1Blacksmith Institute Journal of Health & Pollution Vol. 2, No. 3 — June 2012

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Editorial

Introduction

Recent research has identified more than 2,000 locations in 47 poor and middle income countries where people are exposed to toxins at dangerous levels. This is conservatively estimated to adversely affect the health of over 70 million people.1 The actual number of such sites is unknown, but is undoubtedly much greater. Reducing toxins at these sites to safe levels would improve the health of thousands, perhaps millions, of people and save many lives. Although conventional approaches to contaminated site remediation can

Innovative Technologies for Sustainable Environmental Remediation in Poor and Middle Income Countries

Amanda Ludlow, MA, MS; Paul Roux, MA

Corresponding Author: Amanda LudlowRoux Associates, Inc.209 Shafter StreetIslandia, New York 11749

T. (631) 232-2600aludlow@rouxinc.com www.rouxinc.com

Roux Associates, Inc. provides professional consulting services for remediation of contaminated sites to US and multi-national corporations, including many of the remedial technologies mentioned in the paper. In addition, Roux Associates holds a US patent for an enhancement to Constructed Treatment Wetlands technology.

J Health Pollution 3:1-4 (2012)

Ludlow, Roux

often be technologically complex and expensive, there are innovative and emerging technologies that are much simpler and less costly to implement, yet can, in the right circumstances, achieve equivalent results. The widespread use of such technologies could speed much needed remediation of toxic sites in poor and middle income countries.

Many of the innovative and emerging technologies mentioned in this paper are accepted, or are gaining acceptance, in the United States. Many of these are also particularly suitable for site remediation in poor and middle income countries because they are relatively easy to implement; make use of inexpensive, locally available materials, labor and equipment; and require very little or no operation and maintenance (O&M). The examples given here are not intended to be a comprehensive list, but are presented simply to provide a range of the available technologies that have been successfully demonstrated. Also, there are numerous combinations and variations of the example technologies that could be employed based on the specific contaminants of concern, local site conditions and available materials.

Example Technologies

Stabilizing Agents for Contaminated Soil or Solid WasteThe in situ chemical stabilization of heavy metals in contaminated soil is a remediation technique used to reduce contaminant mobility through the addition of amendments to promote sorption (both adsorption and absorption), complexation and precipitation.

Amendments including lime, phosphates, iron oxides, manganese oxides, sewage sludge, zeolite, and certain mining wastes (e.g., red mud from bauxite) have been shown to be effective in reducing the mobility and toxicity of arsenic, chromium, copper, lead and zinc.2-5 Bone char apatite (from fish or cow), being rich in phosphates, is a granular material produced by charring animal bones. Research has demonstrated the ability of bone char amendments to effectively immobilize lead, cadmium, copper, and zinc in contaminated soil,6-8 and thereby significantly decrease the bioavailability of these contaminants.

PhytoremediationPhytoremediation is the use of vegetation for the in situ treatment of contaminants in both soil and water. Phytoremediation is a rapidly emerging “green” approach to site remediation and can be a cost-effective alternative to conventional remedial approaches. Phytoremediation maximizes the natural ability of plants to intercept, consume, and transpire large volumes of water. Plant roots can extend down toward the water table, while establishing a dense root mass that consume large quantities of water and stabilize contaminants to reduce leachability.

Since the early 1990s, basic research, empirical studies, and successful applications have resulted in increasingly widespread application and regulatory acceptance of various phytoremediation technologies, or phytotechnologies, as alternative remedial approaches. For example, phytotechnologies are currently being used to:

2Blacksmith Institute Journal of Health & Pollution Vol. 2, No. 3 — June 2012

Editorial

• Intercept and hydraulically stabilize and bioremediate contaminated shallow groundwater plumes;

• Bioremediate contaminant in the vadose zone;

• Sequester inorganic contaminants in the plant rhizosphere;

• Manage and treat stormwater runoff;

• Replace conventional landfill caps with living covers over on-site disposal areas; and

• Hydraulically isolate and remediate sediment and sludge disposal areas.

Vegetation landfill covers, an alternative to conventional low-permeability clay or geomembrane caps, are composed of soil and plants growing in and/or over waste.

These alternative landfill covers utilize both phytostabilization and evapotranspiration mechanisms for contaminant control. Unlike conventional cover system designs that use material with low hydraulic permeability to minimize the downward migration of water from the cover to the waste, alterative landfill cover systems use water balance components to minimize percolation. These cover systems rely on the properties of soil to store water until it is either transpired through vegetation or evaporated from the soil surface. Plants control erosion and minimize seepage of water that could otherwise percolate through the waste and generate leachate.

Constructed Treatment Wetlands (CTW)CTWs, also referred to as treatment wetlands, or man-made, artificial or engineered wetlands, are highly engineered systems designed to emulate and optimize the physical, chemical and biological removal mechanisms used in conventional treatment technologies. Although CTWs have treated sanitary wastewater since the 1960s, the technology has consistently evolved through numerous engineering enhancements (e.g., aeration) to address more heavily contaminated waste streams world-wide. Examples of industries presently applying the technology include:

municipal and industrial solid waste management, petrochemical, food processing, chemical manufacturing, electroplating, mining, pulp/paper mills, and metal fabrication sectors.

The CTW environment consists of saturated substrates, vegetation, and microbes that mimic natural wetlands. CTWs maximize the removal of contaminants via several synergistic mechanisms, including sedimentation, filtration, sorption, plant uptake, and microbial breakdown. The result is that inorganic and organic constituents can be physically removed through filtration, biologically degraded to non-toxic forms, absorbed by wetland plants, adsorbed to media surfaces, or chemically transformed and stored within the wetland matrix.

Principal advantages of the technology include low relative capital and O&M costs when compared to conventional treatment methods, simplicity of operation and maintenance, treatment effectiveness, tolerance to fluctuations in hydraulic and constituent loading rates, and potential aesthetic attributes including increased green space, new wildlife habitat, and additional recreational and educational areas. In addition, CTWs can be constructed relatively easily and cost-effectively by using locally available materials (i.e., stone, clay, compost, plants). The principal disadvantage of the

Innovative Technologies for Sustainable Environmental Remediation

CTW

NGO

NMF

O&M

PCB

PAH

TCE

Constructed treatment wetlands

Non government organization

Natural media filtration

Operation and maintenance

Polychlorinated biphenyls

Polycyclic aromatic hydrocarbon

Trichloroethylene

Abbreviations

Chromium impacted runoff from industrial plant in Talcher, India.

Photo credit Amanda Ludlow, 2008

Ludlow, Roux

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technology is the relatively large land area required for construction.

Natural FiltersNatural media filtration (NMF) technology has recently been developed as an alternative to conventional gravel, sand, and even activated carbon filters. Applications include, but are not limited to, permeable reactive barriers (PRBs), anaerobic filters, and compost-based filters. NMF technologies can be operated in both aerobic and anaerobic conditions. As the water percolates through the natural material, the contaminants are removed via the following mechanisms:

• Sedimentation — gravity settling of constituents onto the natural media;

• Filtration — mechanical separation of large and fine sediments;

• Adsorption — physical and chemical association of constituents onto the natural media;

• Ion Exchange — transfer of an electrically-charged atom or group of atoms from the water with an electrically-charged atom or group of atoms from the natural media;

• Precipitation — chemical reduction, precipitation and sequestration of metal sulfides;

• Decomposition — abiotic degradation of constituents by processes such as ultra-violet irradiation, oxidation, and reduction; and

• Microbial Metabolism — biological degradation of constituents by bacteria supported by the natural media.

NMFs can be used as permeable reactive barriers for groundwater treatment or high-rate water filters for stormwater/surface water treatment. NMF technologies incorporate natural materials, such as compost or peat,

to filter constituents (e.g. metals, chemicals, suspended solids, oil and grease) from groundwater, process water, and/or stormwater. Proper selection of the filter media is critical to the success of NMF technology. Sand can remove between 75 and 85 percent of the total suspended particulates, but is significantly less effective in removing dissolved metals and organic compounds. In contrast, peat and compost can remove over 80 percent of dissolved metals and organic compounds.9,10

BioremediationBioremediation uses microorganisms to degrade organic contaminants in soil, sludge, and solids either excavated or in situ. The microorganisms break down contaminants by using them as a food source or co-metabolizing them with a food source. Aerobic processes require an oxygen source, and the end products typically are carbon dioxide and water. Anaerobic processes are conducted in the absence of oxygen,

Ludlow, Roux

Garbage incineration adjacent to local market, 2011, Same, Tanzania Photo credit: Madeline Cottingham and Evan Simon

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and the end products can include methane, hydrogen gas, sulfide, elemental sulfur, and dinitrogen gas.

Ex situ bioremediation includes slurry-phase bioremediation, in which the soils are mixed in water to form a slurry to keep solids suspended and microorganisms in contact with the soil contaminants; and solid-phase bioremediation, in which the soils are placed in a cell or building and tilled with added water and nutrients. Land farming, biopiles, and composting are examples of ex situ, solid-phase bioremediation.

In situ bioremediation is bioremediation that takes place at the polluted site, rather than occuring off-site. In situ techniques stimulate and create a favorable environment for microorganisms to grow and use contaminants as a food and energy source. Generally, this means providing some combination of oxygen, nutrients, and moisture, and controlling the temperature and pH. An example of in situ groundwater bioremediation is the use of a water-soluble, high carbon-content substance (e.g. molasses), to degrade chlorinated compounds such as trichloroethylene, or TCE. For example, molasses can be injected into the contaminated portion of an aquifer, whereupon naturally occurring microorganisms feed on the molasses and simultaneously break down the TCE to daughter compounds and finally to carbon dioxide.

Vermi-RemediationVermi-remediation uses natural earthworm processes such as aeration, soil-mixing, and increased microbial activity, to enhance biodegradation processes while also improving the physical, chemical and biological properties of soil. Over 4,400 species of worms have been identified to bioaccumulate (or ingest contaminants, removing them from

soil) and disinfect (devour and kill pathogens through their naturally anti-pathogenic coelomic fluid) soils contaminated with agrochemicals, petroleum and crude oil hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and metals.11,12

Conclusions

There are numerous sites in poor and middle income countries that are contaminated with toxic chemicals. Exposure to these sites sickens and kills many people. Remediation of many of these sites to reduce the toxins to safe levels can be accomplished at relatively low cost using innovative remedial technologies such as those described in this paper. In addition, local materials, supplies, equipment and labor can often be employed.

These remedial technologies have been proven to be effective in the United States and other developed countries. Pilot projects that can be brought to full size are critical to demonstrate the effectiveness of an emerging technology. Technology transfer necessary to employ these technologies in poor and middle income countries can be accomplished through non government organizations (NGOs) and local contracting and engineering firms. Non-profit foundations such as Blacksmith Institute can be instrumental in providing such technical expertise. Conferences and workshops can also be effective means of transferring these technologies to local groups and organizations.

Widespread availability of a broad range of environmental remedial options, including the innovative technologies discussed here, may provide the best hope of effectively reducing human exposure to the numerous toxic sites which currently exist in poor and middle income countries.

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Innovative Technologies for Sustainable Environmental Remediation

Ludlow, Roux