Rhizofiltration is a form of phytoremediation that involves filtering contaminated groundwater, surface water and wastewater through a mass of roots to remove toxic substances or excess nutrients.
Rhizofiltration is a type of phytoremediation, which refers to the approach of using hydroponically cultivated plant roots to remediate contaminated water through absorption, concentration, and precipitation of pollutants. It also filters through water and dirt.[ citation needed ]
The contaminated water is either collected from a waste site and brought to the plants, or the plants are planted in the contaminated area, where the roots then take up the water and the contaminants dissolved in it. Many plant species naturally uptake heavy metals and excess nutrients for a variety of reasons: sequestration, drought resistance, disposal by leaf abscission, interference with other plants, and defense against pathogens and herbivores. [1] Some of these species are better than others and can accumulate extraordinary amounts of these contaminants. Identification of such plant species has led environmental researchers to realize the potential for using these plants for remediation of contaminated soil and wastewater.[ citation needed ]
This process is very similar to phytoextraction in that it removes contaminants by trapping them into harvestable plant biomass. Both phytoextraction and rhizofiltration follow the same basic path to remediation. First, plants that have stable root systems are put in contact with the contamination to get acclimated to the toxins. They absorb contaminants through their root systems and store them in root biomass and/or transport them up into the stems and/or leaves. The plants continue to absorb contaminants until they are harvested. The plants are then replaced to continue the growth/harvest cycle until satisfactory levels of contaminant are achieved. Both processes are also aimed more toward concentrating and precipitating heavy metals than organic contaminants. The major difference between rhizofiltration and phytoextraction is that rhizofiltration is used for treatment in aquatic environments, while phytoextraction deals with soil remediation.[ citation needed ]
Rhizofiltration may be applicable to the treatment of surface water and groundwater, industrial and residential effluents, downwashes from power lines, storm waters, acid mine drainage, agricultural runoffs, diluted sludges, and radionuclide-contaminated solutions. Plants suitable for rhizofiltration applications can efficiently remove toxic metals from a solution using rapid-growth root systems. Various terrestrial plant species have been found to effectively remove toxic metals such as Cu2+, Cd2+, Cr6+, Ni2+, Pb2+, and Zn2+ from aqueous solutions. [2] It was also found that low level radioactive contaminants can successfully be removed from liquid streams. [3] A system to achieve this can consist of a “feeder layer” of soil suspended above a contaminated stream through which plants grow, extending the bulk of their roots into the water. The feeder layer allows the plants to receive fertilizer without contaminating the stream, while simultaneously removing heavy metals from the water. [4] Trees have also been applied to remediation. Trees are the lowest cost plant type. They can grow on land of marginal quality and have long life-spans. This results in little or no maintenance costs. The most commonly used are willows and poplars, which can grow 6 - 8’ per year and have a high flood tolerance. For deep contamination, hybrid poplars with roots extending 30 feet deep have been used. Their roots penetrate microscopic scale pores in the soil matrix and can cycle 100 L of water per day per tree. These trees act almost like a pump and treat remediation system. [5] Willows have been successfully used as “vegetation filters” for nutrient (e.g. nitrogen and phosphorus) removal from municipal wastewater [6] and polluted groundwater. [7]
There are a series of aquatic and land plants that are used for rhizofiltration with varying degrees of success among them. While many of these plants are hyperaccumulators, other plant species can be used as the contaminants do not always reach the shoots (stems and their appendages: leaves, lateral buds, flowering stems and flower buds).[ citation needed ]
Some of the most common plant species that have shown the ability to remove toxins from water via rhizofiltration: [8] [9]
Rhizofiltration is cost-effective for large volumes of water having low concentrations of contaminants that are subjected to stringent standards. [10] It is relatively inexpensive, yet potentially more effective than comparable technologies. The removal of radionuclides from water using sunflowers was estimated to cost between $2 and $6 per thousand gallons of water treated, including waste disposal and capital costs. [11]
Rhizofiltration is a contamination treatment method that may be conducted in situ, with plants being grown directly in the contaminated water body or ex situ, where plants are grown off-site and later introduced to the contaminated water body. [8] This allows for a relatively inexpensive procedure with low capital and operational costs, depending on the type of contaminant.[ citation needed ]
In some cases, contaminants have been shown to be significantly decreased in a very short amount of time. One study found that roots of sunflower reduced levels of Uranium by nearly 95% in just 24 hours. [2]
This treatment method is also aesthetically pleasing and results in a decrease of water infiltration and leaching of contaminants. [5]
After harvesting, the crop may be converted to biofuel briquette, a substitute for fossil fuel. [12]
This contamination treatment method has its limits. Any contaminant that is below the rooting depth will not be extracted. The plants used may not be able to grow in highly contaminated areas. Most importantly, it can take years to reach regulatory levels. This results in long-term maintenance.[ citation needed ]
Also, most contaminated sites are polluted with many different kinds of contaminants. There can be a combination of metals and organics, in which treatment through rhizofiltration will not suffice. [5]
Plants grown on polluted water and soils become a potential threat to human and animal health, and therefore, careful attention must be paid to the harvesting process and only non-fodder crop should be chosen for the rhizofiltration remediation method. [12]
Water pollution is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources: sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Water pollution is either surface water pollution or groundwater pollution. This form of pollution can lead to many problems, such as the degradation of aquatic ecosystems or spreading water-borne diseases when people use polluted water for drinking or irrigation. Another problem is that water pollution reduces the ecosystem services that the water resource would otherwise provide.
Environmental remediation is the cleanup of hazardous substances dealing with the removal, treatment and containment of pollution or contaminants from environmental media such as soil, groundwater, sediment. Remediation may be required by regulations before development of land revitalization projects. Developers who agree to voluntary cleanup may be offered incentives under state or municipal programs like New York State's Brownfield Cleanup Program. If remediation is done by removal the waste materials are simply transported off-site for disposal at another location. The waste material can also be contained by physical barriers like slurry walls. The use of slurry walls is well-established in the construction industry. The application of (low) pressure grouting, used to mitigate soil liquefaction risks in San Francisco and other earthquake zones, has achieved mixed results in field tests to create barriers, and site-specific results depend upon many variable conditions that can greatly impact outcomes.
Bioremediation broadly refers to any process wherein a biological system, living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluents etc., in natural or artificial settings. The natural ability of organisms to adsorb, accumulate, and degrade common and emerging pollutants has attracted the use of biological resources in treatment of contaminated environment. In comparison to conventional physicochemical treatment methods bioremediation may offer considerable advantages as it aims to be sustainable, eco-friendly, cheap, and scalable.
Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronomic techniques to either contain, remove or render toxic environmental contaminants harmless". The term is an amalgam of the Greek phyto (plant) and Latin remedium. Although attractive for its cost, phytoremediation has not been demonstrated to redress any significant environmental challenge to the extent that contaminated space has been reclaimed.
Mycoremediation is a form of bioremediation in which fungi-based remediation methods are used to decontaminate the environment. Fungi have been proven to be a cheap, effective and environmentally sound way for removing a wide array of contaminants from damaged environments or wastewater. These contaminants include heavy metals, organic pollutants, textile dyes, leather tanning chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbons, pharmaceuticals and personal care products, pesticides and herbicides in land, fresh water, and marine environments.
Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals or improper disposal of waste. The most common chemicals involved are petroleum hydrocarbons, polynuclear aromatic hydrocarbons, solvents, pesticides, lead, and other heavy metals. Contamination is correlated with the degree of industrialization and intensity of chemical substance. The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapour from the contaminants, or from secondary contamination of water supplies within and underlying the soil. Mapping of contaminated soil sites and the resulting clean ups are time-consuming and expensive tasks, and require expertise in geology, hydrology, chemistry, computer modelling, and GIS in Environmental Contamination, as well as an appreciation of the history of industrial chemistry.
This list covers hyperaccumulators, plant species which accumulate, or are tolerant of radionuclides, hydrocarbons and organic solvents, and inorganic solvents.
Short rotation coppice (SRC) is coppice grown as an energy crop. This woody solid biomass can be used in applications such as district heating, electric power generating stations, alone or in combination with other fuels. Currently, the leading countries in area planted for energy generation are Sweden and the UK.
Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the subsurface. Globally, between 25 per cent and 40 per cent of the world's drinking water is drawn from boreholes and dug wells. Groundwater is also used by farmers to irrigate crops and by industries to produce everyday goods. Most groundwater is clean, but groundwater can become polluted, or contaminated as a result of human activities or as a result of natural conditions.
Phytoextraction is a subprocess of phytoremediation in which plants remove dangerous elements or compounds from soil or water, most usually heavy metals, metals that have a high density and may be toxic to organisms even at relatively low concentrations. The heavy metals that plants extract are toxic to the plants as well, and the plants used for phytoextraction are known hyperaccumulators that sequester extremely large amounts of heavy metals in their tissues. Phytoextraction can also be performed by plants that uptake lower levels of pollutants, but due to their high growth rate and biomass production, may remove a considerable amount of contaminants from the soil.
Phytotechnology implements solutions to scientific and engineering problems in the form of plants. It is distinct from ecotechnology and biotechnology as these fields encompass the use and study of ecosystems and living beings, respectively. Current study of this field has mostly been directed into contaminate removal (phytoremediation), storage (phytosequestration) and accumulation. Plant-based technologies have become alternatives to traditional cleanup procedures because of their low capital costs, high success rates, low maintenance requirements, end-use value, and aesthetic nature.
The Capitol City Plume, which also is referred to as the Capital City Plume, is an area of contaminated groundwater located beneath the western downtown area of Montgomery, Alabama. The contamination was discovered in 1993 by the Alabama Department of Environmental Management (ADEM) which was investigating soil contamination at the Retirement Systems of Alabama Energy Plant in the city. After assessment by the United States Environmental Protection Agency (EPA) it was proposed for inclusion in the National Priorities List (NPL) in May 2000.
The Koppers Co., Inc. (KCI) Superfund Site is one of three Superfund sites in Oroville, California, along with Louisiana Pacific Sawmill and Western Pacific Railyard. The KCI Superfund Site is a 200-acre site which served as a wood treatment plant for 50 years. Wood was treated with many chemicals to prevent wood deterioration. The accumulation of these chemicals from spills, fires, and uses has caused this site to be contaminated with the hazardous waste material. Due to soil and groundwater contamination, the site was placed on the National Priorities List in 1984 for remedial action plans to clean up the site to protect surrounding residential areas concerning environmental and human health risks.
Nanoremediation is the use of nanoparticles for environmental remediation. It is being explored to treat ground water, wastewater, soil, sediment, or other contaminated environmental materials. Nanoremediation is an emerging industry; by 2009, nanoremediation technologies had been documented in at least 44 cleanup sites around the world, predominantly in the United States. In Europe, nanoremediation is being investigated by the EC funded NanoRem Project. A report produced by the NanoRem consortium has identified around 70 nanoremediation projects worldwide at pilot or full scale. During nanoremediation, a nanoparticle agent must be brought into contact with the target contaminant under conditions that allow a detoxifying or immobilizing reaction. This process typically involves a pump-and-treat process or in situ application.
Groundwater pollution occurs when pollutants are released to the ground and make their way into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as contamination rather than pollution. Groundwater pollution can occur from on-site sanitation systems, landfill leachate, effluent from wastewater treatment plants, leaking sewers, petrol filling stations, hydraulic fracturing (fracking) or from over application of fertilizers in agriculture. Pollution can also occur from naturally occurring contaminants, such as arsenic or fluoride. Using polluted groundwater causes hazards to public health through poisoning or the spread of disease.
The word "hydraulic" originates from the Greek word ὑδραυλικός (hydraulikos) which in turn stems from ὕδωρ and αὐλός, and "containment" refers to the action of keeping something harmful under control or within limits. Thus, hydraulic containment is the attempt of confining the movement of any harmful fluid within a limit. In the pollution management sense, hydraulic containment is a technique used to control the movement of contaminated groundwater, preventing the continued expansion of the contaminated zone. It is the first step of pump and treat technology for environmental remediation.
Bioremediation of radioactive waste or bioremediation of radionuclides is an application of bioremediation based on the use of biological agents bacteria, plants and fungi to catalyze chemical reactions that allow the decontamination of sites affected by radionuclides. These radioactive particles are by-products generated as a result of activities related to nuclear energy and constitute a pollution and a radiotoxicity problem due to its unstable nature of ionizing radiation emissions.
Bioremediation of petroleum contaminated environments is a process in which the biological pathways within microorganisms or plants are used to degrade or sequester toxic hydrocarbons, heavy metals, and other volatile organic compounds found within fossil fuels. Oil spills happen frequently at varying degrees along with all aspects of the petroleum supply chain, presenting a complex array of issues for both environmental and public health. While traditional cleanup methods such as chemical or manual containment and removal often result in rapid results, bioremediation is less labor-intensive, expensive, and averts chemical or mechanical damage. The efficiency and effectiveness of bioremediation efforts are based on maintaining ideal conditions, such as pH, RED-OX potential, temperature, moisture, oxygen abundance, nutrient availability, soil composition, and pollutant structure, for the desired organism or biological pathway to facilitate reactions. Three main types of bioremediation used for petroleum spills include microbial remediation, phytoremediation, and mycoremediation. Bioremediation has been implemented in various notable oil spills including the 1989 Exxon Valdez incident where the application of fertilizer on affected shoreline increased rates of biodegradation.
Bog Creek Farm, located in Howell Township, New Jersey, is a designated Environmental Protection Agency (EPA) Superfund site. Lying on 12 acres of land, Bog Creek Farm is home to several hazardous and life-threatening contamination beginning in 1973 and continuing for a year. Over a decade later, actions began to take place to clean and restore the contaminated soil and water. Bog Creek Farm is situated near several other farms that house horses, growing crops and flowers, and livestock. Less than a mile down the road lies Allaire State Park, a park used by golfers, hunters, and fisherman.
The Chernobyl disaster remains the major and most detrimental nuclear catastrophe which completely altered the radioactive background of the Northern Hemisphere. It happened in April 1986 on the territory of the former Soviet Union. The catastrophe led to the increase of radiation in nearly one million times in some parts of Europe and North America compared to the pre-disaster state. Air, water, soils, vegetation and animals were contaminated to a varying degree. Apart from Ukraine and Belarus as the worst hit areas, adversely affected countries included Russia, Austria, Finland and Sweden. The full impact on the aquatic systems, including primarily adjacent valleys of Pripyat river and Dnieper river, are still unexplored.
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