Waste Disposal Technologies

BEM 3701, Hazardous Waste Management 1

Course Learning Outcomes for Unit V Upon completion of this unit, students should be able to:

5. Evaluate the efficacy of hazardous waste related mandates and programs.

6. Describe hazardous waste characteristics, pathways in the environment, and toxicological impacts.

7. Evaluate contemporary methods of hazardous waste mitigation and remediation including waste minimization, pollution prevention, reuse, and recycling.

Reading Assignment Chapter 15: Incineration of Hazardous Wastes Chapter 16: Hazardous Waste Treatment Chapter 17: Land Disposal of Hazardous Waste

Unit Lesson Hazardous Waste Treatment In 1984, the Resource Conservation and Recovery Act (RCRA) was amended to prohibit the land disposal of untreated hazardous waste (Hazardous and Solid Waste Amendments). The Environmental Protection Agency (EPA) enacted the Land Disposal Restrictions (LDR) program to make sure that land-disposed hazardous waste does not pose a health or environmental threat. There are three major components to the LDR:

 Disposal Prohibition: Waste disposal is prohibited unless the treatment standards are met.

 Dilution Prohibition: Waste may not be simply diluted in order to meet treatment requirements.

 Storage Prohibition: A TSDF may not store treated waste indefinitely, meaning that TSDFs may not warehouse treated waste.

There are several ways that a waste can be treated to meet the LDR standards. Neutralization This treatment technology is applied to acidic or alkaline wastes, which are usually identified as corrosive under RCRA. Before the waste is neutralized, it must be tested to determine its chemical characteristics. After characterization, neutralization is accomplished by reacting acidic wastes with a base or by reacting basic wastes with an acid. Some common neutralizing chemicals for acidic wastes include sodium hydroxide, sodium carbonate, and ammonia. For basic wastes, sulfuric and hydrochloric acids are often used (Pichtel, 2014).

UNIT V STUDY GUIDE

Incineration, Treatment Technologies,

and Land Disposal of Hazardous Waste

BEM 3701, Hazardous Waste Management 2

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Chemical Precipitation In chemical precipitation, a precipitating chemical is added to a waste to remove a soluble hazardous substance from solution. The precipitate is then separated from the solution through sedimentation or filtration. Metal plating and finishing, mining, and electronics are some industries that produce waste treated by chemical precipitation (Pichtel, 2014). Oxidation and Reduction During oxidation, an element loses electrons. During reduction, an element gains electrons. Oxidation and reduction reactions can convert very toxic substances to less hazardous, and even nonhazardous substances. For example, cyanide waste from metal finishing industries can be oxidized to produce carbon dioxide and nitrogen (Pichtel, 2014). Sorption and Sorption Systems In the sorption process, a sorbent material, such as activated carbon, is used to remove soluble hazardous wastes from a solution. The hazardous contaminant adheres to the sorbent material. Eventually, the sorbent reaches capacity, and must be regenerated by heating in an oxygen-rich environment (Pichtel, 2014). Stabilization In stabilization, hazardous waste is mixed with a binding agent, such as cement (for inorganic wastes), or asphalt (for organic wastes). This converts the waste into a less reactive form by making them physically immobile. This process also makes the waste easier and safer to transport. However, the volume of waste to be disposed of is increased (Pichtel, 2014). Land Disposal of Hazardous Waste Once the hazardous waste has been treated using one of the above methods, it can then be disposed of. Every year, approximately two million tons of hazardous waste is placed into a land-disposal system (Pichtel, 2014). While the disposal directly to land is regulated by RCRA, both RCRA and the Safe Drinking Water Act regulate the injection of wastes. Remember that these regulations apply to treated hazardous wastes. Hazardous waste generators, transporters, TSDFs, and recycling facilities must comply with the LDRs. Two common means of land disposal are secure landfills and deep well injection. Secure Landfills The landfill design is such that movement of leachate below the waste is inhibited by a polymer lining (called geosynthetic liner). The regulations allow for clay liners, synthetic liners, or composite liners. However, the chemical compatibility of the waste with the liner material must be taken into account. The chemical characteristics of the landfill’s leachate must be evaluated to ensure that the liner will not be deteriorated by the leachate. Secure landfills must have leachate collection and removal systems (LCRs). The first collection system is beneath the waste but above the first geomembrane. The second collection system is between the first and second liners. A sump pump is placed in the lowest portion of the landfill to pump out any remaining leachate. The LCR also serves the purpose of leak detection, should the collected leachate be contaminated. LCRs between primary and secondary liners are called the leak detection network (Pichtel, 2014). When the landfill cell is full, it must be securely covered to prevent water from entering the cell. A geomembrane cap is used for this purpose. This cap is similar to the geomembrane liner, but it is designed to prevent water from getting in and permeating through the waste. Once a landfill is closed, the area is covered with a layer of clay followed by a layer of vegetation. Through the use of trenches around the landfill, the surface drainage is collected and removed (Pichtel, 2014). In response to the requirements of the Safe Drinking Water Act (SDWA), the EPA developed the Underground Injection Control program (UIC). The program includes requirements for the siting, operation, and closure of injection wells. In deep-well injection, hazardous waste is pumped into confined geologic formations (Pichtel, 2014). There are six classes of injection wells, each of which are designed for the disposal of different types of waste including hazardous waste, oil and natural gas production waste, mineral

BEM 3701, Hazardous Waste Management 3

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extraction waste, radioactive waste (under very specific circumstances), nonhazardous liquids, and carbon dioxide sequestration (Pichtel, 2014). The majority of hazardous waste management activities occur within general industry and involve generation of hazardous waste. However, it is of value to understand hazardous waste treatment options because oftentimes, choices must be made with regard to HW vendors. Developing an understanding of the wide range of treatment options available is important in making the best decision with consideration of the type and quantity of HW generated. Many organizations simply contract with a HW transportation company and TSDF for waste disposal without understanding the eventual fate of their waste. If you find yourself in this situation, you should contact the vendor, review the waste treatment methods employed, and, if feasible, visit the TSDF.

Reference

Pichtel, J. (2014). Waste management practices: Municipal, hazardous, and industrial (2nd ed.). Boca Raton, FL: CRC Press.