Photocatalytic and combined anaerobic-photocatalytic treatment of textile dyes

A photocatalytic process based on immobilized titanium dioxide was used to treat crude solutions of azo, anthraquinone and phthalocyanine textile dyes. In addition, the process was applied to the treat autoxidized chemically reduced azo dyes, i.e. representatives of recalcitrant dye residues after biological sequential anaerobic-aerobic treatment. Photocatalysis was able to remove more than 90% color from crude as well as autoxidized chemically reduced dye solutions. UV-absorbance and COD were also removed but to a lower extent (50% in average). The end products of photocatalytic treatment were not toxic toward methanogenic bacteria. The results demonstrate that photocatalysis can be used as a pre- or post-treatment method to biological anaerobic treatment of dye-containing textile wastewater.     

Functionally relevant microorganisms to enhanced biological phosphorus removal performance at full-scale wastewater treatment plants in the United States

The abundance and relevance ofAccumulibacter phosphatis (presumed to be polyphosphate-accumulating organisms [PAOs]), Competibacter phosphatis (presumed to be glycogen-accumulating organisms [GAOs]), and tetrad-forming organisms (TFOs) to phosphorus removal performance at six full-scale enhanced biological phosphorus removal (EBPR) wastewater treatment plants were investigated. Coexistence of various levels of candidate PAOs and GAOs were found at these facilities. Accumulibacter were found to be 5 to 20% of the total bacterial population, and Competibacter were 0 to 20% of the total bacteria population. The TFO abundance varied from nondetectable to dominant. Anaerobic phosphorus (P) release to acetate uptake ratios (P(rel)/HAc(up)) obtained from bench tests were correlated positively with the abundance ratio of Accumulibacter/(Competibacter +TFOs) and negatively with the abundance of (Competibacter +TFOs) for all plants except one, suggesting the relevance of these candidate organisms to EBPR processes. However, effluent phosphorus concentration, amount of phosphorus removed, and process stability in an EBPR system were not directly related to high PAO abundance or mutually exclusive with a high GAO fraction. The plant that had the lowest average effluent phosphorus and highest stability rating had the lowest P(rel)/HAc(up) and the most TFOs. Evaluation of full-scale EBPR performance data indicated that low effluent phosphorus concentration and high process stability are positively correlated with the influent readily biodegradable chemical oxygen demand-to-phosphorus ratio. A system-level carbon-distribution-based conceptual model is proposed for capturing the dynamic competition between PAOs and GAOs and their effect on an EBPR process, and the results from this study seem to support the model hypothesis.     

Field and laboratory simulations of storm water pulses: behavioural avoidance by marine epifauna

Epifaunal communities associated with macroalgae were exposed to storm water pulses using a custom made irrigation system. Treatments included Millipore freshwater, freshwater spiked with trace metals and seawater controls to allow for the relative importance of freshwater inundation, trace metals and increased flow to be determined. Experimental pulses created conditions similar to those that occur following real storm water events. Brief storm water pulses reduced the abundance of amphipods and gastropods. Freshwater was the causative agent as there were no additional effects of trace metals on the assemblages. Laboratory assays indicated that neither direct nor latent mortality was likely following experimental pulses and that epifauna readily avoid storm water. Indirect effects upon epifauna through salinity-induced changes to algal habitats were not found in field recolonisation experiments. Results demonstrate the importance of examining the effects of pulsed contaminants under realistic exposure conditions and the need to consider ecologically relevant endpoints.     

Use of principal component analysis to profile temporal and spatial variations of chlorinated solvent concentration in groundwater

This work aims at evaluating spatial distribution patterns of concentration variations for chlorinated solvents in groundwater, based on principal component analysis and geographic information system (GIS) tools. The study investigates long-time series of chlorinated solvent concentrations in groundwater measured for 18 contaminated industrial sites. The characterization of contaminant plumes and delineation of pollutant sources are essential for choosing appropriate monitoring and remediation strategies, as contaminated groundwaters are characterized by complex patterns of spatial and temporal concentration variability, with wide unpredictable fluctuations over time. The present work describes the results of a new exploratory statistical method called the Variability Index Method (VIM) applied to environmental data to assess the performance of using concentration variations as molecular tracers to reveal aquifer dynamics, industrial impacts, and point sources for contamination plumes. The application of this method provides a useful assessment of controls over contaminant concentration variations as well as support for remediation techniques.     

Long-term survey of heavy-metal pollution, biofilm contamination and diatom community structure in the Riou Mort watershed, South-West France

In a metal-polluted stream in the Riou Mort watershed in SW France, periphytic biofilm was analyzed for diatom cell densities and taxonomic composition, dry weight and metal bio-accumulation (cadmium and zinc). Periphytic diatom communities were affected by the metal but displayed induced tolerance, seen through structural impact (dominance of small, adnate species) as well as morphological abnormalities particularly in the genera Ulnaria and Fragilaria. Species assemblages were characterized by taxa known to occur in metal-polluted environments, and shifts in the community structure expressed seasonal patterns: high numbers of Eolimna minima, Nitzschia palea and Pinnularia parvulissima were recorded in Summer and Autumn, whereas the species Surirella brebissonii, Achnanthidium minutissimum, Navicula lanceolata and Surirella angusta were dominant in Winter and Spring. Commonly used indices such as the Shannon diversity index and Specific Pollution Sensitivity Index reflected the level of pollution and suggest seasonal periodicity, the lowest diversities being observed in Summer.     

Particle fluxes above forests: observations, methodological considerations and method comparisons

This paper reports a study designed to test, evaluate and compare micro-meteorological methods for determining the particle number flux above forest canopies. Half-hour average particle number fluxes above a representative broad-leaved forest in Denmark derived using eddy covariance range from -7x10(7) m(-2) s(-1) (1st percentile) to 5x10(7) m(-2) s(-1) (99th percentile), and have a median value of -1.6x10(6) m(-2) s(-1). The statistical uncertainties associated with the particle number flux estimates are larger than those for momentum fluxes and imply that in this data set approximately half of the particle number fluxes are not statistically different to zero. Particle number fluxes from relaxed eddy accumulation (REA) and eddy covariance are highly correlated and of almost identical magnitude. Flux estimates from the co-spectral and dissipation methods are also correlated with those from eddy covariance but exhibit higher absolute magnitude of fluxes.     

Assessment of sediment contamination in Casco Bay, Maine, USA

The current status of contaminant concentrations in Casco Bay, decadal trends of these contaminants and changes in their geographical distribution are assessed using sediment samples collected approximately 10 years apart. In general, regulated contaminants appeared to be decreasing in concentration. Total PAH and dioxins/furans concentrations did not significantly change over this period. Total organochlorine pesticides, 4,4-DDE, 4,4-DDD, total DDT, PCB, tributyltin and total butyltin decreased in concentration. Trace element concentrations in sediments decreased at the majority of the sampling sites for chromium, nickel, and selenium while arsenic, cadmium, copper, lead, mercury, silver, and zinc remained relatively constant. None of the contaminants measured has increased by more than a factor of 2. Selected sites located in the Inner Bay, where concentrations are higher and new inputs were more likely, showed increased concentrations of contaminants. Most contaminants were not found at concentrations expected to adversely affect sediment biota based on ERL/ERM guidelines.     

Effective elution of RDX and TNT from particles of Comp B in surface soil

During live fire training exercises, large amounts of explosives are consumed. Low order detonations of high explosive payloads result in the patchy dispersal of particles of high explosive formulations over large areas of firing range soils. Dissolution of explosives from explosive formulation particles into soil pore water is a controlling factor for transport, fate, and effects of explosive compounds. We developed an empirical method to evaluate soils based on functionally defined effective dissolution rates. An automated Accelerated Solvent Extractor was used to determine the effective elution rates under controlled conditions of RDX and TNT from soil columns containing particles of Comp B. Contrived soils containing selected soil geosorbants and reactive surfaces were used to quantitatively determine the importance of these materials. Natural soils from training ranges of various soil types were also evaluated. The effects of geosorbants on effective elution rates were compound- and sorbent-specific. TNT elution was less than that of RDX and was greatly slowed by humic acid. Iron and iron-bearing clays reduced the effective elution rates of both RDX and TNT. This empirical method is a useful tool for directly generating data on the potential for explosives to leach from firing range soils, to identify general bulk soil characteristics that can be used to predict the potential, and to identify means to engineer soil treatments to mitigate potential transport.     

Heavy metals' content of automotive shredder residues (ASR): evaluation of environmental risk

Every year between 8 and 9 millions of vehicles in the European Union arrive to their end of life. Car wastes can have a very high metal content, falling into hazardous waste class. A preliminary evaluation of these wastes could be made by metals' leaching test runs which is the main objective of the present study. Evaluation of the total metal content was carried out by X-ray fluorescence and the mobility of these metals using two simple standardized extractions such as the TCLP (Toxicity Characterisation Leaching Procedure) of the US EPA and the German leaching test DIN 38414-S4. Additionally, an extraction test with acetone was performed in order to recognise metals bounded to organic matter. The results show that the total metal content of the ASR can overpass the established values for inert residues. Lead and zinc contents are fairly well correlated with grain-size, whilst other metals' contents do not exhibit clear grain-size dependence.     

Multiscale analysis of heavy metal contents in Spanish agricultural topsoils

This study characterized and mapped the spatial variability patterns of seven topsoil heavy metals (Cr, Ni, Pb, Cu, Zn, Hg and Cd) within the Ebro river basin (9.3 million ha) by Multivariate Factorial Kriging. The variograms and cross-variograms of heavy metal concentrations showed the presence of multiscale variation that was modeled using three variogram models with ranges of 20km (short-range), 100km (medium-range) and 225km (long-range). Our results indicate that the heavy metal concentration is influenced by bedrock composition and dynamics at all the spatial scales, while human activities have a notorious effect only at the short- and medium-range scale of variation. Sources of Cu, Pb and Zn (and secondary Cd) are associated with agricultural practices (at the short-range scale of variation), whereas Hg variation at the short- and medium-range scale of variation is related to atmospheric deposition.