The influence of perforation of foil reactors on greenhouse gas emission rates during aerobic biostabilization of the undersize fraction of municipal wastes.

The opinion, that the use of foil reactors for the aerobic biostabilization of municipal wastes is not a valid method, due to vulnerability to perforation, and risk of uncontrolled release of exhaust gasses, was verified. This study aimed to determine the intensity of greenhouse gas (GHG) emissions to the atmosphere from the surface of foil reactors in relation to the extent of foil surface perforation. Three scenarios were tested: intact (airtight) foil reactor, perforated foil reactor, and torn foil reactor. Each experimental variant was triplicated, and the duration of each experiment cycle was 5 weeks. Temperature measurements demonstrated a significant decrease in temperature of the biostabilization in the torn reactor. The highest emissions of CO2, CO and SO2 were observed at the beginning of the process, and mostly in the torn reactor. During the whole experiment, observed emissions of CO, H2S, NO, NO2, and SO2 were at a very low level which in extreme cases did not exceed 0.25 mg t-1.h-1 (emission of gasses mass unit per waste mass unit per unit time). The lowest average emissions of greenhouse gases were determined in the case of the intact reactor, which shows that maintaining the foil reactors in an airtight condition during the process is extremely important.

Nitrogen removal from landfill leachate in constructed wetlands with reed and willow: redox potential in the root zone.

This study investigated the effects of reed and willow on bioremediation of landfill leachate in comparison with an unplanted control by measuring redox potential levels in the rhizosphere of microcosm systems in a greenhouse. Plants had a significant influence on redox potential relative to the plant-less system. Redox potential in the reed rhizosphere was anoxic (mean -102±85 mV), but it was the least negative, being significantly higher than in the willow (mean -286±118 mV), which had the lowest Eh. Redox potential fluctuated significantly in the willow rhizosphere during daylight hours, with large decreases in the morning. Levels of NH(4)(+) decreased significantly in the first day of the experiment and remained at similar low levels in all three variants for the next four weeks of the experiment. Following this removal of ammonia significant peaks in NO(2)(-) occurred in the control and reed tanks on the 1st day, and again on 14th day in the control tank up to 13 mg/dm(3). In the willow tank there was also one significant peak of NO(2)(-) in the first week, but only up to 0.5 mg/dm(3). Significant accumulation, within 21 days of NO(3)(-) in all variants was observed, but in tanks with reed and willow the concentration of NO(3)(-) remained significantly lower (<4 mg/dm(3)) than in the unplanted tank (∼35 mg/dm(3)). Final levels of total-nitrogen, nitrate and chemical oxygen demand were considerably lower in the reed and willow tank than in the unplanted tank.

Aerobic Biostabilization of the Organic Fraction of Municipal Solid Waste-Monitoring Hot and Cold Spots in the Reactor as a Novel Tool for Process Optimization.

The process of aerobic biostabilization (AB) has been adopted for treatment of the organic fraction of municipal solid waste (OFMSW). However, thermal gradients and some side effects in the bioreactors present difficulties in optimization of AB. Forced aeration is more effective than natural ventilation of waste piles, but "hot and cold spots" exist due to inhomogeneous distribution of air and heat. This study identified the occurrence of hot and cold spots during the OFMSW biostabilization process at full technical scale. It was shown that the number of hot and cold spots depended on the size of the pile and aeration rate. When the mass of stabilized waste was significantly lower and the aeration rate was two-fold higher the number of anaerobic hot spots decreased, while cold spots increased. In addition, the results indicated that pile construction with sidewalls decreased the number of hot spots. However, channelizing the airflow under similar conditions increased the number of cold spots. Knowledge of the spatial and temporal distribution of process gases can enable optimization and adoption of the OFMSW flow aeration regime. Temperature monitoring within the waste pile enables the operator to eliminate undesirable "hot spots" by modifying the aeration regime and hence improve the overall treatment efficiency.

Phytotoxicity of landfill leachate on willow--Salix amygdalina L.

Because of low investment and operational costs, interest is increasing in the use of willow plants in landfill leachate disposal. Toxic effects of leachate on the plants should be avoided in the initial period of growth and phytotoxicological testing may be helpful to select appropriate leachate dose rates. The aim of this study was to determine the phytotoxicity of landfill leachate on young willow (Salix amygdalina L.) cuttings, as a criterion for dose rate selection in the early phase of growth. Over a test period of 6 weeks plants were exposed to six concentrations of landfill leachate solutions (0%; 6.25%; 12.5%; 25%; 50% and 100%), under two different regimes. In regime A willow plants were cultivated in leachate solution from the beginning, whereas in regime B they were grown initially in clean water for 4 weeks, after which the water was exchanged for leachate solutions. The lowest effective concentration causing toxic effects (LOEC) was calculated (p<0.05). In regime A LOEC was between 5.44% and 6.50% of leachate concentration, but slightly higher in regime B (5.32-6.59%). Willow plants were able to survive in landfill leachate solutions with electrical conductivity (EC) values up to 5.0 mS/cm in regime A, whereas in regime B plants were killed when EC exceeded 3.0 mS/cm. This indicates an ability of willow plants to tolerate higher strengths of landfill leachate if they are cultivated in such concentrations from the beginning.

Using fractal geometry to determine phytotoxicity of landfill leachate on willow.

Phytotoxicological tests were conducted during 6weeks on the willow Salix amygdalina using six concentrations of landfill leachate. Plants were exposed to landfill leachate solutions using two regimes: (A) - the willow shoots were watered by leachate solution from the beginning of the test; (B) - the willow shoots were cultivated in pots with clean water during 4weeks, then water was exchanged for leachate solutions. The tolerance of plants to prepared leachate concentration was determined by observations of morphological parameters of leaves including their fractal dimension. The lowest effective concentration (LOEC) was calculated. Results showed that in regime A, all measured parameters indicated similar response of plants to phytotoxic compounds in leachate. The LOEC was in the range 4.69-5.63% of leachate concentration. In regime B, only such parameters as leaf length and fractal dimension indicated a marked response (LOEC was much lower for other parameters, 0.8% and 1.84% respectively). Leaf length and, especially, fractal dimension are shown to be good indicators of plant response to toxicants in their environment.

Contrasting effects of n-3 and n-6 fatty acids on cyclooxygenase-2 in model systems for arthritis.

Cyclooxygenase-2 (COX-2) is intimately involved in symptoms of arthritis while dietary n-3 polyunsaturated fatty acids (PUFA) are thought to be beneficial. In these experiments, using both bovine and human in vitro systems that mimic features of arthritis, we show that the n-3 PUFA eicosapentaenoic acid (EPA) is able to reduce mRNA and protein levels of COX-2. Activity, as assessed through prostaglandin E(2) formation, was also reduced in a dose-dependent manner. These effects of EPA contrasted noticeably with the n-6 PUFA, arachidonic acid. The data provide direct evidence for a molecular mechanism by which dietary n-3 PUFA, such as EPA, can reduce inflammation and, hence, associated symptoms in arthritis.

Cu and Cd effects on the earthworm Lumbricus rubellus in the laboratory: multivariate statistical analysis of relationships between exposure, biomarkers, and ecologically relevant parameters.

This study sets out to examine the potential of a suite of novel molecular biomarkers as early warning indicators of environmental state and damage. Transcriptional responses of four genes, metallothionein 1 and 2, amine oxidase, and the lysosomal associated glycoprotein, were measured in the earthworm Lumbricus rubellus exposed to increasing concentrations of cadmium and copper in OECD soil. These responses were compared to metal body concentrations and lifecycle parameters: survival, cocoon production, and growth. Adverse physiological effects were observed at concentrations 1/3rd to 1/10th those of the artificial soil LC50. Multivariate statistics, principal component analysis (PCA), was used to investigate the correlations between the different variables. Three key components were derived explaining 77.6% of the variance, with component 1 contributing 32.4%, component 2 contributing 26.7%, and component 3 contributing 18.5%. These components were interpreted in terms of population health, pollutant exposure, and detoxification pathways, respectively. It is proposed that the use of such a suite of biomarkers could serve as indicators of the "health" of the soil environment and provide early warning signals of potential danger to the biota or as a means of monitoring soil remediation.

Analysis of microbial community functional diversity using sole-carbon-source utilisation profiles - a critique.

Abstract Information on functional diversity (metabolic potential) is essential for understanding the role of microbial communities in different environments. Variations of the commercially available BIOLOG bacterial identification system plates are now widely used to assess functional diversity of microorganisms from environmental samples, based on utilisation patterns of a wide range (up to 95) of single carbon sources. There are many problems as well as benefits of using the approach, but the former are often disregarded. Here the basis of the approach is summarised, including type of plate to use, treatment of samples, replication, incubation conditions, monitoring of plates, and statistical analysis. The pros and cons of its use are critically assessed, inherent biases and limitations are pointed out and methodological difficulties are considered. Possible ways of overcoming some of the difficulties are suggested.

Flow cytometry and other techniques show that Staphylococcus aureus undergoes significant physiological changes in the early stages of surface-attached culture.

The techniques of flow cytometry, scanning and transmission electron microscopy, and confocal scanning laser microscopy were used to study the physiology of Staphylococcus aureus in the early stages of surface-attached culture, and to make direct comparisons with planktonic bacteria grown under the same conditions. Attached bacteria growing in nutrient-rich batch culture were found to go through the same growth phases as equivalent planktonic cultures, but with an exponential growth rate of about half that of the planktonic bacteria. Viability of attached bacteria was very high (around 100%) throughout the first 24 h of growth. The size and protein content of attached bacteria varied with growth phase, and both measurements were always smaller than in planktonic bacteria at equivalent growth phases. Respiratory activity per bacterium, as measured by flow cytofluorimetry, and corrected for cell volume, peaked very early in attached cultures (before the first cell division) and declined from then on, whereas in planktonic bacteria it peaked in late exponential phase. Attached and planktonic bacteria showed thicker cell walls in stationary phase than in exponential phase. Membrane potentials of planktonic and attached bacteria were similar in stationary phase, but were much lower in exponential-phase attached cells than in the equivalent planktonic cells. It is apparent that a range of significant physiological adaptations occur during the early phases of attached growth.