scholarly journals Enhanced Wastewater Treatment by Immobilized Enzymes

2021 ◽  
Author(s):  
Jakub Zdarta ◽  
Katarzyna Jankowska ◽  
Karolina Bachosz ◽  
Oliwia Degórska ◽  
Karolina Kaźmierczak ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Process Optimization ◽  
Organic Pollutants ◽  
Large Scale ◽  
Removal Rate ◽  
Immobilized Enzymes ◽  
Future Research ◽  
Process Conditions ◽  
Removal Rates ◽  
Catalytic Cycles

Abstract Purpose of Review In the presented review, we have summarized recent achievements on the use of immobilized oxidoreductases for biodegradation of hazardous organic pollutants including mainly dyes, pharmaceuticals, phenols, and bisphenols. In order to facilitate process optimization and achievement of high removal rates, effect of various process conditions on biodegradation has been highlighted and discussed. Recent Findings Current reports clearly show that immobilized oxidoreductases are capable of efficient conversion of organic pollutants, usually reaching over 90% of removal rate. Further, immobilized enzymes showed great recyclability potential, allowing their reuse in numerous of catalytic cycles. Summary Collected data clearly indicates immobilized oxidoreductases as an efficient biocatalytic tools for removal of hazardous phenolic compounds, making them a promising option for future water purification. Data shows, however, that both immobilization and biodegradation conditions affect conversion efficiency; therefore, process optimization is required to achieve high removal rates. Nevertheless, we have demonstrated future trends and highlighted several issues that have to be solved in the near-future research, to facilitate large-scale application of the immobilized oxidoreductases in wastewater treatment.

scholarly journals Principles and Characteristics of Different EDM Processes in Machining Tool and Die Steels

2020 ◽  
Vol 10 (6) ◽  
pp. 2082 ◽  
Author(s):  
Jaber E. Abu Qudeiri ◽  
Aiman Zaiout ◽  
Abdel-Hamid I. Mourad ◽  
Mustufa Haider Abidi ◽  
Ahmed Elkaseer
Keyword(s):  
Large Scale ◽  
Removal Rate ◽  
Surface Characteristics ◽  
Future Research ◽  
Process Conditions ◽  
Process Performance ◽  
Die Steels ◽  
Wide Range ◽  
Complex Shapes ◽  
Manufacturing Technologies

Electric discharge machining (EDM) is one of the most efficient manufacturing technologies used in highly accurate processing of all electrically conductive materials irrespective of their mechanical properties. It is a non-contact thermal energy process applied to a wide range of applications, such as in the aerospace, automotive, tools, molds and dies, and surgical implements, especially for the hard-to-cut materials with simple or complex shapes and geometries. Applications to molds, tools, and dies are among the large-scale initial applications of this process. Machining these items is especially difficult as they are made of hard-to-machine materials, they have very complex shapes of high accuracy, and their surface characteristics are sensitive to machining conditions. The review of this kind with an emphasis on tool and die materials is extremely useful to relevant professions, practitioners, and researchers. This review provides an overview of the studies related to EDM with regard to selection of the process, material, and operating parameters, the effect on responses, various process variants, and new techniques adopted to enhance process performance. This paper reviews research studies on the EDM of different grades of tool steel materials. This article (i) pans out the reported literature in a modular manner with a focus on experimental and theoretical studies aimed at improving process performance, including material removal rate, surface quality, and tool wear rate, among others, (ii) examines evaluation models and techniques used to determine process conditions, and (iii) discusses the developments in EDM and outlines the trends for future research. The conclusion section of the article carves out precise highlights and gaps from each section, thus making the article easy to navigate and extremely useful to the related research community.

scholarly journals Combined Application of UV Photolysis and Ozonation with Biological Aerating Filter in Tertiary Wastewater Treatment

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Zhaoqian Jing ◽  
Shiwei Cao
Keyword(s):  
Molecular Weight ◽  
Wastewater Treatment ◽  
Organic Pollutants ◽  
Wastewater Treatment Plants ◽  
Removal Rate ◽  
Oxygen Demand ◽  
Cod Removal ◽  
Secondary Effluent ◽  
Uv Photolysis ◽  
Combined Application

To enhance the biodegradability of residual organic pollutants in secondary effluent of wastewater treatment plants, UV photolysis and ozonation were used in combination as pretreatment before a biological aerating filter (BAF). The results indicated that UV photolysis could not remove much COD (chemical oxygen demand), and the performance of ozonation was better than the former. With UV photolysis combined with ozonation (UV/O3), COD removal was much higher than the sum of that with UV photolysis and ozonation alone, which indicated that UV photolysis could efficiently promote COD removal during ozonation. This pretreatment also improved molecular weight distribution (MWD) and biodegradability greatly. Proportion of organic compounds with molecular weight (MW) <3 kDalton was increased from 51.9% to 85.9%. COD removal rates with BAF and O3/BAF were only about 25% and 38%, respectively. When UV/O3oxidation was combined with BAF, the average COD removal rate reached above 61%, which was about 2.5 times of that with BAF alone. With influent COD ranging from 65 to 84 mg/L, the effluent COD was stably in the scope of 23–31 mg/L. The combination of UV/O3oxidation with BAF was quite efficient in organic pollutants removal for tertiary wastewater treatment.

Polyacrylamide Wastewater Treatment in a Nested Biofilm Airlift Suspension Reactor

2013 ◽  
Vol 864-867 ◽  
pp. 1608-1611
Author(s):  
Zhong Chen Yu ◽  
Dong Ma ◽  
Song Wang ◽  
Xue Jiao Zhang
Keyword(s):  
Wastewater Treatment ◽  
Oil Recovery ◽  
Large Scale ◽  
Produced Water ◽  
Removal Rate ◽  
Nitrate Removal ◽  
Ammonia Nitrogen ◽  
Walnut Shell ◽  
Biofilm Thickness ◽  
Tertiary Oil Recovery

Polyacrylamide has been widely used in tertiary oil recovery. Oilfield produced water in a large scale contain polyacrylamide, leading to oilfield environment pollution. In this paper, the nested loops biofilm airlift suspension reactor was used in polyacrylamide wastewater treatment. In the reactor, wastewater can alternately flow through the hypoxic environment fixed light carriers and aerobic environment suspended walnut shell biological carriers, achieving simultaneous removal of organic matter and nitrogen. The influencing factors on the organic compound degradation and denitrification performance were studied. Biological and hydrodynamic model of nitrogen and carbon removal was established. Also, the biological phase structure of the carrier biofilm was observed. The results show that polyacrylamide degradation and ammonia nitrogen removal rate are around 30% and 95%, respectively when the experimental hydraulic retention time is 24h. Due to poor denitrification efficiency; nitrate removal rate is only 20%. The carrier biofilm thickness is appropriate, and filamentous bacteria occupy the dominant position.

scholarly journals Carbon-Based Nanocomposites as Fenton-Like Catalysts in Wastewater Treatment Applications: A Review

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2643
Author(s):  
Ling Xin ◽  
Jiwei Hu ◽  
Yiqiu Xiang ◽  
Caifang Li ◽  
Liya Fu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Wastewater Treatment ◽  
Free Radicals ◽  
Organic Pollutants ◽  
Transition Metal Ions ◽  
Future Research ◽  
Hydroxyl Groups ◽  
Edge Structure ◽  
Transmission Electron

Advanced oxidation (e.g., fenton-like reagent oxidation and ozone oxidation) is a highly important technology that uses strong oxidizing free radicals to degrade organic pollutants and mineralize them. The fenton-like reactions have the characteristics of low cost, simple operation, thorough reaction and no secondary pollution. Fenton-like reagents refer to a strong oxidation system composed of transition metal ions (e.g., Fe3+, Mn2+ and Ag+) and oxidants (hydrogen peroxide, potassium persulfate, sodium persulfate, etc). Graphene and carbon nanotube possess a distinctive mechanical strength, flexibility, electrical and thermal conductivity and a very large specific surface area, which can work as an excellent carrier to disperse the catalyst and prevent its agglomeration. Fullerene can synergize with iron-based materials to promote the reaction of hydroxyl groups with organic pollutants and enhance the catalytic effect. Fenton-like catalysts influence the catalytic behavior by inducing electron transfer under strong interactions with the support. Due to the short lifespan of free radicals, the treatment effect is usually enhanced with the assistance of external conditions (ultraviolet and electric fields) to expand the application of fenton-like catalysts in water treatment. There are mainly light-fenton, electro-fenton and photoelectric-fenton methods. Fenton-like catalysts can be prepared by hydrothermal method, impregnation and coordination-precipitation approaches. The structures and properties of the catalysts are characterized by a variety of techniques, such as high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption near-edge structure spectroscopy. In this paper, we review the mechanisms, preparation methods, characterizations and applications status of fenton-like reagents in industrial wastewater treatment, and summarize the recycling of these catalysts and describe prospects for their future research directions.

Effect of Voltage on the Treatment of Cyanide Wastewater by Three-dimensional Electrode

2017 ◽  
Vol 20 (4) ◽  
pp. 151-159 ◽  
Author(s):  
Di Yao ◽  
Yonghui Song ◽  
Shan Zhang ◽  
Yuhong Tian ◽  
Xinzhe Lan
Keyword(s):  
Wastewater Treatment ◽  
Reaction Mechanism ◽  
Heavy Metal Ions ◽  
Electrode Materials ◽  
Removal Rate ◽  
Three Dimensional ◽  
Electrolytic Deposition ◽  
Removal Rates ◽  
Concentration Of Ions ◽  
Scanning Electron

The effects of applied voltage on cyanide wastewater treatment by three-dimensional electrodes were primarily examined. The main electrodes were produced from self-made coal-based electrode materials, and activated carbon was used as a particle electrode to treat cyanide wastewater. Changes in the concentration of ions in wastewater were determined and analyzed through Scanning Electron Microscopy and Energy Dispersive Spectroscopy. Results show that voltage significantly affects wastewater treatment via the three-dimensional electrodes. In particular, the removal rate of the ions in wastewater increases as voltage increases. The reaction mechanism of the three-dimensional electrodes also varies at different voltages. At 1 V, the reaction mechanism of the three-dimensional electrodes involves electro-adsorption. The removal rates of CNT, Cu, Zn, SCN−, and CN− in wastewater are 31.81%, 53.04%, 36.11%, 29.05%, and 29.05%, respectively. The reaction mechanism of the three-dimensional electrodes includes electro-adsorption and enrichment precipitation when voltage is increased to 2 V. The three-dimensional electrode plays a significant role in electrolytic deposition when voltage is further increased to 3 and 4 V. Cu, Zn, and other heavy metal ions are reduced on the cathode and on the particle electrode surface, and the removal rates of CNT, Cu, Zn, SCN−, and CN− in wastewater are 93.94%, 95.22%, 97.23%, 99.38%, and 94.93%, respectively.

Efficiency of removal of nitrogen, phosphorus, and zinc from domestic wastewater by a constructed wetland system in rural areas: a case study

2008 ◽  
Vol 58 (12) ◽  
pp. 2427-2433 ◽  
Author(s):  
Kaoru Abe ◽  
Michio Komada ◽  
Akihito Ookuma
Keyword(s):  
Wastewater Treatment ◽  
Constructed Wetland ◽  
Rural Areas ◽  
Removal Rate ◽  
Domestic Wastewater ◽  
Removal Rates ◽  
Total N ◽  
Household Wastewater ◽  
Percentage Removal ◽  
Total P

The effluent from the combined household wastewater treatment facilities used in unsewered areas of Japan is generally high in nitrogen (N) and phosphorus (P). In Japan, environmental quality standards for zinc (Zn) pollution were enacted recently because of the toxicity of Zn to aquatic ecosystems. In 2004 a fallow paddy field at the Koibuchi College of Agriculture and Nutrition was converted into a surface-water-flow constructed wetland (500 m2) to clean the effluent from the combined household wastewater treatment facility of a dormitory (100 residents) before discharge to a pond. We evaluated N and P removal efficiencies and the fate of soluble Zn in the wetland from April 2006 to March 2007. Wetland influent contained an average of 18.3 mg L−1 total N and 1.86 mg L−1 total P. In the effluent from the wetland, average total N concentration was 10.3 mg L−1 and average total P was 0.90 mg L−1. Average removal rates were 0.37 g m−2 d−1 for total N and 0.050 g m−2 d−1 for total P (percentage removal rates of 40% and 48%, respectively). Soluble Zn concentration decreased from 0.041 in the influent to 0.023 mg L−1 after passing through the wetland. The average Zn removal rate during the year was 0.0007 g m−2 d−1 (percentage removal rate 37%).

Removal of selected non-steroidal anti-inflammatory drugs (NSAIDs), gemfibrozil, carbamazepine, b-blockers, trimethoprim and triclosan in conventional wastewater treatment plants in five EU countries and their discharge to the aquatic environment

2004 ◽  
Vol 50 (5) ◽  
pp. 253-260 ◽  
Author(s):  
N. Paxéus
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Aquatic Environment ◽  
Wastewater Treatment Plants ◽  
Removal Rate ◽  
Average Concentration ◽  
Operating Conditions ◽  
Removal Rates ◽  
Eu Countries ◽  
Acidic Drugs

The removal of commonly used pharmaceuticals (ibuprofen, naproxen, diclofenac, gemfibrozil, carbamazepine, atenolol, metoprolol and trimethoprim) and a biocide (triclosan) in operating wastewater treatment plants in five EU countries has been studied. Under normal operating conditions the acidic drugs and triclosan were partially removed with removal rates varying from ca. 20 to &gt;95%. The highest removal rate was found for ibuprofen and triclosan (&gt;90%) followed by naproxen (80%), gemfibrozil (55%) and diclofenac (39%). Ibuprofen undergoes an oxidative transformation to corresponding hydroxy- and carboxy- metabolites, which contributes to its high removal rate. Disturbances in the activated sludge process resulted in lower removal rates for all acidic drugs, mostly for diclofenac (&lt;10% removed) but also for ibuprofen (&lt;60% removed). The treatment of wastewaters by activated sludge usually did not result in any practical removal (&lt;10%) of neutral carbamazepine or basic atenolol, metoprolol and trimethoprim. The removal rates of the investigated drugs and triclosan are discussed in terms of mechanisms responsible for their removal. Discharges of carbamazepine, diclofenac, gemfibrozil, naproxen, triclosan and trimethoprim from WWTPs to the aquatic environment, expressed as the average concentration in the effluent and the daily discharged quantity per person served by WWTPs were assessed.

scholarly journals Advanced Electric Discharge Machining of Stainless Steels: Assessment of the State of the Art, Gaps and Future Prospect

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 907 ◽  
Author(s):  
Jaber Abu Qudeiri ◽  
Ahmad Saleh ◽  
Aiman Ziout ◽  
Abdel-Hamid Mourad ◽  
Mustufa Abidi ◽  
...  
Keyword(s):  
Electric Discharge ◽  
Material Removal ◽  
Removal Rate ◽  
Future Research ◽  
Process Conditions ◽  
Process Performance ◽  
Electric Discharge Machining ◽  
Electrically Conductive ◽  
Complex Shapes ◽  
Efficient Manufacturing

Electric discharge machining (EDM) is a material removal process that is especially useful for difficult-to-cut materials with complex shapes and is widely used in aerospace, automotive, surgical tools among other fields. EDM is one of the most efficient manufacturing processes and is used to achieve highly accurate production. It is a non-contact thermal energy process used to machine electrically conductive components irrespective of the material’s mechanical properties. Studies related to the EDM have shown that the process performance can be considerably improved by properly selecting the process material and operating parameters. This paper reviews research studies on the application of EDM to different grades of stainless steel materials and describes experimental and theoretical studies of EDM that have attempted to improve the process performance, by considering material removal rate, surface quality and tool wear rate, amongst others. In addition, this paper examines evaluation models and techniques used to determine the EDM process conditions. This review also presents a discussion on developments in EDM and outlines the likely trend for future research.

Poly-Silicon Wet Removal for Replacement Gate Integration Scheme: Impact of Process Parameters on the Removal Rate

2012 ◽  
Vol 187 ◽  
pp. 53-56 ◽  
Author(s):  
Farid Sebaai ◽  
Anabela Veloso ◽  
Martine Claes ◽  
Katia Devriendt ◽  
Stephan Brus ◽  
...  
Keyword(s):  
Process Optimization ◽  
Process Integration ◽  
Removal Rate ◽  
Integration Scheme ◽  
Process Conditions ◽  
Poly Silicon ◽  
Dummy Gate ◽  
The Impact ◽  
Suitable Process ◽  
Wet Removal

We report in this work some process optimization effort in performing poly silicon removal for replacement gate process integration. Successful wet poly silicon removal after dummy gate patterning is not only conditioned by suitable process conditions during wet removal but is also impacted by process steps prior to gate removal A thorough evaluation of the impact on poly removal from dopants or contaminants introduced in the poly silicon by previous processing is done, resulting in an optimized integration flow with successful poly removal. This work also shows that use of diluted TMAH chemistry instead of diluted ammonia in performing poly silicon removal provides better ability in removing poly silicon especially in narrow gate structures.

Electron microscopy study of reactively sputter-deposited Ti/N films on silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1362-1363
Author(s):  
V. C. Kannan ◽  
A. K. Singh ◽  
R. B. Irwin ◽  
S. Chittipeddi ◽  
F. D. Nkansah ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Large Scale ◽  
Hexagonal Phase ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Process Conditions ◽  
Tin Films ◽  
Wide Range ◽  
Fcc Phase ◽  
Circuits Vlsi

Titanium nitride (TiN) films have historically been used as diffusion barrier between silicon and aluminum, as an adhesion layer for tungsten deposition and as an interconnect material etc. Recently, the role of TiN films as contact barriers in very large scale silicon integrated circuits (VLSI) has been extensively studied. TiN films have resistivities on the order of 20μ Ω-cm which is much lower than that of titanium (nearly 66μ Ω-cm). Deposited TiN films show resistivities which vary from 20 to 100μ Ω-cm depending upon the type of deposition and process conditions. TiNx is known to have a NaCl type crystal structure for a wide range of compositions. Change in color from metallic luster to gold reflects the stabilization of the TiNx (FCC) phase over the close packed Ti(N) hexagonal phase. It was found that TiN (1:1) ideal composition with the FCC (NaCl-type) structure gives the best electrical property.

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