Contact Tank Design Impact on Process Performance

In this study three-dimensional numerical models were refined to predict reactive processes in disinfection contact tanks (CTs). The methodology departs from the traditional performance assessment of contact tanks via hydraulic efficiency indicators, as it simulates directly transport and decay of the disinfectant, inactivation of pathogens and accumulation of by-products. The method is applied to study the effects of inlet and compartment design on contact tank performance, with special emphasis on turbulent mixing and minimisation of internal recirculation and short-circuiting. In contrast to the conventional approach of maximising the length-to-width ratio, the proposed design changes are aimed at addressing and mitigating adverse hydrodynamic structures, which have historically led to poor hydraulic efficiency in many existing contact tanks. The results suggest that water treatment facilities can benefit from in-depth analyses of the flow and kinetic processes through computational fluid dynamics, resulting in up to 38 % more efficient pathogen inactivation and 14 % less disinfection by-product formation.     

Human Capital,Innovation, and Climate Policy: an Integrated Assessment

This paper looks at the interplay between human capital and innovation when climate and educational policies are implemented. Following recent empirical studies, human capital and general purpose research and development (R&D) are introduced in an integrated assessment model used to study the dynamics of climate change mitigation. Our results suggest that climate policy stimulates general purpose as well as clean R&D but reduces the incentive to invest in human capital formation. Both innovation and human capital have a scale effect, which increases pollution, as well as a technique effect, which saves emissions for each unit of output produced. While the energy-saving effect prevails when innovation increases, human capital is pollution-using, also because of the gross complementarity between the labor and energy input. When the role of human capital is the key input in the production of general purpose and energy knowledge is accounted for, the crowding-out of education induced by climate policy is mitigated, though not completely offset. By contrast, a policy mix that combines educational as well as climate objectives offsets the human capital crowding-out, at moderate and short-term costs. Over the long run, the policy mix leads to global welfare gains.     

Seafloor ecosystem functioning: the importance of organic matter priming

Organic matter (OM) remineralization may be considered a key function of the benthic compartment of marine ecosystems and in this study we investigated if the input of labile organic carbon alters mineralization of indigenous sediment OM (OM priming). Using ¹³C-enriched diatoms as labile tracer carbon, we examined shallow-water sediments (surface and subsurface layers) containing organic carbon of different reactivity under oxic versus anoxic conditions. The background OM decomposition rates of the sediment used ranged from 0.08 to 0.44 μmol C ml_ws⁻¹ day⁻¹. Algal OM additions induced enhanced levels of background remineralization (priming) up to 31% and these measured excess fluxes were similar to mineralization of the added highly degradable tracer algal carbon. This suggests that OM priming may be important in marine sediments.     

Introduction to the Issue

Welcome to the fifth issue of the Review of Environmental Economicsand Policy, which once again includes articles, a symposium,and a set of features. In the first of two articles in this issue, Geoffrey Heal reviewswhat we have learned about the economics of global climate changeand related public policy from the extensive literature thathas emerged in response to the controversial Stern Review ofthe Economics of Climate Change. Heal provides his own perspectiveon the Stern Review (which was the focus of a symposium in ourWinter 2008 issue) as well as his views on how the recent debateaffects the economic case for action on     

Laser induced fluorescence instrument for NO2 measurements: Observations at a central Italy background site

A laser induced fluorescence (LIF) instrument has been developed to measure tropospheric NO₂ with low detection limit. The instrument design, development and first measurements are reported. There are also details of the temporal gate system built for the fluorescence acquisition. The instrument is able to make fast measurements (up to 4 Hz) and shows a limit of detection of 10 pptv/60 s. Continuous observations (2 weeks in summer 2007) in a small town in central Italy were used to test the performance of the instrument and to study the photochemistry of ozone in a background site. LIF and a commercial chemiluminescence (CL) instrument simultaneous observations of NO₂ show a good linearity (LIF = 1.02 CL + 0.6 (ppb), R² = 0.98) but there is a bias of the commercial instrument of about 0.60 ppbv on average. The overestimation of the CL system is probably due to conversion of NO_y species into NO by the molybdenum converter used in the CL instrument to detect NO₂. Analysis of 1 s data is used to test the instrument response and the coupling between nitrogen oxides and ozone.     

Novel insights in Al-MCM-41 precursor as adsorbent for regulated haloacetic acids and nitrate from water

High concentration of NO ₃ ^? in groundwater has raised concern over possible contamination of drinking water supplies. In addition, the formation of haloacetic acids (HAAs) as by-products during disinfection with chlorine-based agents is still a relevant issue, since HAAs pose serious health hazard. In this work, we investigated the affinity of a precursor of Al-MCM-41 (a mesostructured hexagonal aluminosilicate containing the template surfactant) towards nitrate and HAAs, for its possible application in the removal of these pollutants from natural and drinking waters. Additionally, adsorption kinetics and isotherms were studied. The adsorbent was synthesized using cetyltrimethylammonium bromide as surfactant and characterized by physico?Cchemical techniques. Simulated drinking water was spiked with the EPA-regulated HAAs (monochloroacetic (MCAA), monobromoacetic (MBAA), dichloroacetic (DCAA), dibromoacetic (DBAA), and trichloroacetic (TCAA) acids) and placed in contact with the adsorbent. The effect of matrix composition was studied. Adsorption kinetic studies were performed testing three kinetics models. For the adsorption studies, three adsorption isotherm approaches have been tested to experimental data. The pollutant recoveries were evaluated by suppressed ion chromatography. The affinity of the adsorbent was TCAA = DBAA = DCAA > MBAA > MCAA with DCAA, DBAA, and TCAA completely removed. A removal as high as 77?% was achieved for 13?mg/L nitrate. The adsorption isotherms of NO ₃ ^? and monochloroacetic acid can be modeled by the Freundlich equation, while their adsorption kinetics follow a pseudo-second-order rate mechanism. The adsorbent exhibited high affinity towards HAAs in simulated drinking water even at relevant matrix concentrations, suggesting its potential application for water remediation technologies.     

An international comparative study of end-of-life vehicle (ELV) recycling systems

End-of-life vehicles (ELV) have become a global concern as automobiles have become popular worldwide. An international workshop was held to gather data and to discuss 3R policies and ELV recycling systems, their background and present situation, outcomes of related policies and programs, the framework of recycling and waste management, and case studies on related topics in several countries and regions, as well as the essential points of the comparison. Legislative ELV recycling systems are established in the EU, Japan, Korea, and China, while in the US, ELV recycling is managed under existing laws on environmental protection. Since automobile shredding residue (ASR) has a high calorific value and ash content, and includes heavy metals as well as a mass of unclassified fine particles, recycling ASR is considered highly difficult. Countries with a legislative ELV system commonly set a target for recovery rates, with many aiming for more than 95 % recovery. In order to reach this target, higher efficiency in ASR recovery is needed, in addition to material recycling of collectable components and metals. Environmentally friendly design was considered necessary at the planning and manufacturing stages, and the development of recycling systems and techniques in line with these changes are required for sound ELV management.     

Integrated municipal solid waste treatment using a grate furnace incinerator: the Indaver case

An integrated installation for treatment of municipal solid waste and comparable waste from industrial origin is described. It consists of three grate furnace lines with flue gas treatment by half-wet scrubbing followed by wet scrubbing, and an installation for wet treatment of bottom ash. It is demonstrated that this integrated installation combines high recovery of energy (40.8% net) with high materials recovery. The following fractions were obtained after wet treatment of the bottom ash: ferrous metals, non-ferrous metals, three granulate fractions with different particle sizes, and sludge. The ferrous and non-ferrous metal fractions can both be recycled as high quality raw materials; the two larger particle size particle fractions can be applied as secondary raw materials in building applications; the sand fraction can be used for applications on a landfill; and the sludge is landfilled. For all components of interest, emissions to air are below the limit values. The integrated grate furnace installation is characterised by zero wastewater discharge and high occupational safety. Moreover, with the considered installation, major pollutants, such as PCDD/PCDF, Hg and iodine-136 are to a large extent removed from the environment and concentrated in a small residual waste stream (flue gas cleaning residue), which can be landfilled after stabilisation.     

Enzyme and fungal treatments and a combination thereof reduce olive mill wastewater phytotoxicity on Zea mays L. seeds

The phytotoxicity of olive-mill wastewater (OMW) has been suggested to be mainly due to its phenolic components. This study investigated the impact of three different low-cost dephenolization treatments on the wastewater phytotoxicity. To this aim, germinability of maize (Zea mays L.) seeds sown on a sandy-loamy soil which had been spread with different volumes (from 40 to 160m(3)ha(-1)) of either biologically-treated OMW or relative incubation control was determined. Biological treatments included either Panus tigrinus liquid cultures or incubation with commercial laccase (1UIml(-1)) or an innovative sequential combination of laccase and P. tigrinus cultures. All treatments markedly reduced phytotoxicity and promising results were obtained with commercial laccase. In fact, germinability and mean germination times in soil spread with laccase-treated OMW, did not significantly differ from those observed in soil irrigated with tap water (control) up to OMW volumes of 120m(3)ha(-1). Although the highest phenol reduction (ca. 81%) was obtained by the sequential use of laccase and P. tigrinus, the feasibility of the enzyme treatment is undoubtedly more convincing under the technological point of view.     

Impact of elevated CO(2) and nitrogen fertilization on foliar elemental composition in a short rotation poplar plantation

The experiment was carried out on a short rotation coppice culture of poplars (POP-EUROFACE, Central Italy), growing in a free air carbon dioxide enriched atmosphere (FACE). The specific objective of this work was to study whether elevated CO(2) and fertilization (two CO(2) treatments, elevated CO(2) and control, two N fertilization treatments, fertilized and unfertilized), as well as the interaction between treatments caused an unbalanced nutritional status of leaves in three poplar species (P. x euramericana, P. nigra and P. alba). Finally, we discuss the ecological implications of a possible change in foliar nutrients concentration. CO(2) enrichment reduced foliar nitrogen and increased the concentration of magnesium; whereas nitrogen fertilization had opposite effects on leaf nitrogen and magnesium concentrations. Moreover, the interaction between elevated CO(2) and N fertilization amplified some element unbalances such as the K/N-ratio.