Toxic response of the bacterium Vibrio fischeri to sodium lauryl ether sulphate residues in excavated soils.

Sodium lauryl ether sulphate (SLES) is the main chemical component in several lubricant products used for soil conditioning in the mechanized excavation industry using Earth Pressure Balance-Tunnel Boring Machines. During the tunnelling process, huge amounts of excavated soil are produced and the SLES presence can affect the subsequent re-use of this material as a by-product. Currently, there is still no regulatory indication of reliable and sensitive bioassays for monitoring soil quality during the excavation process. The main objective of this work was to verify if the Vibrio fischeri screening test was suitable as a consistent and precautionary tool for this specific purpose. Firstly, the ecotoxicity (EC20 and EC50) of the SLES standard solution and three commercial products (SLES content from 10 to 50%) were evaluated to select the most environmental friendly product. Subsequently, soil samples from about 2 years of tunnelling in a real construction site, conditioned with the selected product, were evaluated for their environmental compatibility with the prescriptions of an Italian site-specific protocol. The latter established 2 mg/L as a threshold value for SLES concentration in soil water extracts and a no toxic response (≤20%) for the Vibrio fischeri test. The comparison of the bacterium bioluminescence inhibition values (%) with analytical determinations showed an ecotoxicity when SLES was >2 mg/L. The toxicity was directly related to SLES concentration, indicating that the V. fischeri test and the SLES analyses are suitable tools for assessing excavated soil as a by-product, ensuring its safe reuse in accordance with a green production process (circular economy).

Aquatic toxicity and biodegradability of a surfactant produced by Bacillus subtilis ICA56.

In this work, the environmental compatibility of a biosurfactant produced by a Bacillus subtilis strain isolated from the soil of a Brazilian mangrove was investigated. The biosurfactant, identified as surfactin, is able to reduce surface tension (ST) to 31.5 ± 0.1 mN m-1 and exhibits a lowcritical micelle concentration (CMC) value (0.015 ± 0.003 g L-1). The highest crude biosurfactant concentration (224.3 ± 1.9 mg L-1) was reached at 72 h of fermentation. Acute toxicity tests, carried out with Daphnia magna, Vibrio fischeri and Selenastrum capricornutum indicated that the toxicity of the biosurfactant is lower than that of its chemically derived counterparts. The results of the biodegradability tests demonstrated that the crude surfactin extract was degraded by both Pseudomonas putida and a mixed population from a sewage-treatment plant, in both cases the biodegradation efficiency being dependent on the initial concentration of the biosurfactant. Finally, as the biodegradation percentages obtained fall within the acceptance limits established by the Organization for Economic Co-operation and Development (Guidelines for Testing of Chemicals, OECD 301E), crude surfactin can be classified as a "readily" biodegradable compound.

Environmental evaluation of the electric and cogenerative configurations for the energy recovery of the Turin municipal solid waste incineration plant.

Given the desirability of reducing fossil fuel consumption, together with the increasing production of combustible solid wastes, there is clearly a need for waste treatment systems that achieve both volume reduction and energy recovery. Direct incineration method is one such system. The aim of this work was to analyze the municipal solid waste incineration plant currently under construction in the province of Turin (Piedmont, North Italy), especially the potential for energy recovery, and the consequent environmental effects. We analyzed two kinds of energy recovery: electric energy (electrical configuration) only, and both electric and thermal energy (cogenerative configuration), in this case with a different connection hypothesis to the district heating network. After we had evaluated the potential of the incinerator and considered local demographic, energy and urban planning effects, we assumed different possible connections to the district heating network. We computed the local and global environmental balances based on the characteristics of the flue gas emitted from the stack, taking into consideration the emissions avoided by the substituted sources. The global-scale results provided relevant information on the carbon dioxide emissions parameter. The results on the local scale were used as reference values for the implementation of a Gaussian model (Aermod) that allows evaluation of the actual concentration of the pollutants released into the atmosphere. The main results obtained highlight the high energy efficiency of the combined production of heat and electricity, and the opportunity to minimize the environmental impact by including cogeneration in a district heating scheme.

Leaching of Carbon Reinforced Concrete-Part 2: Discussion of Evaluation Concepts and Modelling.

Possible threats on the environment and human health by the leaching of new building materials and composites in contact to water should be prevented from the outset. It is therefore necessary to assess and ensure their environmental compatibility. For irrigated construction elements this is a challenging task, as there is no general correlation between known testing methods and outdoor emissions. A feasible assessment concept is needed for these conditions. In this work the German assessment method for permanently wet building materials is applied on different carbon reinforced concrete (C3) leaching data. Furthermore, emission prediction approaches of the Dutch building Materials Decree and the software COMLEAM are tested. The established methods are not yet suitable to determine the complex long term outdoor emissions of irrigated C3. In order to achieve realistic results in time saving testing methods and to define reasonable release limits, it is necessary to determine and verify the relevant influencing parameters on leaching through intermittent water contact. This research works out leaching patterns and correlations between inorganic substances. It is shown that the input parameters time of exposure, contact time, air temperature, air humidity, runoff and background concentration should be considered to predict the leaching processes from irrigated concrete phenomenologically.

Leaching of Carbon Reinforced Concrete-Part 1: Experimental Investigations.

The composite material 'carbon concrete composite (C3)' is currently capturing the building sector as an 'innovative' and 'sustainable' alternative to steel reinforced concrete. In this work, its environmental compatibility was investigated. The focus of this research was the leaching behavior of C3, especially for the application as irrigated façade elements. Laboratory and outdoor exposure tests were run to determine and assess the heavy metal and trace element emissions. In the wake of this work, the validity of laboratory experiments and the transferability to outdoor behavior were investigated. The experimental results show very low releases of environmental harmful substances from carbon concrete composite. Most heavy metal concentrations were in the range of <0.1-8 µg/L, and higher concentrations (up to 32 µg/L) were found for barium, chromium, and copper. Vanadium and zinc concentrations were in the range of 0.1-60 µg/L, boron and nickel concentrations were clearly exceeding 100 µg/L. Most of the high concentrations were found to be a result of the rainfall background concentrations. The material C3 is therefore considered to be environmentally friendly. There is no general correlation between laboratory leaching data and outdoor emissions. The results depend on the examined substance and used method. The prediction and evaluation of the leaching of building elements submitted to rain is therefore challenging. This topic is debated in the second part of this publication.

Municipal solid waste incineration plant: A multi-step approach to the evaluation of an energy-recovery configuration.

This study proposes a multi-step approach to evaluating the environmental and economic aspects of a thermal treatment plant with an energy-recovery configuration. In order to validate the proposed approach, the Turin incineration plant was analyzed, and the potential of the incinerator and several different possible connections to the district heating network were then considered. Both local and global environmental balances were defined. The global-scale results provided information on carbon dioxide emissions, while the local-scale results were used as reference values for the implementation of a Gaussian model that could evaluate the actual concentrations of pollutants released into the atmosphere. The economic aspects were then analyzed, and a correspondence between the environmental and economic advantages defined. The results showed a high energy efficiency for the combined production of heat and electricity, and the opportunity to minimize environmental impacts by including cogeneration in a district heating scheme. This scheme showed an environmental advantage, whereas the electricity-only configuration showed an economic advantage. A change in the thermal energy price (specifically, to 40 €/MWh), however, would make it possible to obtain both environmental and economic advantages.

Environmental analysis of a potential district heating network powered by a large-scale cogeneration plant.

Among the solutions for the achievement of environmental sustainability in the energy sector, district heating (DH) with combined heat and power (CHP) systems is increasingly being used. The Italian city of Turin is in a leading position in this field, having one of the largest DH networks in Europe. The aim of this work is the analysis of a further development of the network, addressed to reduce the presence of pollutants in a city that has long been subject to high concentration levels. The environmental compatibility of this intervention, especially in terms of nitrogen oxides (NOx) and particulate matter (PM) emissions, is evaluated. The pollutants dispersion is estimated using the CALPUFF model. The forecasting scenario is created firstly by simulating the energy production of the main generation plants in response to the estimated heat demand, and secondly by investigating the amount and the dispersion of pollutants removed due to the elimination of the centralized residential heaters. The results show a future reduction in ground level average NOx concentration ranging between 0.2 and 4 µg/m3. The concentration of PM remains almost unchanged. Measures are then taken to lower the uncertainty in the simulation scenarios. This study provides important information on the effects of a change of the energy configuration on air quality in an urban area. The proposed methodological approach is comprehensive and repeatable.