Applicability of Fenton and H2O2/UV reactions in the treatment of tannery wastewaters

In this paper we evaluated the H2O2/UV and the Fenton's oxidation processes for the treatment of tannery wastewater under different experimental conditions. Efficiencies were judged by the amounts of organic substances degraded or eliminated under these treatment techniques. Daphnia magna and Vibrio fischeri were used to monitor toxicity. Organic compounds contained in the untreated and treated tannery wastewater were determined and identified using substance specific techniques. Gas chromatography-mass spectrometry (GC-MS) in positive electron impact (EI(+)) mode was applied to determine volatile organics. Atmospheric pressure ionization (API) mass (MS) and tandem mass spectrometry (MS-MS) coupled with flow injection analysis (FIA) or liquid chromatography (LC) were used to detect or identify polar organic pollutants. The experimental results indicated that both oxidation processes--H2O2/UV at pH 3 and Fenton at pH 3.5--are able to reduce TOC content by mineralisation of the organic compounds.     

g-C3N4/TiO2复合薄膜光催化降解石油采出水中多环芳烃

针对亟待解决的石油开采废水中的多环芳烃(polycyclic aromatic hydrocarbons, PAHs)污染物的生物毒害性问题,利用紫外光辐照g-C₃N₄/TiO₂复合薄膜光催化剂,对取自内蒙某采油现场的采出水水样进行降解处理,研究多组分PAHs污染物共存条件下的不同环数PAHs发生光催化氧化反应的降解规律及降解动力学。采用扫描电子显微镜(scanning electron microscope, SEM)表征光催化剂表面微观形貌,采用固相微萃取法富集和萃取水样中的PAHs,采用气相色谱-质谱联用法(gas chromatography-mass spectrometry, GC-MS)检测分析PAHs含量。经UV/g-C₃N₄/TiO₂光催化反应处理,采出水中不溶的颗粒态萘优先于溶解态萘被降解去除,经60 min后对萘的总去除率可达61.13%。大于4环不溶性高环PAHs,可被优先光催化降解,从而高毒性的PAHs污染物被逐级转化为相对较低生物毒性的苊烯、蒽、菲、萘等,其中苊烯的含量增长最显著。结论石油采出水的外排处理工艺中增加PAHs光催化脱毒工艺具有一定可行性,对于保障原有水厂中的生化工艺段高效率、稳定运行将极具价值。     

焦化厂A/O出水中的有机污染物分析

采用色谱－质谱（GC／MS）联用仪分析和鉴定了上海宝钢焦化厂A／O生化阶段出水的有机污染物组成,共检出各类有机污染物70多种。结合焦化废水专用混凝剂的混凝处理实验结果,指出了各类有机污染物的去除情况。     

丙烯酸装置废水特征有机污染物及其荧光特性

采用吹扫捕集-气相色谱/质谱法(P&T-GC/MS),液液萃取-气相色谱/质谱法(LLE-GC/MS)等方法对丙烯酸装置废水中主要特征有机污染物进行了定性、定量分析,研究了废水和各主要特征污染物的三维荧光特性。结果表明,废水中共检出有机酸、苯系物、酯、醛、醇等24种有机污染物,其中含量较大的有乙酸55.13%,丙烯酸23%,甲醛21.81%,甲苯0.03%,4-羟基-2-丁酮0.02%,丙烯酸甲酯0.01%,正丁醇0.01%。丙烯酸废水中含有3个荧光峰,区域IV内的荧光峰(λex/em=290/355 nm)主要由废水中高浓度的丙烯酸产生,区域V内的2个荧光峰(λex/em=390/495 nm,λex/em=295/480 nm)由水中的腐殖质产生。丙烯酸抑制了甲苯、甲醛、乙酸等3种荧光物质对丙烯酸废水荧光强度的贡献。4种荧光物质的荧光基团影响力大小:碳碳双键+羧基> 苯环> 羰基> 羧基。     

Heterocatalytic Fenton oxidation process for the treatment of tannery effluent: kinetic and thermodynamic studies

Background, aim, scope

Treatment of wastewater has become significant with the declining water resources. The presence of recalcitrant organics is the major issue in meeting the pollution control board norms in India. The theme of the present investigation was on partial or complete removal of pollutants or their transformation into less toxic and more biodegradable products by heterogeneous Fenton oxidation process using mesoporous activated carbon (MAC) as the catalyst.

Materials and methods

Ferrous sulfate (FeSO₄·7H₂O), sulfuric acid (36?N, specific gravity 1.81, 98% purity), hydrogen peroxide (50% v/v) and all other chemicals used in this study were of analytical grade (Merck). Two reactors, each of height 50?cm and diameter 6?cm, were fabricated with PVC while one reactor was packed with MAC of mass 150?g and other without MAC served as control.

Results and discussion

The oxidation process was presented with kinetic and thermodynamic constants for the removal of COD, BOD, and TOC from the wastewater. The activation energy (Ea) for homogeneous and heterogeneous Fenton oxidation processes were 44.79 and 25.89?kJ/mol, respectively. The thermodynamic parameters ??G, ??H, and ??S were calculated for the oxidation processes using Van??t Hoff equation. Furthermore, the degradation of organics was confirmed through FTIR and UV?Cvisible spectroscopy, and cyclic voltammetry.

Conclusions

The heterocatalytic Fenton oxidation process efficiently increased the biodegradability index (BOD/COD) of the tannery effluent. The optimized conditions for the heterocatalytic Fenton oxidation of organics in tannery effluent were pH 3.5, reaction time?C4?h, and H₂O₂/FeSO₄·7H₂O in the molar ratio of 2:1.     

Biological assessment of bisphenol A degradation in water following direct photolysis and UV advanced oxidation

Endocrine disrupting compounds (EDCs) are exogenous environmental chemicals that can interfere with normal hormone function and present a potential threat to both environmental and human health. The fate, distribution and degradation of EDCs is a subject of considerable investigation. To date, several studies have demonstrated that conventional water treatment processes are ineffective for removal of most EDCs and in some instances produce multiple unknown transformation products. In this study we have investigated the use of direct photolysis with low-pressure (LP) Hg UV lamps and UV+hydrogen peroxide (H(2)O(2)) advanced oxidation process (AOP) for the degradation of a prototypic endocrine disrupter, bisphenol A (BPA), in laboratory water. Removal rates of BPA and formation of degradation products were determined by high performance liquid chromatography (HPLC) analysis. Changes in estrogenic activity were evaluated using both in vitro yeast estrogen screen (YES) and in vivo vitellogenin (VTG) assays with Japanese medaka fish (Oryzias latipes). Our results demonstrate that UV alone did not effectively degrade BPA. However, UV in combination with H(2)O(2) significantly removed BPA parent compound and aqueous estrogenic activity in vitro and in vivo. Removal rates of in vivo estrogenic activity were significantly lower than those observed in vitro, demonstrating differential sensitivities of these bioassays and that certain UV/AOP metabolites may retain estrogenic activity. Furthermore, the UV/H(2)O(2) AOP was effective for reducing larval lethality in treated BPA solutions, suggesting BPA degradation occurred and that the degradation process did not result in the production of acutely toxic intermediates.     

焦化废水臭氧催化氧化过程的污染物降解特征

为了考察焦化废水臭氧催化氧化深度处理过程中污染物的降解特征,对处理过程中的废水进行了COD、TOC、BOD、紫外可见光谱、高效液相色谱、气相色谱-质谱联用（GC-MS）和凝胶色谱等多种分析。结果表明：经臭氧催化氧化处理后,废水的COD、TOC和UV254均降低,降低速度大小为UV254 >COD >TOC;臭氧催化氧化可提高废水的可生化性,但氧化时间进一步延长,可生化性反而降低;液相色谱表明非极性物质优先得到去除;凝胶色谱表明分子量较小的物质优先去除;GC-MS结果表明焦化废水混凝出水中主要成分为苯酚类、杂环化合物、多环芳烃及其衍生物,臭氧催化氧化处理后这些化合物都得到有效降解。     

钠基膨润土、粉煤灰吸附预处理煤气化废水效果及机理

煤气化废水具有可生化性差,酚类物质含量高、毒性强的特点,导致生物处理效果不理想。以煤气化废水厌氧段进水为研究对象,分别以钠基膨润土(Na-BBT)与粉煤灰(PFA)作为吸附剂,探究其对煤气化废水中主要特征污染物的去除效果和吸附机理。结果表明：Na-BBT、PFA对煤气化废水中的化学需氧量(COD)、氨氮(NH₃-N)与总酚(total phenols,Tph)有一定的去除效果,其可生化性得到提升,经过Na-BBT和PFA处理后,BOD₅/COD由0.29分别提高至0.37和0.32;废水中的NH₃-N由221.3 mg·L⁻¹分别降至128.6 mg·L⁻¹和180.8 mg·L⁻¹,总酚由554.8 mg·L⁻¹分别降至360.6 mg·L⁻¹和386.7 mg·L⁻¹。气相色谱质谱(GC-MS)分析结果表明,去除的主要物质为苯酚、4-甲基苯酚、邻苯二酚、(R)-(+)-3-甲基环戊酮和对羟基苯乙酮等毒性物质,废水毒性得到降低,毒性单元(toxic unit,TU)值由 22.3 分别降至 15.2和18.4。通过吸附等温和吸附动力学分析可知,Na-BBT和PFA对煤气化废水的吸附符合 Langmuir模型和准一级动力学模型;三维荧光光谱、孔径比表面积(BET)、扫描电镜(SEM)、红外光谱(FT-IR)、X 射线衍射(XRD)、X射线荧光光谱(XRF)和X射线电子能谱(XPS)等分析结果表明,Na-BBT和PFA对煤气化废水中污染物的吸附去除过程和机理主要受物理扩散控制,为表面和孔道的物理吸附,同时也存在离子交换吸附。以上结果表明Na-BBT和PFA作为吸附剂,可以有效提高煤气化废水的可生化性,降低毒性,将其用于煤气化废水的预处理,具有潜在和广泛的应用前景。     

UV/H2O2协同光降解处理酒石酸镍废水

含镍电镀废水中酒石酸的存在,使得废水中总镍无法通过化学沉淀法去除,无法满足达标排放要求。采用UV/H2O2光降解法处理酒石酸镍体系废水,考察了不同反应pH值、过氧化氢投加量、光照时间对酒石酸镍体系络合废水的处理效果。实验结果表明：UV/H2O2法对酒石酸镍体系废水有很好的协同处理效果,光降解过程呈拟一级动力学过程;优化的酒石酸镍废水处理工艺为反应pH值3.0,30%过氧化氢投加量2 mL·L-1,15 W功率紫外灯光照下反应120 min,在优化的工艺条件下,采用化学沉淀法去除水中镍,处理后电镀废水中总镍可满足《电镀污染物排放标准》（GB 21900-2008）中0.5 mg·L-1要求。     

Slurry-phase ozonation for remediation of sediments contaminated by polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a group of toxic, persistent, bioaccumulating organic compounds containing two or more fused aromatic rings. They are listed by the U.S. Environmental Protection Agency as priority pollutants because of their carcinogenicity and toxicity. Employing ozonation as a remediation technique, this work investigated the treatability of a sediment sample from a freshwater boat slip subjected to coal tar contamination over a long period. The contaminated sediment sample contained high levels of PAHs in the forms of naphthalene, phenanthrene, pyrene, and benzo[a]pyrene, among other byproducts present in the humic and solid phases of the sediment. The objectives of this work were to examine (1) the degradation of PAHs in the contaminated sediment as treated by ozonation in the slurry form, (2) the effects of ozonation upon the soil matrix and the biodegradability of the resultant PAH intermediates, and (3) the feasibility of a combined technique using O3 as a pretreatment followed by biological degradation. The sediment was made into 3% w/w soil slurries and ozonated in a 1.7-L semi-batch, well-stirred reactor equipped with pH control and a cold trap for the gaseous effluent. Samples were collected after different ozonation durations and tested for biochemical oxygen demand (BOD), chemical oxygen demand (COD), UV absorbance, and toxicity, along with quantitative and qualitative determinations of the parent and daughter intermediates using gas chromatography/flame ionization detection (GC/FID), GC/mass spectrometry (MS), and ion chromatography (IC) techniques. The GC/MS technique identified 16 compounds associated with the humic and solid phases of the sediment. Intermediates identified at different ozonation times suggested that the degradation of PAHs was initiated by an O3 attack resulting in ring cleavage, followed by the intermediates' oxidation reactions with O3 and the concomitant OH radical toward their mineralization. Results suggested that ozonation for 2 hr removed 50-100% of various PAHs in the solid and liquid phases (as well as the aqueous and gaseous media resulting from the treatment process) of the sediment sample and that organic and inorganic constituents of the sediment were also altered by ozonation. Measurements and comparisons of BOD, COD, UV absorbance, and toxicity of the samples further suggested that ozonation improved the bioavailability and biodegradability of the contaminants, despite the increased toxicity of the treatment effluent. An integrated chemical-biological system appeared to be feasible for treating recalcitrant compounds.     

The degradation of dissolved organic nitrogen associated with melanoidin using a UV/H2O2 AOP

The aim of this study was to examine the simultaneous degradation of dissolved organic nitrogen (DON) and associated colour from wastewater containing melanoidins by an advanced oxidation process (AOP). UV irradiation of H2O2 was used as the mechanism to create the hydroxyl radical for oxidation. Melanoidins are large nitrogenous organic compounds that are refractory during biological wastewater treatment processes. The simultaneous degradation of DON and colour, present as a result of these compounds, was investigated using an AOP. The oxidation process was much more capable of removing colour (99% degradation), dissolved organic carbon (DOC) (50% degradation) and DON (25% degradation) at the optimal applied dose of hydrogen peroxide for the system (3300 mg l(-1)). This indicated that colour and DON removal were decoupled problems for the purpose of treating melanoidin by an AOP and thus colour removal can not be used as an indication of DON removal Colour was caused by organic molecules with molecular weight greater than 10 kDa. Oxidation caused a partial reduction of the DON (41-15% of the total dissolved nitrogen) and DOC (29-14% of the DOC) associated with the large molecular weight fraction (>10 kDa) and almost complete colour removal (87-3% of the total colour). The degraded DON was mostly accounted for by the formation of ammonia (31% of the nitrogen removed from the large fraction) and small molecular weight compounds (66% of the nitrogen removed from the large fraction). The degraded DOC appeared to be mostly mineralised (to CO2) with only 20% of the degraded compounds appearing as small molecular weight DOC.     

抗生素废水的GC-MS分析与显色物质的初步确定

为确定抗生素废水中有机污染物构成和显色物质,以二氯甲烷为萃取剂,萃取废水中的有机物,经过浓缩纯化后,利用气相色谱质谱联用(GC-MS)技术对制药废水中的有机成分进行了分析鉴定,结合计算机质谱图库,定性确定了废水中60种有机污染物。其中,脂类为主要污染物成分,经对脱色后的废水进一步GC-MS分析后,初步确定油酸甲酯为此类抗生素废水的主要显色有机物。     

Degradation of chelating agents in aqueous solution using advanced oxidation process (AOP)

This article presents an overview with critical analysis of technical applicability of advanced oxidation process (AOP) in removing chelating agents from aqueous solution. Apart from the effect of metals for chelating agents as a major influencing factor, selected information such as pH, oxidant’s dose, concentrations of pollutants and treatment performance is presented. The performance of individual AOP is compared. It is evident from our literature survey that photocatalysis with UV irradiation alone or coupled with TiO₂, ozonation and Fenton’s oxidation are frequently applied to mineralize target pollutants. Overall, the selection of the most suitable AOP depends on the characteristics of effluents, technical applicability, discharge standard, regulatory requirements and environmental impacts.     

Comparisons of polychromatic and monochromatic UV-based treatments of bisphenol-A in water via toxicity assessments

Polychromatic ultraviolet irradiation, such as from medium pressure (MP) Hg lamps may enhance the UV degradation of environmental pollutants as compared to low pressure (LP) Hg UV sources emitting monochromatic irradiation. Typically, studies involving destruction of environmental pollutants such as endocrine disrupting compounds (EDCs) are based on measurement of the parent compound decay using analytical chemistry, but such information is insufficient to determine an effective treatment endpoint because the identity and biological activity of many transformation products remain unknown. Bioanalytical methods to assess residual biological activity of a treated water offers one means to compare removal efficiency of EDC activity between MP- and LP-UV lamps under photolysis and UV/H2O2 oxidation. In this study, changes in estrogenic activity of bisphenol-A (BPA) as a function of UV treatment were evaluated using both an in vitro yeast estrogen screen and in vivo vitellogenin assay with Japanese medaka (Oryzias latipes) fish. Decay of BPA parent compound and formation of degradation products were followed using HPLC analysis. Results demonstrated that MP-UV direct photolysis more effectively removed BPA and associated estrogenic activity compared to LP-UV lamps. UV in combination with H2O2 significantly removed estrogenic activity in vitro and in vivo compared to direct photolysis; however, no significant difference in removal rates was found between the two lamps under UV/H2O2 oxidation. Furthermore, the UV/H2O2 process was effective for reducing embryo toxicity of BPA, but resulted in the production of acidic intermediates, causing acute toxicity and delayed hatching in some medaka embryos.     

微气泡催化臭氧化深度处理制药废水的效果及DOM组分特性的变化

采用镁铝层状双氢氧化物(MAL)微气泡催化臭氧化(MAL/MB/O₃)体系深度处理实际制药废水,考察了该体系对溶解性有机物(DOM)的深度去除性能及DOM组分的变化特性,并与普通气泡臭氧化(CB/O₃)、普通气泡催化臭氧化(MAL/CB/O₃)、微气泡臭氧化(MB/O₃)工艺进行了比较。结果表明,MAL/MB/O₃处理性能优于CB/O₃、MAL/CB/O₃和MB/O₃,在臭氧投加总量与处理废水初始COD值之比为0.6、气流量0.5 L·min⁻¹、催化剂投加量0.5 mg·L⁻¹的条件下,整体COD去除率可达49.79%,COD去除量与臭氧消耗量的比值为0.83,废水的可生化性得到了一定改善,生物毒性显著下降。废水DOM中疏水性组分氧化去除率高于亲水性组分。臭氧直接氧化可去除疏水性组分,而亲水性组分去除主要依赖HO·氧化。MAL/MB/O₃对DOM的去除效率最高,可达到52.51%,其中疏水性组分整体去除率56.67%,亲水性组分整体去除率46.93%。废水DOM在氧化处理中存在官能团向酸性基团转化、类腐殖质向类富里酸和类胡敏酸转化、其他组分向亲水性酸(HIA)组分转化的趋势。MAL/MB/O₃强氧化能力对于DOM组分不饱和结构和荧光结构的破坏作用最为显著。以上研究结果可为制药废水深度处理提供参考。     

臭氧高级氧化技术在废水处理中的应用

综述了近年来迅速发展的臭氧高级氧化技术，包括臭氧氧化技术、臭氧／过氧化氢、臭氧／紫外辐射、臭氧与活性炭协同作用等技术，介绍了各种高级氧化技术的基本原理及在废水处理中的应用，并对其特点进行了评述。     

Fenton氧化对制浆造纸废水分子量及可生化性变化的影响

以制浆造纸废水的初沉池出水为研究对象,对不同剂量的Fenton氧化试剂处理制浆造纸厂初沉废水的效果进行了研究,初沉废水中的分子量大于10 000的有机污染物含量占到83%,废水可生化性较差;在Fe2+与H2O2的摩尔比为1∶5,废水pH为3.5的条件下,H2O2(30%)投加量小于3.25 mL/L时,Fenton试剂的氧化效率更高;H2O2(30%)投加量为6.50 mL/L时,废水中污染物的去除率更高,其中废水COD的去除率为79.5%,AOX的去除率为75.3%,色度去除率为97.5%,同时处理后废水中分子量在500~3 000之间的有机物含量占到82.98%,废水的BOD5/COD值提高到0.56。Fenton氧化作为前置技术处理制浆造纸废水,可以降低废水中的有机物分子量,减少废水的生物毒性,增加废水生物降解性,有助于后续生物处理的正常运行。     

O3、H2O2／O3及UV／O3在焦化废水深度处理中的应用

采用O3、H2O2／O3及UV／O3等高级氧化技术（AOPs）对某焦化公司的生化出水进行深度处理,考察了O3与废水的接触时间、溶液pH、反应温度等因素对废水COD去除率的影响,确定出O3氧化反应的最佳工艺参数为：接触时间40min,溶液pH8．5,反应温度25℃,此条件下废水COD及UV254的去除率最高可达47．14％和73．47％;H2O2／O3及UV／O3两种组合工艺对焦化废水COD及UV254的去除率均有一定程度的提高,但H2O2／O3系统的运行效果取决于H2O2的投加量。研究结论表明,单纯采用COD作为评价指标,并不能准确反映出O3系列AOPs对焦化废水中有机污染物的降解作用。     

Treatment of oily port wastewater effluents using the ultraviolet/hydrogen peroxide photodecomposition system.

This paper presents the nonselective degradation of mechanically pretreated oily wastewater by hydrogen peroxide (H2O2) in the presence and absence of UV irradiation. The effect of chemical oxidation on wastewater biodegradability was also examined. The exclusive use of H2O2 photolyzed by daylight results in quite efficient degradation rates for the low peroxide concentrations used. Higher hydrogen peroxide concentrations inhibit degradation of organic contaminants in the wastewater. The degradation rates of all contaminants are relatively high with an advanced oxidation system (UV/H2O2), but degradation efficiencies are not distinguishably different when 20 or 45 minutes of UV irradiation is used. The excess of H2O2 used in the process can inhibit phenolic degradation and may lead to the formation of a new phenolic fraction. The biodegradability of port wastewater did not increase significantly following the application of the advanced oxidation process.     

采气废水中有机物去除方法

新疆油田天然气开采过程中产生的大量高矿化度、高COD的含油废水,难以处理处置,严重影响了气田的正常生产活动,危害到气田周边土壤安全和荒漠植被的生存。为实现该类废水的达标排放,选取COD和总石油烃含量为考察指标,研究比较了紫外(UV)、臭氧(O3)及紫外臭氧联合处理(UV/O3)法对该类废水的处理效果,进一步考察了pH和O3发生量对UV/O3法处理效果的影响。研究结果表明,3种方法处理废水60 min后,废水COD由处理前的563 mg/L分别下降至处理后的479、334.9和314 mg/L,去除率分别达到14.9%、32.7%和44.2%;而总石油烃含量由处理前的3.86 mg/L分别降至处理后的3.05、1.26和0.20 mg /L,去除率分别达到21.2%、67.4%和94.8%;其中,UV/O3法处理90 min后废水COD降低至148 mg/L,达到《废水综合排放标准GB8978-1996》二级排放标准;pH为7,臭氧发生量为10 g/L时,UV/O3法可应用于采气废水的处理。