Fresh, Mechanical and Absorption Characteristics of Self-Consolidating Concretes Including Low Volume Waste PET Granules

This study evaluates the effect of waste polyethylene terephthalate (PET) granules on the fresh, mechanical and absorption characteristics of self-consolidating concretes (SCCs). Fine aggregates were replaced with different percentages (from 0% to 8%) of PET granules obtained by crushing waste PET bottles. The fresh properties of SCC containing PET granules were determined using slump flow and V-funnel flow time tests. Mechanical properties (compressive strength and splitting tensile strength tests) and absorption properties (sorptivity and water absorption tests) were evaluated. The results indicated that utilization of waste PET granules in production of SCC could be an effective way for recycling purpose. The maximum amount of PET replacement should be limited to 5%. Exceeding 5% of PET content may result in an increase of V-funnel flow time to overpass the limiting value, decrease in compressive strength, reduction in sorptivity and increase in the water absorption. The production of high performance SCC containing 5% PET granules satisfies all the requirements for SCC with satisfactory outputs

Benefits, challenges and success factors of water safety plan implementation: A review

Drinking water supply is a preeminent to public health, environmental protection, quality of life, economic activity, and sustainable development. Many disasters are being recorded due to poor water quality every day. In this case, it is essential to assure safe water demand through continuous enhancement and improvement of all practices and processes related to the water supply. The Water Safety Plan (WSP) concept has become a globally recognized and accepted approach to drinking water supply management and operation. This study aims at reviewing the WSP as a risk management approach and the implementation status around the world. In addition, the four success factors of WSP implementation are discussed. The benefits, difficulties, as well as recommendation from recent studies that implemented WSP is presented. The benefits include Improved operational efficiency, improved water quality, reduced consumers, reduced production cost and reduced potential hazardous incidents. However, the main difficulties for effective WSP implementation were lack of staff training, insufficient time and fund were the main challenges. According to a literature scan, the water utilities in Arab gulf region countries do not implement WSP, thus, the author encourages water utilities in these countries to conduct WSP to improve water quality management. © 2022 Global NEST

Punching Shear Characterization of Steel Fiber-Reinforced Concrete Flat Slabs

Punching shear failure in thin slabs under concentrated loads can cause shear stresses near columns. The use of steel fiber is a practical way to improve a slab-column connection's punching strength and deformation capacity. In this study, the capacity and behavior of steel fiber-reinforced concrete flat slabs are examined under punching shear force. Ten small-scale flat slabs were tested, eight of which had steel fiber and two without. Two parameters are studied in this paper, which are the fiber volume ratio (from 0% to 2%) and the stub column load shape (circle and square). The test results include the concrete compressive strength, crack patterns, punching shear, and load-defection behavior of the slabs. Based on the experimental results, it was found that the punching shear capacity of slabs with steel fiber (S5) increased by 21.8% compared to slabs without steel fiber (S1), and the slabs with steel fiber had more ductility compared to the slabs without fiber. Doi: 10.28991/HIJ-2022-03-04-08 Full Text: PD

Role of natural coagulants in the removal of heavy metals from different wastewaters: principal mechanisms, applications, challenges, and prospects

Industrial wastewater has become a great concern due to high concentrations of several hazardous contaminants, particularly heavy metals. Heavy metal contamination and its consequences for human health and the environment have gained interest in developing low-cost, long-term cleanup technologies. Biologically based wastewater treatment approaches being more effective than conventional treatment methods are getting more attention recently. Applying natural coagulants in wastewater treatments has progressively improved the coagulation-flocculation process efficiency. The main mechanism for heavy metals removal by coagulation is adsorption; therefore, natural coagulants perform better than chemical coagulants in heavy metals removal as natural coagulants contain biopolymers with active sites for heavy metals adsorption. This systematic review focuses on applying nature coagulants for heavy metals removal from different environmental systems. A systematic and comprehensive search for related articles on Web of Science, PubMed, and Scopus on the use of natural coagulant for heavy metal removal from wastewater was conducted up to May 2022. After examining, extracting and deleting duplicate records, 81 relevant articles containing data on types of natural coagulants, extraction methods of active compounds, mechanisms of metal removal by coagulation process, and the performance of natural coagulants for the removal of heavy metals have been reviewed. Their major findings with technical gaps and possible solutions are summarized. The review is novel as it summarizes the main findings of a series of previously published articles on the role of natural coagulants, particularly the removal of heavy metals. The review also identified gaps and research questions and suggested possible solutions for the successful practical application of natural coagulants in wastewater treatment. © 2022 Global NEST Printed in Greece. All rights reserved

Microplastic in the environment: identification, occurrencand mitigation measures

Microplastic is an emerging pollutant causing trouble worldwide due to its extensive distribution and potential hazards to the ecological system. Some fundamental questions about micro-plastics, such as their presence, source, and possible hazards, remain unanswered. These issues develop because of a lack of systematic and comprehensive microplastic analysis. As a result, we thoroughly evaluated current knowledge on microplastics, including detection, characterization, occurrence, source, and potential harm. Microplastics are found in seawater, soil, wetlands, and air matrices worldwide based on findings. Visual classification, which can be enhanced by com-bining it with additional tools, is one of the most used methods for identifying microplastics. As soon as is practicable, microplastics analytical methods ought to be standardized. New techniques for analyzing nano-plastics are urgently needed in the meantime. Numerous studies have shown that microplastics’ impacts on people and soil are significantly influenced by their size, shape, and surface physicochemical characteristics. Finally, this study suggests areas for future research based on the knowledge gaps in the area of microplastics. © 2022 Desalination Publications. All rights reserved

Biofuel production using cultivated algae: technologies, economics, and its environmental impacts

The process of looking for alternative energy sources is driven by the increasing demand for energy and environmental contamination caused by using fossil fuels. Recent investigations reported the efficiency of microalgae for biofuel production due to its low cost of production, high speed of growth, and ability to grow in harsh environments. In addition, many microalgae are photosynthetic, consuming CO2 and solar light to grow in biomass and providing a promising bioenergy source. This review presents the recent advances in the application of microalgae for biofuel production. In addition, cultivation and harvesting systems and environmental factors that affect microalgae cultivation for biofuel production have also been discussed. Moreover, lipid extraction and conversion technologies to biofuel are presented. The mixotrophic cultivation strategy is promising as it combines the advantages of heterotrophy and autotrophy. Green harvesting methods such as using bio-coagulants and flocculants are promising technologies to reduce the cost of microalgal biomass production. In the future, more investigations into co-cultivation systems, new green harvesting methods, high lipids extraction methods, and the optimization of lipid extraction and converting processes should be implemented to increase the sustainability of microalgae application for biofuel production

Thermal based remediation technologies for soil and groundwater: a review

Thermal remediation technologies are fast and effective tools for the remediation of contaminated soils and sediments. Nevertheless, the high energy consumption and the effect of high temperature on the soil properties may hinder the wide applications of thermal remediation methods. This review highlights the recent studies focused on thermal remediation. Eight types of thermal remediation processes are discussed, including incineration, thermal desorption, stream enhanced extraction, electrical resistance heating, microwave heating, smoldering, vitrification, and pyrol-ysis. In addition, the combination of thermal remediation with other remediation technologies is presented. Finally, thermal remediation sustainability is evaluated in terms of energy efficiency and their impact on soil properties. The developments of the past decade show that thermal-based technologies are quite effective in terms of contaminant removal but that these technologies are associated with high energy use and costs and can has an adverse impact on soil properties. Nonetheless, it is anticipated that continued research on thermally based technologies can increase their sustainability and expand their applications. Low temperature thermal desorption is a prom-ising remediation technology in terms of land use and energy cost as it has no adverse effect on soil function after treatment and low temperature is required. Overall, selecting the sustainable remediation technology depends on the contaminant properties, soil properties and predicted risk level. © 2022 Desalination Publications. All rights reserved

Jeopolimer Harcın Mukavemet Özellikleri Üzerine Deneysel Çalışma

This study investigates the effect of fly ash (FA) class F content and curing temperature on the compressive strength of Geopolymer Mortar (GPLM). GPLM is produced from FA mixed with the alkaline solution. The experimental test was performed on GPLM cubeswith curing temperature of 70, 90 and 110 °C with curing period of one day. The alkaline activator was a combination of 12M NaOHsolution with sodium silicate in the ratio of 1:2.5. The ratio of alkaline solution to binder equal to 0.50. Test results indicate that theincrement in the FA content increases the compressive strength of GPLM. The strength increases with the increase of curingtemperature of GPLM. Moreover, blended GPLM with high percentage of fly ash has less sorptivity.Bu çalışma, uçucu kül (FA) içeriğinin ve kür sıcaklığının Jeopolimer Harcın (GPLM) basınç dayanımı üzerindeki etkisiniaraştırmaktadır. GPLM, alkali çözelti ile karıştırılmış FA'dan üretilir. Deneysel test, bir günlük kürlenme süresi ile 70, 90 ve 110 ° Ckürleme sıcaklığı ile GPLM küpleri üzerinde gerçekleştirilmiştir. Alkalin aktivatör, 12M NaOH çözeltisinin 1: 2.5 oranında sodyumsilikat ile bir kombinasyonuydu. Alkali çözeltinin bağlayıcıya oranı 0,50'ye eşittir. Test sonuçları, FA içeriğindeki artışın GPLM'ninbasınç dayanımını artırdığını göstermektedir. GPLM'nin kürleme sıcaklığının artmasıyla mukavemet artar. Ayrıca, yüksek orandauçucu kül içeren harmanlanmış GPLM daha az sorptiviteye sahiptir