Pollution Remediation

Pollution Remediation

Remediation

- The act or process of remedying something that is undesirable or deficient.

. Deals with the removal of pollution or contaminants from environmental media such as soil, groundwater, sediment or surface water.

Immediate action should be taken as this can impact negatively on human health and the environment.

Generally subject to an array ofregulatory requirements, and also can be based on assessments of human health and ecological risks.

Pollution Remediation

In theUSAthe most comprehensive set of Preliminary Remediation Goals (PRGs) is from theEnvironmental Protection Agency(EPA) Region 9. A set of standards used inEuropeexists and is often called theDutch standards. TheEuropean Union(EU) is rapidly moving towards Europe-wide standards, although most of theindustrializednations inEuropehave their own standards at present.

Remediation standards

Dutch Standardsare environmental pollutant reference values (i.e., concentrations in environmental medium) used inenvironmental remediation, investigation and cleanup.The soil remediation intervention values indicate when the functional properties of the soil for humans, plants and animals is seriously impaired or threatened. They are representative of the level of contamination above which a serious case ofsoil contaminationis deemed to exist.Dutch Standards

Remediation technologies are many and varied but can be categorized into ex-situ and in-situ methods. Ex-situ (off-site) methods involve excavation of affected soils and subsequent treatment at the surface, In-situ (on-site) methods seek to treat the contamination without removing the soils. The more traditional remediation approach (used almost exclusively on contaminated sites from the 1970s to the 1990s) consists primarily of soil excavation and disposal tolandfill"dig and dump" and groundwater"pump and treat". In situ technologies includeSolidification and Stabilization and have been used extensively in the USA.Remediation Technologies

Thermal desorptionis anenvironmental remediationtechnology that utilizes heat to increase thevolatilityof contaminants such that they can be removed (separated) from the solid matrix (typically soil, sludge or filter cake). Thermal desorption is not incineration. The volatilized contaminants are then either collected or thermally destroyed. A thermal desorption system therefore has two major components; the desorber itself and the off gas treatment system.1) Thermal Desorption

Numerous desorber types are available today. Some of the more common types are listed below.Indirect Fired RotaryDirect Fired RotaryHeated Screw (Hot Oil, Molten Salt, Electric)InfraredMicrowave *Out of all the methods, Direct Fired Rotary is the most commonly used. (Petroleum/Hazardous waste contaminated soil)

Desorbers

The majority of these systems utilize a secondary combustion chamber (afterburner) or catalytic oxidizer to thermally destroy the volatilized organics. A few of these systems also have a quench and scrubber after the oxidizer which allows them to treat soils containing chlorinated organics such assolventsandpesticides. The desorbing cylinder for full scale transportable systems is typically four to ten feet in diameter with heated lengths ranging from twenty to fifty feet. The maximum practical solids temperature for these systems is around 750 to 900 F depending on the material of construction of the cylinder. Total residence time in this type of desorber normally ranges from 3 to 15 minutes. Treatment capacities can range from 6 to over 100 tons per hour for transportable units.Direct Fired Rotary

The volatilized contaminants in the offgas can either be discharged to atmosphere, collected or destroyed. In addition to managing the volatilized components, the particulate solids (dust) that exit the desorber must also be removed from the offgas.

When a collection system is used, the offgas must be cooled to condense the bulk of the volatilized components into a liquid.The cooled offgas may be treated by carbon adsorption, or thermal oxidation.

Desorbers using offgas destruction systems use combustion to thermally destroy the volatilized organics components formingCO,CO2,NOx, SOx andHCl. Offgas Treatment

Thermal Desorption

Excavation processes can be as simple as hauling thecontaminated soilto a regulatedlandfill, but can also involveaeratingthe excavated material in the case ofvolatile organic compounds (VOCs). Recent advancements in bio-augmentation and bio-stimulation of the excavated material have also proven to be able to remediate semi-volatile organic compounds (SVOCs) onsite. If the contamination affects a river or bay bottom, then dredging ofbay mudor othersiltclayscontaining contaminants may be conducted. 2) Excavation

Excavation

Pump and treatinvolves pumping out contaminated groundwater with the use of a submersible orvacuum pump, and allowing the extracted groundwater to bepurifiedby slowly proceeding through a series of vessels that contain materials designed toadsorbthe contaminants from the groundwater. For petroleum-contaminated sites this material is usuallyactivated carbonin granular form. Chemical reagentssuch asflocculantsfollowed bysand filtersmay also be used to decrease the contamination of groundwater.Air strippingis a method that can be effective for volatile pollutants such asBTEX compounds found in gasoline.3) Pump and Treat

For most biodegradable materials likeBTEX,MTBEand most hydrocarbons, bioreactors can be used to clean the contaminated water to non-detectable levels. Depending ongeologyand soil type, pump and treat may be a good method to quickly reduce high concentrations of pollutants. However, pump and treat is typically not the best form of remediation. It is expensive to treat the groundwater, and typically is a very slow process to cleanup a release with pump and treat. It is best suited to control the hydraulic gradient and keep a release from spreading further.

Pump and Treat

Solidification and stabilizationStabilization- involves the addition of reagents to a contaminated material (e.g. soil or sludge) to produce more chemically stable constituents; andSolidification- involves the addition of reagents to a contaminated material to impart physical/dimensional stability to contain contaminants in a solid product and reduce access by external agents (e.g. air, rainfall).Conventional S/S is an established remediation technology for contaminated soils and treatment technology for hazardous wastes in many countries in the world.4) Solidification and Stabilization

Solidification/stabilization work has a reasonably good track record but also a set of serious deficiencies related to durability of solutions and potential long term effects. In addition CO2emissions due to the use of cement are also becoming a major obstacle to its widespread use in solidification/stabilization projects. Stabilization/solidification (S/S) is a remediation/treatment technology that relies on the reaction between a binder and soil to stop/prevent or reduce the mobility of contaminants.

Disadvantages

Solidification and Stabilization

Soil vapor extraction(SVE) is a physical treatment process forin situremediation of volatile contaminants invadose zone(unsaturated) soils. SVE consists of passing an air stream through the soil, thereby transferring contaminants from the soil (soil/or water) matrix to the air stream. SVE has several advantages as a vadose zone remediation technology. The system can be implemented with standard wells and off-the-shelf equipment (blowers, instrumentation, vapor treatment, etc.). Depending on the nature of the contamination and the subsurface geology, SVE has the potential to treat large soil volumes at reasonable costs.5) Soil Vapor Extraction

The soil vapor extraction remediation technology uses vacuum blowers and extraction wells to induce gas flow through the subsurface, collecting contaminated soil vapor, which is subsequently treated aboveground. SVE systems can rely on gas inflow through natural routes or specific wells may be installed for gas inflow (forced or natural). The vacuum extraction of soil gas induces gas flow across a site, increasing the mass transfer driving force from aqueous (soil moisture), non-aqueous (pure phase), and solid (soil) phase into the gas phase. Air flow across a site is thus a key aspect, but soil moisture and subsurface heterogeneity (i.e., a mixture of low and high permeability materials) can result in less gas flow across some zones. Mechanism

Soil Vapor Extraction

Nanoremediation uses nano-sized reactive agents to degrade or immobilize contaminants is termednanoremediation. In soil or groundwater nanoremediation,nanoparticlesare brought into contact with the contaminant through eitherin situinjection or a pump-and-treat process. The nanomaterials then degrade organic contaminants throughredoxreactions or adsorb to and immobilize metals such asleadorarsenic. In commercial settings, this technology has been dominantly applied togroundwater remediation, with research into waste water treatment.Research is also investigating how nanoparticles may be applied to cleanup of soil and gases.

6) Nanoremediation

Once a nanoparticle contacts the contaminant, it may degrade the contaminant, typically through aredoxreaction, oradsorbto the contaminant to immobilize it. In some cases, such as with magnetic nano-iron, adsorbed complexes may be separated from the treated substrate, removing the contaminant.Target contaminants include organic molecules such aspesticidesororganic solventsand metals such asarsenicorlead. Some research is also exploring the use of nanoparticles to remove excessive nutrients such as nitrogen and phosphorus.

Mechanism

Titanium dioxideTitanium dioxide(TiO2) is also a leading candidate for nanoremediation and wastewater treatment, although as of 2010 it is reported to have not yet been expanded to full-scale commercialization. When exposed toultraviolet light, such as insunlight, titanium dioxide produceshydroxyl radicals, which are highly reactive and canoxidize contaminants. Hydroxyl radicals are used for water treatment in methods generally termedadvanced oxidation processes. Because light is required for this reaction, TiO2is not appropriate for undergroundin situremediation, but it may be used for wastewater treatment or pump-and-treat groundwater remediation.

Example of Compounds

Nano zero-valent ironNanozero-valent iron(nZVI) was the nanoscale material most commonly used in bench and field remediation tests.nZVI may be mixed or coated with another metal, such aspalladium, silver orcopper, that acts as acatalystin what is called a bimetallic nanoparticle. nZVI appears to be useful for degrading organic contaminants, includingchlorinated organic compoundssuch aspolychlorinated biphenyls(PCBs) andtrichloroethene(TCE), as well as immobilizing or removing metals.nZVI and other nanoparticles that do not require light can be injected belowground into the contaminated zone forin situgroundwater remediation and, potentially, soil remediation.

When usingin situremediation the reactive products must be considered for two reasons. One reason is that a reactive product might be more harmful or mobile than the parent compound. Another reason is that the products can affect the effectiveness and/or cost of remediation.TCE (trichloroethylene), under reducing conditions by nanoiron, may sequentially dechlorinate toDCE(dichloroethene) andVC(vinyl chloride). VC is known to be more harmful than TCE, meaning this process would be undesirable.

Nanoparticles also react with non-target compounds. Bare nanoparticles tend to clump together and also react rapidly with soil, sediment, or other material in ground water.Forin situremediation, this action inhibits the particles from dispersing in the contaminated area, reducing their effectiveness for remediation.

Disadvantages

Bioremediationis a waste management technique that involves the use of organisms to remove or neutralize pollutants from a contaminated site.According to the EPA, bioremediation is a treatment that uses naturally occurring organisms to break down hazardous substances into less toxic or non toxic substances. Technologies can be generally classified asin situorex situ.In situ bioremediation involves treating the contaminated material at the site, whileex situinvolves the removal of the contaminated material to be treated elsewhere. Some examples of bioremediation related technologies arephytoremediation,bioventing,bioleaching,landfarming,bioreactor,composting,bioaugmentation,rhizofiltrationandbiostimulation.7) Bioremediation

Mycoremediation is a form of bioremediation in whichfungiare used to decontaminate the area. The termmycoremediationrefers specifically to the use of fungalmyceliain bioremediation.One of the primary roles offungiin theecosystemisdecomposition, which is performed by the mycelium. The mycelium secretesextracellular enzymesandacidsthat break downligninandcellulose, the two main building blocks of plant fiber. These are organic compounds composed of long chains ofcarbonandhydrogen, structurally similar to many organic pollutants. The key to mycoremediation is determining the right fungal species to target a specific pollutant. Certain strains have been reported to successfully degrade thenerve gasesVX andsarin.

Mycoremediation

In one conducted experiment, a plot of soil contaminated withdieseloil was inoculated with mycelia ofoyster mushrooms; traditional bioremediation techniques (bacteria) were used on control plots. After four weeks, more than 95% of many of the PAH (polycyclic aromatic hydrocarbons) had been reduced to non-toxic components in the mycelial-inoculated plots. It appears that the natural microbial community participates with the fungi to break down contaminants, eventually into carbon dioxide and water. Wood-degrading fungi are particularly effective in breaking down aromatic pollutants (toxic components ofpetroleum), as well as chlorinated compounds (certain persistentpesticides)

Two species of the Ecuadorian fungus Pestalotiopsis are capable of consuming Polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills.

There are a number of cost/efficiency advantages to bioremediation, which can be employed in areas that are inaccessible withoutexcavation. For example,hydrocarbon spills (specifically,petrolspills) or certain chlorinated solvents may contaminategroundwater, and introducing the appropriate electron acceptor or electron donor amendment, as appropriate, may significantly reduce contaminant concentrations after a long time allowing for acclimation. This is typically much less expensive than excavation followed by disposal elsewhere,incineration or otherex situtreatment strategies, and reduces or eliminates the need for "pump and treat", a practice common at sites where hydrocarbons have contaminated clean groundwater.Advantages

TheGuimaras oil spilloccurred in thePanay Gulfon August 11, 2006, when theoil tankerM/TSolar 1sank off the coast ofGuimarasandNegrosIslands in thePhilippines, causing what is considered as the worstoil spillin the Philippines. Several causes have been cited, including bad weather andhuman error. Allegations have been made stating that the tanker only had a capacity of 1.2 million liters, implying the possibility of overloading. Other investigations have claimed that the ship's Captain was not qualified to sail the vessel.

Guimaras Oil Spill

The spill damagedTaklong Island National Marine Reserve, a marine sanctuary for feeding and breeding ground for fish and other species.The oil slick also posed a threat to theblue crabindustry in the municipality ofEnrique B. MagalonainNegros Occidental.Dr. Jose Ingles, eco-region coordinator of theWorld Wide Fund for Naturein the Philippines, Indonesia and Malaysia, said that the damage may be felt by at least two generations. He warned that the disaster may have damaged the reefs and mangroves, scarring the ecosystem and causing seafood yields to significantly decrease.Effects

In the south-southeast of the spill site is located theSulu Sea, a deep-water area frequented by commercially valued fish such asBlue marlinand the Yellow fin tuna, prized by the towns of southern Negros Occidental province as an important source of income for the communities. The oil slick may damage this thriving local industry.On August 22, 2006, thePhilippine Coast Guardstated that the spill has affected 20 communities in 4 municipalities in Guimaras. It also threatened 27 communities inIloilo provinceand 17 others inNegros Occidental.

Implemented solutions for the oil spill

Use of containment boomUse of hair/ animal fur to adsorb oilUse of chemical retardants (, )Use of skimmer

JORDAN, GuimarasGuimaras Island has continued its recovery five years after a massive oil spill devastated it but its marine resources continue to be affected by contamination, scientists said.

We cannot yet say that there has been a full recovery five years after the oil spill. But there are encouraging signs of recovery and growth, said Lemnuel Aragones, associate professor of the UP Institute of Environmental Science and Meteorology and head of the Guimaras Post-Oil Spill Monitoring Program.

August 13, 2011. Taken from Inquirer Visayas.

Aftermath

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