Search

Summarization: The electrochemical oxidation of stabilized landfill leachate with 2960 mg L(-1) chemical oxygen demand (COD) over a Ti/IrO(2)-RuO(2) anode was investigated in the presence of HClO(4) as the supporting electrolyte. Emphasis was given on the effect of electrolysis time (up to 240 min) and temperature (30, 60 and 80°C), current density (8, 16 and 32 mA cm(-2)), initial effluent's pH (0.25, 3, 5 and 6), HClO(4) concentration (0.25 and 1M) and the addition of NaCl (20 and 100mM) or Na(2)SO(4) (20mM) as source of extra electrogenerated oxidants on performance; the latter was evaluated regarding COD, total carbon (TC), total phenols (TPh) and color removal. Moreover, the anode was studied by scanning electron microscopy and cyclic voltammetry. The main parameters affecting the process were the effluent's pH and the addition of salts. Treatment for 240 min at 32 mA cm(-2) current density, 80°C and the pH adjusted from its inherent value of 0.25 (i.e. after the addition of HClO(4)) to 3 yielded 90% COD, 65% TC and complete color and TPh removal at an electricity consumption of 35 kWh kg(-1) COD removed. Comparable performance (i.e. 75% COD reduction) could be achieved without pH adjustment but with the addition of 100mM NaCl consuming 20 kWh kg(-1) COD removed. Presented on: Journal of Hazardous Materials

Summarization: The removal of BTEX (benzene, toluene, ethyl-benzene and xylenes) and MTBE (methyl tertiary butyl ether) from aqueous solution by raw (DR) and thermally modified diatomite at 550, 750 and 950 °C (D550, D750 and D950 respectively) was studied. Physical characteristics of both raw and modified diatomite such as specific surface, pore volume distribution, porosity and pHsolution were determined, indicating important structural changes in the modified diatomite, due to exposure to high temperatures. Both adsorption kinetic and isotherm experiments were carried out. The kinetics data proved a closer fit to the pseudo-second order model. Maximum values for the rate constant, k2, were obtained for MTBE and benzene (48.9326 and 18.0996 g mg−1 h−1, respectively) in sample D550. The isotherm data proved to fit the Freundlich model more closely, which produced values of the isotherm constant 1/n higher than one, indicating unfavorable adsorption. The highest adsorption capacity, calculated through the values of the isotherm constant kF, was obtained for MTBE (48.42 mg kg−1 (mg/L)n) in sample D950. Presented on: Journal of Hazardous Materials

Summarization: The uncontrolled disposal of bottom ash from incineration units of hazardous and infected wastes in many countries causes significant scale damage, since it contaminates the soil as well as surface and underground waters, putting both the environment and the public health at risk. In view of the above, a study of bottom ash produced at a hospital medical waste incinerator (HMWI) in Greece was conducted, in order to detect the presence of heavy metals and therefore assess its toxicity; this led to conclusions on the possible contamination of the soil as well as surface and underground waters as a result of its disposal in landfills. The study was conducted at a typical general hospital with 500-bed capacity. About 880 kg of infectious waste coming from a general hospital with all medical departments are pyrolyticly incinerated at the HMWI every day. International literature contains many references to research that characterizes bottom ash as either dangerous, not dangerous, or inert, in an effort to diagnose its proper management and disposal. For this reason, this study focuses on the characterization of bottom ash. Samples were collected from a combustion chamber, over a period of 1 year, and a series of tests were conducted, including an analysis of particle size distribution, morphology, mineralogical and chemical composition, heavy metal leaching behavior and PCDD/F. Presented on: Journal of Hazardous Materials

An examination regarding the determination of recyclables and hazardous substances in small waste electrical and electronic equipment (WEEE) found in the residual household waste stream of the city of Dresden, Germany, is described. Firstly, attitudes towards the disposal of small WEEE in the latter are assessed, and product types and categories which mostly contribute to its composition are identified. Physical parameters which could be used as mechanical sorting criteria are measured, and the material composition of the small WEEE found is determined. The hazardous substances' "base" charge in the residual waste is established by means of atomic absorption spectrometry and ionic chromatography, as a first step in estimating the contribution of small WEEE to its pollutant load. Consequently, the content of small WEEE plastics in key heavy metals and halogens is determined. Key conclusions are drawn concerning the future strategic development and practical implementation of the 2002/96/EC Directive, in relation to small WEEE management and recycling.

Summarization: This paper presents the course and the remediation results of a 4-year application of bioslurping technology on the subsurface of a Greek petroleum refinery, which is still under full operation and has important and complicated subsurface contamination problems, mainly due to the presence of light non-aqueous phase liquids (LNAPL). About 55 wells are connected to the central bioslurping unit, while a mobile bioslurping unit is also used whenever and wherever is necessary. Moreover, there are about 120 additional wells for the monitoring of the subsurface of the facilities that cover a total area of 1,000,000 m(2). An integrated monitoring program has also been developed and applied on the site, including frequent LNAPL layer depth and thickness measurements, conduction of bail-down and recovery tests, sampling and chemical analysis of the free oil phase, etc., so as to evaluate the remediation technique's efficiency and ensure a prompt tracing of any new potential leak. Despite the occurrence of new leaks within the last 4 years and the observed entrapment of LNAPL in the vadoze zone, bioslurping has managed to greatly restrict the original plume within certain and relatively small parts of the refinery facilities. Presented on: Journal of Hazardous Materials

Summarization: Long-term biodegradation of MSW in an aerobic landfill bioreactor was monitored as a function of time during 510 days of operation. Operational characteristics such as air importation, temperature and leachate recirculation were monitored. The oxygen utilization rates and biodegradation of organic matter rates showed that aerobic biodegradation was feasible and appropriate to proceed in aerobic landfill bioreactor. Leachate analyses showed that the aerobic bioreactor could remove above 90% of chemical oxygen demand (COD) and close to 100% of biochemical oxygen demand (BOD5) from leachate. Ammonium (View the MathML source), nitrate (View the MathML source) and sulphate (View the MathML source) concentrations of leachate samples were regularly measured. Results suggest that nitrification and denitrification occurred simultaneously, and the increase in nitrate did not reach the levels predicted stoichiometrically, suggesting that other processes were occurring. Leachate recirculation reduced the concentrations of heavy metals because of the effect of the high pH of the leachate, causing heavy metals to be retained by processes such as sorption on MSW, carbonate precipitation, and hydroxide precipitation. Furthermore, the compost derived from the aerobic biodegradation of the organic matter of MSW may be considered as soil improvement in the agricultural plant production. Bio-essays indicated that the ecotoxicity of leachate from the aerobic bioreactor was not toxic at the end of the experiment. Finally, after 510 days of degradation, waste settlement reached 26% mainly due to the compost of the organic matter. Presented on: Waste Management

Summarization: Hospital waste management is an imperative environmental and public safety issue, due to the waste’s infectious and hazardous character. This paper examines the existing waste strategy of a typical hospital in Greece with a bed capacity of 400–600. The segregation, collection, packaging, storage, transportation and disposal of waste were monitored and the observed problematic areas documented. The concentrations of BOD, COD and heavy metals were measured in the wastewater the hospital generated. The wastewater’s toxicity was also investigated. During the study, omissions and negligence were observed at every stage of the waste management system, particularly with regard to the treatment of infectious waste. Inappropriate collection and transportation procedures for infectious waste, which jeopardized the safety of staff and patients, were recorded. However, inappropriate segregation practices were the dominant problem, which led to increased quantities of generated infectious waste and hence higher costs for their disposal. Infectious waste production was estimated using two different methods: one by weighing the incinerated waste (880 kg day−1) and the other by estimating the number of waste bags produced each day (650 kg day−1). Furthermore, measurements of the EC50 parameter in wastewater samples revealed an increased toxicity in all samples. In addition, hazardous organic compounds were detected in wastewater samples using a gas chromatograph/mass spectrograph. Proposals recommending the application of a comprehensive hospital waste management system are presented that will ensure that any potential risks hospital wastes pose to public health and to the environment are minimized. Presented on: Waste Management

Summarization: The effect of natural attenuation, biostimulation and bioaugmentation-biostimulation on the removal of petroleum pollutants, specifically Total Petroleum Hydrocarbons (TPH), as well as Polycyclic Aromatic Hydrocarbons (PAHs) in a refinery solid waste was estimated. The experimental procedure took place on a laboratory scale in three separate tanks (natural attenuation, biostimulation and biostimulation-bioaugmentation tank) for a period of 80 days. Optimal conditions of temperature, humidity and ventilation were applied in order to ensure an efficient performance of the microdigesters. According to the results, addition of indigenous microorganisms and nutrients in biostimulation-bioaugmentation tank, proved to be particularly effective on the biodegradation of petroleum pollutants, achieving a removal efficiency of 52 and 87% for TPH and PAHs, respectively. In the biostimulation tank, the efficiency of TPH and PAHs removal was 47 and 59%, accordingly. Less effective appeared to be the natural attenuation process with a reduction efficiency of 37% for TPH and 42% for PAHs. Παρουσιάστηκε στο: Journal of Environmental Chemical Engineering

Summarization: This study investigates an innovative approach for the valorization of specific wastes generated from the energy sector and the production of glass-ceramics. The wastes used were photovoltaic (P/V) glass, produced from the renewable energy sector, and lignite fly ash, produced from the conventional energy sector. The process first involved the production of glass after melting specific mixtures of wastes, namely (i) 70% P/V glass and 30% lignite fly ash, and (ii) 80% P/V glass and 20% lignite fly ash, at 1200 °C for 1 h as revealed by the use of a heating microscope. The results indicated that the P/V glass, as a sodium-potassium-rich inorganic waste, reduces energy requirements of the melting process. The produced glass was then used for the production of glass-ceramics. Dense and homogeneous glass-ceramics, exhibiting high chemical stability and no toxicity, were produced after controlled thermal treatment of glass at 800 °C. The mechanical (compressive strength, Vickers hardness) and physical (open porosity, bulk density and water absorption) properties of the produced glass-ceramics were evaluated. X-ray diffraction (XRD) and Energy Dispersive X-ray fluorescence (ED-XRF) were used for the characterization of the raw materials and the produced glass-ceramics. Scanning electron microscopy (SEM) provided further insights on the microstructure of the final products. The properties of the produced glass-ceramics, namely water absorption and compressive strength, render them suitable for applications in the construction industry. The waste valorization approach followed in this study is in line with the principles of circular economy. Παρουσιάστηκε στο: Waste Management

Summarization: This study investigates the effect of different chemical pretreatments on the solubilization and the degradability of different solid agroindustrial waste, namely winery waste, cotton gin waste, olive pomace and juice industry waste. Eight different reagents were investigated, i.e. sodium hydroxide (NaOH), sodium bicarbonate (NaHCO3), sodium chloride (NaCl), citric acid (H3Cit), acetic acid (AcOH), hydrogen peroxide (H2O2), acetone (Me2CO) and ethanol (EtOH), under three condition sets resulting in treatments of varying intensity, depending on process duration, reagent dosage and temperature. Results indicated that chemical pretreatment under more severe conditions is more effective on the solubilization of lignocellulosic substrates, such as those of the present study and among the investigated reagents, H3Cit, H2O2 and EtOH appeared to be the most effective to this regard. At the same time, although chemical pretreatment in general did not improve the methane potential of the substrates, moderate to high severity conditions were found to generally be the most satisfactory in terms of methane production from pretreated materials. In fact, moderate severity treatments using EtOH for winery waste, H3Cit for olive pomace and H2O2 for juice industry waste and a high severity treatment with EtOH for cotton gin waste, resulted in maximum specific methane yield values. Ultimately, the impact of pretreatment parameters on the different substrates seems to be dependent on their characteristics, in combination with the specific mode of action of each reagent. The overall energy balance of such a system could probably be improved by using lower operating powers and higher solid to liquid ratios. Παρουσιάστηκε στο: Waste Management

Summarization: The use of ethylene diamine tetraacetic acid (EDTA) on the electrokinetic removal of cadmium-contaminated soil was evaluated. A total of four different tests were conducted using EDTA as a washing solution as well as a purging solution at the electrode compartments. The efficiency of electrokinetic extraction was significantly influenced by the pH of the soil medium. The results show that EDTA was effective in desorbing cadmium at a high pH, with Cd–EDTA− anion complexes migrating toward the anode. At low pH values near the anode area, cadmium existed as Cd2+, migrating toward the cathode. Such contradicting directions of cadmium have resulted in its detrimental removal from the soil cell. However, accumulation of cadmium near the cathode was observed at the end of the tests due to the dominating low pH in the soil cell. The phytotoxicity after the electrokinetic process was investigated using Sorghum saccharatum, Lepidium sativum and Sinapis alba plants. The germination index was a major endpoint estimated by measuring seed germination and shoot elongation. The results obtained show that the phytotoxicity was increased after electrokinetic extraction. Despite, the extensive cadmium removal from two-thirds of the cell, the low pH of the soil was the principal parameter exhibiting the phytotoxicity. Presented on: Journal of Environmental Management

Summarization: The removal of BTEX (benzene, toluene, ethyl-benzene and m-,p-,o-xylenes), MTBE (methyl tertiary butyl ether) and TAME (tertiary amyl methyl ether) from aqueous solutions by raw, thermally, chemically and both chemically and thermally treated diatomite was studied, through batch adsorption experiments. In total, 14 different diatomite samples were created and tested. Selected physical characteristics of the adsorbents, such as specific surface area and pore volume distribution, were determined. Matrix and competitive adsorption effects were also explored. It was proved that the diatomite samples were effective in removing BTEX, MTBE and TAME from aqueous solutions, with the sample treated with HCl being the most effective, as far as its adsorption capacity and equilibrium time are concerned. Among the contaminants, BTEX appeared to have the strongest affinity, based on mass uptake by the diatomite samples. Matrix effects were proved to be strong, significantly decreasing the adsorption of the contaminants onto diatomite. The kinetics data proved a closer fit to the pseudo second order model, while the isotherm experimental data were a better fit to the Freundlich model. However, the latter produced values of the isotherm constant 1/n greater than one, indicating unfavorable adsorption. Presented on: Journal of Hazardous Materials

Summarization: Over the last years, emerging incentives for secondary production of high tech-metals, found in e-waste, are created because of their increasing demand and economic issues associated with their primary production. Due to the very low share of these metals in e-waste, pre-treatment methods can result in an output fraction rich in the metals of interest and may, therefore, be essential. To this scope, the present article evaluates and compares the efficiency of four different pre-treatment approaches containing various steps for recovering indium (In) from liquid crystal displays (LCDs) in laptop computers. The pre-treatment steps, used in various combinations, are (a) dry mechanical crushing and sieving, (b) pyrolysis, (c) thermal shock and (d) gravimetric process. Also, in all approaches, liquid crystals were removed from the samples, before applying the mechanical crushing step, as these are toxic and potentially harmful to human health and the environment. The removal was achieved by ultrasonic irradiation or mild agitation and optimized in terms of time, temperature and solvent type and concentration. Then, the feasibility of each pre-treatment approach was evaluated based on two parameters: (a) the content of In in the resulting sample after pre-treatment and (b) the separated mass share (%) with larger indium content as compared to the original LCD panel. The results showed that In is highly liberated in the fractions consisting of finest particles (