A review on industrial wastewater treatment via electrocoagulation processes

Every year, a large amount of wastewater is discharged from various industries into the environment, and various methods are used to treat wastewater to reduce the amount of pollutants. Electrocoagulation (EC) is an electrochemically based technique that generates coagulant species in situ from the electrodissolution of sacrificial anodes, usually made of iron or aluminum destabilizes suspended, dissolved, or emulsified pollutants by using an electric current. It has a potential in removing various kinds of pollutants including organic and inorganic contaminants for various types of wastewater. The effectiveness of EC process depends on various parameters including pH, electrode, operation time, and current density. The goal of this study is to review the most relevant literatures that were published recently. The main challenges associated with the EC process are electrode passivation and energy consumption. EC compared with other common methods has advantages such as reducing energy consumption and reducing operating costs.     

Parametric study for the treatment of tannery dye wastewater by electro-oxidation

Degradation of tannery effluents is a difficult operation because of their intricate chemical structures. Most of the conventional approaches are becoming ineffective because of the wide variation in the composition of tannery effluent. Dyes from the wastewater is also dangerous, as the wastewater has negative impact on the health of human being, plants and aquatic animals. For the first time once through continuous approach was employed for the removal of Acid yellow 110 tannery dye in electro-oxidation process on Mix Metal Oxide of ruthenium and iridium on titanium sheet electrode. The effects of pH, time (t) and current (i) on % color removal and energy consumed were investigated in a batch setup and found the optimum condition with the help of RSM design. The values of the responses Y₁ and Y₂ were found to be 93.08% and 1.07 kWh/m³ respectively at the optimum condition. Toxicity Bioassay analysis, GC-MS analysis and the kinetic study were performed at optimum condition. At the flow rates of 10–40 ml/min once through continuous experiments was conducted to found the feasibility of the process at pilot scale or industrial scale application.     

Advanced mass spectrometric methods applied to the study of fate and removal of pharmaceuticals in wastewater treatment

This overview is of analytical methodologies based on gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry, applied in environmental monitoring of pharmaceutical residues and their known degradation products. We also consider the ability of time-of-flight (TOF) and quadrupole-TOF instruments to provide sufficiently accurate-mass measurements and full-scan spectra for unequivocal confirmation of target compounds and investigation of their degradation products, which are either known or unknown.

We focus attention on the fate and the behavior of pharmaceutical residues during conventional and advanced wastewater treatments. Wastewater-treatment plants are designed to remove conventional pollutants (e.g., suspended solids and biodegradable organic compounds), but not low concentrations of synthetic pollutants (e.g., pharmaceutically active compounds).

Membrane bioreactor systems represent a new generation of processes that have proved to outperform conventional activated sludge treatment in terms of sludge production and effluent quality. In the past few years, there has been much attention paid to their capability for removing trace organic contaminants from sewage. This review highlights their improved performance in removing pharmaceutical residues from wastewater compared to conventional treatment.     

A metal-free carbon dots for wastewater treatment by visible light active photo-Fenton-like reaction in the broad pH range

Carbon dots (Cdots) has been proved to possess the catalytic decomposition of H2O2 in the photocatalytic system. It is a potential photo-Fenton catalyst. Since ...     

树脂吸附法处理1,4-二羟基蒽醌生产废水的研究

本文研究了树脂吸附法处理1,4-二羟基蒽醌生产废水。结果表明,NDA-404大孔吸附脂对该废水具有良好的吸附-脱附效果。原废水中邻苯二甲酸浓度约为4700-12000mg/L,CODCr约为6800-24000mg/L,经树脂吸附处理后,邻苯二甲酸的吸附率≥99.5%,CODCr去除率≥99.5%,树脂的脱附率为100%。邻苯二甲酸的回收率≥80%,在废水有效处理的同时实现了废物资源化。     

处理含铅废水的现状及研究进展

废水中的铅严重危害环境及人体的健康,如何处理含铅废水引起了很多科研人员的重视。本文综述了近年来处理含铅废水的研究进展,详细介绍了吸附法、膜分离法、离子液体萃取法、化学沉淀法、电解法、电絮凝法、微生物絮凝法和植物修复法等处理含铅废水的现状,分析了各种处理方法的优缺点,并展望了未来深度处理含铅废水的发展趋势。     

碳酸氢盐活化的过氧化氢：一种有机废水处理的新技术

水污染问题已成为影响我国可持续发展的关键问题之一,为有效提高现有污水处理的效率及其回收利用,各种催化氧化技术受到了广泛的关注。目前发展的各类高级氧化技术在实际的应用过程中明显受到了氧化剂的利用率、催化剂的浸出、寿命及成本等问题的严重限制。因此基于新的理念、发展新的催化氧化技术仍然受到广泛的关注。
　　最近几年,利用碳酸氢盐活化过氧化氢,应用于有机废水的降解逐渐受到环境催化领域的关注。碳酸氢盐本身是一种低毒性、广泛存在于环境及生物体系的化学物质,通过它活化过氧化氢产生过碳酸氢盐氧化剂,该氧化剂能够直接氧化有机物。同时,在各种过渡金属催化剂的存在下,通过该过碳酸氢盐可以形成氧化能力更强的各种自由基(如羟基自由基等) 及高价态的过渡金属离子参与有机废水的降解。虽然传统认为碳酸盐及碳酸氢盐对高级氧化法降解有机废水不利,原因是认为它们能捕捉羟基自由基,形成氧化能力更低的碳酸根自由基。现有的研究已充分表明,较低浓度的碳酸氢盐能够加快有机废水的氧化降解,而且通常比单独使用过氧化氢效率更高,这些新的发现已明显突破了传统意义上对碳酸氢盐作用的理解。更为重要的是,在微量碳酸氢盐的存在下,其产生的微碱性环境极大地消除了负载型氧化物催化剂在废水降解过程中的金属离子流失、从而极大地延长了催化剂的寿命。该缺点是各种基于过渡金属氧化物催化剂的高级氧化技术难以广泛推广的关键性挑战,原因是随着氧化降解的进行,废水体系由于有机酸的生成而逐渐酸化,进而引发氧化物催化剂的酸溶而流失。在这点上,碳酸氢盐活化过氧化氢系统由于其天然的微碱性环境体现出了其明显的优势。
　　本文即是在本课题组工作基础上,对该领域内国内外研究进展加以总结,以期获得国内外同行的进一步关注。综述的主要内容包括：(1)碳酸氢氧活化过氧化氢的相关知识介绍,(2)均相碳酸氢氧活化过氧化氢降解有机废水的研究进展,(3)基于金属氧化物催化剂的碳酸氢氧活化过氧化氢降解有机废水的研究进展,和(4)碳酸氢盐在其他高级氧化技术中的应用。虽然基于碳酸氢氧活化过氧化氢降解有机废水的研究还处于早期探索阶段,还有很多基础科学问题如降解机理等值得进一步探索,期望通过该综述的介绍能够让同行对碳酸氢氧活化过氧化氢降解有机废水有一个比较全面的了解,进而推动该研究方向的发展,为有机废水的催化处理提供新的机会。     

Membranes based on non-synthetic (natural) polymers for wastewater treatment

During the last decades, rising environmental concerns about the widespread usage of petroleum-based synthetic polymers has caused naturally occurring polymers to gain momentous. As a biocompatible and environmentally friendly alternative, bio-based polymers are continuously gaining new domains of application in drug delivery systems, tissue engineering, membrane technology, bio-sensor devices, etc. There is an increasing number of scientists who have applied various kinds of biopolymers, such as cellulose, chitin, starch, and alginate to fabricate fully or semi-biodegradable membranes for wastewater treatment. Beside biocompatibility, biopolymers combine many attractive features such as hydrophilicity and functionalizability that makes them great candidates to enhance the performance of composite membranes to effectively purify water from hazardous pollutants. On the other hand, elevating thermo-mechanical and chemical stability of these bio-based materials by introducing new organic and inorganic additives is another main focus area. This review is concerned with 1) introducing the promising feature of biopolymers that can be used as a raw material to synthesize membranes for water treatment, 2) proposing a comprehensive categorization of these membranes based on their structure, and 3) discussing the performance of these membranes in eliminating various kinds of contaminants from effluents and their strength and weakness points.     

Whole cell immobilised biosensors for toxicity assessment of a wastewater treatment plant treating phenolics-containing waste

Wastewater treatment plants dealing with industrial wastes are often susceptible to overload of toxic influent that can partially or completely destroy treatment for extended periods. An obvious candidate for monitoring toxicity in such wastewater systems is bioluminescent bacteria. However, the natural bioluminescent bacteria can be particularly sensitive to some industrial wastes and therefore their response to normal operational conditions does not reflect the status of the microbial community responsible for treatment. Moreover, the salt dependence of the marine bioluminescent bacteria, and the temperature sensitivity of some strains, further complicate their use. Here we describe the construction of whole cell genetically modified bioluminescent biosensors and their immobilisation for use in monitoring the toxicity of a complex industrial wastewater containing phenolic materials. A hand-held luminometer was designed for laboratory or field use, and the immobilisation system designed with several things in mind: the geometry of the instrument; the need for containment of GM bacteria; the maximisation of the bioavailability of the wastewater to the biosensor. The performance of a candidate GM sensor was compared with Vibrio fischeri in liquid culture and after immobilisation in thin films of poly(vinyl alcohol) (PVA) cryogels. The biosensors were tested against pure phenol and 3-chlorophenol as a reference toxic chemical known to be much more toxic to bacteria than phenol. The biosensors were then tested with the phenolics-containing industrial wastewater. The immobilisation system proved to operate predictably with pure toxicants, and was able to discriminate toxicity of various zones within the wastewater treatment plant.     

The efficacy and progress in using radiation as a quarantine treatment of tropical fruits—a case study in Hawaii

Most tropical fruits for export must be treated with an approved quarantine treatment. Three and a half decades of research have demonstrated the efficacy of irradiation as a quarantine treatment in terms of efficiency, effectiveness, and product quality retention. The USFDA and the USDA-APHIS approved irradiation to disinfest fresh foods/fresh papayas in 1986 and 1989, respectively. In early 1995, the Hawaii Department of Agriculture was granted a special permit from USDA-APHIS allowing untreated Hawaiian fruits to be irradiated on the US mainland. The objectives were to gain experience in commercial irradiation as a quarantine treatment and to gather data on shipping and handling procedures, and on product quality. In April 1995, the first shipment of Hawaiian fruit was irradiated at a minimum quarantine dose of 0.25 kGy in an Isomedix plant near Chicago, and then distributed to supermarkets in Illinois and Ohio. Continuous shipments, irradiation, and marketing of various tropical fruits in the US have shown commercial efficacy, quality retention, and excellent consumer acceptance. A commercial e-beam/converted X-ray facility was installed by Titan Corp. on the Island of Hawaii and was operational by late July 2000. Hawaii has become the first place in the world to use irradiation as a quarantine treatment of fruits.     

Development of an up-flow irradiation device for electron beam wastewater treatment

Electron beam irradiation processing is an available technology to treat sludge, groundwater, surface water and industrial and municipal wastewater. The use of this technology into environmental areas has moved slowly because industry and government are always conservative in the adoption of new processes, especially when they can not observe the efficiency and cost effectiveness of a treatment in a full scale facility.

In this direction the hydraulic system where the water is presented to the electron beam governs the efficacy of this technology. The present work is based on the development of the irradiation device, an up-flow delivery system that alleviates the dependence of energy transfer to the stream with the beam accelerating voltage (penetration capability).

In this work a series of experiments were performed to establish the relationships between accelerating voltage ranging from 0.5 to 1.5 MeV, current, water flow and deposited dose in order to optimize the operating parameters and the selection of a cost-effective commercial electron beam.     

Electrochemical production and use of chlorinated oxidants for the treatment of wastewater contaminated by organic pollutants and disinfection

In the last years, an increasing attention has been devoted to the use of electrogenerated chlorinated oxidants for the treatment of wastewater polluted by recalcitrant organics and/or for the disinfection of water contaminated by pathogen microorganisms. In this review, more recent and relevant findings were presented and critically discussed. The main advantages and disadvantages of this technique were commented, including the potential formation of toxic chlorinated organic specie and of chlorate and perchlorate or the difficult selection of proper operative parameters, as well as the key points that should be addressed to enhance the use on an applicative scale.     

Interlaboratory study of the bioluminescence inhibition tests for rapid wastewater toxicity assessment

Several toxicity procedures are currently being used for the wastewater toxicity assessment. We have undertaken an interlaboratory comparison of the use of different bioluminescence inhibition toxicity tests based on Vibrio fischeri, in order to evaluate their reproducibility for the rapid wastewater toxicity assessment. Twenty-two laboratories took part in this study organized by the Institut Català de Tecnologia (ICT) and the Consejo Superior de Investigaciones Cientificas (CSIC). During the exercise, six series of six samples were analyzed along 5 months. Every batch of samples was composed by three real samples and three standard solutions. The real samples were: an untreated effluent of a paper industry, a sample from a first settlement of a wastewater treatment plant (WWTP) and the final effluent of the WWTP. The goals of the interlaboratory study were to evaluate the repeatability (r) and reproducibility (R) when different laboratories conduct the test, the influence of different matrix samples, the variability between different tests based on the same principle: the bioluminescence inhibition of V. fischeri, but involving different commercial devices and to determine the rate at which participating laboratories successfully completed tests initiated. The maximum number of outlier values was corresponding to a non-treated effluent from a paper industry. This also was the most complex and toxic sample analyzed. An increase on the non-convergent values obtained for the participants was observed at higher matrix complexity and at lower toxicity level. In comparison with other editions of this interlaboratory study the matrixes of real samples analyzed were more complex, nevertheless the final variability coefficient for the exercise was nearby to the average value for the past editions. Due to the high complexity of some samples involved in this intercalibration the stability of real samples were also followed during the test. On the other hand, no relation was found between final results and the different devices, as show the cluster analysis.     

Metal content variation in wastewater and biosludge from Bangkok's central wastewater treatment plants

The objectives of this study were to determine the metal contents and their variations in influent, effluent and biosludge, and to evaluate the potential environmental impact of biosludge generated from the Bangkok, Thailand central wastewater treatment plants. The variation in influent metal content was site-specific and could be related to the economic activities of small-scale companies. An activated sludge process could remove some level of the metal content via a combination of biological and physicochemical processes. The variation in metal removal efficiencies strongly depended upon the influent wastewater characteristics and composition. Metal occurrence in biosludge was similar to the metals found in the influent. Iron was the most abundant while Cd had the lowest occurrence. A longer excess sludge operational condition and storage time may increase metal contents in biosludge due to the decomposition of biodegradable organic matter by microorganisms. According to the speciation results, the biosludge studied had a low mobility and availability index, except the RK plant biosludge. Most trace metals of interest were in the less mobile and bioavailable forms. The most mobile exchangeable and moderately mobile carbonate fractions of Cd, Mn, Ni and Zn were relatively low (5–30%). Biosludge from RK had a total Cu concentration higher than the limits, and to some extent exchangeable and carbonate fractions that were relatively high (∼ 40%).     

Recent advances in electrochemical water technologies for the treatment of antibiotics: A short review

This short review presents a critical overview of the most recent works published in the literature related to the use of electrochemical advanced oxidation processes (EAOPs) for the treatment of antibiotics present in synthetic and real wastewaters. The first section focuses on novelties within the traditional EAOPs, including electrochemical oxidation and electrochemical Fenton-based processes. The second section is devoted to new electrochemical technologies, including heterogeneous electro-Fenton, electrochemically activated persulfate processes, and combined processes. Future perspectives about these processes are also presented to aid the continuous evolution of research in the area.     

New trends in removing heavy metals from industrial wastewater

Innovative processes for treating industrial wastewater containing heavy metals often involve technologies for reduction of toxicity in order to meet technology-based treatment standards. This article reviews the recent developments and technical applicability of various treatments for the removal of heavy metals from industrial wastewater. A particular focus is given to innovative physico-chemical removal processes such as; adsorption on new adsorbents, membrane filtration, electrodialysis, and photocatalysis. Their advantages and limitations in application are evaluated. The main operating conditions such as pH and treatment performance are presented. Published studies of 94 cited references (1999–2008) are reviewed.It is evident from survey that new adsorbents and membrane filtration are the most frequently studied and widely applied for the treatment of metal-contaminated wastewater. However, in the near future, the most promising methods to treat such complex systems will be the photocatalytic ones which consume cheap photons from the UV-near visible region. They induce both degradation of organic pollutants and recovery of metals in one-pot systems. On the other hand, from the conventional processes, lime precipitation has been found as one of the most effective means to treat inorganic effluent with a metal concentration of >1000 mg/L. It is important to note that the overall treatment cost of metal-contaminated water varies, depending on the process employed and the local conditions. In general, the technical applicability, plant simplicity and cost-effectiveness are the key factors in selecting the most suitable treatment for inorganic effluent     

Identification of toxic compounds in wastewater treatment plants during a field experiment

Chemical analysis and toxicity bioassays were used in conjunction to determine the toxic compounds present in wastewater. This combined methodology was applied to wastewater samples collected at two wastewater treatment plants (WWTP) from the area of Barcelona (Spain), during a field experiment carried out from 1-4 April 2000. The efficiency of the WWTP was evaluated by collecting and analyzing samples at various stages of the water treatment process. The samples corresponded to the raw influent, from first settlement—before biological treatment—and from the effluent.Two bioluminescence inhibition assays: ToxAlert^®10 and ToxAlert^®100 from Merck both based on the bioluminescence inhibition of Vibrio fischeri (marine bacterial specie) were used. ToxAlert^®10 is a portable device with no temperature control and uses freeze-dried bacterial reagent and ToxAlert^®100 uses liquid-dried bacterial reagent and the incubation takes place at controlled temperature. Both tests showed similar results.Besides the toxicity studies, the wastewater samples were characterized by various analytical protocols involving the use of solid phase extraction (SPE) followed by liquid chromatography-mass spectrometry (LC-MS). Phenols, non-ionic surfactants, linear alkyl benzene sulphonates, benzene and naphthalene sulphonates and micro-pollutants with high endocrine-disrupting effects like estradiol and ethynyl estradiol were identified at the WWTP.The toxic responses obtained for the samples collected at WWTP were defined by the 50% effective concentration (EC₅₀), the Toxicity Units (TU) and the toxicity impact index (TII₅₀). The toxic effect at the different steps of the WWTP was attributed to the compounds identified and quantified by LC-MS like transformation products of nonylphenol polyethoxylate such as nonylphenol and nonylphenol carboxylate.     

Analysis of pharmaceuticals in wastewater and removal using a membrane bioreactor

Much attention has recently been devoted to the life and behaviour of pharmaceuticals in the water cycle. In this study the behaviour of several pharmaceutical products in different therapeutic categories (analgesics and anti-inflammatory drugs, lipid regulators, antibiotics, etc.) was monitored during treatment of wastewater in a laboratory-scale membrane bioreactor (MBR). The results were compared with removal in a conventional activated-sludge (CAS) process in a wastewater-treatment facility. The performance of an MBR was monitored for approximately two months to investigate the long-term operational stability of the system and possible effects of solids retention time on the efficiency of removal of target compounds. Pharmaceuticals were, in general, removed to a greater extent by the MBR integrated system than during the CAS process. For most of the compounds investigated the performance of MBR treatment was better (removal rates >80%) and effluent concentrations of, e.g., diclofenac, ketoprofen, ranitidine, gemfibrozil, bezafibrate, pravastatin, and ofloxacin were steadier than for the conventional system. Occasionally removal efficiency was very similar, and high, for both treatments (e.g. for ibuprofen, naproxen, acetaminophen, paroxetine, and hydrochlorothiazide). The antiepileptic drug carbamazepine was the most persistent pharmaceutical and it passed through both the MBR and CAS systems untransformed. Because there was no washout of biomass from the reactor, high-quality effluent in terms of chemical oxygen demand (COD), ammonium content (N-NH₄), total suspended solids (TSS), and total organic carbon (TOC) was obtained.     

GC-MS analysis of organic compounds in wastewater and sewage sludge

A multimethod based on liquid-liquid extraction and solid-liquid extraction for the analysis of persistent organic pollutants in water and sludge from sewage treatment plants has been established. Traces of 22 organic compounds used in industry and personal care products (PCPs) were analyzed by GC/MS. The LODs for the analytes were less than 2.3 ng/L for wastewater and 31 microg/kg (dry weight matter) for sewage sludge. Satisfactory recoveries (70-130%) were achieved. The validated method permits the analysis of water and sludge samples at various stages of the treatment from different sewage treatment plants. Thus, the distribution between water and sludge as well as the dissipation of the compounds analyzed were balanced. By this means, the efficiency of different wastewater treatment plants (WWTPs) can be evaluated and measures can be taken to optimize the treatment process at different stages.