Applications of Fenton oxidation processes for decontamination of palm oil mill effluent: A review

Oil palm agro-industry is a major revenue earner for Malaysia with the country being one of the major producers of crude palm oil (CPO) and oil palm products. Its growth has, however, led to massive water consumption and high generation of highly polluting palm oil mill effluent (POME). The inadequacies of ponding system adopted by most palm oil mills (POMs) for the treatment of POME to alleviate environmental and public health concerns are quite alarming. Fenton advanced oxidation technologies are a current research area providing viable alternatives for POME treatment, recovery and managing high demand for water. Its major setback is the generation of a large amount of unwanted sludge of iron (III) complexes thus increasing the costs of sludge management, treatment, and disposal. The salient and promising features of this technique for industrial applications motivate researchers to find ways to overcome its inherent drawbacks. This brief review aimed at discussing and evaluating the performances of the various Fenton oxidation processes, including homogeneous, heterogeneous, photo-Fenton, electro-Fenton, sono-Fenton etc., for POME treatment. Discussions on the future direction of these Fenton processes points towards the utilization of abundant magnetically separable heterogeneous composites as catalysts with high stability, activity, recyclability, and cost-effectiveness for decontamination of POME and other agro-industrial effluents from recalcitrant organic pollutants. The low deployment of such composite catalyst coupled with scarce literature on POME treatment in this regard offers a vast opportunity for research exploration.     

Mixotrophic Cultivation of Microalgae for Biodiesel Production: Status and Prospects

Biodiesel from microalgae provides a promising alternative for biofuel production. Microalgae can be produced under three major cultivation modes, namely photoautotrophic cultivation, heterotrophic cultivation, and mixotrophic cultivation. Potentials and practices of biodiesel production from microalgae have been demonstrated mostly focusing on photoautotrophic cultivation; mixotrophic cultivation of microalgae for biodiesel production has rarely been reviewed. This paper summarizes the mechanisms and virtues of mixotrophic microalgae cultivation through comparison with other major cultivation modes. Influencing factors of microalgal biodiesel production under mixotrophic cultivation are presented, development of combining microalgal biodiesel production with wastewater treatment is especially reviewed, and bottlenecks and strategies for future commercial production are also identified.     

Biogas Potential of the Side Streams Obtained in a Novel Phenolic Extraction System from Olive Mill Solid Waste

The olive oil production is an important industrial sector in many Mediterranean areas, but it is currently struggled by the necessity of a proper valorisation of the olive mill solid waste or alperujo. The alperujo is the main by-product generated during the two-phase olive oil extraction, accounting for up to 80% of the initial olive mass. The alperujo is a source of valuable compounds, such as the pomace olive oil or highly interesting phenolic compounds. In the present research, a novel biorefinery approach has been used for phenolic compounds recovery. However, the extraction of these valuables compounds generates different exhausted phases with high organic matter content that are required to be managed. This study consists of the evaluation of the anaerobic biodegradability of the different fractions obtained in a novel biorefinery approach for the integral valorisation of alperujo. The results show that the different phases obtained during the biorefinery of the alperujo can be effectively subjected to anaerobic digestion and no inhibition processes were detected. The highest methane yield coefficients were obtained for the phases obtained after a two-months storages, i.e., suspended solids and liquid phase free of suspended solids, which generated 366 ± 7 mL CH₄/g VS and 358 ± 6 mL CH₄/g VS, respectively. The phenol extraction process reduced the methane yield coefficient around 25% due to the retention of biodegradable compounds during the extraction process. Regardless of this drop, the anaerobic digestion is a suitable technology for the stabilization of the different generated residual phases, whereas the high market price of the extracted phenols can largely compensate the slight decrease in the methane generation.     

环境样品分析

本文是"分析试验室"定期评述"环境样品分析"的第9篇综述。它全面评述了2006年1月至2007年12月间我国环境样品分析方面的进展,主要内容包括:概述,大气、水体、土壤和沉积物、生物样品、城市污泥、垃圾堆肥和垃圾渗滤液分析等。引用参考文献990篇。     

Integrated assessment of the impact on the natural environment components from the solid domestic waste landfill of the city of Arkhangel’sk

The leachate generated by the solid domestic waste landfill in the city of Arkhangel’sk affects the natural waters of the swamp in the landfill location site. Based on the results from laboratory studies, the main pollutants brought by the landfill leachate were identified and quantitatively determined, and the environmental condition of the area adjacent to the landfill was characterized. The pollutant migration routes were determined. The contribution of the landfill leachate to the chemical composition of the natural environment components in the adjacent swamplands was determined, and the impact it exerts on the environmental condition of the area surveyed was assessed.     

Oil Production Towards Biofuel from Autotrophic Microalgae Semicontinuous Cultivations Monitorized by Flow Cytometry

Two microalgae species (Scenedesmus obliquus and Neochloris oleoabundans) were cultivated in closed sleeve photobioreactors in order to select the best oil producer for further large-scale open raceway pond cultivations, aiming at biofuel production. Scenedesmus obliquus reached a higher maximum biomass concentration (1.41 g l⁻¹) with a lower lipid content (12.8% w/w), as compared to N. oleoabundans [maximum biomass concentration of 0.92 g l⁻¹ with 16.5% (w/w) lipid content]. Both microalgae showed adequate fatty acid composition and iodine values as substitutes for diesel fuel. Based on these results, N. oleoabundans was selected for further open raceway pond cultivations. Under these conditions, N. oleoabundans reached a maximum biomass concentration of 2.8 g l⁻¹ with 11% (w/w) of lipid content. A high correlation between the Nile Red fluorescence intensity measured by flow cytometry and total lipid content assayed by the traditional gravimetric lipid analysis was found for both microalgae, making this method a suitable and quick technique for the screening of microalgae strains for lipid production and optimization of biofuel production bioprocesses. Medium growth optimization for enhancement of microalgal oil production is now in progress.     

Carbonaceous residues from biomass gasification as catalysts for biodiesel production

Tars and alkali ashes from biomass gasification processes currently constitute one of the major problems in biomass valorisation,generating clogging of filters and issues related with the purity of syngas production.To date,these waste residues find no useful applications and they are generally disposed upon generation in the gasification process.A detailed analysis of these residues pointed out the presence of high quantities of Ca(>30 wt%).TG experiments indicated that a treatment under air at moderate temperatures(400-800 C) decomposed the majority of carbon species,while XRD indicated the presence of a crystalline CaO phase.CaO enriched valorized materials turned out to be good heterogeneous catalysts for biodiesel production from vegetable oils,providing moderate to good activities(50%-70% after 12 h) to fatty acid methyl esters in the transesterification of sunflower oil with methanol.     

Application of ultra-high-pressure liquid chromatography–tandem mass spectrometry to the determination of multi-class pesticides in environmental and wastewater samples: Study of matrix effects

An ultra-high-pressure liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method for the determination of 37 pesticides (herbicides, insecticides and fungicides) in environmental and wastewater has been developed. To efficiently combine UHPLC with MS/MS, a fast-acquisition triple quadrupole mass analyzer was used. This analyzer (minimum dwell time, 5 ms) allows acquiring up to three simultaneous transitions in the selected reaction monitoring mode for each compound assuring a reliable identification without resolution or sensitivity losses. A pre-concentration step based on solid-phase extraction using Waters Oasis HLB cartridges (0.2 g) was applied with a 100-fold pre-concentration factor along the whole analytical procedure. The method was validated based on European SANCO guidelines using surface, ground, drinking and treated water (from an urban solid residues treatment plant) spiked at two concentration levels (0.025 and 0.1 μg/L), the lowest having been established as the limit of quantification objective. The method showed excellent sensitivity, with instrumental limits of detection ranging from 0.1 to 7 pg. It was applied to environmental water samples (ground and surface water) as well as to samples of urban solid waste leachates (raw leachate and treated leachate after applying reversed osmosis) collected from a municipal treatment plant. Matrix effects have been studied in the different types of water samples analyzed, and several isotope-labelled internal standards have been evaluated as a way to compensate the signal suppression observed for most of the compounds studied, especially in wastewater samples. As a general remark, only those pesticides which response was corrected using their own isotope-labelled molecule, could be satisfactorily corrected in all type of samples, assuring in this way the accurate quantification in all matrix samples.     

Microalgae and bioremediation of domestic wastewater

Domestic wastewaters are produced in huge volumes and abundant with carbon, nitrogen and phosphorous, which are a promising source of nutrients for production of microalgae. Microalgae-based bioremediation of domestic wastewater offers various advantages over traditional treatment approaches because the process consumes CO₂, completely removes nitrogen and phosphorous for production of green biomass and oxygen. Moreover, the abundance of biochemical compositions (e.g., lipids, proteins, carbohydrates, bioactive compounds) of microalgae biomass is superior to terrestrial plant biomass in refining to multi-products having variety of commercial values. In this review, the most dominant microalgae used for simultaneous removal of pollutants and production of biomass and metabolites from domestic wastewater are presented. Biorefinery of microalgae biomass produced from domestic wastewater for production of multiple products is also explored. Finally, challenges and perspectives of successful microalgae-based bioremediation of domestic wastewater toward the biorefinery are briefly discussed.     

Triangle of AKT2, miRNA,and Tumorigenesis in Different Cancers

Producing biodiesel from microalgae grown in wastewater is environment-friendly and cost-effective. The present study investigated the algae found in wastewater of a local dairy farm for their potential as biodiesel feedstocks. Thirteen native algal strains were isolated. On the basis of morphology and 16S/18S rRNA gene sequences, one strain was identified to be a member of cyanobacteria, while other 12 strains belong to green algae. After screening, two Scenedesmus strains out of the 13 microalgae isolates demonstrated superiority in growth rate, lipid productivity, and sedimentation properties, and therefore were selected for further scale-up outdoor cultivation. Both Scenedesmus strains quickly adapted to the outdoor conditions, exhibiting reasonably good growth and strong anti-contamination capabilities. In flat-plate photobioreactors (PBRs), algal cells accumulated predominantly neutral lipids that accounted for over 60% of total lipids with almost 70% being triacylglycerol. In addition, Scenedesmus obliquus had a high content of monounsaturated fatty acids, of which the amount of oleic acid (C18:1) was up to 27.11%. Based on these findings, the dairy farm wastewater-isolated Scenedesmus strains represent promising sources of low-cost, high-quality oil for biofuel production.     

Mass Cultivation of Microalgae on Animal Wastewater: a Sequential Two-Stage Cultivation Process for Energy Crop and Omega-3-Rich Animal Feed Production

In this study, 97 microalgal strains purchased from algae bank and 50 microalgal strains isolated from local waters in Minnesota were screened for their adaptability growing on a 20-fold diluted digested swine manure wastewater (DSMW). A pool of candidate strains well adapted to the DSMW was established through a high-throughput screening process. Two top-performing facultative heterotrophic strains with high growth rate (0.536?day^?1 for UMN 271 and 0.433?day^?1 for UMN 231) and one strain with high omega-3 unsaturated fatty acid (EPA, 3.75?% of total fatty acids for UMN 231) were selected. Subsequently, a sequential two-stage mixo-photoautotrophic culture strategy was developed for biofuel and animal feed production as well as simultaneous swine wastewater treatment using above two strains. The maximal biomass concentration and lipid content at the first and second stages reached 2.03?g/L and 23.0?%, and 0.83?g/L and 19.0?% for UMN 271 and UMN 231, respectively. The maximal nutrient removals for total phosphorus and ammonia after second-stage cultivation were 100 and 89.46?%, respectively. The experiments showed that this sequential two-stage cultivation process has great potential for economically viable and environmentally friendly production of both renewable biofuel and high-value animal feed and at the same time for animal wastewater treatment.     

Synthetic fluorescent probes to apprehend calcium signalling in lipid droplet accumulation in microalgae——an updated review

Lipid bodies are dynamic organelles of photosynthetic microalgae that can be used as the third generation resources for biofuel production.Biosynthesis of lipids can be influenced by different signalling processes.Visualisation of these processes can provide useful information about the fate and associated roles of lipid molecules in different biological systems.In photosynthetic organisms,however,studies of calcium ediated lipid biosynthesis is bottlenecked due to the limitation of proper and efficient technologies,which also include visualisation techniques.Currently,most studies to visualise lipid droplets in vivo have used traditional dyes,and proper visualisation of lipid drops is hindered by dye-specific limitations.This hurdle could be overcome by using recently developed aggregation-induced emission biooprobes.This review reveals current knowledge gaps in the studies of lipid drops and calcium ions in microalgae,as calcium signaling is important secondary messenger to detect a wide variety of environmental stimuli in plant and animal cells.To obtain insight into the mechanisms of these processes,the merits and demerits of currently available visualisation techniques for lipid drops and calcium are also detailed.Finally,opportunities and possibilities are proposed to recommend further improvement of techniques for detecting the role of calcium during lipid formation in microalgae for biofuel production.     

Ultrasound‐enhanced and microwave‐assisted extraction of lipid from Dunaliella tertiolecta and fatty acid profile analysis

Microalgal lipid is considered as a potential biodiesel resource due to its advantages compared to other bioresources. The production of biofuel from microalgae includes several stages like microalgae cultivation, biomass harvest, biomass treatment, lipid extraction, and the ultimate biodiesel synthesis. Lipid extraction is closely associated with the productivity and cost of energy production. In the present study, lipid of green algae Dunaliella tertiolecta was extracted by chemical agents with involvement of ultrasound and microwave. The optimization of experimental conditions was carried out by response surface methodology and orthogonal test design. Using the ultrasonic technique, an extraction rate of 45.94% was obtained under the optimum conditions of ultrasonic power 370 W, extraction time 5 min and liquid/solid ratio 125 mL/g. The extraction rate of 57.02% was obtained by the means of microwave assistance under the optimized conditions of extraction time 160 s, microwave power 490 W and liquid/solid ratio 100 mL/g. The comparison of the two results indicated microwave was more effective than ultrasound in extracting process. When the two techniques were utilized in combination, the optimized condition was ultrasonic power 320 W, ultrasonic time 4 min, microwave power 280 W, microwave time 120 s and liquid/solid ratio 100 mL/g, and the extraction rate was 49.97%.     

A roadmap towards a circular and sustainable bioeconomy through waste valorization

Municipal solid waste and food supply chain waste are globally generated in large quantities from various sectors including various stages of food supply chains, municipalities, open markets and catering services. A prevailing priority in the EU is to stimulate the transition towards a circular economy that fosters the promotion of sustainable and resource-efficient policies for long-term socio-economic and environmental benefits. Common practices for waste management include landfill disposal, anaerobic digestion, composting and wastewater treatment. Recently, new technologies have been introduced to produce value-added products from agricultural residues and food processing side streams. Integrated and holistic approaches for organic waste utilization as industrial feedstocks will boost the transition towards the bio-economy era. The establishment of circular economy would expand and diversify the market outlets of bio-based products. This review provides an overview of the current methods on waste and by-product streams bioconversion to develop biorefinery concepts.     

Pilot scale thermolysis of municipal solid waste: Combustibility of the products of the process and gas cleaning treatment of the combustion gases

This paper describes the process of thermolysis of the organic fraction of municipal solid waste in a pilot scale reactor and the results are compared with others obtained under laboratory conditions (semi-pilot scale). The aim of this study was to get the energetic valorisation of the products. Owing to the specific characteristics of the plant, two products were obtained from the process: gas and carbonized solid, no liquid fraction was obtained, so the gas fraction is a greater percentage made up both condensable and non-condensable compounds, while at the laboratory scale were obtained separately. The pilot plant was designed so that the gases produced by thermolysis were burnt continuously in a combustion chamber, while the carbonized fraction was fed in batches for co-combustion. To determining composition and combustibility a chromatographic analysis of the gas fraction was undertaken, the solid fraction also being subjected to analyses. The gas composition, rich in light hydrocarbons, and the carbon present in the carbonized fraction make possible the energetic valorisation of these products. The combustion gases were subjected to a cleaning process and their composition analysed twice: before and after the gas cleaning treatment. An energy production system based on the Rankine cycle is proposed. The study led to a positive assessment of the possible use of the process products as fuel, provided that the combustion gases are treated. The neutralization treatment used was seen to be effective in the cleaning of combustion gases. Electricity production yields would have to be raised by means of a co-generation process.     

Wastewater To Resource: Design of a Sustainable Phosphorus Recovery System

To enable a more sustainable wastewater treatment processes, a transition towards resource recovery methods that have minimal environmental impact while being financially viable is imperative. Phosphorus (P) is a finite resource that is being discharged into the aqueous environment in excessive quantities. As such, understanding the financial and environmental effectiveness of different approaches for removing and recovering P from wastewater streams is important to reduce the overall impact of wastewater treatment. In this study, a process-systems modelling framework for comprehensively evaluating these approaches in terms of both economic and environmental impacts is developed. Applying this framework, treatment pathways are designed, simulated and analysed to determine the most suitable approaches for P removal and recovery. The purpose of this methodology is not only to assist with plant design, but also to identify the principal economic and environmental factors acting as barriers to implementing a given technology, incorporating the impact of waste recovery. The results suggest that the chemical and ion-exchange approaches studied deliver sustainable advantages over biological pathways, both economically and environmentally, with each possessing different strengths. The assessment methodology developed enables a more rational and environmentally sound wastewater plant design approach to be taken.     

HNO3-H2O2反萃取-火焰原子吸收法测定高盐废水中的镉

为解决实际生产中高盐废水中镉的测定,将一定体积的高盐废水加硝酸、高氯酸于电热板消解,消解完全后用APDC(吡咯二硫代氨基甲铵)在pH=3.0条件下与样品中镉生成螯合物,再用四氯乙烯萃取高盐废水消解液中APDC与镉生成的螯合物,继而用硝酸-过氧化氢混合液将有机相中的镉反萃取至水相,最后后用火焰原子吸收光谱法在检测波长228.8nm处测定镉的含量。结果显示10%高盐废水样品5次测定的相对标准偏差为1.1%~5.6%,加标回收的回收率为95%~110%。     

The Perspective and Challenge of Nanomaterials in Oil and Gas Wastewater Treatment

Oil and gas wastewater refers to the waste stream produced in special production activities such as drilling and fracturing. This kind of wastewater has the following characteristics: high salinity, high chromaticity, toxic and harmful substances, poor biodegradability, and a difficulty to treat. Interestingly, nanomaterials show great potential in water treatment technology because of their small size, large surface area, and high surface energy. When nanotechnology is combined with membrane treatment materials, nanofiber membranes with a controllable pore size and high porosity can be prepared, which provides more possibilities for oil–water separation. In this review, the important applications of nanomaterials in wastewater treatment, including membrane separation technology and photocatalysis technology, are summarized. Membrane separation technology is mainly manifested in ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). It also focuses on the application of semiconductor photocatalysis technology induced by TiO₂ in the degradation of oil and gas wastewater. Finally, the development trends of nanomaterials in oil and gas wastewater treatment are prospected.     

Hydrothermal treatment of organic waste

The yield and properties of solid and liquid products of hydrothermal treatment of organic waste were determined with cheese, meat, and apples as an example. The solid products of hydrothermal treatment of cheese and apples have higher carbon content, lower oxygen content, and, correspondingly, higher heat of combustion compared to the initial biomass, which allows these products to be considered as a promising solid biofuel. The oils obtained in experiments with cheese and meat also have higher carbon content and higher heat of combustion compared to the initial substances, which allows these products to be considered as a promising liquid biofuel.     

Iron-based nanoparticles in wastewater treatment: A review on synthesis methods,applications, and removal mechanisms

Nanomaterial is an emerging material with potential technological impacts in various applications. It imposes great opportunities in various disciplines including wastewater remediation. Industrial wastewater is generated with anthropogenic activities and is the most environmental threat that needs remediation to overcome the environmental damages, thereby reducing human risks. Currently, several wastewater treatment techniques are applied and the utilization of nanomaterials for pollutant removal is an emerging technology. This is evident that the publication trends in the field of iron-based wastewater have been drastically increased. In this work, the overview of the preparation of iron-based nanoparticles, such as different polymorphs of iron-oxides, oxyhydroxides, iron hydroxide, and zero-valent iron nanoparticles are reviewed. In addition to the detailed discussion on the preparation of iron-based nanoparticles, their application on waste water treatment, removal mechanisms, advantages, and limitations are also assessed and discussed. Moreover, the iron-based nanoparticles' removal efficiency for specific pollutants and perspective in environmental remediation are also analyzed. Additionally, the advancements and future perspectives of iron-based nanoparticles are highlighted.