Estimation of the environmental impact of MSWI bottom ash for reuse as a building material based on its composition

A procedure for the determination of the total element composition of municipal solid waste incineration (MSWI) bottom ash (BA) based on borate fusion sample preparation followed by ICP–AES is developed as an alternative for a leaching test. Quantification limits for all the tested hazardous elements (Al, Ba, Cа, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Si, Sr, Sb, Sn, Ti, V, Zn, Zr, S, P) are below the leaching ranges and total amounts for trace elements in MSWI BA, thus providing a quantitative assessment with low errors, including trace components. The total error of measurement is below 10% for most elements. Using ICP–AES and ion chromatography, good concordance of the data for trace elements and chloride and sulfate is shown. The comparison of the results from the standard leaching test with the data for untreated and washed MSWI BA samples shows good agreement for major, medium, and trace elements. The data on the dependence of the BA composition and a leaching capacity for various particle-size fractions of BA are compared. The advantages of the proposed approach are discussed

Thermal treatment on MSWI bottom ash fines

The municipal solid waste incineration (MSWI) bottom ash is the main by-product in the waste-to-energy plant, which accounts for about 80% of the total by-products. The further challenge after incineration is to find a suitable way to dispose or use the solid residue. It is well understood that the bottom ash contains contaminants, such as heavy metals, which pose an environmental risk. In order to reduce landfill of these residues and enhance the recycling of resources, different treatments are applied to upgrade the quality of the bottom ash, for instance, weathering, washing, etc. However, the treatments on the MSWI fine bottom ash particles are less sufficient. Hence, in this study the thermal treatment is applied on fine bottom ash and its effect on the bottom ash properties are investigated

A model describing water and salt migration in concrete during wetting/drying cycles

In order to predict the life span of concrete structures, models describing the migration of chloride are needed. In this paper, a start is made with a simple, theoretical model describing water and chloride transport in a concrete sample. First, transport of water in concrete is considered with Fick’s second law of diffusion, which describes the time-evolution of the water content. Chloride can be transported through concrete by advection with water and by diffusion due to a difference in the chloride concentration of the pore solution. Furthermore, chloride can be bound to the surface of the pore walls. This bound chloride is immobile, thus unavailable for transport. The result is a partial differential equation for the time-evolution of the chloride concentration, coupled to the partial differential equation for water transport. This partial differential equation is solved using the Crank-Nicolson implicit method for a situation in which chloride enters, and in a certain extent also leaves the sample. Because the goal is to describe the migration behavior in the sample during wetting and drying cycles, the sample gets wet during one half of a day and dries during the other half

First report of the cyanotoxins cylindrospermopsin and deoxycylindrospermopsin from Raphidiopsis curvata (Cyantobacteria)

A strain of Raphidiopsis (Cyanobacteria) isolated from a fish pond in Wuhan, P. R. China was examined for its taxonomy and production of the alkaloidal hepatotoxins cylindrospermopsin (CYN) and deoxy-cylindrospermopsin (deoxy-CYN). Strain HB1 was identified as R. curvata Fritsch et Rich based on morphological examination of the laboratory culture. HB1 produced mainly deoxy-CYN at a concentration of 1.3 mg(.)g(-1) (dry ut cells) by HPLC and HPLC-MS/MS. CYN was also detected in trace amounts (0.56 mug(.)g(-1)). A mouse bioassay did not show lethal toxicity when tested at doses up to 1500 mg dry weight cells(.)kg(-1) body weight within 96 h, demonstrating that production of primarily deoxy CYN does not lead to significant mouse toxicity by strain BB I. The presence of deoxy-CYN and CYN in R curvata suggests that Raphidiopsis belongs to the Nostocaceae, but this requires confirmation by molecular systematic studies. Production of these cyanotoxins by Raphidiopsis adds another genus, in addition to Cylindrospemopsis, Aphanizomenon, and Umezakia, now known to produce this group of hepatotoxic cyanotoxins. This is also the first report from China of a CYN and deoxy-CYN producing cyanobacterium