Showing papers in "International Journal of Environmental Science and Technology in 2013"

Adsorption isotherms, kinetics and mechanism for the adsorption of cationic and anionic dyes onto carbonaceous particles prepared from Juglans regia shell biomass

Abstract: In the present study, Juglans regia shells were used to prepare activated carbon by acid treatment method. J. regia shell-based activated carbon was used for the adsorption of two synthetic dyes namely, a basic dye malachite green and an acid dye amido black 10B. The prepared adsorbent was crushed and sieved to three different mesh sizes 100, 600 and 1,000 μm. The adsorbent was characterized by scanning electron microscopy, surface acidity and zero-point charge. Batch experiments were carried out by varying the parameters like initial aqueous phase pH, adsorbent dosage and initial dye concentration. The equilibrium data were tested with Langmuir, Freundlich, Redlich–Peterson and Sips isotherm at three different temperatures 293, 300 and 313 K and it was found that the Freundlich isotherm best fitted the adsorption of both the dyes. Kinetic data were tested with pseudo first-order model and pseudo second-order model. The mechanism for the adsorption of both the dyes onto the adsorbent was studied by fitting the kinetic data with intraparticle diffusion model and Boyd plot. External mass transfer was found to be the rate-determining step. Based on the ionic nature of the adsorbates, the extent of film diffusion and intraparticle diffusion varied; both being system specific. Thermodynamic parameters were also calculated. Finally, the process parameters of each adsorption system were compared to develop the understanding of the best suitable system.

Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass

Abstract: Heavy metals affect the biochemical reactions that take place during anaerobic digestion processes of organic matter. In this review, the different effects observed in anaerobic digestion processes and during the production of biomethane and biohydrogen from several substrates contaminated with and/or inheriting heavy metals from the substrates themselves were discussed. It has been found that heavy metals exert important roles in biochemical reactions. Heavy metals like copper, nickel, zinc, cadmium, chromium and lead have been overwhelmingly reported to be inhibitory and under certain conditions toxic in biochemical reactions depending on their concentrations. Heavy metals like iron may also exhibit stimulatory effects, but these effects have been scantily observed. This review also concludes that the severity of heavy metal inhibition depends upon factors like metal concentration in a soluble, ionic form in the solution, type of metal species, and amount and distribution of biomass in the digester or chain of biochemical reactions which constitute the anaerobic digestion process. A majority of studies have demonstrated that the toxic effect of heavy metals like chromium, cadmium and nickel is attributable to a disruption of enzyme function and structure by binding of the metal ions with thiol and other groups on protein molecules or by replacing naturally occurring metals in enzyme prosthetic groups. This review has not found published data on the effects of heavy metals on the hydrolysis stage of anaerobic digestion process chemistry, and hence further studies are required to depict any changes.

Occurrence, physiological responses and toxicity of nickel in plants

Abstract: The focus of the review is on the specific aspects of nickel’s effects on growth, morphology, photosynthesis, mineral nutrition and enzyme activity of plants The mobility of nickel in the environment and the consequent contamination in soil and water is of great concern Also, the detrimental effects of excessive nickel on plant growth have been well known for many years Toxic effects of nickel on plants include alterations in the germination process as well as in the growth of roots, stems and leaves Total dry matter production and yield was significantly affected by nickel and also causes deleterious effects on plant physiological processes, such as photosynthesis, water relations and mineral nutrition Nickel strongly influences metabolic reactions in plants and has the ability to generate reactive oxygen species which may cause oxidative stress More recent evidence indicates that nickel is required in small amounts for normal plant growth and development Hence, with the increasing level of nickel pollution in the environment, it is essential to understand the functional roles and toxic effects of nickel in plants

Arsenite removal from water by electro-coagulation on zinc–zinc and copper–copper electrodes

Abstract: Removal of arsenite from aqueous solution was carried out using electro-coagulation method. The experi- ments were conducted using copper-copper and zinc-zinc electrodes. The optimized experimental parameters were 2.0 mg/L initial concentration, 16.0-min processing time, 6.0 pH, 3.0-V applied voltage and 30 C temperature for zinc-zinc electrodes while these values for copper-copper electrodes were 2.0 mg/L initial concentration, 20.0-min processing time, 7.0 pH, 5.0-V applied voltage and 30 C temperature. The results demonstrated that zinc-zinc and copper-copper electrodes removed arsenite up to 99.89 and 99.56 %, respectively. The treated water was clear, color- less and odorless without any secondary contamination. There was no change in water quality after the removal of arsenite. The reported method is capable to remove arsenite from water at 6-7 pH range, which is a pH range of natural water. Therefore, this method may be the choice of arsenite removal from natural ground water.

Freshwater ostracods as environmental tracers

Abstract: This paper revises the response of freshwater ostracods to different environmental conditions and anthropogenic impacts, with a worldwide overview of the potential use of these microcrustaceans as bioindicators and several examples of applications in different scenarios. The development of either a single species or an ostracod assemblage is influenced by physical-chemical properties of waters (salinity, temperature, pH, dissolved oxygen), hydraulic conditions, bottom grain sizes or sedimentation rates. In addition to population and community changes, morphological and geochemical changes can also be detected in the ostracod carapace, which serves as a tracer of the water quality. All these features permit to delimit the spatial effects of urban sewages, mining effluents, agri- cultural wastes, watershed deforestation or road building. These data are the basis for the palaeoenvironmental reconstruction of cores, with an interesting application to archaeology. In addition, favourable results of recently developed bioassays, coupled with an important variability of local assemblages under changing conditions in both waters and sediments, suggest that these microcrustaceans may included between the most promising sentinels groups in freshwater areas. These microcrustaceans show high sensitivity to pesticides, herbicides, heavy metal pollution and oil inputs.

Adsorption kinetics of herbicide paraquat in aqueous solution onto a low-cost adsorbent, swine-manure-derived biochar

Abstract: Biochars have received increasing attention in recent years because of their significant properties such as carbon sequestration, soil fertility, and contaminant immobilization In this work, the adsorptive removal of paraquat (1,1 0 -dimethyl-4,4 0 -dipyridinium chloride, one of the most widely used herbicides) from aqueous solution onto the swine-manure-derived biochar has been studied at 25 C in a batch adsorption system The adsorption rate has been investigated under the controlled process parameters including initial pH (ie, 45, 60, 75, and 90), paraquat concentration (ie, 05, 10, 20, 40, and 60 mg/L), and biochar dosage (ie, 010, 015, 020, 025, and 030 g/L) Based on the adsorption affinity between cationic paraquat and carbon-like adsorbent, a pseudo-second order model has been developed using experimental data to predict the adsorption kinetic constant and equilibrium adsorption capacity The results showed that the adsorption process could be satisfactorily described with the reaction model and were reasonably explained by assuming an adsorption mechanism in the ion exchange process Overall, the results from this study demonstrated that the biomass- derived char can be used as a low-cost adsorbent for the removal of environmental cationic organic pollutants from the water environment

Adsorption of cadmium ion using a new composite cation-exchanger polyaniline Sn(IV) silicate: kinetics, thermodynamic and isotherm studies

Abstract: A new organic–inorganic composite cation exchanger polyaniline Sn(IV) silicate has been synthesized. The physicochemical properties of this ion exchanger were determined using different analytical techniques including fourier transform infrared spectroscopy, simultaneous thermogravimetry–differential thermogravimetry analyses, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and elemental analysis studies. Ion exchange capacity and effect of heating temperature on ion exchange capacity were also carried out on this ion exchange material. Adsorption properties for different metal ions have been investigated and the results revealed that polyaniline Sn(IV) silicate had the highest adsorption capacity for Cd2+ ion. It’s selectivity was tested by achieving some important binary separations. Dependence of adsorption on contact time, temperature, pH of the solution and exchanger dose had been studied to achieve the optimum conditions. Adsorption kinetic study showed that the adsorption process followed the first order kinetics. Adsorption data were fitted to linearly transformed Langmuir isotherm with R 2 (correlation coefficient) >0.99. The maximum removal of Cd2+ was found at pH 9. The adsorption was fast and the equilibrium established within 40 min. Thermodynamic parameters viz- entropy change, enthalpy change and Gibb’s free energy change were also calculated.

Removal of heavy metal ions from aqueous solutions with multi-walled carbon nanotubes: Kinetic and thermodynamic studies

Abstract: Multi-walled carbon nanotubes were used successfully for the removal of Copper(II), Lead(II), Cadmium(II), and Zinc(II) from aqueous solution. The results showed that the % adsorption increased by raising the solution temperature due to the endothermic nature of the adsorption process. The kinetics of Cadmium(II), Lead(II), Copper(II), and Zinc(II) adsorption on Multi-walled carbon nanotubes were analyzed using the fraction power function model, Lagergren pseudo-first-order, pseudo-second-order, and Elovich models, and the results showed that the adsorption of heavy metal ions was a pseudo-second-order process, and the adsorption capacity increased with increasing solution temperature. The binding of the metal ions by the carbon nanotubes was evaluated from the adsorption capacities and was found to follow the following order: Copper(II) > Lead(II) > Zinc(II) > Cadmium(II). The thermodynamics parameters were calculated, and the results showed that the values of the free energies were negative for all metals ions, which indicated the spontaneity of the adsorption process, and this spontaneity increased by raising the solution temperature. The change in entropy values were positives, indicating the increase in randomness due to the physical adsorption of heavy metal ions from the aqueous solution to the carbon nanotubes’ surface. Although the enthalpy values were positive for all metal ions, the free energies were negative, and the adsorption was spontaneous, which indicates that the heavy metal adsorption of Multi-walled carbon nanotubes was an entropy-driving process.

Identification of waste management development drivers and potential emerging waste treatment technologies

Abstract: Application and development of municipal solid waste treatment technology depends on various socio-economic and environmental factors All those factors are work as development drivers for waste management systems The study aims to identify key drivers from case studies of waste management development trend in Sweden Social, economic and environmental drivers are identified and presented in this study The study identifies personal behaviour, local waste management practice, consumption and generation of waste as the key social drivers Resource value of waste, economic benefit from waste treatment facilities and landfill tax have been acknowledged as economic drivers for developing waste treatment technology Moreover, global climate change, environmental movement and awareness have been working as environmental drivers for developing various waste treatment methods in Sweden In addition, the study aims to analyse emerging waste treatment technologies based on a number of literature review and questionnaire survey Dry composting, pyrolysis-gasification, plasma arc, and anaerobic digestion have been identified as potential emerging technologies for waste management systems in Sweden

Sources of contaminants and groundwater quality in the coastal part of a river delta

Abstract: Assessment of possible sources that control the groundwater quality was carried out in the Cauvery deltaic region, India, since domestic and agricultural water requirements are largely met by groundwater abstraction. Major ion and bromide contents are high in groundwater in the coastal wells. Spatial and vertical distributions of ions reveal that the shallow wells and wells in coastal parts have high chloride, nitrate, ammonium and phosphate. Groundwater quality assessment was carried out using the prescribed limits of World Health Organization and Bureau of Indian Standards which indicates that 55 % of samples are not fit for drinking. Integrated suitability map for drinking was created based on the concept that if the water sample exceeds any one of the standards by World Health Organization or Bureau of Indian Standards, the well is not fit for drinking. Groundwater quality for agricultural activities was assessed using electrical conductivity, sodium adsorption ratio, residual sodium carbonate, United States salinity laboratory diagram and Food and Agricultural Organization methods. According to Food and Agricultural Organization, 84 % of samples are classified as low sodium water and are suitable for all crops and soils. It was found that the water quality in this area is affected by improper disposal of waste, sewage/drainage canals near the wells, irrigation return flow, application of agrochemicals and saline water intrusion in the coastal region. Further, integrated suitability map produced in this study will be useful for future groundwater development and planning in this area. The suitability map needs to be updated periodically for proper management plan to preserve the groundwater resource in this region.

Synergistic degradation of diazo dye Direct Red 5B by Portulaca grandiflora and Pseudomonas putida

Abstract: Plants and bacterial consortium of Portulaca grandiflora and Pseudomonas putida showed complete decolorization of a sulfonated diazo dye Direct Red 5B within 72 h, while in vitro cultures of P. grandiflora and P. putida independently showed 92 and 81 % decolorization within 96 h, respectively. A significant induction in the activities of lignin peroxidase, tyrosinase, 2,6-dichlorophenol indophenol reductase and riboflavin reductase was observed in the roots of P. grandiflora during dye decolorization; whereas, the activities of laccase, veratryl alcohol oxidase and 2,6-dichlorophenol indophenol reductase were induced in the cells of P. putida. Plant and bacterial enzymes in the consortium gave an enhanced decolorization of Direct Red 5B synergistically. The metabolites formed after dye degradation analyzed by UV–Vis spectroscopy, Fourier transformed infrared spectroscopy and high performance liquid chromatography confirmed the biotransformation of Direct Red 5B. Differential fate of metabolism of Direct Red 5B by P. grandiflora, P. putida and their consortium were proposed with the help of gas chromatography–mass spectroscopy analysis. P. grandiflora metabolized the dye to give 1-(4-diazenylphenyl)-2-phenyldiazene, 7-(benzylamino) naphthalene-2-sulfonic acid, 7-aminonaphthalene-2-sulfonic acid and methylbenzene. P. putida gave 4-hydroxybenzenesulfonic acid and 4-hydroxynaphthalene-2-sulfonic acid and benzamide. Consortium showed the formation of benzenesulfonic acid, 4-diazenylphenol, 6-aminonaphthalen-1-ol, methylbenzene and naphthalen-1-ol. Consortium achieved an enhanced and efficient degradation of Direct Red 5B. Phytotoxicity study revealed the nontoxic nature of metabolites formed after parent dye degradation. Use of such combinatorial systems of plant and bacteria could prove to be an effective and efficient strategy for the removal of textile dyes from soil and waterways.

Application of capacitive deionization technology to the removal of sodium chloride from aqueous solutions

Abstract: Capacitive deionization has been developed as a promising desalination alternative for removing ions from aqueous solutions. In this study, the evaluation of capacitive performance was carried out by galvanostatic charge/discharge and cyclic voltammetry experiments. The good capacitive and electrosorption behaviors suggest carbon aerogel not only treated as an electrical double layer capacitor, but also as a potential electrode in capacitive deionization processes. Also, the capacitive deionization characteristics indicate that electrosorption/regeneration can be controlled by polarization and depolarization of each electrode. It implies that sodium and chloride ions are electrostatically held to form electrical double layer on the surface of charged electrodes. The electrosorption performance at different applied voltages and solution concentrations was investigated. It is found that the removal of sodium chloride increases with increasing applied voltage and solution concentration, resulting from stronger electrostatic interactions, higher concentration gradient, and less double layer overlapping effect. Based on Langmuir isotherm, the equilibrium electrosorption capacity at 1.2 V is determined as 270.59 μmol/g. Under this condition, due to the presence of micropores associated with the double layer overlapping, the effective surface area for electrosorption of ions at 1.2 V is estimated in the range of 12.18–14.25 % of the Brunauer–Emmett–Teller surface area. The results provide a fundamental understanding of electrosorption of ions and help promoting capacitive deionization technology for water purification and desalination.

Life cycle assessment of small-scale constructed wetland and extended aeration activated sludge wastewater treatment system

Abstract: Wastewater treatment plants help to reduce negative impact on the environment by improving the quality of effluent. Different technologies are used in wastewater treatment, and one of the tasks is to find the most environmentally sound option, taking into account the use of resources and energy during construction and operation of the treatment system. The aim of the study is to assess environmental impacts from two different types of small-scale wastewater treatment systems, a constructed wetland and extended aeration activated sludge treatment system using Life Cycle Assessment method. The system boundaries include construction and operation phases. Assessment has been carried out using SimaPro software and Impact 2002? and ReCiPe assessment methods with characterisation and normalisation stages. The results show that the main negative impact of constructed wetland is caused by the construction phase and use of lightweight expanded clay aggregate to construct the hybrid filter. Impacts from extended aeration activated sludge treatment system are mainly caused from the use of electricity and the quality of the effluent, therefore, the use phase has a larger impact on the life cycle. Since a large amount of energy is used to produce lightweight expanded clay aggregate, the impact of 1 population equivalent of con- structed wetland is larger than the impact of extended aeration activated sludge treatment system. Constructed wetland dominates in human toxicity, acidification, land use, ozone layer depletion and the use of non-renewable resources categories. Extended aeration activated sludge treatment system dominates in categories associated with eutrophication and ecotoxicity.

Heavy metals pollution in the soils of suburban areas in big cities: a case study

Abstract: Soil pollution in agricultural areas surrounding big cities is a major environmental problem. Tabriz is the largest city in the northwest of Iran and the fourth largest city in the country. Soil samples were taken from 46 sites in the suburbs of the Tabriz city, and separate samples were taken from control site and analyzed. The results indicated that the mean pH value of the soil samples was 9.29, while the mean EC value was 354.33 ls/cm and the amount of TOC and TOM was 0.99 and 1.7 %, respectively. The mean concentrations of Cd, Pb, Cu, Cr, Ni, and Zn in the soil were determined to be 1.61, 10.56, 101.25, 87.40, 38.73, and 98.27 mg/kg, respectively (dry weight). The concentrations of heavy metals (Cd, Pb, Cu, Cr, and Zn), with the exception of Ni, were higher than the concentra- tions of the same heavy metals at the control site. Despite these elevated concentrations, the concentrations of heavy metals were lower than the toxicity threshold limit of agricultural soils. The values of the pollution index revealed that the metal pollution level was Pb ( Cr ( Cu ( Zn ( Cd ( Ni, and the mean value of the integrated pollution index was determined to be 1.81, indicating moderate pollution. Nevertheless, there were some sites that were severely polluted by Cr (maximum values of 1,364 mg/kg). It was concluded that city probably has affected the surrounding agricultural area. Application of wastewater (municipal and industrial) as irrigation water, using of sludge as soil fertilizer, and atmospheric percep- tions have been considered as main reasons of increased heavy metals concentrations found in the studied area.

Life cycle assessment of pyrolysis–gasification as an emerging municipal solid waste treatment technology

Abstract: Waste-to-energy technologies are considered as one of the key waste treatment technologies due to their energy and heat recovery efficiencies from the waste. A number of research studies were accomplished to understand the potential environmental burdens from emerging waste treatment technologies such as pyrolysis–gasification (PG). The aim of this study was to examine the PG of municipal solid waste (MSW) treatment process through a life cycle assessment (LCA) method. The study also includes a comparative LCA model of PG and incineration to identify the potential environmental burdens from the existing (incineration) and emerging (PG) waste treatment technologies. This study focused on ten environmental impact categories under two different scenarios, namely: (a) LCA model of PG and (b) comparative LCA model of PG and incineration. The scenario (a) showed that PG had significant environmental burdens in the aquatic eco-toxicity and the global warming potential impact categories. The comparative scenario (b) of PG and incineration of MSW showed that PG had comparatively lower potential environmental burdens in acidification, eutrophication, and aquatic eco-toxicity. Both LCA models showed that the environmental burdens were mainly caused by the volume of the thermal gas (emissions) produced from these two technologies and the final residue to disposal. Therefore, the results indicate that the efficiency and environmental burdens of the emerging technologies are dependent on the emissions and the production of final residue to the landfill.

Adsorption of lead, zinc and cadmium ions from contaminated water onto Peganum harmala seeds as biosorbent

Abstract: Peganum harmala seeds were assessed as biosorbent for removing Pb2+, Zn2+and Cd2+ ions from aqueous solutions. The effects of various parameters such as the aqueous solution pH, the contact time, the initial metal concentration and the amount of adsorbent in the process were investigated. The adsorption efficiencies increased with pH. It was found that about 95 % of lead, 75 % of zinc and 90 % of cadmium ions could be removed from 45 ml of aqueous solution containing 20 mg l−1 of each cation with 2 g of adsorbent at pH 4.5 after 15 min. The quantitative desorption of cadmium from adsorbent surface was achieved using 10 ml of a 0.5 M nitric acid solution. This condition was attained for lead and zinc ions with 10 ml of 1 M hydrochloric acid solution. Kinetic investigation of the process was performed by considering a pseudo-second-order model. This model predicts the chemisorption mechanism of the process. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models were tested for describing the equilibrium data. It was found that the Freundlich model describes the experimental data resulting from the adsorption of lead ions. However for cadmium and zinc ions, the adsorption equilibria were interpreted with the Langmuir model.

Water quality index and fractal dimension analysis of water parameters

Abstract: Statistical analysis of water quality parameters were analyzed at Harike Lake on the confluence of Beas and Sutlej rivers of Punjab (India). Mean, median, mode, standard deviation, kurtosis, skewness, coefficient of variation, regression lines, correlation coefficient, Hurst exponent, fractal dimension and predictability index were estimated for each water parameter. Monthly variation of water quality index using month-wise and parameter-wise value of quality rating and actual value present in water sample was calculated and compared with World Health Organization/Environmental Protection Agency standard value of these parameters. It was observed that Brownian time series behavior exists of potential of hydrogen with total dissolved solids, hardness, alkalinity, sulfate, chloride and conductance parameters; biochemical oxygen demand with total dissolved solids, hardness, alkalinity, sulfate, chloride, conductance and calcium parameters; dissolved oxygen with total dissolved solids, hardness, alkalinity, sulfate, chloride, conductance and calcium parameters; ferrous with total dissolved solids, hardness, alkalinity, sulfate, conductance and calcium parameters; chromium with total dissolved solids, hardness, alkalinity, sulfate, chloride, conductance and zinc parameters; zinc with total dissolved solids, hardness, sulfate, chloride, conductance and calcium parameters; fluoride with total dissolved solids, hardness, alkalinity, sulfate, chloride and conductance parameters; nitrate with total dissolved solids, sulfate and conductance parameters; nitrite with potential of hydrogen, total dissolved solids, hardness, alkalinity, sulfate, chloride, conductance and calcium parameters. Also, using water quality index, it was observed that water of the lake was severely contaminated and became unfit for drinking and industrial use.

Assessment of a conceptual hydrological model and artificial neural networks for daily outflows forecasting

Abstract: Artificial neural networks (ANNs) are used by hydrologists and engineers to forecast flows at the outlet of a watershed. They are employed in particular where hydrological data are limited. Despite these developments, practitioners still prefer conventional hydrological models. This study applied the standard conceptual HEC-HMS’s soil moisture accounting (SMA) algorithm and the multi layer perceptron (MLP) for forecasting daily outflows at the outlet of Khosrow Shirin watershed in Iran. The MLP [optimized with the scaled conjugate gradient] used the logistic and tangent sigmoid activation functions resulting into 12 ANNs. The R2 and RMSE values for the best trained MPLs using the tangent and logistic sigmoid transfer function were 0.87, 1.875 m3 s−1 and 0.81, 2.297 m3 s−1, respectively. The results showed that MLPs optimized with the tangent sigmoid predicted peak flows and annual flood volumes more accurately than the HEC-HMS model with the SMA algorithm, with R2 and RMSE values equal to 0.87, 0.84 and 1.875 and 2.1 m3 s−1, respectively. Also, an MLP is easier to develop due to using a simple trial and error procedure. Practitioners of hydrologic modeling and flood flow forecasting may consider this study as an example of the capability of the ANN for real world flow forecasting.

Biosorption of Cu(II) and Pb(II) from aqueous solutions by chemically modified spent coffee grains

Abstract: In this research, spent coffee grains were modified with citric acid solutions (0.1 and 0.6 M) to increase the quantity of carboxylic groups improving its metal adsorption capacity. Added functional groups on modified and non-modified spent coffee grains were identified and quantified by attenuated total reflection Fourier transform infrared analyses and potentiometric titrations, respectively. These adsorbents were used for the removal of lead (II) and copper (II) from aqueous solutions at 30 °C and different pH in batch systems. In addition, adsorption–desorption experiments were conducted to evaluate the possibility of re-using the modified adsorbent. Potentiometric titrations data reveal that the quantity of carboxylic groups was increased from 0.47 to 2.2 mmol/g when spent coffee grains were modified with 0.1 and 0.6 M citric acid. Spent coffee grains treated with 0.6 M citric acid, achieved a maximum adsorption capacity of 0.77 and 1.53 mmol/g for lead (II) and copper (II), respectively, whereas non-modified spent coffee grains only reached 0.24 and 0.19 mmol/g for lead (II) and copper (II), respectively. Desorption of lead (II) and copper (II) achieved around 70 % using 0.1 N HCl for non-modified and modified spent coffee grains with 0.6 M citric acid. It is suggested that lead (II) and copper (II) species were adsorbed mainly on the carboxylic groups of modified spent coffee grains and these metals may be exchanged for hydrogen and calcium (II) ions during adsorption on non-modified spent coffee grains. Finally, the adsorption equilibrium was reached after 400 min for modified spent coffee grains with 0.6 M citric acid. Modified spent coffee grains are a promising option for removing metal cations from aqueous solutions due to its low cost and high adsorption capacity (about 10 times higher than the activated carbons).

Feasibility of red mud neutralization with seawater using Taguchi’s methodology

Abstract: In this study, feasibility of using seawater to neutralize alkaline red mud for its safe disposal has been studied using Taguchi’s design of experimental methodology. Parameters such as weight of red mud, volume of seawater, stirring time and temperature were tested at three levels to study their effect on response characteristic, i.e., pH of the neutralized slurry. The analysis of variance showed that volume of seawater added and quantity of red mud are the two significant parameters with 53.59 and 44.92 % contribution each, respectively. Under the optimized parameters, pH value of red mud slurry reaches to about 8.0 which is within disposable limits. When seawater or other Ca- and Mg-rich brines are added to caustic red mud, the pH of the mixture is reduced causing hydroxide, carbonate or hydroxy carbonate minerals to be precipitated. This mechanism of neutralization process has been explained with emphasis on chemical analysis, mineralogy and morphology of the neutralized red mud. The process improved the physical characteristics of red mud with entrained liquor becoming non-hazardous water with reduced alkalinity. The results would be extremely useful in the process of safe disposal of red mud.

Co-contamination of water with chlorinated hydrocarbons and heavy metals: challenges and current bioremediation strategies

Abstract: Chlorinated hydrocarbons can cause serious environmental and human health problems as a result of their bioaccumulation, persistence and toxicity. Improper disposal practices or accidental spills of these compounds have made them common contaminants of soil and groundwater. Bioremediation is a promising technology for remediation of sites contaminated with chlorinated hydrocarbons. However, sites co-contaminated with heavy metal pollutants can be a problem since heavy metals can adversely affect potentially important biodegradation processes of the microorganisms. These effects include extended acclimation periods, reduced biodegradation rates, and failure of target compound biodegradation. Remediation of sites co-contaminated with chlorinated organic compounds and toxic metals is challenging, as the two components often must be treated differently. Recent approaches to increasing biodegradation of organic compounds in the presence of heavy metals include the use of dual bioaugmentation; involving the utilization of heavy metal-resistant bacteria in conjunction with an organic-degrading bacterium. The use of zero-valent irons as a novel reductant, cyclodextrin as a complexing agent, renewable agricultural biosorbents as adsorbents, biosurfactants that act as chelators of the co-contaminants and phytoremediation approaches that utilize plants for the remediation of organic and inorganic compounds have also been reported. This review provides an overview of the problems associated with co-contamination of sites with chlorinated organics and heavy metals, the current strategies being employed to remediate such sites and the challenges involved.

Alternative refrigerants in vapour compression refrigeration cycle for sustainable environment: a review of recent research

Abstract: Vapour compression refrigeration is used in almost 80 % of the refrigeration industries in the world for refrigeration, heating, ventilating and air conditioning. The high-grade energy consumption of these devices is very high and the working substance creates environmental problems due to environmental unfriendly refrigerants such as chloroflurocarbons, hydrochloroflurocarbons and hydro- flurocarbons. Heating, ventilating, air conditioning and refrigeration industries are searching for ways to increase performance, durability of equipments and energy efficiency in a sustainable way while reducing the cost of manufac- turing. With the present refrigerants, environmental prob- lems such as ozone layer depletion, global warming potential, green house gases and carbon emission are increasing day by day. In this paper, the popular refrigerant is thoroughly studied experimentally and recommendations are given for alternatives such as carbon dioxide, ammonia and hydrocarbons and new artificially created fluid, Hydro- Fluoro-Olefin 1234yf by DuPont and Honeywell which exhibit good thermo-physical and environmental properties and will be commercialized in the near future.

Production of polyhydroxyalkanoates from Ralstonia eutropha using paddy straw as cheap substrate

Abstract: Polyhydroxyalkanoates are polyesters of natural origin accumulated in form of intracellular granules by a wide variety of bacterial strains as candidates for biodegradable polymers, possessing material properties similar to the synthetic thermoplastics and elastomers. Paddy straw (lignocellulosic substrate) after hydrolysis was used as the carbon source for the production of polyhydroxyalkanoates from the predominant polyhydroxyalkanoates producer Ralstonia eutropha MTCC 1472. The effect of hydrolysed straw in the modified mineral salt media on bacterial growth and polyhydroxyalkanoates accumulation was analysed. Fourier transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry were performed on the extracted polyhydroxyalkanoates sample. At a dry cell weight of 19.2 g/L, 37.55 % polyhydroxyalkanoates accumulation was achieved; thus, paddy straw can be efficiently used as a cheap carbon source for industrial production of the polyhydroxyalkanoates.

Photocatalytic degradation of azo dye Orange II in aqueous solutions using copper-impregnated titania

Abstract: During dyeing process, industries consume large quantity of water and subsequently produce large volume of wastewater This wastewater is rich in color and contains different dyes Orange II is one of them In this article, metal-impregnated TiO2 P-25 catalyst was used to enhance the photocatalytic degradation of Orange II dye Photodegradation percentage was followed spectrophotometrically by the measurements of absorbance at λ max = 483 nm The effect of copper-impregnated TiO2 P-25 photocatalyst for the degradation of Orange II has been investigated in terms of percentage removal of color, chemical oxygen demand (COD) and total organic carbon (TOC) As such 98 % color removal efficiency, 97 % percentage removal of COD and 89 % percentage removal of TOC was achieved with TiO2 P-25/Cu catalysts under typical conditions Copper-impregnated TiO2 P-25 photocatalyst showed comparatively higher activity than UV/H2O2 homogeneous photodegradation The relative electrical energy consumption for photocatalytic degradation was considerably lower with TiO2 P-25/Cu photocatalyst than that with homogeneous photodegradation Transmission electron microscopic analysis was used for catalyst characterization

Evaluation of the performance of a new freeze desalination technology

Abstract: The use of desalination technologies which produce concentrated brines is acutely limited by inadequate waste brine disposal mechanisms such that the brine does not contaminate fresh water resources. The treatment of highly saline brine using freeze desalination technique trade marked as HybridICE™ technology was investigated at pilot scale. The capacity of the HybridICE™ process to generate fresh water by freeze desalination of brine was investigated in this study. Brine samples to feed into the HybridICE process unit were prepared in tanks with volume capacities between 1.0 and 10.0 m3 by dissolving common salt into tape water. The effects of refrigerant temperature, initial brine concentration, energy consumption were evaluated in relation to product ice quality. Feed brine samples were processed in batches in a closed system where it was continuously re-circulated to generate product ice and more concentrated residual small volume of brine stream. The quality of ice produced could be turned into potable water it terms of its low total dissolved salts and conductivity. The salt removal, based on the average chloride concentration in the ice samples, was 96 %. The energy utilization efficiency amounted to an average of ZAR 10.0/m3 water assuming energy cost of ZAR 0.39/kWh. The HybridICE™ technology was shown to be a better option than other desalination technologies currently in use, in terms of energy utilization and cleaner by-products.

Recycling of environmentally problematic plant wastes generated from greenhouse tomato crops through vermicomposting

Abstract: The enormous quantity of plant waste produced from greenhouse tomato crops is an environmental problem that should be solved by recycling that waste into valuable organic products through low-cost technologies, such as vermicomposting. Feasibility of vermicomposting greenhouse tomato-plant waste (P) using paper-mill sludge (S) as complementary waste was investigated by this study. Earthworm development in P, S, and two mixtures of both wastes was monitored over 24 weeks and compared with that in cow dung (D), an optimum organic-waste to be vermicomposted. The effectiveness of vermicomposting to biostabilize those wastes was assessed by analysing phospholipid fatty acid composition, chemical features, plant-nutrient content, metal concentration, enzyme activities, and germination index (GI). A commercial vermicompost was also analyzed and taken as a reference of vermicompost quality. Earthworms did not survive in P alone, but a mixture of P with S at a ratio of 2:1 or 1:1 resulted in earthworm development similar to that observed in D. Phospholipid fatty acid analysis revealed that earthworm activity strongly transformed initial microbiota inhabiting the wastes, giving rise to vermicompost microbial communities which were similar to that of a commercial vermicompost. Both mixtures of P and S were properly biostabilized through vermicomposting, as indicated by decreases in their C:N ratio and enzyme activities together with increases in their degree of maturity (GI ~ 100 %) after the process. This study demonstrates that the vermicomposting of tomato-plant waste together with paper-mill sludge allows the recycling of both wastes, thereby improving the environmental sustainability of greenhouse crops.

Dynamics of diesel fuel degradation in contaminated soil using organic wastes

Abstract: Bioremediation is an effective measure in dealing with such contamination, particularly those from petroleum hydrocarbon sources. The effect of soil amendments on diesel fuel degradation in soil was studied. Diesel fuel was introduced into the soil at the concentration of 5 % (w/w) and mixed with three different organic wastes tea leaf, soy cake, and potato skin, for a period of 3 months. Within 84 days, 35 % oil loss was recorded in the unamended polluted soil while 88, 81 and 75 % oil loss were recorded in the soil amended with soy cake, potato skin and tea leaf, respectively. Diesel fuel utilizing bacteria counts were significantly high in all organic wastes amended treatments, ranging from 111 × 106 to 152 × 106 colony forming unit/gram of soil, as compared to the unamended control soil which gave 31 × 106 CFU/g. The diesel fuel utilizing bacteria isolated from the oil-contaminated soil belongs to Bacillus licheniformis, Ochrobactrum tritici and Staphylococcus sp. Oil-polluted soil amended with soy cake recorded the highest oil biodegradation with a net loss of 53 %, as compared to the other treatments. Dehydrogenase enzyme activity, which was assessed by 2,3,5-triphenyltetrazolium chloride technique, correlated significantly with the total petroleum hydrocarbons degradation and accumulation of CO2. First-order kinetic model revealed that soy cake was the best of the three organic wastes used, with biodegradation rate constant of 0.148 day−1 and half life of 4.68 days. The results showed there is potential for soy cake, potato skin and tea leaf to enhance biodegradation of diesel in oil-contaminated soil.

Removal of humic acid from peat water using untreated powdered eggshell as a low cost adsorbent

Abstract: The main objective of this study is to investi- gate the possibility of powdered eggshell used as an adsorbent material for removal of humic acid from peat water. The influences of contact time, dose of eggshells, pH, and temperature were the factors considered in the removal processes of humic acid from peat water. In addition, adsorption isotherms of humic acid onto the powdered eggshell were also evaluated with the Langmuir and Freundlich approximations. Our results showed that the equilibrium of the process was eventually established after 60 min of the contact time, and also found that using 5 g of the powdered eggshell nearly 95 % of humic acid has been successfully removed from the peat water. The removal of humic acid gave better result when it was conducted at low pH, and it was almost unaffected the temperatures variation. The data was well fitted to Fre- undlich isotherm with the correlation coefficient of not \0.999, and could uptake the humic acid about 126.58 mg/g at pH 4.01, estimated from the Langmuir model. The kinetic experimental data proportionally correlated with the pseudo-second-order kinetic model with a rate constant in the range of 0.016-0.112 g mg -1 min -1 , while intra-par- ticle-diffusion were the main rate determining step in the humic acid removal process. The powdered eggshell investigated in this study, thus, exhibited as a high potential adsorbent for the removal of humic acid from peat water.

Response surface methodology mediated optimization of Remazol Orange decolorization in plain distilled water by Pseudomonas aeruginosa BCH

Abstract: The bacterium Pseudomonas aeruginosa BCH decolorized and degraded the sulphonated azo dye Remazol Orange in plain distilled water. The effects of different parameters, i.e. pH, temperature and cell mass concentration on the biodegradation of dye in aqueous phase was evaluated using response surface methodology. Optimization was carried out using three-level Box–Behnken design. Predicted values were found to be in good agreement with experimental values (R 2 0.9997 and pred R 2 0.9984), which indicated suitability of the employed model and the success of response surface methodology. Optimum dye decolorization was maximized and the favourable conditions were pH 7.43, temperature 29.39 °C and cell mass concentration 2.88 g l−1, which resulted in 96.01 % decolorization within 5 h. It was validated from the predicted response (97.37 %). According to the analysis of variance results, the proposed model can be used to navigate the design space. 3D plot analysis disclosed the significant interaction between all three tested factors on decolorization process. The combinations of the three variables predicted during response surface methodology were confirmed through confirmatory experiments. Observations indicated that higher cell mass accelerated the decolorization process. Degradation of the dye was verified through high performance liquid chromatography analysis. Phytotoxicity studies carried out with dye and dye metabolites using Phaseolus mungo, Triticum aestivum and Sorghum vulgare indicated the detoxification of dye.

Willingness to pay for improved residential waste management in a developing country

Abstract: In most developing countries policies and frameworks that govern solid waste management strategies have often been directed at the waste management service providers and less attention is often given to the demand side of the problem. This paper reports a study regarding householders’ willingness to pay for improved residential solid waste management. The data for the study originated from a contingent valuation survey that was conducted in 236 households in Ilorin city in Kwara State, Nigeria. A binary logit model was used to account for some factors influencing the respondents’ willingness to pay. The results show that more than 80 % of the respondents were in support of the residential waste management. The respondents were willing to pay an average of 3,660 Nigerian Naira (US $24) each year. Income, education, dwelling type and whether the respondent is satisfied with private sector participation in provision of waste management service positively influenced the respondents’ willingness to pay. The price, gender, household size and activities of sanitary inspectors had negative influence. The findings from this study could contribute to the knowledge regarding the design of a more sustainable residential waste management strategy in Nigeria and other countries that have similar conditions.