Influence of nitrogen on the degradation of toluene in a compost‐based biofilter

Two identical laboratory‐scale bioreactors were operated simultaneously, each treating an input air flow rate of 1 m³ h^?1. The biofilters consisted of multi‐stage columns, each stage packed with a compost‐based filtering material, which was not previously inoculated. The toluene inlet concentration was fixed at 1.5 g m^?3 of air. Apart from the necessary carbon, the elements nitrogen, phosphorus, sulfur, potassium and other micro‐elements are also essential for microbial metabolism. These were distributed throughout the filter bed material by periodic ‘irrigations’ with various test nutrient solutions. The performance of each biofilter was quantified by determining its toluene removal efficiency, and elimination capacity. Nutrient solution nitrogen levels were varied from 0 to 6.0 g dm^?3, which led to elimination capacities of up to 50 g m^?3 h^?1 being obtained for a toluene inlet load of 80 g m^?3 h^?1. A theoretical analysis also confirmed that the optimum nitrogen solution concentration lays in the range 4.0–6.0 g dm^?3. Validation of the irrigation mode was achieved by watering each biofilter stage individually. Vertical stage‐by‐stage stratification of the biofilter performance was not detected, ie each filter bed section removed the same amount of pollutant, the elimination capacity per stage being about 16 g m^?3 h^?1 per section of column. © 2001 Society of Chemical Industry     

Biodegradation of aromatic hydrocarbons in a compost biofilter

Two laboratory‐scale biofilters filled with the same type of packing material were operated at different gas flow rates and influent concentrations of toluene and xylene in order to investigate their performance in treating waste gas streams. The columns contained a mixture of municipal compost as a base material and wood chips as a bulking agent in an 80:20 ratio; the porosity was 54%. Microbial acclimation was achieved by addition of nutrient‐enriched solution along with pollutants for a week by daily mixing and natural aeration. During the start‐up of the systems with inlet concentrations of 20 and 70 ppm for toluene and xylene, respectively, high biomass growth resulted in pressure drops in excess of 2000 Pam^?1. Under steady state conditions, the response of each biofilter to variations in contaminant mass loading was studied by either changing the influent concentration or flow rate of the inlet waste stream. The results show that organic loading rates of up to 110 and 150 gm^?3h^?1 can be handled without any indication of the elimination capacity being saturated. However, maintaining the pressure drop below 1000 Pam^?1 to avoid operational problems, optimal organic loading rates for toluene and xylene of 78 ± 8 and 80 ± 14 gm^?3h^?1 respectively are suggested for an HRT value of 60 s. Under these conditions, elimination capacities of 73 ± 4 and 73 ± 14 gm^?3h^?1 and removal efficiencies of 94 ± 6% and 91 ± 8% were achieved for toluene and xylene, respectively. Copyright © 2003 Society of Chemical Industry     

Elimination of chlorobenzene vapors from air in a compost‐based biofilter

In this work, the removal of monochlorobenzene (CB) vapors from air was studied, for the first time, in a non‐inoculated, laboratory‐scale, aerobic biofilter. The influence of three parameters on the bioprocess has been evaluated: the rate of nitrogen supplied to the bed, the inlet concentration of CB, and the flow rate. The CB inlet concentration was varied between 0.3 and 3.2 g m^?3, at a constant flow rate of 1.0 m³ h^?1. Removal rates of greater than 90% were achieved for CB inlet concentrations of up to 1.2 g m^?3. Then the flow rate was varied from 0.5 to 3.0 m³ h^?1 with a constant inlet concentration (1.2 g m^?3). Maximum elimination capacities (70 g m^?3 h^?1) were reached for contact times of greater than 60 s. The study of varying flow rates also permitted evaluation of a first order macrokinetic constant (1.1 × 10^?2 s^?1) for the CB biodegradation. Finally, the optimum nitrogen input value was found to lie between 0.3 and 0.4 g N h^?1 and gave rise to elimination capacities as high as 70 g m^?3 h^?1 for an inlet load of near 80 g m^?3 h^?1. Copyright © 2003 Society of Chemical Industry     

生物过滤处理微污染原水的性能研究

以生物过滤作为微污染水处理的末级处理工艺,可使有机污染物和浊度的去除在同一滤层内实现,是一种经济、有效的生物处理方法。作者通过模型试验,深入探讨了生物过滤对微污染水中有机物、氨氮、浊度等的去除效果。试验结果表明：生物过滤能够有效地去除微污染水中的有机物、氨氮等物质,同时能够获得与常规过滤一样低的出水浊度。     

滤池反冲洗水直接回用对给水厂水质的影响

研究了V型滤池反冲洗水直接回用对给水厂水质的影响。结果表明:回用滤池反冲洗废水有利于对沉后水浊度的去除,回用比例小于10%时,沉后水浊度呈下降趋势。回用反冲洗水同时会降低沉后水CODMn,还可以小幅度降低沉后水的UV254。当滤池反冲洗水回用比例大于10%时,沉后水中细菌总数有明显提高。最后通过数学方法确定了水厂反冲洗水的最佳回用比为3%~10%。     

不同给水处理工艺对饮用水生物稳定性的影响

可同化有机碳(AOC)和生物可降解溶解性有机碳(BDOC)是评价饮用水生物稳定性的指标,作者论述了各种饮用水处理工艺对AOC和BDOC影响研究的进展,并指出:为了获得生物稳定性饮用水,把不同净水工艺优化组合,在常规工艺基础上增加生物预氧化、活性炭等深度处理工艺是饮用水处理工艺改进的主要方向,膜分离技术则是未来饮用水处理技术的发展方向。     

饮用水中隐孢子虫与贾第虫的危害及其去除灭活研究

本文在介绍"两虫"即贾第虫和隐孢子虫的生态、危害及传播的基础上,综述了常规水处理工艺、膜法及组合工艺对"两虫"去除效果;分析了各种消毒剂和消毒方法灭活的优缺点,提出多种方法协同灭活将成为水消毒技术研究和开发的一个发展方向。预处理、絮凝、沉淀、澄清和过滤等常规水处理单元不能有效去除两虫,难以保证饮用水安全;膜过滤法两虫去除效率高,但大规模应用困难较大。而常规的氯消毒剂灭活两虫的效果不佳,臭氧对两虫的灭活效果优于氯和二氧化氯;UV能有效灭活两虫,但穿透力弱,UV灯管寿命短,运行费用高;US灭活两虫,能耗比较高。单一的消毒剂灭活两虫效果欠佳,采用多种消毒剂(方法)联合使用,通过协同作用,可达到较高的灭活率。     

Influence of Ca and Na ions in backwash water on ultrafiltration fouling control

The effect of calcium and sodium in backwash water on the fouling control of ultrafiltration is investigated on a bench scale. Besides permeate of ultrafiltration and demineralized water, solutions with different calcium or sodium concentrations were used for backwash. The results show that backwashing with demineralized water is better than with permeate of ultrafiltration. The backwash efficiency decreases when calcium and sodium are added in demineralized water for backwash. That is probably because the presence of calcium and sodium in backwash water increases the Ca-bridging effect between the negatively charged membrane and the negatively charged NOM, and compresses the double layer of the membrane and the NOM, leading to a strong adhesion force on the membrane.     

污泥臭氧减量对淹没式生物膜工艺运行效能的影响

针对淹没生物膜法(SBF)和污泥臭氧化各自在污泥减量方面的优点,提出了化学臭氧化和复合生物膜法相结合的污泥减量工艺,并对臭氧化对SBF运行效能的影响进行了实验研究。通过2个并行的SBF系统污泥臭氧化结果进行对比,结果显示臭氧化能够显著降低系统的污泥产率(0.043 kg/kg,较不加臭氧化的SBF系统下降了76%),同时不对硝化和有机物的去除作用产生明显的影响,系统出水水质良好。     

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     

Applications of biofiltration in drinking water treatment – a review

Biofiltration is a process in which an otherwise conventional granular filter is designed to remove not only fine particulates but also dissolved organic compounds through microbial degradation. Biofiltration can reduce the need for chemicals in drinking water treatment and thus improved applications of biofiltration in drinking water treatment can be viewed as green or sustainable engineering technology. Recent trends in biofiltration technology for drinking water treatment have or have attempted to extend the performance of biofilters through gaining a better understanding of operational constraints. This review articles summarizes important operational parameters influencing biofiltration performance such as hydraulic loading, empty bed contact time (EBCT), temperature, media type, and backwashing conditions. In addition, recent advancements in biofiltration operations including, ozonation, ammonia removal and the influence of nutrient (nitrogen, phosphorous) supplementation to facilitate carbon removal are explored. ? 2015 Society of Chemical Industry     

Effect of pre‐treatments based on UV photocatalysis and photo‐oxidation on toluene biofiltration performance

BACKGROUND: The integration of UV photocatalysis and biofiltration seems to be a promising combination of technologies for the removal of hydrophobic and poorly biodegradable air pollutants. The influence of pre‐treatments based on UV_{254 nm} photocatalysis and photo‐oxidation on the biofiltration of toluene as a target compound was evaluated in a controlled long‐term experimental study using different system configurations: a standalone biofilter, a combined UV photocatalytic reactor‐biofilter, and a combined UV photo‐oxidation reactor (without catalyst)‐biofilter. RESULTS: Under the operational conditions used (residence time of 2.7 s and toluene concentrations 600–1200 mg C m^?3), relatively low removal efficiencies (6–3%) were reached in the photocatalytic reactor and no degradation of toluene was found when the photo‐oxidation reactor was operated without catalyst. A noticeable improvement in the performance of the biofilter combined with a photocatalytic reactor was observed, and the elimination capacity of the biological process increased by more than 12 g C h^?1 m^?3 at the inlet loads studied of 50–100 g C h^?1 m^?3. No positive effect on toluene removal was observed for the combination of UV photoreactor and biofilter. CONCLUSIONS: Biofilter pre‐treatment based on UV_{254 nm} photocatalysis showed promising results for the removal of hydrophobic and recalcitrant air pollutants, providing synergistic improvement in the removal of toluene. Copyright © 2011 Society of Chemical Industry     

气水比对曝气生物滤池SND的影响

采用两段BAF处理城市污水,探讨了气水比对反应器处理效果的影响.在A段水力负荷为0.81 m/h、气水比为3∶1时,分析了B段气水比分别为3∶1、2∶1和1∶1时反应器的运行情况.结果表明:A段反应器对TN基本上没有去除效果,因NH4+ -N的部分氧化使得出水中NO2--N质量浓度介于0.45～0.70 mg/L之间,...     

三维电极法处理污染河水脱氮的试验研究

采用三维电极法处理以城市污水厂二级出水为主要来源的污染河水,考察了电解时间、槽电压、涂膜活性炭体积分数及曝气对脱氮效果的影响。试验结果表明:三维电极法能有效去除废水中的含氮化合物,在未曝气的情况下,反应时间为40min,槽电压为15V,涂膜活性炭体积分数为20%时,脱氮效果最佳,NH3-N、NO2--N、TN的去除率分别达到75%、95%、49%;曝气有利于提高脱氮效率,TN、NH3-N的去除率均提高了20%左右。三维电极法是一种有效的脱氮新技术。     

Response surface methodological approach to optimize the coagulation-flocculation process in drinking water treatment

Performing jar tests often requires carrying out a time consuming iteration procedure to find out the right amount of chemical for coagulation-flocculation process in water treatment plants. Applying the response surface method (RSM) in jar tests as an alternative to the conventional methods was investigated in this study. The purpose is finding out the optimum combination of coagulant dose and pH with respect to the highest removal efficiency of turbidity and dissolved organic carbon (DOC). The results achieved using poly-aluminum chloride (PACl) were compared to those achieved using conventional coagulant such as alum. The quadratic models developed for the two responses (turbidity removal and DOC removal) indicated that the optimum conditions to be PACl concentration of 0.11 mM at pH 7.4 and alum concentration of 0.15 mM at pH 6.6. Compromising to simultaneously optimize the two responses resulted in 91.4% turbidity removal and 31.2% DOC removal using PACl whereas 86.3% turbidity and 34.3% DOC were removed using alum. Confirmation of experimental results was found to be close to the prediction derived from the models. This demonstrates the benefits of the approach based on the RSM in achieving good predictions while minimizing the number of required experiments.     

Influence of anode material on the electrochemical oxidation of 2-naphthol: Part 2. Bulk electrolysis experiments

The electrochemical oxidation of 2-naphthol has been studied by galvanostatic electrolysis, using a range of electrode materials such as lead dioxide, boron-doped diamond (BDD) and Ti-Ru-Sn ternary oxide anodes. The influence of some operating parameters, such as current density, flow-rate and chloride concentration on naphthol oxidation has been investigated in order to find the optimum experimental conditions. Measurements of chemical oxygen demand, HPLC and total organic carbon have been used to follow the oxidation. The experimental data indicate that on PbO₂ and BDD, naphthol oxidation takes place by reaction with electrogenerated hydroxyl radicals and is favoured by low current density and high flow-rate. On the contrary, on a Ti-Ru-Sn ternary oxide the mineralisation of naphthol occurs only in the presence of chloride ions that act as redox mediators and COD removal is affected by chloride concentration and is not significantly influenced by the current density and mass-transfer coefficient. From a comparison of the results of the three electrodes it has been found that boron-doped diamond gives a faster oxidation rate and better current efficiency.     

一种新型甲醛处理装置及处理效果研究

针对目前室内装修甲醛严重超标,严重危害人体健康的现状,设计了一个可以在线检测甲醛浓度并采用光触媒技术进行处理的系统装置,并进行了探索性试验.结果表明,在一定的时间和浓度范围内,光照强度越强、甲醛初始浓度越低、光触媒用量越多,甲醛的去除率越高.在实际应用中,考虑时间和成本的因素,可以选择光照强度31 W,甲醛的初始浓度1.6 ppm,光触媒的用量为2.5％,此时甲醛的去除率较高.     

Influence of stoichiometric ratio on water absorption in epoxy resins

Dielectric, gravimetric, dynamic mechanical, and infrared measurements are reported on the effect of different stoichiometric ratios on the water absorption of diglycidyl ether of bisphenol A (DGEBA), MY720 (Ciba Geigy) cured with stoichiometric variations of triethylenetetramine (TETA), (BDH). Resin samples were prepared with stoichiometric ratios of epoxy:amine from 3 : 1 through 1 : 1 to 1 : 3. Analysis of the water absorption characteristics of these materials showed the existence of water in two different environments; molecules bound to specific sites in the matrix and clustered in microvoids as “free water.” Diffusion coefficients and equilibrium water uptake were shown to markedly increase with an increase in the amine ratio. An anomaly observed in dielectric results is attributed to a high rate of diffusion in the high amine ratio materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2369–2376, 1998