Showing papers in "International Journal of Environmental Science and Technology in 2018"

Biosorption of Cd(II) from synthetic wastewater using dry biofilms from biotrickling filters

Abstract: Biofilms wasted from biotrickling filters was dried and used as biosorbent for Cd(II) removal from aqueous solutions. The adsorption condition and effect, adsorption isotherms and kinetics of Cd(II) removal were investigated, and the effects of competitive metal ions on Cd(II) removal were also examined. Results showed that the dry waste biofilms reached the maximum adsorption capacity of 42 mg/g of Cd(II) at 25 °C for 120 min when the initial concentration of Cd(II) and their pH were 50 mg/L and 6.0, respectively. Under these conditions, the removal efficiency of Cd(II) reached to 89.3% when the biosorbent dosage was 2.0 g/L. The Langmuir isotherm model correlated with the isotherm data better than the Freundlich isotherm model, and the pseudo-second-order model fitted the kinetic data better than the pseudo-first-order model. These results indicated that the adsorption was monolayer accompanied with chemical adsorption. In the presence of other metal ions, divalent metal ions of Ca and Zn inhibited the performance of Cd(II) biosorption significantly, while Na(I), K(I) and Fe(III) which had a higher or lower valence than Ca(II) affected slightly when containing 50 mg/L Cd(II), 0.5 g/L adsorbent dosage and pH 6.0. The analyses of scanning electron microscopy and Fourier transform infrared spectroscopy illuminated that the biosorbent had porous structures and the amide group was the majorly responsible for Cd(II) removal. Dry biofilms were novel sorbents for effective removal Cd(II), and it could be reused and recycled if necessary.

Inoculum -free start-up of biofilm- and sludge-based deammonification systems in pilot scale

Abstract: Undiluted reject water from the dewatering of anaerobic sludge with an average total nitrogen content of 718 ± 117 mg L−1 (n = 63) was used to start-up autotrophic nitrogen removal in three different pilot-scale (3 m3) deammonification configurations: (1) biofilm; (2) activated sludge sequence batch; and (3) two-staged (nitritation–anammox). Time- and concentration-based aeration control with alternating aerobic/anaerobic phases was applied for all reactor configurations. All reactors were initiated without anammox-specific inoculum, and biofilm was grown onto blank carriers. During the initial start-up period, biological nitrogen removal was found to be inhibited by an excessive free ammonia content (>10 mg-N L−1), resulting from the use of high-strength reject water as the process feed. After implementation of free ammonia control by pH adjustment to 6.5–7.5, propagation of the deammonification process was observed with increased nitrogen removal with slight accumulation of NO3 −–N. The highest total nitrogen removal rates were achieved with the single-reactor biofilm- and sludge-based deammonification processes (1.04 and 0.30 kg-N m−3 day−1, respectively). The critical factors for successful start-up and stable operation of deammonification reactors turned out to be control of pH below 7.5, dissolved oxygen at 0.3–0.8 mg-O2 L−1 and influent solids values below 1000 nephelometric turbidity units. Microbial analysis demonstrated that highest anammox enrichment was achieved in the biofilm reactor (9.40 × 108 copies g−1 total suspended solids). These data demonstrate the potential of an in-situ grown sludge- or biofilm-based concept for the development and propagation of deammonification process.

A review of permeable reactive barrier as passive sustainable technology for groundwater remediation

Abstract: The pollution of groundwater by organic or inorganic pollutants, originating from either soil leaching or anthropogenic activities, is one of the major environmental issues. Remediation of this water source is of highest priority because many countries use it for drinking purpose. Pump-and-treat method is represented for many decades the major technique to treat groundwater infected with organic/inorganic pollutants. In last two decades, this technique becomes to be in lack with the sense of modern concepts of sustainability and renewable energy. Permeable reactive barriers (PRBs) technology was introduced as an alternative method for traditional pump-and-treat systems to remediate contaminated groundwater that was achieving these concepts. Within this issue, this technology has been proven to be a successful and most efficient promising method used by many researchers and in several projects due to its direct and simple techniques to remediate groundwater. A rapid progress from bench scale to field scale implementation in the PRB technique is recognized through the last few years. In addition, this technique was modeled theoretically for characterizing the migration of contaminants spatially and temporally through the barrier and, consequently, these models can be used for estimating the longevity of this barrier. An overview of this technique and the promising horizons for scientific research that integrates this method with sustainability and green technology practices are presented in the present study.

Synthesis and nutrient release patterns of a biochar-based N–P–K slow-release fertilizer

Abstract: Biochar has excellent solute adsorption capacity, yet few studies have investigated its application as a nutrient carrier in the development of slow-release fertilizers. The current study developed a biochar-based N–P–K fertilizer (BSRF) and evaluated its nutrient release patterns relative to a conventional fertilizer. SEM and EDX analyses confirmed the coarse and highly porous microstructure of the biochar (SBC) that enabled it to effectively sorb NO3 −, PO4 3−, and K+ and form a nutrient-impregnated BSRF. BSRF had lower NO3 −, PO4 3−, and K+ release than the conventional chemical fertilizer, demonstrating its low release behavior. BSRF-amended sandy soil had higher water retention capacity than that amended with a conventional chemical fertilizer. BSRF has potential to reduce nutrient leaching, improve water retention, and hence increase crop nutrient and water use efficiencies. Future research should focus on understanding nutrient release mechanisms, synchronization of nutrient release with plant uptake, and applications of the BSRF in environmental remediation.

Enhancement of photocatalytic activity of titanium dioxide using non-metal doping methods under visible light: a review

Abstract: Titanium dioxide (TiO2) is an efficient photocatalyst for removing organics in photocatalytic wastewater treatment, but its low photoactivity limits its practical applications in a visible-light-driven chemical reaction. Many efforts have been made in the activation of the visible light absorption property on TiO2 photocatalyst. In this paper, a thorough review of current non-metal doping methods of TiO2 to improve photocatalyst activation under visible light is presented. The focus of this study is on doping non-metals onto TiO2 by several methods to enhance its visible light photoactivity. Besides, the resultant characteristics of the chemical structure, physical structure, and optical properties of the doped photocatalysts are discussed. This review enables a better understanding of current advantages and disadvantages that can arise during the production of non-metal-doped TiO2 and its applications. The annealing and hydrothermal methods are found to be more efficient in preparing doped photocatalysts with respect to time and costs. When choosing between these two approaches, the hydrothermal method can be applied using a variety of precursors, whereas the annealing methods are restricted only to solid form precursors. Thus, the hydrothermal method is a more favorable method of non-metal doping of TiO2. However, studies should focus on the effects of different factors involved in each synthesis/preparation method to determine optimal preparation conditions.

Degradation of traditional and new emerging pesticides in water by nanomaterials: recent trends and future recommendations

Abstract: Rapid industrialization and extensive use of pesticides in agriculture practices have contributed to the leaking of pesticide residues into water. Among them, organochlorines are highly toxic with half-lives of many years followed by organophosphates (OPs). Being banned in many countries, most of the pesticides are still persisting in the environment. Due to high perseverance, toxicity and potential to bioaccumulation, their removal is imperative. In this direction, conventional adsorbents such as commercial activated carbon, agricultural and natural waste were highly employed. In modern era, nanomaterials (including nanocomposites and nanobiocomposite) with high surface area come out as most economic, rapid and effective catalyst. TiO2 (photocatalyst) and Fe0 by itself or with oxidizing agents are playing a promising role in elimination of pesticide pollution and open the opportunities for exploring other nanoparticles as well. Further, their modified, doped or composites form showed enhanced characteristics due to introduction of new energy levels or increase in surface area. In contrast to TiO2 and Fe0, various nanostructured metal oxides found to degrade OP pesticides by rapid reactive adsorption followed by cleavage of P–O bond via SN2 mechanism. The present review focuses on the present status of pesticide removal using nanoparticles through adsorption together with photocatalytic or redox or reactive degradation. Herein, detailed information on several pesticides, problems related to pesticide, their metabolites, environmental concentration and need for degradation has been presented. In addition, importance of green synthesized nanoparticles along with limitation and potential health risk of nanomaterials in degradation of various organic pollutants has been highlighted.

Analysis of 100% renewable energy for Iran in 2030: integrating solar PV, wind energy and storage

Abstract: The devastating effects of fossil fuels on the environment, limited natural sources and increasing demand for energy across the world make renewable energy sources more important than in the past. The 2015 United Nations Climate Change Conference resulted in a global agreement on net zero CO2 emissions shortly after the middle of the twenty-first century, which will lead to a collapse of fossil fuel demand. The focus of the study is to define a cost optimal 100% renewable energy system in Iran by 2030 using an hourly resolution model. The optimal sets of renewable energy technologies, least-cost energy supply, mix of capacities and operation modes were calculated and the role of storage technologies was examined. Two scenarios have been evaluated in this study: a country-wide scenario and an integrated scenario. In the country-wide scenario, renewable energy generation and energy storage technologies cover the country’s power sector electricity demand. In the integrated scenario, the renewable energy generated was able to fulfil both the electricity demand of the power sector and the substantial electricity demand for water desalination and synthesis of industrial gas. By adding sector integration, the total levelized cost of electricity decreased from 45.3 to 40.3 €/MWh. The levelized cost of electricity of 40.3 €/MWh in the integrated scenario is quite cost-effective and beneficial in comparison with other low-carbon but high-cost alternatives such as carbon capture and storage and nuclear energy. A 100% renewable energy system for Iran is found to be a real policy option.

Prediction of an environmental issue of mine blasting: an imperialistic competitive algorithm-based fuzzy system

Abstract: Ground vibration resulting from blasting is one of the most important environmental problems at open-cast mines. Therefore, accurately approximating the blast-induced ground vibration is very significant. By reviewing the previous investigations, many attempts have been done to create the empirical models for estimating ground vibration. Nevertheless, the performance of the empirical models is not good enough. In this research work, a new hybrid model of fuzzy system (FS) designed by imperialistic competitive algorithm (ICA) is proposed for approximating ground vibration resulting from blasting at Miduk copper mine, Iran. For comparison aims, various empirical models were also utilized. Results from different predictor models were compared by using coefficient of multiple determination (R 2), variance account for and root-mean-square error between measured and predicted values of the PPVs. Results prove that the FS–ICA model outperforms the other empirical models in terms of the prediction accuracy. In other words, the FS–ICA model with R 2 of 0.942 can forecast PPV better than the USBM with R 2 of 0.634, Ambraseys–Hendron with R 2 of 0.638, Langefors–Kihlstrom with R 2 of 0.637 and Indian Standard with R 2 of 0.519.

Anaerobic digestion process: technological aspects and recent developments

Abstract: The technology of anaerobic digestion allows the use of biodegradable waste for energy production by breaking down organic matter through a series of biochemical reactions. Such process generates biogas (productivity of 0.45 Nm3/KgSV), which can be used as energy source in industrial activities or as fuel for automotive vehicles. Anaerobic digestion is an economically viable and environmentally friendly process since it makes possible obtaining clean energy at a low cost and without generating greenhouse gases. Searching for clean energy sources has been the target of scientists worldwide, and this technology has excelled on the basis of efficiency in organic matter conversion into biogas (yield in the range of 0.7–2.0 kWh/m3), considered energy carriers for the future. This paper gives an overview of the technology of anaerobic digestion of food waste, describing the metabolism and microorganisms involved in this process, as well as the operational factors that affect it such as temperature, pH, organic loading, moisture, C/N ratio, and co-digestion. The types of reactors that can be used, the methane production, and the most recent developments in this area are also presented and discussed.

Spatial prediction of wildfire probability in the Hyrcanian ecoregion using evidential belief function model and GIS

Abstract: Accurate estimates of wildfire probability and production of distribution maps are the first important steps in wildfire management and risk assessment. In this study, geographical information system (GIS)-automated techniques were integrated with the quantitative data-driven evidential belief function (EBF) model to predict spatial pattern of wildfire probability in a part of the Hyrcanian ecoregion, northern Iran. The historical fire events were identified using earlier reports and MODIS hot spot product as well as by carrying out multiple field surveys. Using the GIS-based EBF model, the relationships among existing fire events and various predictor variables predisposing fire ignition were analyzed. Model results were used to produce a distribution map of wildfire probability. The derived probability map revealed that zones of moderate, high, and very high probability covered nearly 60% of the landscape. Further, the probability map clearly demonstrated that the probability of a fire was strongly dependent upon human infrastructure and associated activities. By comparing the probability map and the historical fire events, a satisfactory spatial agreement between the five probability levels and fire density was observed. The probability map was further validated by receiver operating characteristic using both success rate and prediction rate curves. The validation results confirmed the effectiveness of the GIS-based EBF model that achieved AUC values of 84.14 and 81.03% for success and prediction rates, respectively.

Adsorptive removal of eight heavy metals from aqueous solution by unmodified and modified agricultural waste: tangerine peel

Abstract: Analysis was carried out using tangerine peel aiming its use as a potential adsorbent of eight heavy metal ions (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) from aqueous solution. This agricultural waste was tested both in its untreated and also chemically modified form. Based on Fourier transformation infrared spectra, a comparison of biosorbent structure before and after chemical treatment was made. Batch adsorption tests were conducted at different pH and mass of sorbent to examine the influence on the effectiveness of simultaneous removal of tested ions. Kinetic studies were conducted at optimum pH 5.0 and sorbent dosage 300 mg. The pseudo-second-order kinetic model best fit the experimental data with high correlation coefficients (r2 > 0.9997). By optimizing listed parameters, high removal efficiencies (> 89%) were achieved. According to the results obtained in this study, the remediation of water polluted with heavy metals could be done using modified tangerine peel as an agricultural waste material.

A review on mechanism and future perspectives of cadmium-resistant bacteria

Abstract: Since the last few decades, cadmium anthropocentric sources have been increased drastically. Various chemical and physical approaches for cadmium remediation have been proposed, but these techniques are quite expensive, not healthy for the environment and not efficient at the low concentration of cadmium. Thus, in the last few years, the cadmium removal by biological approaches has received a great interest. Many bacteria can resist against high concentration of cadmium through different mechanisms. The cadmium-resistant bacteria can be grouped into three levels. The main group consists of bacteria which efflux the cadmium from the cells. The bacteria of the other two groups are capable of detoxifying or binding cadmium. The cadA and cadB gene systems are involved in efflux mechanism, and these encode different efflux pump proteins, while the functional groups such as amine, carboxyl, phosphate and hydroxyl facilitate cadmium binding to bacterial surface such as chemisorption. Many enzymes are involved in the detoxifying the cadmium and make the membrane impermeable against cadmium. This paper also reviews the industrial application of cadmium-resistant bacteria and the future perspectives of genetic engineering, bioelectrochemical system, microbial aggregates and biosorption of cadmium by algae.

Removal of ibuprofen from aqueous solution by functionalized strong nano-clay composite adsorbent: kinetic and equilibrium isotherm studies

Abstract: The functionalized nano-clay composite adsorbent was prepared, and its properties were characterized using FT-IR, XRD and SEM techniques. The synthesized nano-clay composite was studied with regard to its capacity to remove ibuprofen under different adsorption conditions such as varying pH levels (5–9), initial ibuprofen concentrations (3, 5 and 10 mg L−1), contact time, and the amount of adsorbent (0.125, 0.25, 0.5 and 1 g). In order to evaluate the nanocomposite adsorption capacity, the adsorption results were assessed using nine isotherm models. The results showed that the optimum adsorption pH was 6 and that an increase or decrease in the pH reduced the adsorption capacity. The adsorption process was fast and reached equilibrium after 120 min. The maximum efficacy of ibuprofen removal was approximately 95.2%, with 1 g of adsorbent, 10 mg L−1 initial concentration of ibuprofen, 120 min contact time and pH = 6. The optimal adsorption isotherm models were the Freundlich, Fritz–Schlunder, Redlich–Peterson, Radke–Prausnitz, Sip, Toth and Khan models. In addition, four adsorption kinetic models were employed for adsorption system evaluation under a variety of experimental conditions. The kinetic data illustrated that the process is very fast, and the reaction followed the Elovich kinetic model. Therefore, this nano-clay composite can be used as an effective adsorbent for the removal of ibuprofen from aqueous solutions, such as water and wastewater.

Impact of a Jet A-1/HEFA blend on the performance and emission characteristics of a miniature turbojet engine

Abstract: It is forecast that in the future, alternative fuels derived from non-petroleum sources will become the basic propellant for turbine aircraft engines. Currently, five types of aviation turbine fuel containing synthesized hydrocarbons are certified and accepted, and allow adding a maximum of 50% of synthetic component to conventional fuel. The experimental performance and the emission characteristics of a turbojet engine were investigated in this paper. The studies were conducted with the use of a miniature turbojet engine, which is the main component of a laboratory test rig. The test rig is an interesting solution for engine research, due to the fact that studies concerning full-scale aircraft engines are very complex and expensive. The literature of the subject contains many papers using small-scale turbojet engines for testing alternative fuels. However, most of them concern components of fuels, e.g. biodiesel, butanol, which do not have direct application in aviation. Two different fuel samples, a conventional Jet A-1 fuel and a blend of 48% synthesized paraffinic kerosene from hydroprocessed esters and fatty acids process with Jet A-1 were tested. This process is one of the routes of producing alternative fuel for aviation, approved by ASTM standard. The test rig studies were performed according to a specific profile of engine test, which models different modes of a turbojet engine’s operation. The obtained results are compared in relation to the results for neat Jet A-1 fuel and then discussed.

Simultaneous detection and removal of cobalt ions from aqueous solution by modified chitosan beads

Abstract: In this paper, we modified chitosan beads in order to simultaneously detect and adsorb Co2+ from aqueous solution. Firstly, 4-(5-chloro-2-pyridylazo)-1,3-phenylenediamine (5-Cl-PADAB) was used as selective probe for Co2+ with color changing from yellow to pink, and the UV–Vis spectra showed that the λ max changed from 439 to 504 nm. Then a novel biomaterial was synthesized with 5-Cl-PADAB (metal indicator), chitosan (biosorbent) and EDTA anhydride (cross-linker and chelating agent). The analysis of Fourier transform infrared and energy-dispersive X-ray spectra proved that 5-Cl-PADAB and EDTA were successfully connected to chitosan. The modified chitosan bead was selective probe for Co2+ with a remarkable color change from white to pink, and the UV–Vis spectra showed that the λ max changed from 441 to 459 nm. The adsorption of cobalt ions onto the modified chitosan beads followed pseudo-second-order (R 2 = 0.99) kinetics and the Langmuir isotherm model (R 2 = 0.80). Comparing with chitosan beads, the q e of the modified one increased from 2.00 to 7.97 mg/g. The modified chitosan beads are promising biomaterial for simultaneous detection and removal of Co2+ from aqueous solution.

Assessment of atmospheric particulate matter and heavy metals: a critical review.

Abstract: This paper gives detailed comprehensive review of atmospheric assessment of particulate matter and heavy metals. Previous research works executed on this subject matter in the past four decades were adequately scrutinized. Various equipments for assessing atmospheric particulate matter and heavy metals were presented. Mathematical modeling equations for source apportionment and characterization, deposition rate prediction and health risk characterization of PM10 were also presented. However, the following conclusions were made: (1) there is need for improvement on the mathematical models by reducing the number of assumptions made in developing them. (2) Comparative analysis of concentrations of heavy metals in the atmosphere under the same environment for different methodologies should be executed for accuracy purposes. (3) Cost implication of assessing, monitoring and controlling these unfriendly substances should be examined, and hence, involvement of cost engineers may be of immense help. (4) Further research works should be done on Air-Q 2.2.3 model currently identified as a new methodology for provision of quantitative data on the impact of particulate matter exposure on the health of people. (5) Compliance monitoring networks should be designed to ease data collection for the observables, locations and time periods that allowed receptor models to be applied. (6) There is need for much more research works that enable optimal control and regulation of emission of heavy metals into the atmosphere in order to reduce health effects of these inhalable substances.

Comparative analysis of exhaust emissions caused by chainsaws with soft computing and statistical approaches

Abstract: This research compares the nitrogen monoxide and methane exhaust emissions produced by the engines of two conventional chainsaws (a professional and an amateur one) to those produced by a catalytic. For all the three types of chainsaws, measurements were taken under the following three different functional modes: (a) normal conditions with respect to infrequent acceleration, (b) normal conditions, (c) use of high-quality motor oil with a clean filter. The experiment was extended much further by considering measurements of nitrogen monoxide and methane concentrations for all the three types of chainsaws, in respect to four additional operation forms. More specifically, the emissions were measured (a) under normal conditions, (b) under the application of frequent acceleration, (c) with the use of poor-quality motor oil and (d) with chainsaws using impure filters. The experiments and data collection were performed in the forest under “real conditions.” Measurements conducted under real conditions were named “control” measurements and were used for future comparisons. The authors used a portable analyzer (Drager X-am 5000 a Drager Sensor XXSNO and a CatEx 125 PRCH 4 ) for the measurement of exhaust emissions. The said analyzer can measure the concentrations of exhaust gas components online, while the engine is running under field conditions. In this paper, we have been employed fuzzy sets and fuzzy Chi-square tests in order to model air pollution produced by each type of chainsaw under each type of operation condition. The overall conclusion is that the catalytic chainsaw is the most environmentally friendly.

Kinetic and equilibrium studies on the removal of 14C-ethion residues from wastewater by copper-based metal–organic framework

Abstract: There are compelling economic and environmental reasons to remove pesticides from wastewater because they are toxic and carcinogenic. The effectiveness of copper-based metal–organic framework (Cu-BTC) for adsorbing the insecticide ¹⁴C-ethion from wastewater has been studied as function of contact time, adsorbent dosage, temperature and pH. ¹⁴C-ethion/Cu-BTC isotherms exhibit two plateaus (BET type IV) and are reliably represented by Brunauer–Deming–Deming–Teller and Zhu–Gu models, with deviations of only 1.99 and 3.95%, respectively. The removal curve measured under batch operation is well represented by a pseudo-first-order equation, yielding results equivalent to the theoretical linear driving force model of Glueckauf. At pH 7, 75 mg L⁻¹ ethion concentration, 150 min, 25 °C and 0.425 g L⁻¹ Cu-BTC dose, the sorbent capacity is ca. 122 mg g⁻¹. Moreover, Cu-BTC has a good stability after six adsorptions cycles. Finally, our results disclose the fundamental understanding of the adsorption mechanism: the ethion molecule coordinates to two copper(II) atoms across the metal–organic framework channel via the phosphoryl (P–O) group.

Advanced technologies for the treatment of wastewaters from agro-processing industries and cogeneration of by-products: a case of slaughterhouse, dairy and beverage industries

Abstract: Agro-industrial wastewaters are known by high strength of organic pollutants that cause an adverse effect on the water bodies. Wastewater management becomes a major task, leads environmental regulations to be stricter worldwide. Increased disposal of untreated/partially treated industrial wastewaters are major environmental problems in Ethiopia. In Ethiopia, industries most commonly dispose their untreated wastewater straight into the nearby rivers. Somewhat, constructed wetlands are used by some industries for treatment of wastewaters. The objective of this review paper was to summarize the characteristics and recent research efforts done on anaerobic treatment of some selected agro-industrial wastewaters and innovative technologies used for cogeneration of byproducts. Many developed countries designed cost effective approaches for agro-industrial wastewater management. The full-scale anaerobic treatment system in China generates 40,000 m3 biogas daily for 20,000 households from agro-industrial wastes. Likewise, the Brewery, Addis Ababa, Ethiopia used full-scale anaerobic treatment technology and produce average methane yield of 487 Nm3/day. The estimated maximum methane production potential of Kera, Luna slaughterhouses, and Ada milk factory were 4.5599LCH4, 0.1878LCH4, and 0.9952LCH4, respectively. These indicate that they can be potential sources of biogas production. Limitations of the brewery are burning of the produced energy and some quantified parameters being become above national standards while meat processing and diary industries are discharging their wastewater without treatment into the rivers. We devised the brewery to use the produced energy properly and extend its treatment to achieve the national standards using integrated sequencing batch reactor. Similarly, slaughterhouse and diary industries should install anaerobic–aerobic integrated treatment techniques.

Microalgae: a potential tool for remediating aquatic environments from toxic metals

Abstract: In the last few years, due to vigorous expansion of industrialization, toxic metals appear to be in excessive levels in the environment. Ecosystems are now severely threatened by such widespread pollutants. Current reviews show that technologies that are used to remediate infected areas appear to have low efficiency, and this has brought on the need for further investigation. Among biological and non-biological methods which have been proposed for removing such pollutants from the environment, phycoremediation seems to be advantageous. Until recently, many microorganisms (such as fungi, bacteria and waste biomass) have been studied for their ability to remove toxic metals from the aqueous environment. In this review, it is shown that in particular, microalgae have received great attention lately, because of their ability to bind essential quantities of these pollutants. Phycoremediation involves the process of biosorption and bioaccumulation, both of which take part in the metal sequestration. A detailed description of either mechanism with respect to the parameters affecting them is reviewed in this work.

Population structures shift during the biodegradation of crude and fuel oil by an indigenous consortium

Abstract: Petroleum and fuel oil are complex mixtures of recalcitrant hydrocarbons. The biodegradation of these hydrocarbons needs the action of a vast variety of enzymatic capacities. A microbial consortium offers the capability to degrade complex substrates through the assembly of different biochemical reactions, providing a metabolic versatility superior to axenic cultures. In this work, the microbial population dynamics, taxonomy, and the catabolic capacity of a stabilized consortium exposed to fuel and crude oil was analyzed through metagenomics. The stabilized consortium degraded 59% of crude oil components after 8 days, and 34% of fuel oil components after 130 days. Population dynamics analysis indicates that in fuel oil the biodiversity richness was higher; however, denaturing gradient gel electrophoresis similarity dendrogram shows significant changes in the microbial population during crude oil degradation. Taxonomy studies indicate a great genera divergence; only eight microbial genera were common in both samples. In crude oil, the Limnobacter sp. was the most abundant specie (15.6%), while Sphingomonas wittichii (7.9%) and Novosphingobium aromaticivorans (7.6%) were abundant in fuel oil. These microorganisms have been reported to participate in the degradation of aliphatic and aromatic hydrocarbons. Functional analysis suggests that fuel and crude oil components changed the interactions between the consortium members affecting the collective metabolic functionality.

Bioremediation of chromium(VI) by Stenotrophomonas maltophilia isolated from tannery effluent

Abstract: Bioremediation of chromates using bacteria primarily involves the removal/reduction of heavy metals in effluent using indigenous micro-organisms such as chromium reducing bacteria as biosorbents for cleaner and healthier environment. In the present study, the removal of hexavalent chromium by micro-organisms isolated from acclimatized tannery effluent was investigated. Biochemical assays and molecular sequencing revealed strain SRS05 to be Stenotrophomonas maltophilia. Resistance to chromium was determined by agar and broth dilution assays followed by determination of minimal inhibitory concentration. Strain SRS05 was able to resist 400 mg/ml of chromium which reflects that the heavy metal could be utilized by the micro-organism for its growth. Results by atomic absorption spectroscopy, Fourier transform infrared spectroscopic analysis and scanning electron microscopy revealed effective biosorption of chromium by S. maltophilia SRS05 with no intracellular changes morphologically indicating the stability of the organism in the presence of chromium. It is therefore recommended that this bacterium can be used widely for remediation of hexavalent chromium although the genetic basis for observations concluded in this study is to be confirmed.

Evaluation of moving-bed biofilm sequencing batch reactor (MBSBR) in operating A2O process with emphasis on biological removal of nutrients existing in wastewater

Abstract: In this study, the performance of moving-bed biofilm sequencing batch reactor in operating the anaerobic/anoxic/oxic (A2O) process for treatment of wastewaters containing nitrogen and phosphorous was evaluated For this purpose, a pilot system with two bench-scale sequencing batch reactors with a total volume of 30 L and functional volume of 10 L was used The installation was elaborated using plexiglass, in which 60% of the functional volume consisted of PVC suspended carriers (Kaldnes K3) with a specific surface area of 560 m2/m3 The independent variables used in this study were hydraulic retention time (HRT) (15, 2, 25, 3, and 35 h) and the initial organic load (300, 500, 800, 1000 mg O2/L) The results showed impressive performance in the case of an initial organic load of 300 mg O2/L and HRT of 3 h with maximum removal of COD and TN, respectively, by 951 and 898% In the case of an initial organic load of 1000 mg O2/L and HRT of 35 h, the maximum total phosphorus removal was 723% Therefore, according to the analysis of data obtained by different HRTs, it was revealed that the system of A2O has greater efficiency in removing organic matter from wastewater in the shortest possible time

Extraction and recovery of precious metals from electronic waste printed circuit boards by bioleaching acidophilic fungi

Abstract: Printed circuit boards contain precious metals. They are produced in large volumes, rendering them an important component of the electronic waste. In view of the heterogeneity of the metals present, reprocessing of electronic waste is a heinous task. The present study focused on leaching of valuable metals from electronic waste printed circuit boards using Aspergillus niger DDNS1. The adaptation phases began at 0.1, 0.5 and 1.0% of fine powder of printed circuit boards with 10% inoculum and were optimized with three effective factors, viz. initial pH, particle size and pulp density, to achieve the maximum simultaneous recovery of the valuable metals. The interactions of these metals were also deciphered using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectrum and atomic absorption spectroscopy. The results indicated that extraction of the precious metals was accomplished mainly through the unique organic acids originating from A. niger DDNS1. The initial pH played an important role in the extraction of the precious metals and the metals precipitate formation. The leaching rate of the metals was generally higher at low powder dosage of printed circuit boards. The toxicity of the printed circuit boards had little effect on two-step bioleaching at the pulp density of 0.1% compared to one-step bioleaching. The two-step bioleaching process was followed under organic acid-forming conditions for the maximum mobilization of metals. Thus, the precious metals from printed circuit boards could be mobilized through fungal bioleaching which promises an important industrial application in recycling of electronic wastes.

Bioremediation of salt affected soils using cyanobacteria in terms of physical structure, nutrient status and microbial activity

Abstract: In present investigation, consortia of two indigenous heterocystous cyanobacteria, Nostoc ellipsosporum HH-205 and Nostoc punctiforme HH-206 isolated from a salt affected area of Hisar, Haryana (India) were used as biofertilizer in bioremediation of salt affected soils having high electrical conductivity (13.5 dS/m) and pH (8) with poor organic carbon (0.3%) as well as nitrogen content (0.008%). The experiments were conducted in a pot house for the period of 240 days. There was a significant (P < 0.05) increase in carbon, phosphate, nitrogen, potassium, magnesium, cation exchange capacity, mean weight diameter and hydraulic conductivity of soil with biofertilizer treatment whereas sodium ion and electrical conductivity were found to be decreased. Improvement in soil aggregation and stability due to increased soil microbial activities (dehydrogenase, invertase and phosphomonoesterase) were also observed. Significant increase in growth and yield of pearl millet–wheat crop was observed in amended pots even under low water regime. Thus, the indigenous cyanobacterial species show promise in effective exploitation for phytoremediation and improved productivity of saline soils under semi-arid condition.

Equilibrium studies on removal of lead (II) ions from aqueous solution by adsorption using modified red mud

Abstract: In the present experimental study, solid waste was used as an adsorbent and the effectiveness of the adsorbent was increased by novel treatment methods. Red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were used for the removal of lead (II). The structural and functional groups were identified to confirm the removal of lead (II) by powder X-ray diffraction and Fourier transform infrared spectroscopy analyses. The enhancement of surface area was confirmed by Brunauer–Emmett–Teller analysis. Batch adsorption experiment was also conducted, and various parameters such as the effect of adsorbent dosage, pH, contact time and initial ion concentration were analyzed and reported. Adsorption equilibrium data were investigated using Langmuir, Freundlich and Dubinin–Radushkevich isotherm models with three parameters, and the rate of reaction was examined through kinetic models. The results indicate that in particular a novel modified form of red mud, namely iron oxide-coated acid-treated activated red mud was well fitted in lead (II) removal compared with reported adsorbents. The Langmuir isotherm shows that the maximum adsorption of adsorbate per gram was greater than other adsorbents (27.02 mg/g). In Freundlich isotherm, the Freundlich constant n values lie between 1 and 10 indicate the favorable adsorption. The calculated n values for normal red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were found to be 1.9, 2.1 and 2.0 respectively. The correlation coefficient value was higher and the rate of reaction follows the pseudo-second-order kinetic model.

Lindane, kepone and pentachlorobenzene: chloropesticides banned by Stockholm convention

Abstract: Persistent organic pollutants are a serious problem to the environment due to their toxicity to both fauna and flora. Extremely resistant to biodegradation and prone to transfer through long distances via atmosphere can contaminate almost any place in the planet. They tend to bioaccumulate in fat tissue due to their lipophilicity and seriously affect poisoned organism’s nervous, hepatic, reproductive or hormonal system. Since 2009, due to the Stockholm convention on persistent organic pollutants production and utilisation of certain halogenated pesticides has been prohibited. This group includes hexachlorocyclohexane, chlordecone (kepone) and pentachlorobenzene. All of these chloropesticides pose a serious threat to environment, and careful control of their production and release to the environment is required. This paper is a review of physical and chemical properties as well as sources in environment, impact on animal organisms, methods of degradation of most broadly used chlorinated persistent organic pollutants and suggestions concerning their utilisation.

Comparative study for environmental performances of traditional manufacturing and directed energy deposition processes

Abstract: Additive manufacturing is considered more sustainable than traditional manufacturing due to its efficient energy and materials usage. However, previous literature indicates that this suggestion is applicable only for the polymer materials, and the environmental issues of additive manufacturing with metallic materials are still not clear. With the method of life cycle assessment, this paper analyzes and compares the energy consumptions and environmental impacts of direct energy deposition and traditional machining processes for a typical metal part. Further, the article attempts to identify the significant issues in the two manufacturing options that contribute most to the environmental impacts. Six environmental impacts were assessed in this study: global warming potential (GWP); acidification potential (AP); eutrophication potential; ozone depletion potential (ODP); photochemical ozone creation potential (POCP); and abiotic depletion potential (ADP). The results show that the gear laser fabrication process consumes more energy and releases more negative emissions compared with traditional gear manufacturing processes. The results of GWP, AP, ODP, ADP and POCP of the traditional gear manufacturing are only 30.33, 43.42, 17, 65.05 and 54.68% of the gear laser fabrication.

Feasibility study of waste (d) potential: co-digestion of organic wastes, synergistic effect and kinetics of biogas production

Abstract: The present study investigated the synergistic effect of co-digesting food and green waste from institute campus for enhanced biogas production in different ratios in batch tests (37 ± 1 °C, 90 rpm, 45 days). The results showed that blending improved the biogas production significantly, with highest biogas yield (660 ± 24 mL g−1 volatile solids) that was achieved at 75:25 of food and green waste ratio on volatile solids basis. The yield was 1.7- and 1.9-fold higher than the mono-digestion of food and green waste (370 ± 34; 342 ± 36 mL g−1 volatile solids), respectively. The increase in biogas production may be attributed to optimum carbon to nitrogen ratio resulting in higher yield. The addition of TiO2 nanoparticles showed virtually no effect on biogas production. Characterization was carried out to gain an insight of feedstocks. Modified Gompertz and logistics models were applied for kinetic study of biogas production where modified Gompertz model showed goodness of fit (R 2 = 0.9978) with the experimental results.

Lanthanides removal from mine water using banana peels nanosorbent

Abstract: This study focuses on the performance of nanostructured banana peels in lanthanide-laden mine water treatment. Specifically, nanostructure formation via mechanical milling, characterization in detail and application of this sorbent media in rare earth elements (REEs) removal from synthetic and real mine water are thoroughly investigated. The sorbent samples were characterized by transmission electron microscopy, Brunauer–Emmett–Teller, X-ray diffraction and Fourier transform infrared analyses, while the amount of REEs adsorbed was analysed using inductively coupled plasma optical emission spectroscopy. Results revealed that the particle and crystallite sizes were reduced from <65,000 to <25 nm and 108 to 12 nm, respectively, as the milling progressed. Furthermore, the fracture of particles resulted in a surface area increment from 1.07 to 4.55 m2 g−1. Through Fourier transform infrared analysis, the functional groups responsible for the coordination and removal of metal ions were found to be carboxylic group (at absorption bands of 1730 cm−1) and amine groups (889 cm−1). The Langmuir maximum adsorption capacity was 47.8 mg g−1 for lanthanum and 52.6 mg g−1 for gadolinium. Meanwhile, results revealed that banana peels have a high affinity for Sm, Eu, Nd, Pr, Gd, Tb and Lu compared to other lanthanides present in the mine water samples. The results obtained so far indicate that nanostructured banana peel is a potential adsorbent for REEs removal from mine water. However, for any application, the water matrix to be treated substantially influences the choice of the sorbent material.