Combination with other remediation methods

Abstract This chapter explores the role of abiotic reactions such as acid catalysis (hydrolysis) as well as the adsorption of methyl tert-butyl ether (MTBE) and other fuel oxygenates in environmental issues as the remediation of these substances is notoriously difficult. First of all, these methods are briefly classified with other abiotic technologies. The suitability of hydrolysis and adsorption for the remediation of water contaminated by fuel oxygenates is then discussed in detail, with information being provided about the principle of the reactions, potential catalysts and sorbents, limitations of the reactions, and practical implications. To conclude, the possible application of hydrolysis and adsorption in combination with other remediation techniques is also examined. 

DSM technology has been combined with several other remediation methods, including ambient air stripping, heated air stripping, peroxide injection, in situ creation of impermeable barriers, permeable barrier creation for in situ treatment, and in situ stabilization and sohdification of contaminants. 

The torsional motion of biphenyl and related compounds is a typical large amplitude motion. The accumulated knowledge from a series of molecules in this group has led to a fairly good qualitative description of the motion. Unfortunately the quantitative description leaves much to be desired. Taking advantage of the improvements in the electron-diffraction method and applying suitable combinations with other methods, there are reasons to believe that this deficiency should be remedied. 

The majority of AOTs can be applied to the remediation and detoxification of low or medium volumes of waters. Ground, surface, and wastewater can be treated, giving rise to the destruction or transformation of hazardous or refractory pollutants. Point sources of toxic pollutants such as pesticides, heavy metals and others can be treated in small-scale mobile treatment units, easy to install in industrial plants. The methods can be used alone or combined with other AOTs or with conventional methods. The use of modular units allows the selection of the best technology or combination of technologies to treat a specific wastewater. AOTs can also be applied to pollutants in the air and soil, and they may even allow disinfection or sterilization of bacteria, viruses, and other microorganisms. 

As soon as it has been decided to remediate a site, a remediation plan has to be drawn up. The first step is to work out possible remediation options in relation to the basic assumptions. This phase is called the remediation investigation. When assessing the remediation options, it is necessary to consider the technical as well as the environmental and financial aspects. Sometimes, ER is not the sole remediation option in certain cases, it should be combined with other methods in order to maximize the remediation efficiency. 

In CRIOP, the team does not make any probability assessments. It is thus not possible to evaluate the effectiveness of remedial actions in terms of risk reduction. CRIOP may be combined with other risk analysis methods such as event tree analysis, which is suited for calculations of probabilities. A probability assessment requires access to human reliability data. 

Combination of EK with Other Soil Remediation Methods and Changes in Process Design... 

Another way to improve the remediation efficiency is to combine the EK principle with other methods, or to manipulate the electric field in such a way that the efficiency is increased. The main reasons for this combination/manipulation are (a) to reduce the concentration gradients generated during the process with a constant electric field, (b) to speed up the desorption/dissolution of the heavy metals, or (c) to decrease the heavy metal migration distance. 

Enhancement can involve the addition of additives to the soil for chemical manipulation of the redox condition or to aid desorption by formation of complexes with the heavy metals. Enhancement can also be focused at shortening the duration of the action either by placement of the electrodes or by combining the EK soil remediation method witt other methods. 

The remediation of contaminated sites may be efficient when a combination of electrokinetics with other methods is designed. 

CNTs can be combined with various metal oxides for the degradation of some organic pollutants too. Carbon nanotubes/metal oxide (CNT/MO) composites can be prepared by various methods such as wet chemical, sol gel, physical and mechanical methods. To form nanocomposite, CNTs can be combined with various metal oxides like Ti Oj, ZnO, WO3, Fc203, and AI2O3. The produced nanocomposite can be used for the removal of various pollutants. Nanoscale Pd/Fe particles were combined with MWNTs and the resulted composite was used to remove 2,4-dichlorophenol (2,4-DCP). It was reported that the MB adsorption was pH-dependent and adsorption kinetics was best described by the pseudo-second-order model. Iron oxide/CNT composite was reported to be efficient adsorbent for remediation of chlorinated hydrocarbons. The efficiency of some other nanocomposites such as CNT/ alumina, CNT/titania and CNT/ZnO has also been reported [60-62]. 

When intelligently used, electrokinetic soil remediation methods can be used for remediation of even highly complicated cases of soil pollution, and this is where research is developing. Yetmg and Gu [25] compiled the research literature related to enhancing electrokinetic remediation. Use of enhancement solutions during electrokinetic remediation in order to solubilize the contaminants and keep them in the mobile state is one major research line, and the other is to combine electrokinetic remediation synergisti-cally with other soil remediation techniques. 

A permeable reactive barrier (PRB) is defined as an in situ method for remediating contaminated groundwater that combines a passive chemical or biological treatment zone with subsurface fluid flow management. Treatment media may include zero-valent iron, chelators, sorbents, and microbes to address a wide variety of groundwater contaminants, such as chlorinated solvents, other organics,... 

Several remedies have been suggested for improving the PB based pKa prediction methods. Most of them are based on strategies that combine conformational flexibility with the PB calculation. You and Bashford included multiple conformers by systematically scanning the side chain torsion angles [107], Alexov and Gunner used Monte-Carlo protocol to sample positions of hydroxyl and other polar protons [1], This method, referred to as the multi-conformation continuum electrostatic (MCCE), was later extended to include rotamers for residues that have strong electrostatic... 

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