Recycling of lead-contaminated EDTA wastewater.
Ethylene diaminetetraacetic acid (EDTA) is one of the chelating agents used in the soil washing process for the decontamination of lead-contaminated soil. Lead-EDTA complexes in the wastewater from the soil washing process must be removed before the wastewater can be safely discharged. This study outlines a method to recycle Pb-EDTA wastewater by substituting the Pb complexed with EDTA with Fe(III) ions at low pH, followed by precipitation of Pb ions with phosphate or sulfate ions. Fe(III) ions complexed with EDTA were then precipitated at high pH using sodium hydroxide. The resulting solution (Fe-precipitated solution) was tested on three lead-contaminated soils. The Fe-precipitated EDTA solution was found to have similar extraction capabilities as fresh EDTA solution. Experimental results showed that the recycled EDTA solution may be recycled several times without losing its extractive power. Recycled EDTA wastewater with phosphate precipitation was found to be slightly more effective than recycled EDTA solution using sulfate precipitation. The recycling procedure may be applied to wastewater generated during soil washing of lead-contaminated soil, resulting in a reduction in wastewater generated and savings in the amount of EDTA used.
The use of chelating agents in the remediation of metal-contaminated soils – 1 a review 2 3
* Corresponding author (X. D. Li). E-mail address: 4 a Agronomy Department, Centre for Soil and Environmental Science, Biotechnical Faculty, 5 University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia 6 Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, 7 Hung Hom, Kowloon, Hong Kong 8 9 Capsule: The use of synthetic chelants for soil washing and enhanced phytoextraction by 10 plants has been well-studied for the remediation of metal contaminated soils in the last two 11 decades. 12 13 Abstract 14 15 This paper reviews current remediation technologies that use chelating agents for the 16 mobilization and removal of potentially toxic metals from contaminated soils. These 17 processes can be done in situ as enhanced phytoextraction, chelant enhanced electrokinetic 18 extraction and soil flushing, or ex situ as the extraction of soil slurry and soil heap/column 19 leaching. Current proposals on how to treat and recycle waste washing solutions after soil is 20 washed are discussed. The major controlling factors in phytoextraction and possible strategies 21 for reducing the leaching of metals associated with the application of chelants are also 22 reviewed. Finally, the possible impact of abiotic and biotic soil factors on the toxicity of 23 metals left after the washing of soil and enhanced phytoextraction are briefly addressed. 24 25
Impacts of climate and land use changes on flood risk management for the Schijn River, Belgium
Abstract Flooding is the most common natural disaster in Europe. Modern flood risk management relies not only infrastructure development but also on governmental and non-governmental actors applying legal, economic and communicative water management instruments. Within the European Union (EU), flood management closely relies on policy set at the EU and national levels. It is now recognized that a sound understanding of climate change is required in addition to current management by taking into account land use change and socio-political context, as climate and land use changes have major impacts on hydrological responses. This paper investigates the hydrological behavior due to urbanization under current and future climate scenarios of high summer and high winter rainfall for 20 sub-catchments of the Schijn River, located in the Flanders region near Antwerp, Belgium. As urbanization increases and existing rainfall-runoff models neglecting the specific behavior of urban runoff, a hydrological model was developed based on a basic reservoir concept and applied to the existing rainfall-runoff model (PDM) flow to examine the specific urban contribution. Results revealed that peak flow for urban runoff and the total peak flow (i.e. rural and urban runoff) were significantly higher (i.e. ranges from 200% to 500%) than the existing rainfall-runoff model (PDM) flows, because of faster and more peaked urban runoff response. The impact of climate change on current and future conditions was also assessed by estimating peak flows with respect to return periods from the flood frequency curve. The predicted peak flow of high summer future climate scenario was significantly higher (i.e. ranges from 200% to 250%) than that of the current climatic condition for this region. Furthermore, hourly peak flow and daily volume ratios of 100-year return period for the highest, lowest and average impervious area were projected for the time horizon of the year 2100. It is concluded that climate change impacts contribute the most in producing peak flow in coming years, while increased urbanization takes the second place for both hourly and daily values. Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry.