Archives 2012

Chemicals Found in Coal Sludge and Slurry

Chemicals Found in Coal Sludge and Slurry

To process Appalachian coal for the market, companies wash and prepare it using water, coagulants, flocculants and surfactants.  Coal slurry consists of this chemically treated water and very fine particles of coal, rock and clay. 

The rock, coal, and clays contain a wide range of heavy metals including arsenic, lead, cadmium, chromium, iron, manganese, aluminium and nickel—all of which dissolve in the water—and some hydrocarbons and other organic chemicals.  While patent law limits the information available about the chemicals used in coal processing, serious concerns about their neurotoxic and carcinogenic effects particularly on workers in the plants [link] have been raised.

Reagents used in processing coal include acrylamides, (some acrylamides are carcinogenic), lime (pH adjuster), natural and modified starches, caustic starch, denatured alcohol, sulfuric acid (pH adjuster), nitric acid (pH adjuster), aluminium sulfate (pH adjuster), iron oxide, diesel fuel and anhydrous ammonia. 

There have been very few independent tests of the composition of coal slurry.  Since the chemical composition of slurry can be variable depending on the chemical make-up of the coal being processed as well as the chemicals used in a particular prep plant’s washing technique, this means that citizens can have a hard time figuring out exactly what chemicals they are at risk of exposure to.

Underground Injections

Underground Injections

An underground injection is a form of coal waste disposal whereby the coal sludge is mixed with water and pumped into abandoned underground mine workings.   Once underground, the slurry can mix with water and migrate into nearby aquifers contaminating local water supplies with dangerous levels of heavy metals.  In the heavily mined Appalachian coalfields, cracks often develop in old mines from subsidence or blasting from surface mines above them.  Once the slurry injection has begun, there is no practical way to seal cracks or remove the slurry if there is a problem.  The old mines can stretch for miles underground and billions of gallons of slurry can be injected at a single site.  In some places, the slurry has been injected for over 30 years.

In at least two communities in West Virginia, there is extensive evidence that slurry injection has contaminated well water.  In the Rawl area of Mingo County and the Seth-Prenter area of Boone County, billions of gallons of coal slurry were injected into abandoned mines near small communities that relied on well water.  Residents of both communities watched their once pristine well water begin to run yellow, orange or black at times.   Sinks, tubs, and clothes became permanently stained and all kinds of metal fixtures and appliances started corroding rapidly.  Worse yet, sicknesses began to spread throughout the community from skin rashes and severe diarrhoea to cancer and kidney failure.  Testing revealed iron, manganese, lead, aluminium, arsenic and other heavy metals, sometimes at hundreds of times the safe drinking water limits.  Toxic amounts of hydrogen sulfide gas (that rotten egg smell) were also throughout homes.  The Sludge Safety Project worked with both communities to secure municipal water line extensions.  In both communities, hundreds of residents sued the companies for damage to their health and property.

Nobody knows when the practice of slurry injection first began, since initially there was no regulation of the practice.  It was heavily used in Appalachia in the late 1970s and early 1980s when impoundments were difficult to build after the Buffalo Creek Disaster.  The Safe Drinking Water Act gave the Environmental Protection Agency (EPA) the power to regulate underground injection and made unpermitted injection illegal in 1974.  However, coal companies injected slurry illegally anyway.  In 1984, the EPA caught Eastern Coal Company injecting illegally into a mine that was being used as a public water source in Pike County, Ky., by investigating a citizen complaint.  The EPA ordered the injection stopped and began to try to regulate slurry injection.  It wasn’t until 1999 that the West Virginia Department of Environmental Protection (DEP) developed its own Underground Injection Control (UIC) office and “modern” regulation of slurry began. 

The DEP says that groundwater is protected by requiring the slurry to be watered down to meet Safe Drinking Water Act standards before it is injected.  However,  a DEP hydrologist admitted in a legislative hearing that the only reason that black coal slurry met Safe Drinking Water Act standards was that the standards did not cover the contaminants that make it black.  The inadequate regulations that are in place are poorly enforced.  Until recently, mining injections were overseen by a single person.  In 2007, the Sludge Safety Project successfully lobbied the West Virginia Legislature to order a study of the impact of slurry injection on groundwater and human health.  Despite being over-deadline, flawed, and inconclusive, the study revealed troubling facts about the UIC program.  Every plant in the study had had a least one major slurry spill.  The injectate at some plants was chronically in violations of the standards; plants were frequently using unapproved chemicals in the washing process, and monitoring of the mines getting injected into was inadequate or totally absent.

The problems were so severe that the DEP declared a temporary moratorium on new slurry injection permits and extensive changes to the regulations immediately upon releasing their report in the spring of 2009.  Companies were required to test for many more contaminants and, for the first time, were required to regularly test the water in the mine receiving an injection and nearby groundwater for contamination.  They also doubled the program staff to two people.  Since the new regulations, the number of plants injecting slurry has been cut nearly in half with only around a half dozen left.  The Sludge Safety Project continues to work to make the current moratorium permanent and phase-out of the remaining active injection sites.

What is Coal Slurry

What is Coal Slurry

Coal slurry or sludge is a waste fluid produced by washing coal with water and chemicals prior to shipping the coal to market.  When coal is mined underground or by high walls or auger miners, there are significant amounts of rocks and clays mixed in.  These materials must be removed before the coal can be sold to power plants or steel mills.  In Appalachia and the Illinois Basin, coal companies use a process called “wet washing” to reduce the amount of non-combustible material.  There are other methods of separating coal and non-coal used in other places, primarily where mining occurs in arid areas with limited water supplies. 

In a wet washing plant or coal preparation plant, the raw coal is crushed and mixed with a large amount of water, magnetite, and organic chemicals.  The chemicals are primarily patented surfactants, designed to separate clays from the coal, and flocculants, designed to make small particles clump together.  In massive “flotation columns”, most of the coal floats to the surface, and most of the other material (called “coarse refuse”) sinks to the bottom.  The huge volume of wastewater left over is coal slurry.  In the slurry are particles of rock, clay, and coal too small to float or sink as well as all the chemicals used to wash the coal.  While the coal industry likes to claim that the particles of “natural rock strata” and chemicals are perfectly safe, testing has shown coal slurry to be highly toxic.

More on Chemicals in Coal Slurry


Chronic exposure to the metals found in coal slurry can damage virtually every part of the body. Health problems caused by these metals include intestinal lesions, neuropathy, kidney and liver failure, cancer, high blood pressure, brittle bones, miscarriages, and birth defects among others.  Studies of the effects of coal slurry on human cell tissues have found evidence that coal slurry causes cancerous proliferation, cell death, and damage to kidney cells. 

More on Coal Slurry and Health

Impoundments and slurry cells

Every preparation plant produces many thousands of gallons of coal slurry each day, requiring massive disposal areas.  The most slurry is disposed of above ground either in massive toxic lakes called impoundments (made by damming up a hollow) or in smaller pits constructed of coarse refuse called slurry cells.  Not only do these facilities often leach toxins and cause black water spills, but there have also been several catastrophic failures resulting to toxic floods, massive property destruction, and death.

More on Impoundments and Slurry Cells


Slurry not stored above ground is pumped, or “injected,” into abandoned underground mines.  Once underground it can migrate into the groundwater contaminating local well water, especially when blasting from surface mining occurs in the area.  Several communities have had their water supply contaminated by underground injection causing widespread, often life-threatening illnesses.

More on Coal Slurry Injection


Technologies exist to remove and reuse the water in slurry, resulting in a dry waste product that can be more safely and easily contained.  While some of these technologies were in widespread use in Appalachia in the early 1980s, today few plants use them due to the increased costs.

More on Alternatives to Coal Slurry