Continuous Cloud Point Extraction of Volatile Organic Contaminants from Wastewater in a Multi-Stage Rotating Disc Contactor: Effect of Structure and Concentration of Solutes

Abstract

Cloud point extraction (CPE) has been successfully scaled up to continuously remove aromatic contaminants from wastewater in a multi-stage rotating disc contactor (RDC) using t-octylphenolpolyethoxylate. The extraction performances for the removal of organic solutes with different structures and degrees of hydrophobicity were compared here for both batch and continuous CPE. Included are the volatile aromatics benzene, toluene, and ethylbenzene; volatile chlorinated compounds dichloroethane, trichloroethylene, and tetrachloroethylene; and non-volatile phenolics phenol, o-cresol, and catechol. The higher the K_ow (octanol-water partition coefficient) or hydrophobicity of the solutes, the better the extraction due to the greater affinity of solutes to solubilize into micelles. The empirical linear correlations between log K_ow, log (solute partition ratio), and log (height of transfer unit or HTU) were developed. Toluene is used as a model solute for the study of effect of initial solute concentrations in the continuous RDC. The extraction ability decreases as the concentration of toluene in the wastewater increases mainly due to coacervate entrainment into the overhead effluent.     

兰炭废水深度处理效果及污染物去除特性研究

采用混凝沉淀-活性炭吸附的方法对兰炭废水的生化处理出水进行深度处理,利用气相色谱分析了处理前后废水中有机物的组成变化。试验结果表明,经过混凝处理,兰炭废水CODCr和色度的去除率分别达到61.8%和84.7%,甲苯去除率达到93.83%,多环芳烃、酚类物质和杂环化合物的去除率分别达到94.76%、86.93%和93.65%,苯酚、邻甲酚和邻苯二甲酸二丁酯被完全去除。沉淀出水采用颗粒活性炭吸附,最终出水色度为16倍,CODCr的质量浓度为76 mg/L,酚类、多环芳烃去除率分别达到99.4%和97%,苯类和杂环化合物被全部去除。     

Benzene,Toluene and p‐xylene Interactions and the Role of Microbial Communities in Remediation Using Bioventing

Aromatic hydrocarbons, particularly benzene, toluene and xylene (BTX), are major contaminants at many hazardous waste sites. We studied volatilization and biodegradation of BTX from unsaturated soil through bioventing. Following inoculation with indigenous soil microorganisms obtained from the Dagang Oil Field in Tianjin, China, varying amounts of BTX were added to soil in a stainless steel column provided with a constant flow of CO₂‐ free air and pure N₂. Volatilization‐to‐biodegradation ratios of benzene, toluene and p‐xylene were 6:1, 2:1 and 2:1 respectively. Final concentrations recorded in soil gas after three weeks were 0.128 mg/L benzene, 0.377 mg/L toluene and 0.143 mg/L p‐xylene. Interactions between the contaminants occurred: benzene and p‐xylene degradation were accelerated while toluene was being degraded, and the presence of p‐xylene increased the lag period for benzene degradation.     

On-Site Recovery of Hemicelluloses from Thermomechanical Pulp Mill Process Water by Microfiltration and Ultrafiltration

During mechanical defibration of wood, a minor fraction of the wood mass is dissolved in the process water. These dissolved substances represent an extra energy demand when they are treated in the mill’s wastewater treatment plant. Galactoglucomannan, the main hemicellulose in spruce, can be recovered from thermomechanical pulp mill process water by a process based on microfiltration (MF) and ultrafiltration (UF). The purpose of this work was to study the scale-up of the process from laboratory scale to continuous industrial scale. MF was first studied in the laboratory, and then combined with UF in a continuous pilot process on-site at a pulp mill. The data obtained were used to estimate the cost of the membrane processes for galactoglucomannan recovery which was found to be about €1160 per ton hemicelluloses.     

Effect of co‐contaminant phenol on performance of a laboratory‐scale RBC with algal‐bacterial biofilm treating petroleum hydrocarbon‐rich wastewater

BACKGROUND: Hydrocarbon degradation by algal‐bacterial systems has advantages over degradation by conventional heterotrophic systems. However, oily wastewaters often contain co‐contaminants that may inhibit the degradation of total petroleum hydrocarbons (TPH), leading to system failure. RESULTS: This paper reports the effect of phenol on treatment of wastewater containing petroleum hydrocarbons, i.e. diesel oil in a lab‐scale rotating biological contactor with biofilm consisting predominantly of Burkholderia cepacia and a freshwater algal culture. The effect of phenol loading from 0.11–0.69 g phenol m^?2 d^?1 on diesel degradation was studied with 21 h hydraulic retention time and TPH loading of 27.33 g TPH m^?2 d^?1. With increase in phenol loading, complete removal of phenol was observed. However, TPH removal decreased from 99% to 94% and significant decrease in TCOD removal was observed possibly due to biomass growth in suspension. Presence of algal culture in the biofilm made it feasible to operate the RBC at a high organic loading. The benefits included better immobilization of the bacterial culture, release of oxygen and generation of alkalinity. Lowering in pH due to accumulation of acidic intermediates formed during oil biodegradation was not observed in this study. CONCLUSION: This system can be recommended for treatment of industrial wastewaters containing TPH and phenols, with proper handling of biosolids. Copyright © 2010 Society of Chemical Industry     

Efficient phenol removal of wastewater from phenolic resin plants using crosslinked cyclodextrin particles

Removal of phenolic compounds from a raw industrial wastewater from phenolic resin processing, of which the components are phenol (8.9 wt%), m‐ and p‐cresols (0.33 wt%), and xylenols (0.044 wt%), was carried out by using crosslinked cyclodextrin particles as a sorbent. A series of sorbents was prepared by varying the combination of cyclodextrin (CyD), β‐CyD, γ‐CyD, Mix‐CyD (α‐CyD:β‐CyD:γ‐CyD:dextrin = 30:10:10:50 wt/wt), the crosslinker, hexamethylene diisocyanate (HDI) or toluene‐2,6‐diisocyanate, and their molar ratio in the reaction batch. The removal of the phenolic compounds from raw industrial wastewater was an instantaneous process and was completed within about 5 min. The best removal efficiency was obtained by the crosslinked β‐CyD with HDI in a 1:8 molar ratio or the crosslinked Mix‐CyD with HDI, also in a 1:8 molar ratio. The prepared sorbents were efficiently regenerated by elution of the adsorbed phenols from the crosslinked polymers with methanol. Copyright © 2006 Society of Chemical Industry     

Treatment of paper and pulp wastewater and removal of odorous compounds by a Fenton‐like process at the pilot scale

A Fenton‐like process, involving oxidation and coagulation, was evaluated for the removal of odorous compounds and treatment of a pulp and paper wastewater. The main parameters that govern the complex reactive system [pH and Fe(III) and hydrogen peroxide concentrations] were studied. Concentrations of Fe(III) between 100 and 1000 mg L^?1 and of H₂O₂ between 0 and 2000 mg L^?1 were chosen. The main mechanism for color removal was coagulation. The maximum COD, color and aromatic compound removals were 75, 98 and 95%, respectively, under optimal operating conditions ([Fe(III)] = 400 mg L^?1; [H₂O₂] = 500–1000 mg L^?1; pH = 2.5; followed by coagulation at pH 5.0). The biodegradability of the wastewater treated increased from 0.4 to 0.7 under optimal conditions and no residual hydrogen peroxide was found after treatment. However, partially or non‐oxidized compounds present in the treated wastewater presented higher acute toxicity to Artemia salina than the untreated wastewater. Based on the optimum conditions, pilot‐scale experiments were conducted and revealed a high efficiency in relation to the mineralization of organic compounds. Terpenes [(1S)‐α‐pinene, β‐pinene, (1R)‐α‐pinene and limonene] were identified in the wastewater and were completely eliminated by the Fenton‐like treatment. Copyright © 2006 Society of Chemical Industry     

Phase Transfer Catalyzed Extraction of Phenolic Substances from Aqueous Alkaline Stream

Abstract

Experimental investigations are presented on the extraction/removal of such phenolic compounds as phenol, m-cresol, and resorcinol from alkaline medium via reaction with benzoyl chloride dissolved in toluene as the solvent under two-phase conditions using hexadecyltributyl phosphonium bromide as a phase transfer catalyst. Two types of experiments were performed in order to assess the utility of the reaction scheme for treatment of industrial wastewater. The results of stirred cell experiments revealed that the reactions of phenolics conform to a diffusion-limited fast pseudo-first-order regime. The rate enhancement of the reaction was found to be reasonably low as compared to that reported when Aliquat 336 was used as the catalyst. The specific rate of extraction decreases for the phenolics in the order phenol > m-cresol > resorcinol. Batch experiments conducted in a baffled agitated reactor with individual phenolic compounds as well as mixtures of all components, representing compositions typical of industrial wastewater, revealed that the volumetric rate of extraction is dependent on the stirring speed under otherwise identical conditions. Conversion of phenolics in a batch agitated reactor was found to be more than 99.5% under suitable conditions of stirring speed and reaction time, and the products of reaction, essentially esters, are completely partitioned to the organic phase. Some aspects of product recovery, solvent, and catalyst recycle are discussed.     

Impact and threshold concentration of toxic materials in the stripped gas liquor on nitrification

The impact of the threshold concentration of toxic materials on nitrification in stripped gas liquor was investigated. Ammonia nitrogen, phenol, thiocyanide, cyanide, m-cresol, toluene, quionoline, and aniline were selected as toxic materials in the wastewater treatment experiments. The concentrations of organic materials that are contained in raw wastewater of stripped gas liquor were 400 to 600 mg/l phenol, 5.95 mg/l aniline, 17.85 mg/l quinoline, 197.43 mg/l m-cresol, and 85.57 mg/l toluene. When the ammonia nitrogen concentration was lower than 200 mg/l, the nitrification was stable. However, in the case of higher than 200 mg/l in the concentration of ammonia nitrogen, the removal efficiency of nitrogen was very low. Cyanide with concentration higher than 0.5 mg/l acted as a toxic material to microorganisms because it produced excessive foam and made the activity of microorganisms decrease. The threshold concentrations of organic materials such as m-cresol, toluene, quiline, and aniline that influence nitrification of microorganisms were 100 mg/l, 50 mg/l, and 200 mg/l, respectively. The change in the dilution ratio of raw wastewater and the additional amount of PAC did not make a big difference on the COD removal. On the other hand, the higher the dilution ratio of wastewater and additional amount of PAC increases, the higher the removal efficiency of ammonia nitrogen increases.     

Micellar enhanced ultrafiltration of phenol with dodecylpyridinium chloride and sodium dodecylbenzene sulfonate

Micellar enhanced ultrafiltration is a surfactant-based separation process for wastewater treatment. The ultrafiltration of dodecyl pyridinium chloride (DPC) and sodium dodecyl benzene sulfonate (SDBS) solutions was realized with 5 kDa and 15 kDa molecular weight cut-off ceramic membranes. Surfactant concentrations under and over the micellar critical concentration at three different pressures were studied, and their effects on permeate flux and retention are reported. It was found that an increase in pressure operation, in 0.8–1.8 bar range, causes a lower surfactant concentration in permeate by the presence of a polarization layer. These systems were studied for phenol removal. DPC/phenol system (73.5 mM/0.53 mM) reaches a 61% removal of organic solute. SDBS/phenol system (14.7 mM/0.58 mM) reaches a 25% removal, both with 5 kDa membrane at 1.8 bar. In the case of the cationic surfactant the micelle's positive charge plays a preponderant role in attracting the phenol molecules, while the SDBS does not present this electrostatic interaction.     

Feasibility Study of a Solar Reactor for Phenol Treatment by the Photo‐Fenton process in Aqueous Solution

Solar reactors can be attractive in photodegradation processes due to lower electrical energy demand. The performance of a solar reactor for two flow configurations, i.e., plug flow and mixed flow, is compared based on experimental results with a pilot‐scale solar reactor. Aqueous solutions of phenol were used as a model for industrial wastewater containing organic contaminants. Batch experiments were carried out under clear sky, resulting in removal rates in the range of 96–100 %. The dissolved organic carbon removal rate was simulated by an empirical model based on neural networks, which was adjusted to the experimental data, resulting in a correlation coefficient of 0.9856. This approach enabled to estimate effects of process variables which could not be evaluated from the experiments. Simulations with different reactor configurations indicated relevant aspects for the design of solar reactors.     

高铁酸钾对COD去除作用的机理研究

研究了高铁酸钾对各种污水的COD去除效果,发现高铁酸钾对水可溶性有机物如苯酚、葡萄糖等引起的高COD污水处理效果不好,而对COD主要来源于不溶或微溶于水的有机物的污水,如皮革综合废水、造纸综合废水、鱼塘水、人工甲苯污水等效果较好,结合理论分析,认为高铁酸钾对COD的强力去除功能主要依靠于新生成的Fe(OH)3的多相絮凝...     

黄铁矿烧渣催化H_2O_2氧化废水中难降解污染物

传统Fenton氧化是以Fe2+离子为催化剂进行催化H2O2氧化,以含铁矿物为催化剂的非均相类Fenton反应最近受到重视。以酸性红B染料、苯酚等污染物以及实际工业废水为处理对象,研究了黄铁矿烧渣为催化剂的非均相类Fenton反应。考察了催化剂、H2O2投加量、初始pH、反应时间、催化剂回收重复利用等因素的影响和优化。在烧渣投加量为10g.L-1,双氧水投加量为20ml.L-1,体系pH在1～11范围内,反应6h后,酸性红B染料、苯酚的去除率接近100%,工业废水处理后脱色效果明显,而且BOD5/COD比值能大幅提高。研究表明:黄铁矿烧渣对催化H2O2氧化具有很强的催化活性,是有效的类Fenton反应催化剂,而且相比于单一含铁矿物具有更好的催化性能,反应受pH影响很小,解决了传统Fenton反应需要调节pH的难题。催化剂易于沉淀分离,能回收重复利用。     

生物通风修复含石油污染物土壤过程

以苯、甲苯和对二甲苯（BTX）为模拟污染物,研究了生物通风原位土壤修复方法去除土壤中石油污染物的效果.用一维生物通风土柱实验和控制实验对比了有生物降解和无生物降解土柱中BTX的去除情况.在通风后期,控制实验中发现了很长的拖尾阶段,污染物不能进一步被有效去除,而生物通风土柱中由于生物降解作用可使土壤中污染物残留浓度更小,修复效率更高.根据实验数据估算得到生物通风过程中苯、甲苯及对二甲苯的生物降解贡献率分别为17.8%, 30.0% 和 32.3%.还用间歇实验探讨了多组分污染物之间的相互影响作用,发现甲苯的降解能够促进对二甲苯和苯的降解,而对二甲苯的存在则增加了甲苯和苯的降解滞后期.     

The use of wood pulp and radiation‐modified starch in wastewater treatment

Radiation‐induced graft copolymerization of maize starch/acrylic acid has been performed. Also, natural byproduct wood pulp was used after chemical treatment for the removal of metal ions from the investigated wastewater. The surface and structure morphology of the wood pulp and starch/acrylic acid were investigated by scanning electron microscopy and infrared spectroscopy. The physical parameters, such as swelling, gel percentage, and grafting efficiency (%) of starch/acrylic acid copolymer, were studied. The factors affecting the abilities of the prepared materials for removing heavy metal ions and dyes from aqueous solutions were studied. It was found that the maximum metal uptake is in the following sequence: Fe³⁺ > Cr³⁺ > Pb²⁺ > Cd²⁺. The adsorption capacity of such investigated metal ions increases with the increase of pH values. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Removal of TEX vapours from air in a peat biofilter: influence of inlet concentration and inlet load

This paper presents the results of the study of the removal of toluene, ethylbenzene, and o‐xylene (TEX) by biofiltration using a commercial peat as filter‐bed material. Runs with a single organic compound in air, and with the mixture of TEX in air, were carried out for at least 55 days in laboratory‐scale reactors inoculated with a conditioned culture. The influence of organic compound inlet load and of gas flow rate on the biofilter's performance was studied, including relatively high values of pollutant inlet concentration (up to 4.3 gC m^?3 for ethylbenzene, 3.2 gC m^?3 for toluene, and 2.7 gC m^?3 for o‐xylene). Results obtained show maximum elimination capacities of 65 gC m^?3 h^?1 for o‐xylene, 90 gC m^?3 h^?1 for toluene, and 100 gC m^?3 h^?1 for ethylbenzene, and high removal efficiency (>90%) even for moderately elevated concentrations: 3.0, 2.5 and 1.8 gC m^?3 for ethylbenzene, toluene and o‐xylene, respectively. The behaviour of the TEX mixture was in good agreement with the results obtained for the runs in which only one organic compound was present. Ethylbenzene and toluene are degraded easier than o‐xylene, and inhibitory effects due to the presence of multiple substrates were not observed. Copyright © 2005 Society of Chemical Industry     

Copper‐Catalyzed Peroxide Oxidation Testing for Tetraphenylborate Decomposition

Abstract

A new processing option, copper‐catalyzed hydrogen peroxide oxidation of tetraphenylborate under alkaline conditions, was demonstrated in laboratory testing. Laboratory‐scale tests were conducted to evaluate the use of copper‐catalyzed hydrogen peroxide oxidation to treat simulants of the Savannah River Site tank waste. The oxidation process involves the reaction of hydrogen peroxide with a copper catalyst to form hydroxyl free radicals. With an oxidation potential of 2.8 volts, the hydroxyl free radical is a very powerful oxidant, second only to fluorine, and will react with a wide range of organic molecules. The goal is to oxidize the tetraphenylborate completely to carbon dioxide, with minimal benzene generation. Testing was completed in a lab‐scale demonstration apparatus at the Savannah River National Laboratory. Greater than 99.8% tetraphenylborate destruction was achieved in less than three weeks. Offgas benzene analysis by a gas chromatograph demonstrated low benzene generation. Analysis of the resulting slurry demonstrated >82.3% organic carbon destruction. The only carbon compounds detected were formate, oxalate, benzene (vapor), carbonate, p‐terphenyl, quaterphenyl, phenol, and phenol 3‐dimethylamino.     

Effect of Electrolyte and Temperature on Volatile Organic Compounds Removal from Wastewater Using Aqueous Surfactant Two-Phase System of Cationic and Anionic Surfactant Mixtures

Abstract

Benzene, toluene, ethylbenzene, and xylene are frequently observed contaminants in industrial wastewaters causing concerns about environmental and health effects. An aqueous surfactant two-phase (ASTP) extraction system using mixtures of cationic and anionic surfactants have been shown to be a promising surfactant-based separation technique to concentrate solutes such as proteins and dyes from aqueous solution. A phase separation of a surfactant solution occurs at certain surfactant compositions and concentrations, forming two isotropic phases. One is rich in surfactant aggregates (surfactant-rich phase) and the other is lean in surfactant aggregates (surfactant-dilute phase). Most of the organic contaminants tend to solubilize and concentrate in the surfactant-rich phase, leaving the surfactant-dilute phase containing only small amounts of contaminants as remediated water. The effect of NaCl addition on the critical micelle concentration (CMC) and the extraction ability of ASTP formed by mixtures of cationic surfactant (dodecyltrimethylammonium bromide; DTAB) and anionic surfactant (alkyl diphenyloxide disulfonate; DPDS) at 50 mM total surfactant concentration with a 2:1 molar ratio of DTAB:DPDS was investigated; the CMC of the mixture slightly decreases with increasing NaCl concentration. The extraction and preconcentration of benzene are greatly enhanced by added NaCl. The higher the degree of hydrophobicity of contaminants, the greater the extraction into the surfactant-rich phases. At 1.0 M NaCl addition, about 95% of xylene, 92% of ethylbenzene, 90% of toluene, and 79% of benzene are extracted into the surfactant-rich phase within a single stage extraction and the contaminant partition ratios can be as high as 395 for xylene, 273 for ethylbenzene, 206 for toluene, and 84 for benzene, which are greater than those obtained from the conventional ASTP extraction system using nonionic surfactants.     

Preparation of CPB-modified FAU zeolite for the removal of tannery wastewater contaminants

The preparation of organomodified zeolites with different framework structures (FAU, LTA and MOR) using N-cetylpyridinium bromide (CPB) as tailoring agent was studied. The sorption properties of CPB-modified zeolites were evaluated in the removal of tannery contaminants from aqueous solution. The CPB-modified FAU-type zeolite presented the highest Cr(VI) retention capacity (37 mmol/kg) due to the higher Cr(VI) retention of its unmodified form (larger pore opening) and its high CPB sorption capacity. CPB-modified FAU zeolite also exhibited high thermal stability as consequence of special interactions between the CPB molecules and the zeolite surface. In addition, the intrinsic Cr(III) exchange capacity of FAU zeolite increased with CPB loading (162–527 mmol/kg), which appear to be due to an additional retention mechanism provided by the sorbed cetylpyridinium surfactant layer. On other hand, CPB-modified FAU zeolite also exhibited high toluene retention capacity (62 mmol/kg) due to of the hydrophobic character of its surfactant-modified surface and toluene adsorption on internal sorption sites of FAU zeolite. Thus, CPB-modified FAU zeolite appears as a promising adsorbent for simultaneous removal of Cr(III), Cr(VI) and toluene contaminants from aqueous solution.     

有机膨润土吸附废水中苯酚的机理

以C12阳离子烷基多糖苷季铵盐对膨润土改性制备有机膨润土,探讨了有机膨润土的制备因素对去除废水中苯酚效果的影响,结果表明,在有机改性剂/膨润土的质量比为40 mg/g,反应温度为30℃,pH=8的条件下,反应30 min制备的有机膨润土,对初始浓度为50 mg/L的含苯酚废水去除率达到89.50%,其对苯酚的吸附符合Freundish方程。