Valorization of Spirodela polyrrhiza biomass for the production of biofuels for distributed energy.

Considering the main objectives of a circular economy, Lemnaceae plants have great potential for different types of techniques to valorize their biomass for use in biofuel production. For this reason, scientific interest in this group of plants has increased in recent years. The aim of this study was to evaluate the effects of salt stress on the growth and development of S. polyrrhiza and the valorization of biomass for biofuel and energy production in a circular economy. Plants were grown in a variety of culture media, including standard 'Z' medium, tap water, 1% digestate from a biogas plant in Piaszczyna (54° 01' 21″ N, 17° 10' 19″ E), Poland) and supplemented with different concentrations of NaCl (from 25 to 100 mM). Plants were cultured under phytotron conditions at 24 °C. After 10 days of culture, plant growth, fresh and dry biomass, as well as physio-chemical parameters such as chlorophyll content index, gas exchange parameters (net photosynthesis, transpiration, stomatal conductance and intercellular CO2 concentration), chlorophyll fluorescence measurements were analyzed. After 10 days of the experiment, the percentage starch content of Spirodela shoot segments was determined. S. polyrrhiza was shown to have a high starch storage capacity under certain unfavorable growth conditions, such as salt stress and nutrient deficiency. In the W2 (50 mM NaCl) series, compared to the control (Control2), starch levels were 76% higher in shoots and 30% lower in roots. The analysis of the individual growth and development parameters of S. polyrrhiza plants in the experiment carried out indicates new possibilities for the use of this group of plants in biofuel and bioethanol production.

Source apportionment of PM10 and PM2.5 in major urban Greek agglomerations using a hybrid source-receptor modeling process.

A hybrid source-receptor modeling process was assembled, to apportion and infer source locations of PM10 and PM2.5 in three heavily-impacted urban areas of Greece, during the warm period of 2011, and the cold period of 2012. The assembled process involved application of an advanced computational procedure, the so-called Robotic Chemical Mass Balance (RCMB) model. Source locations were inferred using two well-established probability functions: (a) the Conditional Probability Function (CPF), to correlate the output of RCMB with local wind directional data, and (b) the Potential Source Contribution Function (PSCF), to correlate the output of RCMB with 72h air-mass back-trajectories, arriving at the receptor sites, during sampling. Regarding CPF, a higher-level conditional probability function was defined as well, from the common locus of CPF sectors derived for neighboring receptor sites. With respect to PSCF, a non-parametric bootstrapping method was applied to discriminate the statistically significant values. RCMB modeling showed that resuspended dust is actually one of the main barriers for attaining the European Union (EU) limit values in Mediterranean urban agglomerations, where the drier climate favors build-up. The shift in the energy mix of Greece (caused by the economic recession) was also evidenced, since biomass burning was found to contribute more significantly to the sampling sites belonging to the coldest climatic zone, particularly during the cold period. The CPF analysis showed that short-range transport of anthropogenic emissions from urban traffic to urban background sites was very likely to have occurred, within all the examined urban agglomerations. The PSCF analysis confirmed that long-range transport of primary and/or secondary aerosols may indeed be possible, even from distances over 1000km away from study areas.

Environmental hazard assessment of coal fly ashes using leaching and ecotoxicity tests.

The environmental hazard of six coal fly ash samples collected from various coal incineration plants were examined in the present study, using various leaching tests along with physicochemical and ecotoxicological analyses. Physicochemical analyses indicated that the concentration of Ba, Cr, Mo, Se, sulfates and total dissolved solids (TDS) exceeded the threshold values, according to the European Council decision 2003/33/EC for inert, non-hazardous or hazardous waste. The highest sensitivity, among examined organisms, was presented by Daphnia magna and was ascribed to the lowest tolerance of the organism to Cr. The toxic effect profile of the leachates toward Vibrio fischeri revealed that its bioluminescence was significantly altered by the presence of heavy metals in the leachates (such as Cu, Ni and Zn) in low or sub-lethal doses. Although the toxicity of the leachates toward Pseudokirchneriella subcapitata was relatively high, the correlation between the toxicity and heavy metals concentration was rather poor, indicating the significance of the bioavailability of constituents and the importance of toxicity testing. Based on the classification of the samples resulted by physicochemical analyses of the leachates and the results of ecotoxicity tests, Physicochemical and Ecotoxicological indices were also defined, for an overall evaluation of the environmental impact assessment of fly ashes. The suggested indices showed that ecotoxicity tests were in some cases inconsistent with the outcome of waste classification based on physicochemical analyses. Moreover, the examination of leaching protocols and obtained results showed that one stage leaching test (L/S=10 L/kg) underestimated the fly ash classification, when compared with the two stage test EN 12457-3 at the cumulative ratio L/S=10 L/kg. In addition, the application of availability test NEN 7341 provided useful results about the ecotoxicity wastes. Thus, NEN 7341 is strongly suggested for the implementation of such studies, since the bioavailability of constituents may not be altered by pH adjustment tactics and pH-originated toxicity effects may be avoided.

Assessment of wastewater effluent quality in Thessaly region, Greece, for determining its irrigation reuse potential.

The objective of the present study is to assess wastewater effluent quality in Thessaly region, Greece, in relation to its physicochemical and microbiological burden as well as its toxic potential on a number of organisms. Wastewater may be used for agricultural as well as for landscape irrigation purposes; therefore, its toxicity potential is quite important. Thessaly region has been chosen since this region suffers from a distinct water shortage in summer period necessitating alternative water resources. During our research, treated effluents from four wastewater treatment plants operating in the region (Larissa, Volos, Karditsa, and Tirnavos) were tested for specific physicochemical and microbiological parameters [biochemical oxygen demand (BOD(5)), chemical oxygen demand (COD), total suspended solids (TSS), pH, electrical conductivity, selected metals presence (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn, As), and fecal coliforms' (FC) number]. The effluents were also tested for their toxicity using two different bioassays (Daphnia magna immobilization test and Phytotoxkit microbiotest). The findings were compared to relative regulations and guidelines regarding wastewater reuse for irrigation. The results overall show that secondary effluents in Thessaly region are generally acceptable for reuse for irrigation purposes according to limits set by legislation, if effective advanced treatment methods are applied prior to reuse. However, their potential toxicity should be closely monitored, since it was found that it may vary significantly in relation to season and location, when indicator plant and zooplankton organisms are used.

Evaluation of toxic and interactive toxic effects of three agrochemicals and copper using a battery of microbiotests.

Three commonly used test organisms of different trophic levels (Vibrio fischeri, Pseudokirchneriella subcapitata and Daphnia magna) were exposed to selected agrochemicals (fosthiazate, metalaxyl-M, imidacloprid) and copper, in single doses or in binary mixtures. The toxicity of each single compound varied up to two orders of magnitude, depending on the test species examined. V. fischeri was the most sensitive test organism regarding fosthiazate and metalaxyl-M, indicating an IC(50) value of 0.20 mg/L (0.17-0.25 mg/L) and 0.88 mg/L (0.35-1.57 mg/L), respectively. Imidacloprid was the least toxic compound, indicating an EC(50) value on D. magna of 64.6 mg/L (43.3-122.5 mg/L) and an IC(50) value on V. fischeri of 226 mg/L (159-322 mg/L), while for imidacloprid at a concentration of 1000 mg/L the effect on P. subcapitata was lower than 50%. Copper was the most toxic compound towards all test organisms exhibiting the highest toxic effect on P. subcapitata, with an IC(50) value of 0.05 mg/L (0.003-0.008 mg/L). The toxic effects of the binary mixtures have been compared to the theoretically expected effect, resulting from a simple mathematical model based on the theory of probabilities. The independent action model was used in order to predict the theoretically expected effect. The interactive effects were mostly antagonistic or additive, while in few cases (interactive effects of metalaxyl-M and copper on V. fischeri) a synergistic mode of action was observed for some concentration combinations. Experiments showed that interactive effects of chemicals may vary depending on the test species used as well as on the chemicals and their respective concentrations. Although most of the concentrations of chemicals tested in this study are higher than the ones usually found in natural environment, the evaluation of their interactive toxic effects using a battery of bioassays may comprise a useful tool for the estimation of the environmental hazard of chemicals.

Marginalised social groups in contemporary weee management within social enterprises investments: A study in Greece.

This paper deals with the creation of appropriate conditions aimed at developing social services for reuse and recycling of waste electrical and electronic equipment (WEEE), by the inclusion of handicapped and Roma people in the workforce. Application areas for the project are the Hellenic (Greek) regions of Thessaly and North Aegean, where these groups suffer from professional and social exclusion. The efforts to reduce unemployment in the two aforementioned groups, together with the efforts to implement related Greek and European legislation for sustainable WEEE management, are examined here. Furthermore, networking and cooperation at local, regional and central levels between small enterprises, entrepreneurships and local authorities are examined, so that these social enterprises and their corresponding investments may support the development of the Greek alternative WEEE recycling system.

Influence of ozonation on the in vitro mutagenic and toxic potential of secondary effluents.

Reclamation of municipal effluents by advanced treatment processes is an attractive perspective for facing certain water shortage problems. However, the application of tertiary techniques should be thoroughly examined for their potential hazardous effects. Ozonation is an efficient chemical oxidation method, often used in wastewater reclamation, which may result in by-products that may alter the toxic and mutagenic properties of effluents. In this study, Ames test and Microtox test were used for the evaluation of ozonation efficiency to upgrade secondary effluents quality. In general, the toxic response and mutagenic effect without metabolic activation of test species were influenced mainly by the ozone dose and ozonation duration, whereas the mutagenic effect with metabolic activation was influenced mainly by ozone dose, indicating that ozone conditions strongly affect the formation of by-products. In most cases, the toxicity was increased and reached up to 100% (in relation to that of secondary effluent) after ozonation with 8.0 mg O3/L for 5 min. On the contrary, in most cases the mutagenic activity towards strain TA98 without metabolic activation was reduced, when ozone dose and contact time increased. However, the mutagenicity was also increased after ozonation at low ozone doses and for contact times less than 5 min. The mutagenic activity of treated effluents towards strain TA98 with metabolic activation remained about the same or was reduced, compared to that of secondary effluent, and was even eliminated after ozonation with 8.0 mg O3/L for contact times higher than 5 min.

Application of leaching tests for toxicity evaluation of coal fly ash.

The toxic properties of coal fly ash samples obtained from various coal combustion power plants were evaluated in this work using physicochemical analyses and bioassays. Physicochemical analyses showed that heavy metals present in solid samples included Cr, Cu, Mn, Ni, Pb, and Zn. The results of the chemical analysis of eluates deduced by the application of standard leaching tests according to EN 12457-2 and Toxicity Characteristic Leaching Procedure (TCLP) methods indicated that the compounds contained in fly ashes could potentially be transferred to the liquid phase depending upon the leaching method used. Heavy metal concentrations were higher in TCLP eluates, indicating that the initial pH value of the leaching medium significantly affected the transfer of these elements to the liquid phase. Tests conducted with the photobacterium Vibrio fischeri (Microtox test), the crustacean Daphnia magna, and the rotifer Brachionus calyciflorus were used to assess toxicity of eluates obtained by both leaching tests. Daphnia magna was the most sensitive test organism. The EN 12457-2 method proved to be more reliable for toxicity evaluation of eluates. In contrast, the TCLP method showed some interference owing to acetic acid toxicity, and precipitation occurred after pH adjustment of eluates from acid to neutral range. The toxicity of both fly ashes and the corresponding solid leaching residues of EN 12457-2 and TCLP leaching tests was also measured using the Microtox Basic Solid phase Test. The results generated with this bioassay indicated that toxicity was greatly influenced by the pH status of the solid samples.

Ecotoxicological properties of wastewater treated using tertiary methods.

The objective of this work was the examination of the efficiency of coagulation and ozonation processes for the production of reclaimed wastewater with low toxicity. Municipal secondary effluents were treated by FeCl3, Al2(SO4)3 (alum), and a commercial substance at metal ion concentrations of 0.5 and 1 mmol/L. Alternatively, the effluents were treated by ozonation in a semibatch ozone reactor. The feed gas was introduced at a flowrate of 3 L/min containing ozone at various concentrations, ranging between 2.5 and 8 mg/L; ozone residence times were 2, 5, 15, and 30 min. The toxic effects of the advanced treated effluents were examined by a battery of tests using the marine bacteria Vibrio fischeri, the freshwater crustaceans Daphnia magna, Daphnia pulex, and Thamnocephalus platyurus, and the rotifers Brachionus calyciflorus. The addition of alum decreased the toxic effect of reclaimed wastewater on immobilization of D. pulex, from 90 to 60%. Ozonation was also effective for toxicity removal, which decreased to 25% effect on D. pulex after treatment by 2.5 mg O3/L for 2 min. However, acute toxic effects after ozonation, were observed on V. fischeri and were related to ozone gas concentration and contact time. At the highest ozone dosage, the toxicity reached almost 100% inhibition of bioluminescence after 15 min. The toxicity of the ozonated effluents to bacteria decreased with sample storage time and was almost negligible after 48 h, indicating that the potential adverse effect of reclaimed wastewaters on receiving waters might be reduced by storage for a certain time.

Bioavailability and toxicity of heavy metals in the presence of natural organic matter.

The effect of humic acids (HA) on the toxicity of copper, zinc and lead was investigated in this study, using the photobacterium Vibrio fischeri (Microtox test) as a test organism. The metal species and the complexation capacity of HA were predicted using model WinHumicV for speciation modeling. The toxicities of copper and lead were generally comparable, while the toxicity of zinc was lower than the ones of the other two method. The toxicity of copper decreased with the addition of HA, while the toxicity of zinc remained almost constant. The complexation of Zn with HA was low. Thus the presence of HA did not significantly influence the toxicity of Zn. For Cu and Zn, the free metal ion species showed to be basically responsible for the toxicity of these metals, while for Pb the chlorocomplexes and Pb-HA complexes contributed to the toxicity of Pb, indicating that the toxicity of heavy metals depends not only on the free metal ion species concentration but on different metal species that may be bioavailable.

The effect of coagulation on the toxicity and mutagenicity of reclaimed municipal effluents.

The objectives of this work were the assessment of the effectiveness of coagulation on the reclamation of secondary effluents and the evaluation of the quality of reclaimed waters by the examination of their ecotoxic and mutagenic properties. Aluminum coagulants resulted in higher removal of organic content, than iron coagulant, reaching up to 40%; the removal of heavy metals, such as zinc and copper was enhanced by the addition of a low strength anionic flocculant. The toxicity of pre-concentrated samples to the bacteria Vibrio fischerii was related to the heavy metal content, especially zinc and copper, indicating the significance of the metals bioavailability and their potential interactive effects. The secondary effluents exhibited mutagenic effects on strain TA 98; these effects were increased during coagulation with ferric chloride (both in absence and presence of flocculant). However, the addition of aluminum coagulants resulted in a decrease of mutagenic potential of secondary effluents, due to the extended removal of organic matter.

Interactive toxic effects of heavy metals and humic acids on Vibrio fischeri.

The effect of humic acids (HAs) on the toxicity of copper, zinc, and lead was investigated using the photobacterium Vibrio fischeri (Microtox test) as a test organism. The effects of HAs on metal toxicity were evaluated as functions of time and concentration in pure compound solutions. The toxicities of copper and lead were generally comparable, while the toxicity of zinc was lower than those of the other two metals. The toxicity of copper decreased with the addition of HAs, while the toxicity of zinc remained almost constant. On the other hand, the toxicity of lead increased, depending on the concentration of HAs. The interactive effects between copper and zinc and between lead and zinc were synergistic, while the interactive effect between copper and lead on the bioluminescence of V. fischeri was additive. The presence of HAs caused relatively high toxicity reduction in the binary mixtures of zinc and copper or zinc and lead, while the toxicity reduction in the case of the binary mixture of copper and lead was negligible.

Comparison of several toxicity tests applied to complex wastewaters and mussel biomarkers in receiving waters.

In this study, the complex wastewaters/effluents discharged to coastal regions of Turkey and Greece were sampled, and various toxicity tests were applied. The bioassays used included the assessment of the luminescence inhibition of the bacterium Vibrio fisheri, the photosynthesis inhibition (14C uptake rate) and growth inhibition of the algal species Phaeodactylum tricornutum, and the mortality of the crustacean Artemia franciscana and rotifer Brachionus plicatilis. Additionally, "neutral red retention" and "filtration rate" sublethal biomarker techniques were performed by utilizing the mussel species Mytilus galloproviancialis, inhabiting the points of discharges in Turkey. All discharges tested were found to be acutely toxic to P. tricornutum and slightly toxic to V. fisheri, A. franciscana, and B. plicatilis. Test results showed that the 14C uptake rate toxicity test was the most sensitive one among the other bioassays. The biomarker results showed that the health status of mussels in the coastal areas decreased significantly, indicating the pollution of the receiving waters in Turkey. The conclusions drawn highlight the necessity for an intesive ecotoxicological monitoring scheme that will incorporate the most suitable bioassays and biomarkers to adequately contribute to the upgrading and maintenance of the ecological quality of the coastal waters in Greece and in Turkey.

Evaluation of toxic properties of industrial wastewater using on-line respirometry.

An on-line respirometric biosensor using activated sludge microorganisms was used in this work for the assessment of toxic properties of industrial effluents and for the evaluation of their effect on the performance of a municipal wastewater treatment plant. Continuous monitoring of combined industrial discharges was carried out for a period of six months, and increased toxicity values were observed during the evening times and the weekends, possibly due to the discharge of partially treated wastewaters from certain processing units. Furthermore, no direct correlation was observed between toxicity values and organic content, indicating that simply monitoring organic load, as it usually happens in most wastewater treatment plants, does not help in predicting the toxic properties of the effluent. Therefore, the installation and operation of an on-line respirometer is required, in combination with chemical analysis, for the protection of the operation of a municipal wastewater treatment plant from toxic shocks. The assessment of toxicity of wastewaters from certain industrial plants showed that bioluminescence inhibition on Vibrio fischeri was generally higher than the respirometric inhibition on activated sludge microorganisms. It was concluded that for the evaluation of potential toxicity of influents on a wastewater treatment plant, activated sludge microorganisms should be preferred as test species.

Using bioassays for testing seawater quality in Greece.

The objective of this work was the assessment of seawater quality in Thermaikos Gulf, Pagassitikos Gulf and Skiathos island in Northern Aegean Sea by the use of bioassays. Two bioassays using marine organisms as indicators of seawater quality were applied in this study; the invertebrate Artemia franciscana and the marine bioluminescent bacterium Vibrio fischeri. Bioassays are required for the integrated evaluation of water pollution, as physical and chemical tests alone are not sufficient enough for the assessment of potential effects on aquatic organisms. According to the result of this study, improvement in coastal water quality of Thermaikos Gulf was observed between September 1997 and April-May 2000. However, coastal water quality of Pagassitikos Gulf varied during the test period; it was generally good during April-May 2000, while in October 1999 it was generally poor. Between the two bioassays that have been applied in this study, the Microtox test, where the marine bacterium V. fischeri was used as a test organism, was more sensitive in detecting toxicity in seawater.

Toxicity, bioaccumulation, and interactive effects of organotin, cadmium, and chromium on Artemia franciscana.

The effects of three organotin compounds-trimethyltin chloride, dimethyltin dichloride, and dibutyltin diacetate-and two heavy metals-cadmium and hexavalent chromium-on Artemia franciscana mortality are investigated in this study. Of all the compounds tested in this work, trimethyltin chloride was, by far, the most toxic. The toxicity order for the five compounds was trimethyltin chloride > potassium dichromate > dimethyltin dichloride > dibutyltin diacetate > cadmium chloride. The big difference in toxicity between dialkyltin and trialkyltin was not accompanied by an equally big difference in bioaccumulation. At a Sn concentration in water of 10 mg/L, the bioconcentration factor was 50 for dimethyltin dichloride and 75 for trimethyltin chloride. At a Sn concentration in water of 100 mg/L, the bioconcentration factor for 6 for dimethyltin dichloride and 9 for trimethyltin chloride. The interactive effect of trimethyltin chloride and cadmium, as well as that of trimethyltin chloride and chromium, was found to be synergistic. Also found to be synergistic was the interactive effect of trimethyltin chloride with cadmium and chromium applied together.

Statistical evaluation of PCDD/F emission data during solid waste combustion by fuzzy clustering techniques.

An advanced statistical analysis technique using the fuzzy clustering method was employed in this work, for the evaluation of PCDD/F emissions during solid waste combustion. In addition, this technique was applied for the assessment of the effect of an inhibitor (urea) on the toxic compound releases and on the various isomer distributions. Municipal solid wastes were combusted in a lab-scale reactor and the toxic gas emissions were measured at the unit outlet. Combustion tests of urea-fuel mixtures were classified in the same group, indicating that urea affected the formation mechanisms of toxic gases. Combustion tests of single fuel were not included in the same group. Furthermore, urea ability to modify the gas emissions pathways was not affected by the method of its addition to the fuel.

Toxicity of organic and inorganic mercury to Saccharomyces cerevisiae.

In this study the effect if six different forms of mercury on the growth of the yeast Saccharomyces cerevisiae is presented. Five kinds of strains of S. cerevisiae were used. They were a wild type, a mercury-resistant type, and three mutants: mutation repair-deficient mutant, excision repair-deficient mutant, and recombination repair-deficient mutant. In terms of EC50 toward the wild-type strain, the toxicity order for the inorganic forms was Hg(NO3)2>HgSO4>HgCl2. Monovalent nitrate mercury Hg(NO3)2 was more toxic than bivalent Hg(NO3)2. The toxicity of organic mercury CH3HgCl on cell growth was two orders of magnitude higher than that of inorganic HgCl2. Between the two organic forms, CH3HgCl was more toxic than CH3HgOH. The survival rate in the presence of a certain concentration of CH3HgCl was about one-hundredth of the survival in presence of the same concentration of HgCl2. On the other hand, the concentration of CH3HgCl in the cell was about 170 times that of HgCl2. The addition of chelating agents, EDTA and methyl-penicillamine, to the medium did not reduce the toxicity of mercury. Among the three mutants tested, the one deficient in recombination repair systems was the most sensitive to mercury.