Use of submerged anaerobic–anoxic–oxic membrane bioreactor to treat highly toxic coke wastewater with complete sludge retention

Coke wastewater is an extremely toxic industrial effluent that requires treatment before discharge. A bench-scale, anaerobic–anoxic–oxic membrane bioreactor (A₁/A₂/O-MBR) system was utilized to treat real coke wastewater with complete sludge retention. In a 160-d test, the A₁/A₂/O-MBR system stably removed 87.9 ± 1.6% of chemical oxygen demand, 99.4 ± 0.3% of turbidity, and 99.7 ± 3.5% of NH₄⁺-N from coke wastewater. The membrane rejected almost all suspended solids; hence, a low food-to-microorganism environment was created to degrade refractory substances and reduce sludge production rates. The microbial diversity in the MBR system declined over time; however, neither pollutant removal efficiency nor total biological activity was adversely affected. Membrane fouling, which occurred during the operation of the MBR system, was principally resulted from the colloidal fraction of supernatant in suspension. Physical cleaning removed initial deposits of particles; however, prolonged operation resulted in severe clogging that can only be removed by chemical cleaning. An A₁/A₂/O-MBR system with short intermittent physical cleaning was recommended for coke wastewater treatment.     

Industrial wastewater treatment wastes used as oxygen carriers in energy generation processes

The paper contains the results of a study on a promising combustion technology known as chemical looping combustion (CLC). The main advantage of CLC is the production of a highly concentrated CO₂ stream without any energy penalty for its separation, together with NO_x emissions reduction. The objective of this work was to examine novel oxygen carrier (OC) materials for their practical applications with gaseous fuel/air. We report a simple, economical and environmentally friendly method for the large-scale synthesis of OCs from wastes. The reactivity tests for OCs made from wastewater from a coking plant were performed in a thermogravimetric analyser. For selected temperatures, reduction–oxidation cycles were performed. The effect of temperature on the reaction rates, the effect of waste treatment and the oxygen transport capacity were determined. The waste material demonstrated good thermal stability and maintained its redox behaviour over cycling. ICP-OES and XRD data revealed these materials that contained beneficial amounts of Fe species and silicon oxide, which improved stability. The study showed that these waste materials are excellent examples of raw materials that can enable a decrease in OC production costs with the additional benefit of the practical management of post-wastewater sediments from coke oven wastewater plants.

     

A simple non-invasive optical pyrometric method for plotting temperature—Time profiles of high temperature reactions in microwave ovens

A simple optical pyrometric method is described, based on a photocell with red and blue filters calibrated by the disappearing filament technique. The method, which is cheap, non-invasive and reproducible, is used for measurement of the rate of heating of solid materials such as coke, CuO or Fe₃O₄ in a microwave oven. All materials were heated under dinitrogen in a silica reaction vessel over 3 min in a 650 W oven. Coke (which contains graphitic phases) and magnetite heat smoothly to maximum temperatures of 1180 and 1050°C respectively. CuO heats erratically with plasma discharges from the surface, however when covered with a layer of coke the oxide heats smoothly achieving a maximum temperature of 1210°C. The observations are discussed.     

Electrochemical Treatment of Heavy Metal‐containing Wastewater with the Removal of COD and Heavy Metal Ions

The use of electricity to treat water was employed for the first time in the UK a century ago, and since then has been considered a highly reliable method for wastewater treatment. In recent years, the demand for hydrogen gas as a valuable, clean energy source has increased considerably; from this point of view, the electrolysis of wastewater can meet the demand for energy during the process of treating wastewater. In this work, wastewater containing heavy metal ions has been treated by an electrochemical method which not only decreased the chemical oxygen demand value and lowered the number of heavy metals ions but also generated hydrogen throughout the process. A series of experiments were performed under optimum conditions of selected electrode materials, pH values, supply power, and working time. The results obtained indicate that by controlling the key factors of the process, a practical method can be achieved for wastewater treatment which also produces a noticeable amount of green energy. Differential pulse voltammetry measurements were used to determine the properties of an industrial wastewater source before and after treatment, while scanning electron microscopy and energy dispersive X‐ray spectroscopy were applied to investigate the proficiency of the electrode material.     

Experimental Study on COD Composition and Electrochemical Degradation of Wastewater in Offshore Oilfields

Chemical oxygen demand (COD ) of standard discharge wastewater in offshore oilfields is an important part of oilfield wastewater treatment. Polymer‐containing oily wastewater from oilfields in Bohai Sea was taken as the subject of this study. Combined with wastewater treatment experiments, the major composition of COD such as oils, polymer, and chemical agents is studied. Under certain conditions, the two‐dimensional plug‐flow electrochemical reactor was used to treat wastewater, and a linear relation between COD and concentration was established in the low concentration range. A preliminary study was carried out on the main factors of COD removal, and the results show that, compared to the polymer, oils are more easily electrolyzed whereas the chemical agents are more difficult to be electrolyzed. The highest COD removal by electrochemical treatment of wastewater was 75.34%, and the residual COD in wastewater was mainly contributed by the chemical agents and polymer that were not degraded completely.     

Removal of COD,aromaticity and color of a pretreated chemical producing industrial wastewater: a comparison between adsorption,ozonation, and advanced oxidation processes

A wide range of products are produced in the chemical producing industry such as textile dyes, chemicals, printing dyes and chemicals, paper chemicals, electrostatic powder dyes, and optical brighteners. The aim of this study is to investigate the treatability of chemical oxygen demand (COD), aromaticity, and color in the wastewater of this sector, where highly complex chemicals are used. Most of the studies in the literature are related to the treatment of synthetically prepared dyed wastewater. This study is important as it is carried out with real wastewater and gives results of many treatment methods. In the study, COD, UV-vis absorbance, and color values were attempted to be removed from the wastewater of a chemical producing industry that was pretreated by coagulation-flocculation. The COD value of the pretreated wastewater discharged to the central treatment system was restricted as 1000 mg/L. Pretreated wastewater characterization is as follows: COD: 2117 mg/L, UV-vis absorbance values at; 254 nm: 9.91, 280 nm: 8.65, 341 nm: 12.77, 436 nm: 5.01, 525 nm: 2.24, and 620 nm: 1.59. In the study, adsorption, ozonation, and advanced oxidation processes (Fenton and persulfate oxidation) were used to remove COD and UV-vis absorbance values (aromaticity, organics, and color). The method by which the best removal efficiency was obtained for all parameters was the adsorption process using powdered activated carbon (PAC). The equilibrium PAC dose was found as 6 g/L. At this adsorbent dose, the removal efficiencies of UV-vis absorbance values were all around 99% and the efficiency of COD removal was 77%. The Langmuir isotherm constants were found to be q_max= 30.4 mg/g and K_L = 487.9 (L/mg). The COD concentration at this adsorbent dose was 486 mg/L and wastewater was suitable for discharge to the central wastewater treatment plant in that region.     

Treatment of coke plant wastewater by A/O fixed biofilm system

The long-term environmental impacts of wastewa-ter from coke plant can be very high, especially due to the discharge of large amounts of wastewater. The composition of coke plant wastewater is complicated and varies from one factory to another, depending …     

COD速测仪测定工业废水中CODCr

采用标准回流法和仪器法（用ＣＯＤ速测仪）对工业废水化学需氧量进行对照测定，结果发现，用ＣＯＤ速测仪测定工业废水，简便、快速、精密度好、准确度高。     

Gliding Arc Discharge for Decolorization and Biodegradability of Azo Dyes and Printing and Dyeing Wastewater

Gliding arc discharge process was used for the pretreatment of four azo dye solutions, which are classified to acidic, reactive and chemical indicator, as well as printing and dyeing wastewater with the objective of improving their overall biodegradability. The percentage color removal of all samples were found to be over 92% after 40?min treatment, and the color disappearance of four azo dyes followed the first-order kinetics completely. The biochemical oxygen demand (BOD₅)/chemical oxygen demand (COD) ratio increased from 0.02 to 0.46 for acid orange II (AO7), 0.173 to 0.55 for methyl orange, 0.019 to 0.4 for direct fast black, 0 to 0.65 for reactive red K-2BP. The decolorization of printing and dyeing wastewater achieved 97.5% and the COD removal efficiency was 76.6%. The BOD₅/COD ratio increased to 0.55 after 20?min treatment. The experimental results indicates it is possible to combine gliding arc discharge with conventional biological treatment for the remedy of wastewater containing generally non-biodegradable dye.     

Electrochemical Technologies to Decrease the Chemical Risk of Hospital Wastewater and Urine

The inefficiency of conventional biological processes to remove pharmaceutical compounds (PhCs) in wastewater is leading to their accumulation in aquatic environments. These compounds are characterized by high toxicity, high antibiotic activity and low biodegradability, and their presence is causing serious environmental risks. Because much of the PhCs consumed by humans are excreted in the urine, hospital effluents have been considered one of the main routes of entry of PhCs into the environment. In this work, a critical review of the technologies employed for the removal of PhCs in hospital wastewater was carried out. This review provides an overview of the current state of the developed technologies for decreasing the chemical risks associated with the presence of PhCs in hospital wastewater or urine in the last years, including conventional treatments (filtration, adsorption, or biological processes), advanced oxidation processes (AOPs) and electrochemical advanced oxidation processes (EAOPs).     

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics,efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al₂O₃ was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O₂^–, and ¹O₂), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al₂O₃ catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ～ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ～ 0.032$/m³, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al₂O₃ exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.     

Sewage sludge coke estimation using thermal analysis

The imposition of more stringent legislation by CETESB in the State of São Paulo (Brazil) governing the disposal and utilization of sewage sludge, coupled with the growth in its generation has prompted a drive for alternative uses of sewage sludge. One option that is especially promising, due to its potential to valorize sludge, is its conversion into carbonaceous adsorbents or coke for industrial effluents treatment. Thus, a methodology is presented to estimate the coke produced from the sludge of a sewage treatment station using thermal analysis. The used sewage sludge, which comes from aerobic treatment, was collected in the wastewater treatment station of Barueri, one of the largest of the São Paulo metropolitan area. The sludge samples were collected, dried, ground, and milled until they passed an ABNT 200 sieve. The inert ambient used during its thermal treatment produces inorganic matter and coke as residual materials. Coke formation occurs in the 200–500 °C range and, between 500 and 900 °C, its thermal decomposition occurs. The highest formation of coke occurs at 500 °C.     

强力霉素废水的吸附-混凝预处理研究

根据强力霉素废水的特点,采用吸附-混凝联合处理工艺对其进行预处理研究。筛选出最佳吸附剂、混凝剂、助凝剂,考察了其投加量、pH、反应时间、搅拌强度等因素对处理效果的影响。实验表明,选用粉煤灰作为吸附剂、聚合氯化铝(PAC)作为混凝剂、羟乙基田菁胶(ESG)作为助凝剂,F-去除率达到99.9%,氟浓度降至10mg/L以下;化学需氧量(CODCr)去除率达到37.5%,生化需氧量/化学需氧量(BOD5/CODCr)由原来的小于0.1提高至0.16,提高了原废水的可生化性。而且处理后的灰渣烧制成砖块,不会对环境造成二次污染,达到了以废治废的目的。     

高氯废水化学需氧量分析方法综述

对高氯废水化学需氧量分析方法进行归纳和综述。常用的高氯废水化学需氧量分析方法有氯气校正容量法、降氯密闭消解分光光度法以及高温氧化总有机碳系数换算法等。其中氯气校正容量法操控要求较高,分析耗时较长,不适用于大批量样品同步分析;降氯密闭消解分光光度法灵敏度高,但在降氯过程中增加了重金属盐硫酸汞的用量,分析成本较高,易产生二次污染,且对样品的均质性要求较高;高温氧化总有机碳系数换算法操作便捷、抗干扰能力强,但是换算系数易随不同来源、不同组分的样品发生波动,数据可比性需要通过实验验证。经过梳理归纳,明确各种分析方法的特点和适用范围,为研究人员选择合适的分析方法或进一步开展相关的方法研究提供参考。     

水中铬污染治理的研究进展

综述了水中铬污染治理的研究进展,包括物理法、物理化学法、化学法、电化学法和生物处理法,并分别评述了各种处理方法的优缺点,提出了未来含铬废水治理的发展方向。     

A method for determination of COD in a domestic wastewater treatment plant by using near-infrared reflectance spectrometry of seston

This paper proposes a method for determination of chemical oxygen demand (COD) in domestic wastewater. The proposed method is based on near-infrared reflectance (NIRR) measurements of seston collected from wastewater samples by filtration. The analysis does not require any special reagent, catalyst or solvent. Inherent baseline and noise features present in NIRR spectra are removed by a Savitzky-Golay derivative procedure followed by wavelet denoising. The resulting wavelet approximation coefficients are used for partial-least-squares modelling and subsequent prediction of COD values in new samples. The model is calibrated by using COD values obtained according to the American Public Health Association (APHA) reference method. The proposed method is applied to effluent samples from the anaerobic ponds of the Mangabeira municipal wastewater treatment plant in the city of João Pessoa (Paraíba, Brazil). By comparing the NIRR prediction results with the APHA reference values, a root-mean-square error of prediction (RMSEP) of 19 mg O₂ L⁻¹ and a correlation of 0.97 were obtained. Such results are deemed adequate in view of the joint estimate of the standard error of the reference method, which was calculated as 21 mg O₂ L⁻¹.     

Miniaturized and green method for determination of chemical oxygen demand using UV-induced oxidation with hydrogen peroxide and single drop microextraction

We report on a green method for the determination of low levels of chemical oxygen demand. It is based on the combination of (a) UV-induced oxidation with hydrogen peroxide, (b) headspace single-drop microextraction with in-drop precipitation, and (c) micro-turbidimetry. The generation of CO₂ after photolytic oxidation followed by its sequestration onto a microdrop of barium hydroxide gives rise to a precipitate of barium carbonate which is quantified by turbidimetry. UV-light induced oxidation was studied in the absence and presence of H₂O₂, ultrasound, and ferrous ion. Determinations of chemical oxygen demand were performed using potassium hydrogen phthalate as a model compound. The optimized method gives a calibration curve that is linear between 3.4 and 20 mg L^?1 oxygen. The detection limit was 1.2 mg L^?1 of oxygen, and the repeatability (as relative standard deviation) was around 5 %. The method was successfully applied to the determination of chemical oxygen demand in different natural waters and a synthetic wastewater.

电化学氧化和臭氧化预处理酸性化工废水的效能研究

保持一定酸度条件下对比了电化学氧化和臭氧氧化预处理酸性化工废水的效能（废水原pH 0.85）. 结果表明,在废水中添加2 g·L^-1 NaCl电化学氧化预处理效果较佳,30 mA·cm^-2条件下电解20 min后水样的CODCr（化学需氧量）去除率达43.4%,BOD₅/COD_Cr（生化需氧量与化学需氧量的比值）值从原来的0.034上升至0.14,可生化性明显提高. 单独臭氧化仅在pH 7.0才能取得一定的预处理效能. Ti(Ⅳ)/O₃/H₂O₂高级氧化体系在pH 2.85条件下亦有较好的预处理效果,16 min后水样COD_Cr去除率达22.9%,BOD₅/COD_Cr值则提高至0.072.     

双极室联合处理啤酒废水的微生物燃料电池

构建了双极室连续流联合处理废水的微生物燃料电池(MFC), 该MFC阳极室的出水直接用于阴极室的进水, 利用阴极室的好氧微生物进一步降解有机物. 以啤酒废水作底物, 研究了该MFC的产电性能和废水处理效果. 结果表明, 采用双极室连续流MFC可以大大提高废水的处理效果, 对啤酒废水化学需氧量(COD)的总去除率可达92.2%~95.1%, 其中阳极室中COD去除率为47.6%~56.5%. MFC的开路电压为0.451 V, 最大输出功率为2.89 W/m³. 实验中抑制MFC性能的主要因素是阴极的极化损失, 通过降低进入阴极室溶液的COD浓度、采用优质的阴极材料和加大阴极室内的曝气量等方法进一步优化电池的性能.     

Recent trends and advances in microbial electrochemical sensing technologies: An overview

Microbial electrochemical systems utilize the electrochemical interaction between microorganisms and electrode surfaces to convert chemical energy into electrical energy, offering a promise as technologies for wastewater treatment, bioremediation, and biofuel production. Recently, growing research attention has been devoted to the development of microbial electrochemical sensrs as biosensing platforms. Microbial electrochemical sensors are a type of microbial electrochemical technology (MET) capable of sensing through the anodic or the cathodic electroactive microorganisms and/or biofilms. Herein, we review and summarize the recent advances in the design of microbial electrochemical sensing approaches with a specific overview and discussion of anodic and cathodic microbial electrochemical sensor devices, highlighting both the advantages and disadvantages. Particular emphasis is given on the current trends and strategies in the design of low-cost, convenient, efficient, and high performing METs with different biosensing applications, including toxicity monitoring, pathogen detection, corrosion monitoring, as well as measurements of biological oxygen demand, chemical oxygen demand, and dissolved oxygen. The conclusion provides perspectives and an outlook to understand the shortcomings in the design, development status, and sensing applications of microbial electrochemical platforms. Namely, we discuss key challenges that limit the practical implementation of METs for sensing purposes and deliberate potential solutions, necessary developments, and improvements in the field.