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Constructed wetlands are man-made complex of substrates, emergent/submergent vegetation, and water. Constructed wetlands have been known as an efficient and low-cost treatment process. Constructed wetland is a natural treatment system that physical, chemical, and biological processes occur when water, soil, plants, and microorganisms interact. They are considered as natural treatment ecosystems that are designed to take advantages of the natural processes to provide wastewater treatment. Constructed wetlands treat different types of wastewaters such as municipal, industrial, agricultural, and storm water. The removal of heavy metals within wetlands is performed generally by plant uptake and by adsorption onto sediments. Heavy metal treatment examples and some specifications and regulations are finally discussed.

In this paper, adaptive neuro-fuzzy inference system ANFIS is used to assess conditions required for aquatic systems to serve as a sink for metal removal; it is used to generate information on the behavior of heavy metals (mercury) in water in relation to its uptake by bio-species (e.g. bacteria, fungi, algae, etc.) and adsorption to sediments. The approach of this research entails training fuzzy inference system by neural networks. The process is useful when there is interrelation between variables and no enough experience about mercury behavior, furthermore it is easy and fast process. Experimental work on mercury removal in wetlands for specific environmental conditions was previously conducted in bench scale at Concordia University laboratories. Fuzzy inference system FIS is constructed comprising knowledge base (<i>i.e.</i> premises and conclusions), fuzzy sets, and fuzzy rules. Knowledge base and rules are adapted and trained by neural networks, and then tested. ANFIS simulates and predicts mercury speciation for biological uptake and mercury adsorption to sediments. Modeling of mercury bioavailability for bio-species and adsorption to sediments shows strong correlation of more than 98% between simulation results and experimental data. The fuzzy models obtained are used to simulate and forecast further information on mercury partitioning to species and sediments. The findings of this research give information about metal removal by aquatic systems and their efficiency

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Methane and carbon dioxide are of major concern as greenhouse gases; the landfills have the problem of controlling these gases. Al Akaider in Jordan is the second biggest landfill suffers controlling gases as it lacks a cover design system. In this work, the main goal is to investigate the appropriateness of amended expansive clayey soil in Irbid as a cover barrier. The expansive soil is unwanted in construction projects, thus the modification of this expelled soil enables using it as a low cost landfill cover barrier. In this research, the effect of adding nano-clay material (Hydrophilic Nano Bentonite) on the geotechnical characteristics, hydraulic conductivity, and gas transport coefficients of the clayey soil are studied. The soil samples were obtained from Irbid city. Unconfined compressive strength and free swelling tests were performed on soil samples with different percentages of nano-clay added in the range (0.1% to 1.2%) by weight. The results indicated that the addition of nano-clay at low percentages increases the strength of expansive soil up to 315 kPa at 0.6% of nano-clay and the swelling potential decreased dramatically with the addition of nano-clay. The optimal percent of nano-clay was found to be 0.6%. The intrinsic permeability of the amended soil was 6.03×10–15 m2. The average values of fluid transport coefficients were determined at 25 °C. The hydraulic conductivity for water was about 6.5×10–10 m/s. Gas conductivity coefficients for CO2 and CH4 were 5×10–9 m/s and 2.5×10–9 m/s respectively. Gas diffusion coefficients for CO2 and CH4 were 3×10–6 m2/s and 4×10–6 m2/s respectively.