (MDW) as a major composition. Using fractional factorial design, our study first identified load volume, agitation, and inoculum size as statistically significant factors. Optimal preferences and mutual interactions of the factors were then determined by the response surface method, which is based on the center composite design. A quadratic model was used to fit the experimental data. The optimized operational parameters for laccase production were determined to be the following: culture temperature of 25°C, pH 4, load volume of 40 mL diluted MDW in 150 mL flask, agitation rate of 183 r·min^?1, inoculation of 11.5% v/v, and cultivation time of 6 d. The experimental validation under these conditions (the maximum laccase production of 2198.2 U·mL^?1 was within the confidence interval) subsequently verified the accuracy of the constructed model. Moreover, the removal of chemical oxygen demand and nitrogen of MDW reached 62.85% and 48.00% respectively, and the decolorization ratio under the optimal condition was 41.85%. The enhanced production of laccase by C. hirsutus is a new recovery strategy for MDW.     

Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic matter

The formation of a dynamic membrane (DM) was investigated using polyethylene glycol (PEG) (molecular weight of 35000 g/mol, concentration of 1 g/L). Two natural organic matters (NOM), Dongbok Lake NOM (DLNOM) and Suwannee River NOM (SRNOM) were used in the ultrafiltration experiments along with PEG. To evaluate the effects of the DM with PEG on ultrafiltration, various transport experiments were conducted, and the analyses of the NOM in the membrane feed and permeate were performed using high performance size exclusion chromatography, and the effective pore size distribution (effective PSD) and effective molecular weight cut off (effective MWCO) were determined. The advantages of DM formed with PEG can be summarized as follows: (1) PEG interferes with NOM transmission through the ultrafiltration membrane pores by increasing the retention coefficient of NOM in UF membranes, and (2) low removal of NOM by the DM is affected by external factors, such as pressure increases during UF membrane filtration, which decreases the effective PSD and effective MWCO of UF membranes. However, a disadvantage of the DM with PEG was severe flux decline; thus, one must be mindful of both the positive and negative influences of the DM when optimizing the UF performance of the membrane.     

六方水钠锰矿对罗丹明B的去除效果及机理

六方水钠锰矿作为环境中一种具有较强氧化与吸附能力的氧化锰矿物,对环境中的有机染料有着一定的去除作用。采用常压回流法一步合成纳米六方水钠锰矿,运用X射线衍射(XRD)、电感耦合等离子体光谱仪(ICP-AES)、BET氮气吸附法、场发射扫描电镜(FESEM)和透射电镜(TEM)对其矿物晶体结构、化学组成、比表面积、孔径分布和微观形貌进行表征,选用罗丹明(RB)作为目标有机染料,研究反应条件对纳米六方水钠锰矿对RB的去除效果的影响(包括pH值、六方水钠锰矿浓度、染料浓度和温度)。进而研究六方水钠锰矿对RB的去除机制,通过在反应后的溶液中加入盐酸羟胺,使矿物溶解,吸附在矿物上的染料重新释放到溶液中,以区分吸附去除率和氧化去除率。结果表明,降低反应pH、增加六方水钠锰矿浓度、减小染料浓度以及提高温度均有利于六方水钠锰矿对罗丹明B(RB)的去除。其中影响最大的pH,反应体系pH为2.87时,RB的去除率达到99.9%,而pH为10.29时,RB的去除率仅为8.33%。通过去除机制实验结果表明,在pH为4.5时,RB的氧化去除率是36.3%,吸附去除率为4.6%,六方水钠锰矿去除RB以氧化去除为主。纳米六方水钠锰矿材料的重复利用效果很好,重复使用3次去除率,RB的去除率仅从90.6%降至85.9%。合成的纳米六方水钠锰矿有着很好的去除有机染料的效果,并且有一定的重复利用性,机制的研究也有利于提升对有机染料的去除效果。     

真菌漆酶介导自由基偶联和接枝反应在绿色化学中的应用

漆酶(p-苯二醇:分子氧氧化还原酶;EC 1.10.3.2)是自然界中普遍存在的一类胞外含铜多酚氧化还原酶.漆酶能够以环境中氧分子作为电子接受体,催化4个底物分子的单电子氧化形成4个相应的反应活性自由基或醌类中间体,随后这些活性中间体在酶促位点外发生步进式偶联反应,生成多种具有复杂结构的大分子C—C、C—O—C或C—N—C共价聚合产物.该反应过程中仅生成唯一副产物水,具有反应温和、底物广谱、催化效率高、操作可控和经济环保等优点.目前,真菌漆酶介导低分子有机物和高分子化合物的自由基偶联和接枝反应已经被应用于生物技术领域,该技术克服了传统物理化学方法存在的弊端,在保护人群健康和生态安全等方面具有广泛地应用前景和商业价值.本文详细地概述了真菌漆酶催化不同底物分子的自由基偶联和接枝反应在环境修复、生物监测、食品加工、纤维改性、纺织染色、制药行业和有机合成等绿色化学中的最新研究进展,旨在为开发和拓展真菌漆酶在绿色化学技术领域中的多功能应用提供科学的理论依据和技术指导.     

云下气体湿清除过程参数化

本文发展一个雨水对云下气体清除的一维拉氏模式,它包括了气体对雨滴的对流质量输送,物种在雨水中溶解、离解和液相氧化反应。应用这模式计算了不同参数情况下,雨水对SO_2气体的湿清除系数,并讨论了雨强,SO_2,NH_3和氧化剂浓度以及雨水pH_0初值与雨水清除系数的关系。     

蚯蚓和堆肥固定化添加模式对漆酶降解土壤五氯酚的影响

利用土壤五氯酚（PCP）污染模拟实验,研究两种不同生态型蚯蚓（赤子爱胜蚓Eisenia foetida和壮尾环毛蚓Amynthas robustus E.Perrie）和堆肥固定化添加模式对漆酶降解土壤PCP的影响。在42 d培养期内,测试了不同处理下PCP质量分数、漆酶活性,以及土壤呼吸和微生物碳氮等微生物指标。结果表明：堆肥固定化漆酶降解土壤PCP的效果优于壳聚糖固定化漆酶和自由漆酶,主要原因是堆肥固定化漆酶能够有效地提高漆酶稳定性,减缓其活性下降速度。此外,堆肥还能提高土壤微生物的数量与活性,显著提升土壤漆酶的活性。添加两种生态型蚯蚓对漆酶活性影响不显著,但均可以显著提高土壤微生物的数量与活性,加速土壤中PCP的降解。壮尾环毛蚓对土壤微生物数量与活性的提升效果优于赤子爱胜蚓。     

Pyrene partition behavior to the NOM: Effect of NOM characteristics and its modification by ozone preoxidation

Hydrophobic organic contaminants (HOCs)—pyrene, and natural organic matters (NOM) from different sources were taken as the test compounds to investigate the impact of physicochemical characteristics of NOM on HOCs’ partition to the NOM in this study. The effects of solution property, NOM characteristics, and modification by ozone preoxidation on pyrene partition to NOM were systematically evaluated. According to the fluorescence quenching method, the partition coefficient K _oc of pyrene to NOM was calculated, which was found to have a great relationship with the aromatic structures and hydrophobic functional groups of the NOM. The NOM characteristic modification corresponding to solution property could influence the interactions between the NOM and pyrene. Preozonation could destroy the aromatic or hydrophobic structures of the NOM and decrease K _oc of pyrene.     

Adsorption of humic acid from aqueous solution on bilayer hexadecyltrimethyl ammonium bromide-modified zeolite

Surfactant-modified natural zeolites (SMNZ) with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide (HTAB) onto the surface of a natural zeolite. The adsorption behavior of humic acid (HA) on SMNZ was investigated. Results indicate that the adsorbent SMNZ exhibited a higher affinity toward HA than the natural zeolite. HA removal efficiency by SMNZ increased with HTAB loading. Coexisting Ca²⁺ in solution favored HA adsorption onto SMNZ. Adsorption capacity decreased with an increasing solution pH. For typical SMNZ with bilayer HTAB coverage, HA adsorption process is well described by a pseudo-second-order kinetic model. The experimental isotherm data fitted well with the Langmuir model. Calculated maximum HA adsorption capacities for SMNZ with bilayer HTAB coverage at pH 5.5 and 7.5 were 63 and 41 mg·g^-1, respectively. E2/E3 (absorbance at 250 nm to that at 365 nm) and E4/E6 (absorbance at 465 nm to that at 665 nm) ratios of the residual HA in solution were lower than that of the original HA solution. This indicates that the HA fractions with high polar functional groups, low molecular weight (MW), and aromaticity had a stronger tendency for adsorption onto SMNZ with bilayer HTAB coverage. Results show that HTAB-modified natural zeolite is a promising adsorbent for removal of HA from aqueous solution.     

Effect of natural organic matter on arsenic release from soils and sediments into groundwater

Arsenic (As) contamination in groundwater has received significant attention recently. Natural and anthropogenic sources contribute to the worldwide occurrence of As contamination. As speciation is an important factor related to its toxic and mobile behavior. The release of As from soils and sediments into groundwater is governed by several geophysicochemical processes, of which, As sorption behavior is of principle significance. This review paper summarizes existing information regarding the effects of natural organic matter (NOM) on the fate and mobility of As species in the environment. NOM may enhance the release of As from soils and sediments into the soil solution, thereby facilitating As leaching into the groundwater. The main influencing mechanisms include competition for available adsorption sites, formation of aqueous complexes, and/or changes in the redox potential of site surfaces and As redox speciation. NOM may also serve as binding agents, thereby reducing As mobility. However, comparably little research has been performed on this aspect. Since most investigations have been done on purified minerals under laboratory conditions, further research involving various geological materials under natural environmental conditions is required. Development of proper geochemical conceptual models may provide means of predicting the role of NOM in arsenic leaching and/or immobilization.     

3D model for a secondary facultative pond

This paper describes a comprehensive model of wastewater treatment in secondary facultative ponds, which combines 3D hydrodynamics with a mechanistic water quality model. The hydrodynamics are based on the Navier-Stokes equation for incompressible fluids under shallow water and Boussinesq assumptions capturing the flow dynamics along length, breadth and depth of the pond. The water quality sub model is based on the Activated Sludge Model (ASM) concept, describing COD and nutrient removal as function of bacterial growth following Monod kinetics, except for Escherichia coli removal, which was modelled as first order decay. The model was implemented in the Delft3D software and was used to evaluate the effect of wind and the addition of baffles on the water flow pattern, temperature profiles in the pond and treatment efficiency. In contrast to earlier models reported in the literature, our simulation results did not show any significant improvement in COD removal (based on the ASM concept) with addition of baffles or under intermittent wind-induced mixing. However, E. coli removal efficiency, based on a first order decay approach, showed a fair improvement in the presence of baffles or intermittent wind-induced mixing. Furthermore, simulations with continuous wind effect showed a decrease in removal efficiency for COD but a further increase in E. coli removal efficiency. Such contrasting results for two different approaches in modelling could indicate that the first order decay concept might not be appropriate to describe all the interactions between biochemical processes in a pond. However, these interpretations remain theoretical, as the model needs validation with field data.     

Sonocatalytic degradation of tetracycline antibiotic in aqueous solution by sonocatalysis

Tetracycline (TC), one of the most common antibiotics, is often poorly bio-degraded in conventional wastewater treatment plants. In this study, the sonocatalytic degradation of TC was investigated using TiO₂ nano-particles as catalyst. The effect of pH, initial TC concentrations, reaction times, and H₂O₂ concentrations were evaluated. The efficacy of ultrasonic irradiation alone in the removal of this pollutant was negligible but removal efficiency increased upon addition of TiO₂ up to 250 mg L^?1; increase of pH and initial TC concentration attenuated TC degradation. Addition of H₂O₂ raised the removal efficiency so that complete removal of TC was achieved within 75 min.