What Is Hazardous Waste? - Definition and Types

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  • 0:05 What Is Hazardous Waste?
  • 1:19 Sources
  • 3:02 Disposal
  • 4:56 Types of Hazardous Waste
  • 6:29 Summary
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Lesson Transcript
Instructor: Margaret Cunningham

Margaret has taught many Biology and Environmental Science courses and has Master's degrees in Environmental Science and Education.

Not all waste is something to throw in the trash and forget about. In this lesson, we will explore hazardous waste and what makes it dangerous. We will also investigate disposal methods and types of hazardous waste.

What Is Hazardous Waste?

What would you do if you found a container with a skull and crossbones on it or an image of a bomb exploding? For most people, these symbols would indicate that something dangerous was in the container. Luckily, we do not encounter these symbols often, but it is important to know what they mean.

These two symbols, along with several others, represent a form of hazardous waste, which is any solid or liquid waste that is considered toxic, chemically reactive, flammable or corrosive. In terms of hazardous waste, something is considered toxic if it is harmful to human health when a person is exposed to the substance through inhalation, ingestion or touch.

A substance is chemically reactive when it is unstable or could react when exposed to another compound. Hazardous waste that is considered chemically reactive is likely to explode or produce harmful fumes when exposed to other compounds. A flammable substance is anything that is likely to catch on fire, and a corrosive substance is something that can corrode, or break down, metals.

The largest amount of hazardous waste is created in industry, in particular the petroleum and chemical industries, which produce around 70% of all hazardous waste in the United States. The most common examples of hazardous waste from industries in general include solvents used in cleaning, wastewater from petroleum refiners and ash produced from incinerators or coal-burning power plants.

The most dangerous hazardous waste is the waste created by nuclear power plants and nuclear weapons facilities. Although industry creates a large amount of hazardous waste in the United States and other industrial countries, this waste is highly regulated and controlled.

Take a look around your home. Do you think you have any hazardous waste? Although at first you might say no, upon closer inspection most homes contain a variety of hazardous waste items. At any given time, the average household in the United States has approximately 100lbs of hazardous waste on the premises. The most common examples of hazardous waste found within the home include paints, batteries, solvents, cleaning agents and pesticides. Now think about your home again. Do you have any of these items in it?

Each year in the United States, around 1.6 million tons of hazardous waste is disposed of by households. Unfortunately, hazardous waste produced from households is far less regulated than industry and more likely to be disposed of improperly, like down the drain, and have a negative impact on the environment.

Disposing of Hazardous Waste

Being that hazardous waste can be harmful in a variety of ways, it needs to be disposed of differently than non-hazardous waste. There are three main methods for disposing of hazardous waste.

The first method is to put solid hazardous waste in sanitary landfills, which are a method of waste disposal where the waste is buried either underground or in large piles. Although non-hazardous waste is often disposed of in landfills, the landfills for hazardous waste are constructed and monitored differently. Landfills for hazardous waste are made with thicker, impervious liners and with more heavy-duty removal systems for leaching materials. They are also constructed far from aquifers to reduce the risk of water contamination.

Hazardous waste that is liquid or has been dissolved is often placed in surface impoundments, which are shallow depressions in the earth that are lined with plastic and impervious materials. The liquid hazardous waste is dumped in the impoundment and left to evaporate. Once the liquid has evaporated, the solid hazardous waste residue remains at the bottom of the impoundment and can be removed and transported to a landfill. Surface impoundments pose many risks, including contamination, and are only used for temporary processing and storage.

The third method of hazardous waste disposal is deep-well injection, which is when liquid waste is injected into a well that has been created in the porous rock deep below the water table. Around nine billion gallons of hazardous waste are injected into deep-wells each year in the United States. Although this method of hazardous waste disposal is designed to be long-term and keep the waste away from humans and ground water, sometimes the wells leak or are damaged and waste contaminates the water supply.

Types of Hazardous Waste

As we now know, there are many different types of hazardous waste. Although the list is long, there are two types of hazardous waste that have been in the spotlight for years, dioxins and PCBs. Dioxins are a group of toxic chemical that are formed during the combustion process. Although dioxins can occur naturally from fires or volcanoes, the largest producers of dioxins are factories that bleach paper pulp or produce herbicides.

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