Mixing contamination

Because the biological degradation rate of MTBE has been observed to be slower than for other common contaminants, such as BTEX, MTBE will typically be the rate-limiting contaminant that determines the necessary hydraulic retention time for a mixed contaminant system, since it will typically be the slowest to degrade. 

MARCOR Environmental, Inc. s, Advanced Chemical Treatment (ACT) is a chemical fixation method for the treatment of contaminated soils, sediments, and sludges. The vendor claims that by mixing contaminated materials with ACT reagents, the contaminants are oxidized, catalyzed, and mineralized. Target contaminants may include coal tar wastes polycyclic aromatic hydrocarbons (PAHs) benzene, toluene, ethylbenzene, and xylenes (BTEX) chromium copper and lead. 

The presence of chlorine radical chain reactions in a photocatalytic reaction system may significantly increase reaction rates and photocatalytic efficiencies. These enhancements would appear to have the potential to overcome the shortcomings typically associated with the photocatalytic oxidation of aromatic contaminants if a chlorine radical chain reaction could be initiated in conjunction with an aromatic photocatalytic reaction and if the chlorine radicals were capable of reacting with (and thus accelerating the conversion of) the aromatic contaminant of interest. Two potential configurations for combining chlorine radical promotion with the photocatalytic oxidation of aromatic contaminants have been examined in some detail mixed contaminant feeds and prechlorinated catalysts. 

This chapter describes the effects of dc fields on ions transport in soils, electrolysis and geochemical reactions, microbial adhesion and transport, and microbial activity. The interest in these in these processes is derived from the potential of using electric fields for transporting and mixing contaminants, biostimulants, and bioaugmentation inoculants to enhance in situ bioremediation. 

The use of surfactant-modified zeolite (SMZ) as a permeable barrier sorbent may offer several unique advantages when dealing with mixed contaminant plumes. Zeolites are hydrated aluminosilicate minerals characterized by cage-like structures, high internal and external surface areas, and high cation exchange capacities. Both natural and synthetic zeolites find use in industry as sorbents, soil amendments, ion exchangers,... 

Morkin M, Devlin JF, Barker JF, Butler BJ. In situ sequential treatment of a mixed contaminant plume. J Contam Hydrol 2000 45 2302-2833. 

Oregon—X Umatilla Depot Activity Mustard, VX, other "mixed contamination"... 

Polettini et al. (2004) investigated cement-based S/S on a mixed Cr(III)-, Cu(II)-, and Pb(II)- contaminated soil and showed that stabilization of the mixed metal(loid)-contamuiated soil was not compromized by the mixed contaminant status, which may have been related to similar immobilization mechanisms for all... 

Semer, R., and Reddy, K. R. (1996). Evaluation of soil washing process to remove mixed contaminants from a sandy loam. J. Hazard. Mater. 45(1), 45-57. 

Many large cities are ced with soil contamination problems inherited from past industrial activities. There are some 3,000 contaminated "Brownfields" sites in Canada (1) and some 450,000 such sites in the United States (2). A number of these urban sites within the Idand of Montreal, have mixed contamination problems. Ha dous (mixed) contamination can be found in soils and groundwater where it commonly corresponds to a mfarture of inorganic and organic contaminants. Lands that contain such contaminants, in varying concentrations, caimot be redeveloped unless they have been decontaminated. 

The mobility of contaminants and their subsequent removal depend also on their sorption capacity to soil components. Therefore, soil properties, particularly those related to the presence of mineral colloids (e.g. montmorillonite, chlorite, kaolinite) and organic matter, additionally challenge the remediation of mixed contaminated soils. 

Reddy and Maturi (2005) examined the feasibility of using electrokinetic remediation for the removal of mixed contaminants (i.e. mixtures of heavy metals and PAHs) from kaolin (low permeability soU). Likewise, different types of flushing solution were evaluated by a laboratory experimental program, including a cosolvent (n-butylamine), surfactants (3% Tween 80 and 5% Igepal CA-720), and a cyclodextrin (10% hydroxypropyl-j8-cyclodextrin or HPCD). It was reported that... 

SEKRIOP Technology for the Simultaneous Treatment of Mixed Contaminated Soils... 

Figure 15.2. pH distribution of soil in cells C1-C4 after the treatment of the mixed contaminated soil. CET, cation exchange textile AET, anion exchange textile. 

For this optimal removal with the application of both conditioning liquids, the energy consumption was calculated to be 28.4kWh/m of mixed contaminated soil. Assuming in Canadian dollar (CAD) that CAD 0.03/kWh is the unitary cost, the electrical energy cost for soil remediation would be CAD 0.85 perm The lowest energy cost (beside control cell) of CAD 0.65/m was observed when a surfactant... 

The major factors significantly affecting the unit price of mixed contamination treatment are (a) site properties (e.g. soil matrix, initial and target contaminant concentrations, moisture content, depth of contamination, concentration of nontarget ions), (b) electrokinetic system applied (e.g. array of electrodes, voltage, type of electrodes), (c) costs of conditioners and their application time, (d) site preparation requirements, (e) variable operation costs (e.g. electricity, labor, residual waste processing). 

Considering the effectiveness of the simultaneous heavy metals and PAH removal, it can be concluded that SEKRIOP might be used for an electrokinetic in situ remediation of mixed contaminated soils. The development of the above-described multifunctional method permits remediating the soils, particularly those characterized with low permeability. The results from the research can be applied to various municipal and industrial sites containing petroleum products and heavy metals. 

Numerous sites are contaminated with both inorganic (heavy metals) and organic contaminants (e.g. PAHs), and the technologies that treat such mixed contaminants are very limited. Electrokinetic technologies have the potential to remediate mixed contaminated soils however, the efficiency of this technology depends on... 

Electrokinetics can be applied in situ and ex situ into a mixed contamination in low permeability soil, mud, sludge, and marine dredging in fact, soil type does not pose any significant limitation on the technology. 

The costs of mixed contaminated site in situ remediation are still comparatively lower than other treatment methods. 

Elektorowicz M, Emon MH, Ayadat T. (2008b). Stabilization of metals and PAHs in mix contaminated soil. Proceedings, CSCE Conference, June 10-13, Quebec, QC, Canada. 

Elektorowicz M, Hakimipour M. (2003b). Electrokinetic soil remediation method for mixed contaminated soil. 6th Conference on Civil Engineering, May 5-7, 2003, Isfahan, Iran. 

Reddy KR, Karri MR. (2006b). Integrated electrochemical remediation of mixed contaminants in subsurface. 5th International Congress on Environmental Geotechnics, Cardiff) Wales, UK. London Thomas Telford Publishing, pp. 271-278. 

Since all the tests presented were performed in the laboratory, before field application approaches are undertaken, scaled-up research and further on-site testing experiences are highly recommended. The heterogeneity nature of the soil textures and mixed contaminants that may coexist in the site are the major concerns in the development of this EK-PRB process. In addition, highly contaminated hazardous waste sites can have extreme pH and Eh (redox potential) values that may accelerate the corrosion of Fe° in the barrier or change the barrier reactivity. More research is needed to address such influences as to ultimate the performance of EK-PRB. 

---