Guest Column | September 16, 2014

Why All The Hype About Chlorine Gas Safety?


By Howard Specker, President, Chemical Injection Technologies, Inc.

Remember when “Little Old Lady” Clara Peller rolled up to the drive-through window of Big Bun and asked “Where’s the beef?” She was asking a literal question, but also making a figurative statement. 

Today, water and wastewater plant operators should be asking “Where’s the facts?”  Actually, more and more operations personnel are asking this question.  They are asking why there has been such an aggressive push from legislators, regulators, media, and a lot of uninformed laypeople to eliminate the use of chlorine gas at treatment plants in favor of so-called “Inherently Safer Technologies” (sic).  This initiative flies in the face of logic with an utter lack of supporting data, input from actual operations professionals, or any factual historical evidence to support the change. Chlorine gas is one of the safest possible alternatives in water treatment and is clearly the economical winner in the debate.

So, let's take a look at this and try to determine the genesis for this unprecedented movement. There is simply no denying that chlorine has been one of the most beneficial chemicals of all time and that water and wastewater treatment with chlorine has been one of the most beneficial processes in the 20th century.  As far as safety and increased life expectancy, chlorine has been one of the most effective purveyors of both. It is hard to imagine what the public health outlook would be today without the introduction of chlorination of municipal water supplies and the subsequent chlorination of wastewater treatment plants early in the 20th century. In both the United States and Western Europe in the 19th century, cholera, diphtheria, typhoid, and other water borne diseases were responsible for massive epidemics that killed millions of people on a regular basis. While most of these diseases are now unheard of in these highly industrialized countries, they are by no means extinct. In less developed countries, millions continue to perish every year from those same dreaded diseases. Millions more are sickened with various gastrointestinal disorders caused by waterborne bacteria. All of these could be essentially eliminated with low cost, safe chlorine treatment.

There is really very little dispute about the efficacy of chlorination in water and wastewater treatment. And so, this discussion is really centered around the recent media and legislative attacks, not on chlorination in general. The key question is why the use of gas chlorination as a treatment method has been targeted with such strong emotional arguments, usually not anchored in facts.

Use of chlorine gas, or gas chlorination, in a public water supply was first introduced early in the 20th century in Union City, NJ. The equipment was quite complicated, but it made an immediate difference in reducing the number of gastrointestinal outbreaks, and in eliminating most of the diseases mentioned above in a relatively short span of time. Through the 20th century, chlorination, and especially gas chlorination, became a common method of disinfecting water supplies and, subsequently, wastewater effluents. Many of those early gas chlorination systems were massive pieces of equipment, prone to chlorine leaks, and highly susceptible to the corrosive effects of chlorine. But,  gas chlorinators became vastly improved in the second half of the 20th century with widespread use of engineered plastics, new metal alloys resistant to the effects of chlorine, and design advancements that not only simplified the equipment, but greatly improved operator safety. By the end of the 20th century, deaths or serious injuries due to the use of gas chlorine in water and wastewater treatment plants, both municipal and industrial, were virtually non-existent.

Chlorination can be accomplished in a number of different forms. These processes are important to understand at a basic level if we are to fully understand the risks in each process and stick to the facts when assessing safety:

  1. Sodium Hypochlorite (aka: Liquid Bleach) Containers
    1. Bleach is manufactured using a solution of sodium hydroxide (caustic soda) into which chlorine gas or pure elemental liquid chlorine (liquefied chlorine gas) is injected.  Industrial strength bleach is manufactured at approximately 15 percent concentration of chlorine by weight.  Most industrial strength bleach is delivered to customers at 12 percent due to loss of chlorine by heat, sunlight, and time.  Ironically, large chlorine gas containers are required at these bleach manufacturing plants.  Sodium hypochlorite will continue to lose strength after it has been delivered and has a limited “shelf” life.
  2. On-Site Sodium Hypochlorite Generators
    1. A relative newcomer in the chlorination field, “hypo generators” create a weak solution of sodium hypochlorite through electrolysis of a brine-salt solution.  Electricity is applied to an anode and cathode, releasing chlorine and sodium from the NaCl salt, and hydrogen and oxygen from the water.  Some of the sodium and oxygen combines with chlorine to form sodium hypochlorite.  However, excess hydrogen will be produced and must be safely vented from the equipment.
    2. Sodium hypochlorite generators fall  into two main categories:
      1. Flow-through systems: larger volumes of water are introduced into the generator along with salt solution.  The resulting dilute sodium hypochlorite solution is immediately injected into the water to be treated.  Most systems of this type produce hypochlorite that is less than 1 percent strength.
      2. “Day tank” (batch) systems:  more highly concentrated brine solutions are moved more slowly through the anode/cathode reactor chambers, and a somewhat higher strength sodium hypochlorite is then stored in a tank, to be used as needed.  Usually, some type of chemical metering pump is employed to inject the bleach into the water treatment system.  Again, excess hydrogen from the process must be safely vented.
  3. Calcium Hypochlorite (Solid Chlorine)
    1. Powdered calcium hypochlorite is available in small or large containers: from bags, to drums, to carboys to bulk trucks. It can be applied directly into open, non-pressurized systems (swimming pools, open storage tanks, etc.) or mixed with water to form a solution which can then be applied using metering pumps or other injection devices.  Powdered calcium hypochlorite is very flammable, and may spontaneously combust if some types of organic materials come in contact with it.
    2. Solid calcium hypochlorite “tablets” or “sticks” are used, primarily in equipment that allows a controlled erosion of the solid material into water to form a solution.  This is the most expensive form of chlorine, by weight.  Generally, a pound of available chlorine in solid form is many times more expensive than a pound of gas chlorine.  Maintaining precise chlorine dosages is more difficult with this form of chlorine.
  4. On-Site Chlorine Gas Generation
    1. Chlorine gas can be produced from a brine solution and immediately injected into the water treatment system.  These gas generators differ from the sodium hypochlorite generators mentioned above, in that they employ a special semi-permeable membrane that separates the anode and cathode.  Brine solution enters the anode compartment, while the cathode compartment on the other side of the membrane contains some sodium hydroxide.  The electrolysis breaks down the brine solution with chlorine, hydrogen, oxygen, and sodium being liberated on the anode side.  The sodium, hydrogen and oxygen are attracted to the cathode and will pass through the membrane, while the chlorine molecules remain in the anode compartment.  These chlorine gas molecules are scavenged from the brine storage tank through which the solution is re-circulated.  Additional sodium hydroxide is produced in the cathode compartment, which can then be used for other purposes, while excess hydrogen must be safely vented.  On-site chlorine gas generators have not been widely produced or employed in water and wastewater treatment plants.
  5. Gas Chlorination
    1. Use of pure, elemental chlorine is the most economical method of chlorination, per pound of chlorine used.  The chlorine is supplied as a liquefied gas, in steel containers, as well as in railroad tank cars.  The typical containers are the 150-lb. cylinder and the one-ton container.  The weight refers to the amount of chlorine liquid inside when the container is full.  Use of railroad tank cars is limited to a very small number of the largest water and wastewater treatment plants.  Elemental chlorine is non-flammable, non-explosive, will not support combustion, and it does not lose its strength in storage.  It offers the most precise dosage control of all of the forms of chlorination, due to its consistent concentration.  Handling and transferring of chemicals also involves the least exposure to operations personnel, in normal use.  Modern gas chlorination equipment used to precisely control the injection of chlorine gas into treatment systems, tend to require the least maintenance and servicing of all types of chlorine feeding equipment.

The Safety Record

Gas chlorine, while a hazardous material, is actually responsible for very few incidents in water and wastewater treatment facilities.  In over 95 percent of all treatment facilities the amount of gas chlorine on hand is relatively small, by comparison to industrial use in non-water and wastewater treatment applications.  Pharmaceuticals and chemical manufacturing account for the vast majority of chlorine usage, and railroad tank cars are not an uncommon sight at those facilities.  Another use that requires those same railroad tank cars of liquefied chlorine gas is sodium hypochlorite (bleach) manufacturing.

Yes, there are incidents where operations personnel improperly handle the gas chlorine containers or accidentally remove a regulator or fitting without turning off the cylinder valve, as there are incidents with the handling of virtually every hazardous chemical known to mankind.  But, with chlorine gas, these are very isolated incidents, and, most importantly, no one dies.  It can be very unpleasant, and preventive hospitalization may be necessary for observation, but in the end, personnel return to their jobs in virtually all cases.  And, even more importantly, there has been no loss of life, mass evacuations, or mass hospitalizations as a result of chlorine gas leaks at water and wastewater treatment facilities in the USA in more than 20 years, where 150-lb. chlorine cylinders were in use.  This is the vast majority of treatment facilities.  Where one ton containers were in use, a very few incidents called for erring on the side of caution and people were evacuated from an area around the facility until the leakage was brought under control.  But again, no loss of life.

One might assume, from the public outcry that has been raised recently in favor of these so-called “Inherently Safer Technologies” that they are incident free and that no one has been injured during their use.  Nothing could be further from the truth!  The other forms of chlorination, detailed above, have all had their significant accidents, and on a very regular basis.  Improper mixing of chemicals has repeatedly resulted in large scale releases of chlorine gas from sodium hypochlorite treatment facilities that HAD NO CHLORINE GAS CONTAINERS ON SITE.  Large fires and explosions have rocked calcium hypochlorite storage facilities, with the resultant toxic clouds carried over large areas.  The media reports state that chlorine gas was released, but rarely, if ever, do they mention that the cause was anything other than chlorine gas containers. 

A large water treatment facility in Michigan had used gas chlorination for many decades and had an enviable safety record.  Concerns by city officials about the storage of gas chlorine containers led them to change the facility over to sodium hypochlorite.  Very large storage tanks were installed in the facility for the bleach.  A tank truck delivering aluminum sulfate for part of the treatment process, accidentally pumped the chemical into one of the bleach tanks, and 12 workers went to the hospital with chemical inhalation distress.  Countless cases of personnel accidentally spilling or adding the wrong chemical around bleach storage areas results in hundreds of injuries every year.

Hydrogen gas is a significant explosion hazard and is produced as a byproduct of some of these on-site generation processes offered up as “safer technology.”  The reality is that there have been many, many incidents in which these generators failed to properly vent the excess hydrogen, which resulted in explosions of varying dimensions.  One actually lifted the roof off of a storage building.  And people have been injured.  A large sodium hypochlorite generator at a treatment plant in West Palm Beach, FL, exploded due to a failure of the hydrogen venting system, and peppered the walls of the chlorination room with plastic shrapnel.  Luckily, this happened in the very early morning hours when no one was present in the room.  This was the SECOND incident at this same plant!

Every treatment technology has some risks. There are no “magic wands” that will whisk away the potential for injury, while at the same time offering the public safe drinking water and wastewater free of dangerous pathogens.  Chlorine, in all of its forms, continues to offer us the most affordable and most well understood means of eliminating water borne diseases.  Both government as well as private researchers, in addition to health agencies and water treatment professionals, acknowledge that chlorination is a vital part of our water infrastructure and should remain so into the foreseeable future.  Even the newest, limited application, treatment processes still require some chlorination to protect a public water distribution system from contamination after the water leaves the treatment plant.

Follow The Money

Knowing all of this, there is still a movement to eliminate or reduce the use of gas chlorination.  One really has to wonder about the motivation for such zealotry.  It will cost consumers (rate payers) a lot more money because there is just no alternative as economical as gas chlorination.  There is no other form of chlorination that is as trouble-free and easy to maintain.  There is no justification based on the safety record. 

Replacing gas chlorination with large sodium hypochlorite installations has been a movement that goes back to the 1960s, with very little success.  Beginning in the early 21st century, the propaganda machine of certain chemical interests began to beat this drum in earnest.  Large bulk bleach suppliers started to offer seemingly irresistible package deals whereby they would supply all of the feeding and storage equipment for “free,” if treatment plants would only sign a long-term contract that guaranteed the bleach supplier a monopoly on the chemical supply.  Sometimes, other chemicals were tied into the deal.  Some of these suppliers were also in the chlorine gas supply business, which was not as profitable.  These suppliers make far more profit selling bleach than they do selling chlorine gas. As a famous investigator once said, “follow the money.”

By 2006, many municipalities that had switched to bleach under these arrangements were having second thoughts.  Their budgets were being eaten up by very high chemical costs, as well as equipment failures, high maintenance, and operator complaints.   Still, those chemical suppliers, and even some chemical feed equipment suppliers, were spreading rumors that the U.S. Environmental Protection Agency was going to “outlaw” gas chlorination, and that legislators and regulatory agencies would limit the amount of chlorine gas allowed on site at a treatment plant.  That kept most customers in line.  They didn’t want to switch back to gas chlorination only to be forced to give it up, even though it made very good sense from both a financial and technical perspective. 

In many cases the decisions were being made by “town fathers” who, while possibly acknowledging the financial realities, had no idea of the problems facing the plant operators and maintenance personnel.  Operations people, who had experience with the gas chlorination systems before they were eliminated, wanted those gas systems back.  They were the people who knew the entire reality.  While walking around many of the major water and wastewater treatment trade shows during that period, the author and many colleagues were presented with “rumors” that these things were going to happen and we should make plans to change.  Every time we tracked down one of these rumors, it led to either a supplier or manufacturer of alternative feeding equipment, or to the sales representatives of suppliers and manufacturers of other forms of chlorine, especially sodium hypochlorite.  But it’s one thing to spread rumors, and another to actually effect that change.

Enter Homeland Security

After the national tragedy of 9/11, the Patriot Act was legislated into existence.  This also created the U.S. Department of Homeland Security.  Much of the decision making that had previously been entrusted to agencies with R&D departments, scientific investigative experience, and decades of dealing directly with factual evidence was suddenly trumped by the oversight of a super agency whose mandate and focus was very narrowly honed in on one overriding concern – security.  Terrorism became the one subject that no lawmaker could, or would, dare to step away from.  And when that one subject was so pervasive in our daily consciousness, it was inevitable that politicians would seize every opportunity to jump on whatever bandwagon gave them a platform from which to garner high profile publicity connected to any perceived homeland security issue. 

By 2006 the Iraq War had settled into a fight against terrorist insurgency.  The U.S. military was losing a lot of good men and women in ambushes and to IEDs (improvised explosive devices) and the media was having a field day.  The political implications of the failure to find any Weapons of Mass Destruction made every new development in Iraq seem like just more fuel for the media fire.  Stories were being fired off to U.S. media centers by in-country journalists on a non-stop basis.  But, such overload begins to get less and less attention when it’s the same thing day after day.  Thus, the editors back home were clamoring for new and different angles, things we hadn’t seen or heard before.  Then, on February 22, 2007, a story broke about two insurgent attacks using “chlorine bombs.”  Instantly, this story was on every network. Of course, here was something they never heard of before, and they had no knowledgeable person on hand to get some factual perspective as to what might have actually happened.  The Associated Press headline that day was “Chlorine gas attacks hint at new enemy strategy.”    That was followed within two days by a USA Today front page headline of “Chlorine bombs pose new terror risk.”  News channels were talking about “chlorine clouds” and “explosive chlorine.” The inference in all of this was that this was some new and horrible weapon that had been unleashed by the insurgents and had terrific potential for destruction and loss of life.  The reports stated that trucks carrying chlorine cylinders, and large amounts of high explosives, were detonated in Baghdad and a nearby city.  There was mention of some deaths and large-scale property damage, and fear that there could be a “chlorine cloud” drifting over the area.

By April, 2007, there had been five of what was then being called “chlorine truck bombs” exploded in Iraq.  By this time it was not front page news and the media had moved on.  They never followed up with any expert analysis to determine what actually took place.  Military spokesmen had made the announcements and gave appallingly ignorant statements about chlorine, its physical and chemical properties, physiological consequences, and what could have possibly happened.   The deaths were from the effects of up to 2000 pounds of high explosives obliterating everything in a one block radius.  Chlorine does not explode or burn and could not have added to the destructive force of the explosion.  The vast majority of the chlorine would have been destroyed in the explosion itself, and the remaining amount so rapidly dispersed by the shock wave and rising heated air column, that little, if any would have remained in the vicinity.  They did not know this... they did not have a clue.  But, the terrorists knew.  They saw the ineffectiveness of this tactic, and moved on.  It just did not have any appreciable effect, other than the deaths caused by the explosives.  By June there was no hint of another so-called “chlorine bomb.”  That fact was NEVER mentioned in the media.  In fact, the entire subject of chlorine bombs never received any follow-up whatsoever to present the story of what actually happened.  The media just wasn’t interested any more.

In February 2007, the emotional arguments against chlorine gas and its possible use in terrorism were being championed in Congress. Statements were issued and promises were made to pass legislation that would safeguard the public.  The cause was launched and gathered steam. By the time the Iraqi chlorine bomb situation fizzled out, this political juggernaut was in full swing.  On April 23, 2007, four members of Congress (Markey, Lange in, Thompson, and Solis) wrote to Homeland Security Secretary Michael Chertoff, demanding answers to questions they posed regarding security at water treatment plants and the reported theft of three 150-lb. chlorine cylinders in California.  It later turns out that the thieves apparently thought they were stealing ammonia cylinders for use in illegal methamphetamine production.

Chertoff issued warnings to water treatment plant operators to “secure chlorine from terrorists.” He cited terrorists’ use of chlorine in truck bombs in Iraq.  The directive was issued in spite of the fact that the terrorists in Iraq had already abandoned this technique because it was ineffective.  This was the climate in 2007. No one wanted to be bothered with facts.  In the midst of all of this grandstanding, Joe Biden and Barbara Boxer sought to introduce legislation that would force changes in the CFATS, Chemical Facility Anti-Terrorism Standards, which had exempted water treatment plants from its provisions.  They wanted to force treatment plants to use “Inherently Safer Technologies” and eliminate use of chlorine gas, as a means to thwart perceived terrorist treats at water treatment plants.  So, through 2008 and 2009 this was a political football.  Hence the genesis of the rumors and doomsday talk about government legislation to eliminate use of chlorine gas.  After the mid-term elections of 2010 this attempt to change the treatment plant exemption was dropped with our legislators moving on to more pressing matters.

Most recently, there were reports that the Syrian government had used “chlorine bombs” against its own populace, in May 2014.  In an NPR Radio interview on May 29, 2014, it was pointed out that these “chlorine bombs” or barrels were dropped as a part of a strategy to “create a panic amongst the residents of the area.” The interviewee stated that “while chlorine is not very lethal, it does actually end up affecting a lot of people.  And, you know, your hospitals are going to be submerged by people who are having problems breathing for, at minimum, a few hours.” Here we had a deliberate attempt to release chlorine gas in a concentrated area, with no loss of life and minimal injury.  Again, the media ran with the story and a big fuss was generated for a few days but died out when it became apparent to both the Syrian government and the media that chlorine gas was totally ineffective as a weapon. 

The idea that terrorists would target water and wastewater treatment plants for the purpose of releasing chlorine gas, or even other chemicals used in the treatment process, in order to facilitate “mass destruction” is both ludicrous and disingenuous. It harms the populace to spread inaccurate and misinformed opinions that may result in actions taken which are, at best costly to the public in terms of the what they must pay for their utilities, and at worst could result in a public health problem due to inadequate treatment regimens which are less effective than chlorination.  Adoption of the term “Inherently safer technologies,” which has become a buzzword in legislative circles of late, is nothing more than an attempt by special interests to drum up fear through ignorance.  I often wonder, as I drive along major roads in urban areas, why this fear that terrorists may use water treatment chemicals in fenced and guarded facilities for purposes of destruction is becoming so accepted as fact, while that huge propane tank sitting, unfenced and unguarded by the side of the road is OK.  If I were a terrorist intent on creating havoc, blowing up that propane tank would be vastly higher (and easier) on my list since the resulting fireball and overpressure could wipe out a few city blocks.  But, do you hear the legislative lobbying to do away with propane tanks in urban areas?  Follow the money.

The use of chlorine generally in water treatment, and chlorine gas specifically, has engendered much irrational and misinformed rhetoric over the past 40-plus years.  Some more radical environmental groups persist in outrageous claims, while those with a more personal monetary agenda continue to feed the rumor mill.  The bottom line is that chlorine gas is here to stay in water and wastewater treatment.  After a steady decline through the first decade of the 21st century, use of chlorine gas has been on the rise as operators came back to what works, is safe, and is affordable.  When they lifted that “Big Bun” of alternative disinfection, the “beef” was truly wanting.

Image credit: "Water Fountain," JefferyTurner © 2008, used under an Attribution 2.0 Generic license: