**8. The countermeasures and suggestions**

#### **8.1. The countermeasures for groundwater pollutions**

Groundwater treatment technologies are mainly as follows: pump and treat, air sparging, in-situ groundwater bioremediation and in-situ reactive walls.

#### *8.1.1. Pump and treat technology*

*U EF ED IAD BW AT*

´´ ´ <sup>=</sup> ´ (6)

HI CDI / RfD = (7)

CDI SF ´ (8)

1 exp( CDI SF) - -´ (9)

r

The DAD and IAD can be represent with continuous ingestion dose (CDI).

Based on the carcinogenesis of contamination, the risk could be classified into cancer risk

**1.** Noncancer hazard: Generally, the reaction of the body to non-carcinogenic substance

Lower than the threshold, they could not affect our health adversely. The non-carcinogenic risk to represent with hazard index (HI). It is defined as a ratio that continuous ingestion

Where: CDI= continuous ingestion dose (mg/kg-days), RfD= reference dose (mg/kg-days).

**2.** Cancer risk: There does not have dose threshold for the carcinogenic. Once it exist in environments, it will affect human health adversely. Cancer risk will be represent with risk. It is defined as a product of continuous ingestion dose with carcinogenesis slope

Where:

IAD= Ingestion absorbed dose (mg/kg-day),

U=Drinking amount per days (L/d),

102 Organic Pollutants - Monitoring, Risk and Treatment

EF=Exposure frequency (days/year),

ED=Exposure duration (years),

BW=Body weight (kg),

and noncancer hazard.

has a dose threshold.

dose with reference dose [28].

(If the low dose exposure risk>0.01)

Where: SF= carcinogenesis slope factor (mg-1•kg•d)

factor.

AT=Averaging time (days).

ρ= Pollutant concentration in groundwater (mg/L),

Pump and treat is the most common form of groundwater remediation. It is often associated with treatment technologies such as Air Stripping and Liquid-phase Granular Activated Charcoal.

Pump and treat involves pumping out contaminated groundwater with the use of a submersi‐ ble or vacuum pump, and allowing the extracted groundwater to be purified by slowly pro‐ ceeding through a series of vessels that contain materials designed to adsorb the contaminants from the groundwater. For petroleum-contaminated sites this material is usually activated car‐ bon in granular form. Chemical reagents such as flocculants followed by sand filters may also be used to decrease the contamination of groundwater. Air stripping is a method that can be ef‐ fective for volatile pollutants such as BTEX compounds found in gasoline.

For most biodegradable materials like BTEX, MTBE and most hydrocarbons, bioreactors can be used to clean the contaminated water to non-detectable levels. With fluidized bed bio‐ reactors it is possible to achieve very low discharge concentrations which will meet or ex‐ ceed discharge standards for most pollutants.

Depending on geology and soil type, pump and treat may be a good method to quickly re‐ duce high concentrations of pollutants. It is more difficult to reach sufficiently low concen‐ trations to satisfy remediation standards, due to the equilibrium of absorption (chemistry)/ desorption processes in the soil.

At the figure 2, we can know how does pump and treat technology work. This system usual‐ ly consists of one or more wells equipped with pumps. When the pumps are turned on, they pull the polluted groundwater into the wells and up to the surface. At the surface, the water goes into a holding tank and then on to a treatment system, where it is cleaned [29].

#### *8.1.2. Air sparging [30]*

Air sparging is an in situ groundwater remediation technology that involves the injection of a gas (usually air/oxygen) under pressure into a well installed into the saturated zone. Air sparg‐ ing technology extends the applicability of soil vapor extraction to saturated soils and ground‐ water through physical removal of volatilized groundwater contaminants and enhanced biodegradation in the saturated and unsaturated zones. Oxygen injected below the water ta‐ ble volatilizes contaminants that are dissolved in groundwater, existing as a separate aqueous phase, and/or sobbed onto saturated soil particles. The volatilized contaminants migrate up‐ ward in the vadose zone, where they are removed, and generally using soil vapor extraction techniques. This process of moving dissolved and non-aqueous volatile organic compounds (VOCs), originally located below the water table, into the unsaturated zone has been likened to an in situ, saturated zone, air stripping system. In addition to this air stripping process, air sparging also promotes biodegradation by increasing oxygen concentrations in the subsur‐ face, stimulating aerobic biodegradation in the saturated and unsaturated zones(figure 3). Depending on geology and soil type, pump and treat may be a good method to quickly reduce high concentrations of pollutants. It is more difficult to reach sufficiently low concentrations to satisfy remediation standards, due to the equilibrium of absorption (chemistry)/desorption processes in the soil. At the figure 2, we can know how does pump and treat technology work. This systemusually consists of one or more wells equipped with pumps. When the pumps are turned on,they pull the polluted groundwater into the wells and up to the surface. At the surface, the watergoes into a holding

*8.1.3. In-situ groundwater bioremediation [32]*

extraction, bioventing).

most critical components of any delivery system.

water or to publicly owned treatment works (POTW).

diation industry as "funnel and gate systems" or "treatment walls".

*8.1.4. In–situ reactive walls [33]*

In-situ groundwater bioremediation is a technology that encourages growth and reproduc‐ tion of indigenous microorganisms to enhance biodegradation of organic constituents in the saturated zone. In-situ groundwater bioremediation can effectively degrade organic constit‐

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In-situ groundwater bioremediation can be effective for the full range of petroleum hydro‐ carbons. While there are some notable exceptions (e.g., MTBE) the short-chain, low-molecu‐ lar-weight, more water soluble constituents are degraded more rapidly and to lower residual levels than are long-chain, high-molecular-weight, less soluble constituents. Recov‐ erable free product should be removed from the subsurface prior to operation of the in-situ groundwater bioremediation system. This will mitigate the major source of contaminants as well as reduce the potential for smearing or spreading high concentrations of contaminants.

In-situ bioremediation of groundwater can be combined with other saturated zone remedial technologies (e.g., air sparging) and unsaturated zone remedial operations (e.g., soil vapor

Bioremediation generally requires a mechanism for stimulating and maintaining the activity of these microorganisms. This mechanism is usually a delivery system for providing one or more of the following: An electron acceptor (oxygen, nitrate); nutrients (nitrogen, phospho‐ rus); and an energy source (carbon). Generally, electron acceptors and nutrients are the two

In a typical in-situ bioremediation system, groundwater is extracted using one or more wells and, if necessary, treated to remove residual dissolved constituents. The treated groundwa‐ ter is then mixed with an electron acceptor and nutrients, and other constituents if required, and re-injected upgradient of or within the contaminant source. Infiltration galleries or injec‐ tion wells may be used to re-inject treated water. In an ideal configuration, a "closed-loop" system would be established. All water extracted would be re-injected without treatment and all remediation would occur in situ. This ideal system would continually recirculate the water until cleanup levels had been achieved. If your state does not allow re-injection of ex‐ tracted groundwater, it may be feasible to mix the electron acceptor and nutrients with fresh water instead. Extracted water that is not re-injected must be discharged, typically to surface

In-situ reactive walls are an emerging technology that have been evaluated, developed, and implemented only within the last few years. This technology is gaining widespread atten‐ tion due to the increasing recognition of the limitations of pump and treat systems, and the ability to implement various treatment processes that have historically only been used in above-ground systems in an in situ environment. This technology is also known in the reme‐

uents which are dissolved in groundwater and adsorbed onto the aquifer matrix.

tank and then on to a treatment system, where it is cleaned[29].

Figure2.Pump and Treat Technology[29]

Air sparging is an in situ groundwater remediation technology that involves the injection of a

**7.1.2 Air Sparging**[30] **Figure 2.** Pump and Treat Technology [29]

**Figure 3.** Air Sparging [31]

### *8.1.3. In-situ groundwater bioremediation [32]*

biodegradation in the saturated and unsaturated zones. Oxygen injected below the water ta‐ ble volatilizes contaminants that are dissolved in groundwater, existing as a separate aqueous phase, and/or sobbed onto saturated soil particles. The volatilized contaminants migrate up‐ ward in the vadose zone, where they are removed, and generally using soil vapor extraction techniques. This process of moving dissolved and non-aqueous volatile organic compounds (VOCs), originally located below the water table, into the unsaturated zone has been likened to an in situ, saturated zone, air stripping system. In addition to this air stripping process, air sparging also promotes biodegradation by increasing oxygen concentrations in the subsur‐ face, stimulating aerobic biodegradation in the saturated and unsaturated zones(figure 3).

soil.

104 Organic Pollutants - Monitoring, Risk and Treatment

**7.1.2 Air Sparging**[30]

**Figure 2.** Pump and Treat Technology [29]

**Figure 3.** Air Sparging [31]

Depending on geology and soil type, pump and treat may be a good method to quickly reduce high concentrations of pollutants. It is more difficult to reach sufficiently low concentrations to satisfy remediation standards, due to the equilibrium of absorption (chemistry)/desorption processes in the

At the figure 2, we can know how does pump and treat technology work. This systemusually consists of one or more wells equipped with pumps. When the pumps are turned on,they pull the polluted groundwater into the wells and up to the surface. At the surface, the watergoes into a holding

tank

extraction well

groundwater level

Figure2.Pump and Treat Technology[29]

polluted groundwater

Air sparging is an in situ groundwater remediation technology that involves the injection of a

enhancedbiodegradation in the saturated and unsaturated zones.Oxygen injected below the water tablevolatilizes contaminants that are dissolved in groundwater, existing as a separate aqueous phase,and/or sobbed onto saturated soil particles. The volatilized contaminants migrate upward in thevadose zone, where they are removed, and generally using soil vapor extraction techniques. Thisprocess of moving dissolved and non-aqueous volatile organic compounds (VOCs), originally locatedbelow the water table, into the unsaturated zone has been likened to an in situ, saturated zone,

gas(usually air/oxygen) under pressure into a well installed into the saturated zone.Air spargingtechnology extends the applicability of soil vapor extraction to saturated soils and groundwaterthrough physical removal of volatilized groundwater contaminants and

airstripping system. In addition to this air stripping process, air sparging also promotes biodegradationby increasing oxygen concentrations in the subsurface, stimulating aerobic

tank and then on to a treatment system, where it is cleaned[29].

clean water watertreatment system holding

ground surface

In-situ groundwater bioremediation is a technology that encourages growth and reproduc‐ tion of indigenous microorganisms to enhance biodegradation of organic constituents in the saturated zone. In-situ groundwater bioremediation can effectively degrade organic constit‐ uents which are dissolved in groundwater and adsorbed onto the aquifer matrix.

In-situ groundwater bioremediation can be effective for the full range of petroleum hydro‐ carbons. While there are some notable exceptions (e.g., MTBE) the short-chain, low-molecu‐ lar-weight, more water soluble constituents are degraded more rapidly and to lower residual levels than are long-chain, high-molecular-weight, less soluble constituents. Recov‐ erable free product should be removed from the subsurface prior to operation of the in-situ groundwater bioremediation system. This will mitigate the major source of contaminants as well as reduce the potential for smearing or spreading high concentrations of contaminants.

In-situ bioremediation of groundwater can be combined with other saturated zone remedial technologies (e.g., air sparging) and unsaturated zone remedial operations (e.g., soil vapor extraction, bioventing).

Bioremediation generally requires a mechanism for stimulating and maintaining the activity of these microorganisms. This mechanism is usually a delivery system for providing one or more of the following: An electron acceptor (oxygen, nitrate); nutrients (nitrogen, phospho‐ rus); and an energy source (carbon). Generally, electron acceptors and nutrients are the two most critical components of any delivery system.

In a typical in-situ bioremediation system, groundwater is extracted using one or more wells and, if necessary, treated to remove residual dissolved constituents. The treated groundwa‐ ter is then mixed with an electron acceptor and nutrients, and other constituents if required, and re-injected upgradient of or within the contaminant source. Infiltration galleries or injec‐ tion wells may be used to re-inject treated water. In an ideal configuration, a "closed-loop" system would be established. All water extracted would be re-injected without treatment and all remediation would occur in situ. This ideal system would continually recirculate the water until cleanup levels had been achieved. If your state does not allow re-injection of ex‐ tracted groundwater, it may be feasible to mix the electron acceptor and nutrients with fresh water instead. Extracted water that is not re-injected must be discharged, typically to surface water or to publicly owned treatment works (POTW).

#### *8.1.4. In–situ reactive walls [33]*

In-situ reactive walls are an emerging technology that have been evaluated, developed, and implemented only within the last few years. This technology is gaining widespread atten‐ tion due to the increasing recognition of the limitations of pump and treat systems, and the ability to implement various treatment processes that have historically only been used in above-ground systems in an in situ environment. This technology is also known in the reme‐ diation industry as "funnel and gate systems" or "treatment walls".

The concept of in-situ reactive walls involves the installation of impermeable barriers down‐ grading of the contaminated groundwater plume and hydraulic manipulation of impacted groundwater to be directed through porous reactive gates installed within the impermeable barrier. Treatment processes designed specifically to treat the target contaminants can be implemented in these reactive or treatment gates. Treated groundwater follows its natural course after exiting the treatment gates. The flow through the treatment gates is driven by natural groundwater gradients, and hence these systems are often referred to as passive treatment walls. If a groundwater plume is relatively narrow, a permeable reactive trench can be installed across the full width of the plume, and thus preclude the necessity for instal‐ lation of impermeable barriers.

**3.** In recent years, the environmental hormone pollution research and prevention has be‐ gun to attract the attention of the world. Environmental hormone research has become the forefront and hot topic of environmental science research. But the mechanism of en‐

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**4.** The research on groundwater pollution risk assessment to be carried out on the typical regions. To provide practical experience on established an reasonable and feasible

**5.** Exerting governmental function adequately and improving the laws, regulations and norms on groundwater quality monitor and assessment. Strengthening the cross-disci‐ plinary exchanges and studies and establishing the groundwater pollution monitor net‐

With entering a new era of environmental protection, the research of groundwater pollution risk assessment is bound to make new contributions to human survival and to protect and improve the natural environment, and to advance the theory research of environmental sci‐

This study is granted by the Specific Research on Public Service of Environmental Protection

College of Water Sciences, Beijing Normal University, Key Laboratory of Water and Sedi‐

[1] Foundation for Water Research. FWR: Groundwater. http://www.euwfd.com/html/

[2] Barbash, J., P. V. Roberts. Volatile Organic Chemical Contamination of Groundwater Resources in the U.S. Water Pollution Control Federation 1986;58(5) 343-348.

[3] Moran, Michael J. Occurrence and Status of Volatile Organic Compounds In Ground Water From Rural, Untreated, Self-supplied Domestic Wells In the United States,

in China (No. 201009009). The authors appreciate the tutor and classmates for help.

vironmental hormone is not clearly, we should take more attention on these.

groundwater pollution risk assessment system.

work and the chemical toxicological database.

, Shuyuan Liu and Shasha Du

groundwater.html (accessed 18 September 2012)

\*Address all correspondence to: whongqi@126.com

ment Sciences, Ministry of Education.Beijing, China

ence.

**Acknowledgements**

**Author details**

Hongqi Wang\*

**References**

In-situ reactive walls eliminate or at least minimize the need for mechanical systems, there‐ by reducing the long-term operation and maintenance costs that so often drive up the life cycle costs of many remediation projects. In addition, groundwater monitoring and system compliance issues can be streamlined for even greater cost savings.

Bioventing, also a modification of vapor extraction technology, is briefly contrasted with air sparging. With bioventing, extraction or injection of air into the vadose zone increases sub‐ surface oxygen concentration, promoting bioremediation of unsaturated soil contaminants. This technique is applicable to all biodegradable contaminants, but has been applied most frequently and reportedly most successfully to sites with petroleum hydrocarbon contami‐ nation

#### **8.2. The suggestions for groundwater pollutions**

The past 40 years, groundwater subjected to pollution, it cannot be ignored that there has a serious threat to human health and ecological security problems. The research on ground‐ water pollution risk assessment will help understand the relationship between the soil con‐ ditions and groundwater pollution, identify the high-risk regions of groundwater pollution, provide a powerful tools for the land use and groundwater resource management, and help the policy maker and managers to develop effective management strategies and protection measures on groundwater. So we can offer some suggestions as following:


With entering a new era of environmental protection, the research of groundwater pollution risk assessment is bound to make new contributions to human survival and to protect and improve the natural environment, and to advance the theory research of environmental sci‐ ence.
