CHAPTER 16 REMEDIAL TECHNOLOGIES

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1 Hazardous Waste Management, nd ed. Instructors Manual CHAPTER 16 REMEDIAL TECHNOLOGIES Supplemental Questions: The opening quote describes the fifth labor of Hercules. How many labors were there and what are they? King Eurystheus, set Hercules 1 mighty labors: 1. Killing the Nemean lion 7. Capturing the Cretan bull. Killing the mufti-headed Hydra 8. Capturing the mares of Diomedes. Capturing the Arcadian deer 9. Procuring the girdle of Hippolyte 4. Capturing the Erymanthian boar 10. Capturing the cattle of Geryon 5. Cleansing the Augean stables 11. Procuring the golden apples of the Hesperides 6. Driving off the Stymphalian birds 1. Capturing the Cerberus What was so laborous about cleansing the Augean stables? The story of the cleansing of the Augean stables is the earliest recorded instance of site remediation. Augeas, King of Elis, kept 000 oxen in the stables and they had not been cleaned for thirty years. Hercules had to clean the stables out in a single day. He did this by re-routing two rivers through the stables. There is no record of an environmental impact statement ever being filed for this project. When Augeas failed to pay him, Hercules killed the king. Many consultants today use somewhat less extreme measures when dealing with recalcitrant clients The remedial investigation site characterization at an old industrial facility on Long Island revealed a sandy site with shallow ground water contaminated with low levels of volatile organics. The contaminant plume was found to migrate a short distance beyond the property line but had not yet reached residences relying upon ground water for their drinking water supply. What might be the objective for cleanup of this site? The objective might be to immediately contain the contamination from further movement to then allow for treatment or removal to ultimately protect ground water in the area for drinking. Continued migration of contaminants from this site would obviously threaten the nearby water supplies. Thus the immediate objective of this site remediation is the protection of these water supplies by stopping or reversing the migration of the contaminants. Over the longer term, the threat to public health due to contaminated ground water can best be minimized by the removal of the contaminants from the ground water. For this particular site, in order to accomplish the above stated objectives, a remedial system was selected which included a series of groundwater pumping wells and a water treatment system. What goals would be established for the components of this system? Pumping wells: The ground water withdrawal system must alter the groundwater gradients to capture the zone of contaminated ground water. Treatment system: The extracted ground water must be cleaned to some acceptable level; in this case, the drinking water j standards. Duration: The cleanup system must be operated until the remaining contaminants in the ground water are below some acceptable concentration; in this case, the drinking water standards. 001 Environmental Resources Managment Page 1 of 1

2 Hazardous Waste Management, nd ed. Instructors Manual 16-. Cite three advantages and three disadvantages of containment as a means of hazardous waste site remediation. Advantages Disadvantages 1. Cost effectiveness 1. Design uncertainties. Little attention is necessary after implementation. Questionable long-term liability (passive containment). Can be used in conjunction with other treatment. Does not actually clean up the site, contaminants methods remain 16-. Suppose that a section of the circumferential barrier wall described in Example 16-1 Is constructed without adequately keying into an underlying layer of low hydraulic conductivity. A section of the original material 100ft long and ft deep remains with the original aquifer hydraulic conductivity of 1 x 10 - cm/s (a shallow buried valley). What would the leakage through the wall be from this zone? Would this jeopardize the success of the associated pump and treat system? Use: q kia where: k 1 x 10 - cm/s, i 1.67 (from 16.1), A (10)(0) 00 ft. Calculate q: in ft 7.48gal 60s q ( 1 10 cm /sec)(1.67)( 00 ft ) 7. 8gpm.54cm 1in ft 1min This would overwhelm the treatment system design for 5 gpm, rendering it ineffective A 1 m thick up-gradient barrier is planned to control the influx of clean ground water to extraction wells. The down-gradient ground water extraction wells and treatment plant are designed to operate at cm /s. The upgradient barrier is planned to be 500 m long, and the aquifer is 10 m thick. It is estimated that the average drawdown across the wall will be 4 m. By calculating the flow through the wall at various values of hydraulic conductivity, recommend a design value for the barrier. 500m 10m h 4m Q KiA I h 4m 4 L 1m A 10 m x 500 m 5000 m Q KiA K x 4 x x 0,000 m K x 10 8 cm 1 m K (cm/s) Q (cm /s) 1 x x x x 10-9 Select K 1 x 10-8 cm/s Note: Typo in 1st, nd & rd printings: m /s should be cm /s. 001 Environmental Resources Managment Page of 1

3 Hazardous Waste Management, nd ed. Instructors Manual Calculate the volume of water to be mixed with a 100 pound bag of bentonite for a 5% bentonite-water slurry. What will be the unit weight of this slurry? 100 lb bentonite bentonite content 5% Calculate the volume of water: V Calculate the volume of solids: W 100lb (6.4lb / ft ) V W.1ft.1ft (7.48gal/ft ) 40gal V WS G γ 100lb ft.77(6.4lb / ft ) S S S Calculate the weight of water: WW VW γ W (.1 ft )(6.4lb / ft ) 00lb Determine the fluid unit weight: W γ V ( ) ( ) T f T 64.4lb / ft 001 Environmental Resources Managment Page of 1

4 Hazardous Waste Management, nd ed. Instructors Manual What is the factor of safety for a trench 10 m deep excavated in sand having an angle of internal friction of 0. The unit weight of the fluid is as calculated in Problem The sand has a total bulk density of.1 g/cm. How does the factor of safety change for a trench 0 m deep?.1 * KN / m Factor of safety (sand): F γ γ (tanφ) ( γ γ ) f f ( ) where: ; γf 64.4 lb/ft 6.4lb / ft γ.1g / cm 11.04lb / ft 1g / cm Calculate F: F (( 11.04) ( 64.4) ) (tan 0) The factor of safety will not change for a trench of 0 m deep, since the equation for sands is independent of H, the depth of the cut-off wall What is the factor of safety for a trench 10 m deep excavated in clay having a shear strength of 1 kg/cm. The unit weight of the fluid as calculated above. The clay has a total unit weight of. g/cm. How does the factor of safety change for a trench 0 m deep? 4SU Factor of safety (clay): F H ( γ γ ) where: S U 1 kg/cm 1000 g/cm ; H 10 m 1000 cm f 1g / cm ( 64.4lb / ft ) 1.0g / γ g γ f 6.4lb / ft. / cm ; cm Determine F: F 4(1000g / cm ) cm(. 1.0) For a trench 0 m deep, the factor of safety is half as much: 4(1000g / cm ) F cm(. 1.0) Describe the steps to be taken prior to determining a containment alternative at a hazardous waste site. First, a thorough site characterization needs to be done. This will be followed closely by an assessment of risk. Then an analysis of remedial alternatives will be done. Economic environmental factors will play key roles in this decision. 001 Environmental Resources Managment Page 4 of 1

5 Hazardous Waste Management, nd ed. Instructors Manual Describe the hydrologic pathways for contaminant migration at a typical waste disposal site. - migration of leachate - runoff that encounters waste - contaminates transported in groundwater - contaminants in groundwater discharged to surface water List and briefly describe the types of vertical barriers available as passive containment alternatives. Slurry trench cutoff walls - These are commonly made of soil-bentonite, cement-bentonite, or plastic concrete. The process involves excavating a trench around the contaminated area, and replacing it with the low permeability backfill. Grout curtains - These are most commonly used when materials such as rock are involved (and cannot be excavated). The grout curtain is pressure injected into the rock and then sets in place, filling the fractures and voids What are active containment systems? List three alternative techniques. Active systems are systems which require ongoing energy input while controlling and containing contaminant migration. Some additional alternatives might be: - excavation and disposal of the contaminated soil - electrokinetic soil decontamination - biological or chemical permeable treatment beds - soil washing - low-temperature soil treatment 001 Environmental Resources Managment Page 5 of 1

6 Hazardous Waste Management, nd ed. Instructors Manual Construct the flow net for the conditions defined in Example Environmental Resources Managment Page 6 of 1

7 Hazardous Waste Management, nd ed. Instructors Manual Soil on a five-acre site has become contaminated with a mixture of volatile organic compounds. Prepare a brief outline indicating what type of data you would need to collect to begin analyzing remedial measures. The different soil, contaminant and environmental properties are to be found to analyze remedial measures for the compounds. The different soil properties that affect the treatment method are Permeability, Porosity, Grain Size Distribution, Moisture Content, ph, Organic Content, Bulk Density. As the site has been contaminated with different VOC's, only representative compounds should be taken into consideration. For example, TCDD should be taken as a representation for all PCDD's. The contaminant properties which affect the treatment methods are Henry's Law Constant, Solubility, Adsorption Coefficient, VOC Concentration in Soil, Polarity, Vapor Pressure, Diffusion Coefficient. The environmental properties also affect the treatment methods. The different environmental properties that affect the remedial measures are Temperature, Humidity, Wind Speed, Solar Radiation, Precipitation, Terrain, Vegetation Use Hartley's method to estimate the rate of volatilization of trichloroethane. Use an estimated diffusion coefficient of 0.80 cm /s. The following data is provided: TCE saturation in air 76 g/m (Verschueren) Diffusion coefficient 0.80 cm /sec (Lyman et al) Humidity 0.; Temperature 0 C Latent heat of vaporization 7.96 Kcal/mol (Dean) Thickness of stagnant boundary layer 0. cm Specific gravity of TCE 1.5 (Verschueren) 1. Flux: A sat 76 g/m M 1 g/mol λ 7960 cal/mol 1 g/mol x 10-6 m /cc 7. 6 x 10-4 g/cc k 61 x 9-6 Cal/sec cm K cal/g J 1 0.8cm ( g / cc)(0.7) 0. 4 (59.85cal / g) ( g / cc)(1g / mol) + 6 /sec (61 10 cal /sec cm K)(1.987cal / mol K)(9K) 4.74 x 10-5 g/cm sec. Area and mass of chemical Area, 000 Ft x x 10 6 cm Volume x 10 4 gal x m Mass 11.55(1.5)(1000Kg/m ) 15,9 Kg g. Time required: Time Mass/Area Flux 1. 5 x 10 8 g/(1.858 x 10 6 cm ) (4.74 x 10-5 g/cm sec) x 10 6 sec 47.5 hrs ~ 0 days 001 Environmental Resources Managment Page 7 of 1

8 Hazardous Waste Management, nd ed. Instructors Manual 4. Limitations of method: Hartley's method accounts for only a few of the parameters listed in Table 9-. Specifically this problem does not consider soil properties, depth of contamination and many of the environment properties Repeat problem for benzene. Use an estimated diffusion coefficient of cm /s. The following data is provided: Benzene saturation in air 19 g/m (Verschueren) Diffusion coefficient cm /sec (Lyman et al) Humidity 0.; Temperature 0 C Latent heat of vaporization 9.5 Kcal/mol (Dean) Thickness of stagnant boundary layer 0. cm Specific gravity of TCE (Verschueren) 1. Flux: A sat 19 g /m x 10-6 m /cc.19 x 10-4 g/cc M 78 g/mol λ 950 cal/mol 78 g/mol k 61 x 9-6 Cal/sec cm K cal/g J cm ( g / cc)(0.7) 0. 4 (1.179cal / g) ( g / cc)(78g / mol) + 6 /sec (61 10 cal /sec cm K)(1.987cal / mol K)(9K) g / cm sec. Area and mass of chemical Area, 000 ft x x 10 6 cm Volume x 10 4 gal x m Mass (0.8786) (1000Kg/m ) 99,765Kg 1.0 x 10 8 g. Time required: Time Mass/Area Flux 1.0 x 10 8 g / (1.858 x 10 6 cm ) ( x 10-5 g/cm sec ) 8101 sec 9. 6days l week days 4. Limitations of method: Hartley's method accounts for only a few of the parameters listed in Table 9-. Specifically this problem does not consider soil properties, depth of contamination and many of the environment properties. 001 Environmental Resources Managment Page 8 of 1

9 Hazardous Waste Management, nd ed. Instructors Manual Repeat problem for toluene. Use an estimated diffusion coefficient of cm /s. The following data is provided: TCE saturation in air 110 g/m (Verschueren) Diffusion coefficient cm /sec (Lyman et al) Humidity 0. Temperature 0 C Latent heat of vaporization 86.8 cal/g (App. C, Table C-4) Thickness of stagnant boundary layer 0. cm Specific gravity of TCE (Verschueren) 1. Flux: A sat 110 g/m x 10-6 M 9g/mol λ 86.8 cal/g m /cc 1.10 x 10-4 g/cc k 61 x 10-6 Cal/sec cm K J cm ( g / cc)(0.7) 0. 4 (86.8cal / g) ( g / cc)(9g / mol) + 6 /sec (61 10 cal /sec cm K)(1.987cal / mol K)(9K) g / cm sec. Area and Mass of Chemical Area,000 ft x x 10 6 cm Volume x 10 4 gal x m Mass x / (1000 Kg/m ) Kg 1. 0 x 10 8 g r... Time required: Time Mass/(Area Flux) 1.0 x 10 8 g / (1.858 x 10 6 cm ) (.00 x 10-5 g / cm sec).688 x 10 6 sec 1.l days 4 weeks.l days 001 Environmental Resources Managment Page 9 of 1

10 Hazardous Waste Management, nd ed. Instructors Manual Briefly describe the alternative processes that could be considered for removing volatile organics from soils. 1. Soil Vapor Extraction: a non-steady state process by which VOC's are removed from the soil. It may be accomplished in situ in the vadose zone or above ground. It operates by passing an air stream through the soil and transferring the contaminants from the soil to the air. (See Sec. 9-). Soil Washing: The passing of solvent through the soil in a fashion similar to Figs: 10-1 and 10- (pages 596, 597). Organic contaminants are removed from the recovered solvent using solvent extraction and the solvent may be reused.. Chemical Stabilization (see Chap. 11): Stabilization is a process where additives are mixed with waste to reduce the toxicity of the waste and to minimize the rate of contaminant migration. In this process, the contaminants are fully or partially bound by the addition of supporting media, binders, or other modifiers. 4. In-situ bioremediation: The process where the contaminated ground water and subsurface contaminant are treated at the same place where they are found without excavating the overlying soil is called Em-situ Bioremediation. All the treatment actually takes place in the subsurface. (See Section 10-6) 5. In-site vitrification: In-situ Vitrification is a process where the remediation of the contaminated soil is done by melting the soil into a molten mass by applying electric current. As the current flows through the soil, heat builds up, eventually causing the soil to melt. (See Section 11-) 6. Low Temperature Thermal Stripping: Soil is excavated and placed in a device where the soil is mechanically dis-assugated (typically thru the use of a screw conveyor). By passing a heated oil through the center of the screw conveyor, heat is added to the soil and organic vapors are driven off. Additional details may be found in "Hazardous Waste Soil Remediation" (Wilson, D. J. and Clarke, A. N. ed.), Marcel Dekker, Inc., Environmental Resources Managment Page 10 of 1

11 Hazardous Waste Management, nd ed. Instructors Manual An underground storage tank (UST) containing trichloroethane at a chemical plant has ruptured. The plume currently extends west to a distance of 45 feet and is 10 feet wide at this distance. The depth of the plume is 1 feet and the seasonal high ground water table is at a depth of 7 feet. Provide a preliminary design and layout of a soil vapor extraction system. Specifically determine: pressure (a) (b) (c) The required number of extraction wells and their layout. The volumetric capacity in cubic feet per minute (CFM) and operating system of the blower. Equipment layout and any required ancillary facilities. State any assumptions made. Contaminant - Trichloroethane Plume Extension - 45 ft - west; 10 ft - wide Depth of the plume - 1 ft Water table - 7 ft Assumptions: the curves in Fig and 9-11 are applicable to this site. The minimum measurable vacuum pressure at the radius of influence of the extraction wells will be 0.5 inches water gauge (15 pa). Solution: 1) Using Fig. 16-, a vacuum of 0.5 inches water gage can be obtained from either CFM blower, with 5 foot radius of influence per extraction well, or a 40 CFM blower with 40 foot radius of influence. Selecting a 40 CFM blower yields an extraction well spacing of 80 feet. Eight extraction wells should be adequate to cover the plume. ) Using Fig. 16-, a 40 CFM blower per extraction well must be capable of generating a vacuum of 4 inches of water gage. This does not include any losses in the piping system, which would have to be considered after the piping system is designed. Because the blowers will be manifold to all extraction wells, the system must be capable of producing 8 x CFM at 4 inches of water gage (8450 pa). ) Ancillary equipment required includes manifold piping, a Knocrout drum to remove any water removed by the vacuum system, and a Carbon adsorption system or other means of removing organics from the air before release to the atmosphere. As the water table is above the plume depth, ground water extraction pumps has to be installed into the vapor extraction wells to either lower the- ground water table (and therefore enlarge the vadose zone) and/or concurrently remove contaminated ground water. Many of the system options, enhancements discussed above may be considered in this Preliminary design. A schematic representation is shown below in Fig Identify additional parameters other than those presented in Table 16- that might affect SVE system performance. Further, describe how these parameters influence system performance. (Refer to Lyman, et al., Reference 85, for additional information.) The additional parameters that might affect the SVE system performance other than those listed in table 9- are: 1. Vapor density : It is the chemical concentration in air in which the saturated vapor is the maximum concentration. The volatilization rate can be determined by vapor density. Vapor density and vapor pressure are affected by interaction with soils. 001 Environmental Resources Managment Page 11 of 1

12 Hazardous Waste Management, nd ed. Instructors Manual To have a saturated vapor in moist soil, some chemicals may require only a low total soil concentration. The total volatilization rate decreases if the chemicals are incorporated into the soil.. Mass transport by Wick effect : The process of transport of a chemical from the soil body to the surface by capillary action is called Wick effect or Wick evaporation. The rate of evaporation increases with evaporation of water causing capillary action Given the following octanol water partition coefficients, K ow, indicate for which compounds vacuum extraction is a candidate process for removing the compound from the vadose zone of contaminated soil. Compound Log K ow Trichloroethene.8 Pyrene 4.88 Polychlorinated biphenyl congeners 6.01 Vinyl chloride 1.8 Ethyl benzene.15 Phenol Lindane.9 0 DDT Butanone (methyl ethyl ketone) 0.6 The Octanol Water Partition coefficients, K OW Co C where Co concentration in Octanol (mg/ L or µg/ L) C concentration in Water (m g/ L or µg/ L) The Octanol-Water Partition coefficient is useful in estimating fate and transport of chemicals and is related to soil adsorption coefficients. Chemicals with low values of K OW (< 10) tend not to be hydrophilic and have low soil adsorption. As vacuum extraction is used for removing the compound from vadose zone of contaminated soil, that is from soil/water, higher the K OW, more efficient is the vacuum extraction process. Compound Log K OW K OW Vacuum Extraction 1) Trichloroethene Possible ) Pyrene Possible ) Polychlorinated Possible Biphenyl Congeners 4) Vinyl Chloride Possible 5) Ethyl Benzene Possible 6) Phenol Possible 7) Lindane Possible 8) DDT Possible 9) -Butanone Not Possible (methyl ethyl ketone) As for most of the cases K OW > 10, vapor extraction is possible. The efficiency is greater for DDT, followed by Polychlorinated Biphenyl Congeners, Pyrene and Lindane. 001 Environmental Resources Managment Page 1 of 1