Residential Use of Hydrogen Peroxide for Treating Iron and Hydrogen Sulfide

by Scott Crawford

Two common problems found in well water are iron and sulfur. Iron (Fe⁺²) can discolor the water, spot laundry and stain plumbing fixtures. In addition, the growth of iron-related bacteria sometimes present with iron can result in abnormal taste and odor and contributes to biofouling in plumbing systems.

Hydrogen sulfide (H₂S) is characterized by a rotten-egg odor and metallic taste. There is never any doubt as to when it is present due to its offensive odor. It promotes corrosion due to its activity as a weak acid; further, its presence in air causes silver to tarnish in a matter of seconds.

High concentrations of hydrogen sulfide gas are both flammable and poisonous. High concentrations of either iron or sulfide can foul the bed of an ion exchange softener.

There are many methods that dealers incorporate today to treat iron and hydrogen sulfide. Some of these include ozone, air injection, catalytic media and chlorine. Hydrogen peroxide (H₂O₂) is another method that can be used and has gained a lot of popularity because it is easier to handle, is a more powerful oxidizer and, in most cases, doesn’t require a contact tank. This translates to lower operating cost compared other types of chemical feed applications.

Hydrogen peroxide particulars

Hydrogen peroxide is a ”weak acidic, clear, colorless fluid, easily mixed with water in all proportions.” It is a clean oxidant that decomposes to H₂O and O_2, or more simply put, water with extra dissolved oxygen.

Hydrogen peroxide also occurs naturally. Our own bodies produce it naturally as a first line of defense against every single invading organism. Levels of 210 – 720 ppb have been reported in the breath of a normal healthy individual. It can also be found in coffee we drink and honey we eat.

Hydrogen peroxide is one of the most power oxidizers available. It is stronger than chlorine and potassium permanganate. Through catalysis, H₂O₂ can be converted into hydroxyl radicals (OH) with reactivity second only to fluorine.

Safety measures

As with any other oxidant, safety still needs to be considered when handling this product. Hydrogen peroxide of less than eight percent strength is considered non-hazardous. Most dealers today using hydrogen peroxide are using it at a seven percent concentration.

As a result, it can even be shipped through normal processes. This also means it can be safely delivered by a company vehicle without needing special registration or labeling on the truck.

There are many chemical supply companies that can provide it already mixed to a seven-percent solution. If you are delivering higher concentrations, check local and state regulations to determine what is required for proper registration and labeling.

Many dealers, however, have chosen to mix it themselves. While it is readily available at concentrations up to 35 percent, it should never be purchased at concentrations above this level.

Peroxide is very reactive above this level and requires extra care to handle it and, due to Homeland Security regulations and the quantity that might be kept at a facility, it can be purchased only at concentrations under 35 percent. (We purchase and store 34 percent concentrations at our facility and properly mix it to a seven-percent solution.)

Handling procedures

Whether you are handling a seven- or 35-percent solution, ensure that proper safety is used to handle and dilute. There are safety videos available from many of the suppliers and manufacturers of hydrogen peroxide.

The use of safety goggles to cover the eyes and protective gloves and aprons that are not affected by peroxide should always be used for proper handling while dispensing into containers. Leather gloves, for example, are not recommended for handling high concentrations of peroxide. It is very reactive to leather and can actually cause leather to ignite, even though peroxide itself is not flammable.

Customers should never be allowed to handle or dilute peroxide for safety reasons and for the risk of liability of the company providing it. The solution should be provided in a container that has a safety cap attached to prevent children from accessing it and should be properly vented.

Dilution procedures

Many dealers are purchasing 35 percent technical grade peroxide for diluting and using four gallons of water to one gallon of 35 percent peroxide. This works out to a 5.5 percent solution. Dealers should use this figure (5.5percent or 55,000 ppm) for the listed calculations listed to determine chemical feeder size and settings. Many chemical suppliers have seven-percent peroxide already available or can make it up in many cases. Be sure to determine what peroxide strength is being used and adjust for the calculations when sizing and setting chemical feeders¹. It does not work as a simple ratio, however. Dilution calculations are only easy when you’re in the middle of a chemistry class in college. It would require a complete, separate article to provide a refresher course in chemistry to go through the calculations to determine how to properly dilute. Dealers need to know variables such as the density of water at different temperatures, as well as the densities of peroxide at the different dilution concentrations.

Again, the best course of action here is to contact the chemical supplier to either help determine the method of dilution or see if they will dilute the peroxide to your requirements. There are also companies available that are diluting and pre-packaging containers of seven-percent peroxide and making it available to dealers.

Peroxide grades

There are three basic grades of peroxide available: NSF grade, food grade and technical grade. Most dealers are using food or technical grade.

NSF grade is not readily available and is usually only found in concentrations of 35 percent. As soon as you dilute it, it would no longer be considered NSF grade.

A carbon filter is always incorporated to catch precipitated elements and remove any remaining peroxide residuals much like a chlorination system does. As such, it is acceptable to use food or technical grade unless it is to be used with a public water supply. In those cases, you may have to contact local authorities to determine if the NSF grade must be used.

It is important to know your actual concentration when setting up and properly dosing the required amount needed for the application. For those who dilute using a ratio of five parts water to one part of 35 percent peroxide, the resulting concentration is actually 4.6 percent.

This is assuming a water quality to dilute that is equal to one-two meg-ohm is being used. A double-pass RO system can achieve this type of quality.

Using water from a typical RO system will reduce the concentration and stability slightly. Generally speaking, hydrogen peroxide is stable with a decomposition rate of one percent per year when properly handled and stored.

Heat and sunlight can increase the decomposition rate significantly. If using tap water to dilute, the concentration of the solution is significantly reduced, as is the decomposition rate and should not be used. There are a couple of different methods to determine the resulting concentration by testing, weighing or measuring pH (if you know the densities or pH of the different concentrations).

Removing iron and sulfide

From this point, it is relatively easy to set up a system to remove iron or sulfide from water, limiting the maximum amount of iron to be treated to 10 mg/L of iron when using peroxide.

Peroxide systems for iron removal should be limited to less than 10 mg/l. Many problems will occur at higher levels. Hydrogen sulfide does not react the same way and there are no limitations to the amount that can be removed. Dealers have found great success when needing a system that can remove very high levels of hydrogen sulfide.

Limit applications to 20 mg/L unless you have support from companies with experience handling higher levels. The following table can be used as a guideline for the proper dosage of peroxide needed for each milligram per liter of either iron or hydrogen sulfide to be treated.

When compared to other oxidants such as chlorine and potassium permanganate, the dosage of peroxide needed is significantly less. Additional information needed to determine the chemical feed rate is gallons per minute (gpm) to be treated. With the gpm, total amount of iron and/or hydrogen sulfide known and the concentration of the peroxide solution to be used, you can use the following to determine the chemical feed rate required to treat the water.

1. Determine the dosage of peroxide needed by determining the levels of iron and/or hydrogen sulfide and multiple the value with the highest amounts listed above. Most will use 0.4 ppm peroxide for each 1.0 ppm of iron; the amount required for sulfide is based on pH. The more alkaline (7.0>) the pH, the greater dosage required for each ppm of sulfide.
2. With the dosage determined: (gpm X 1440 X Ddosage)/ (percent concentration of H₂O₂) = Chemical feed rate required. NOTE: Multiply the percent concentration by 10,000.

For example: (10 gpm X 1440 X 4.0 mg/L Dosage)/ (70,000) = 0.82 gpd feed rate. In this example, a small feeder can be used and set for 0.82 gpd output. Chemical feed pump suppliers can help determine which pump size to use and how to set it to the required rate if you are not familiar as to how to do this.

Most dealers use a peristaltic pump to inject the peroxide solution. It is not affected by the off-gassing of oxygen from the peroxide. It can be more difficult to use a positive displacement diaphragm pump because of off-gassing that could result in a loss of prime and prevents the peroxide from being injected.

The chemical feeder is usually set up to operate in conjunction with the homeowner’s well pump and is injected ahead of the pressure tank. The use of a static mixer (motionless, in-line mixer) is used in some cases to speed up the reaction of peroxide to oxidize iron and/or sulfide.

The static mixer becomes the injection point. It is unusual to use a contact tank with peroxide. The reaction rates are so much faster than other oxidants that it is usually not necessary. When using a contact tank, keep it smaller for just a few minutes of contact time.

Larger contact tanks have no additional value since peroxide breaks down much faster in water than other oxidants. In some cases, the use of a flowmeter or meter for proportional feed is used instead of the well switch.

This type of set up requires a little more time to calculate feeder dosage rate and can create more problems and maintenance needs than the first method discussed. As with other oxidants, pH and other factors need to be considered and addressed as with any other system.

Water filtration

The final step required is to filter the water of the precipitated elements and any peroxide residual just like a chlorine injection system. Carbon is recommended and always used with peroxide injection.

Use of oxidizing or catalytic media other than carbon is not recommended. Media containing manganese dioxide such as Birm® or Pyrolox can be rapidly destroyed and create other problems if improperly applied.

Many dealers use catalytic carbon to filter and remove peroxide residuals. It rapidly breaks down peroxide as it passes through the bed, which will usually ensure no carryover of peroxide to service.

There are a variety of different types of carbon available, such as coconut shell, that has been used successfully with peroxide. With any type of carbon filter:

1. Check the backwash rate (gpm/ft²) required for your water temperature. Make sure it is backwashing frequently based on water usage per day. Typical applications will probably backwash every three days to keep the filter clean.
2. Keep the flow rate through the filter bed as slow as possible. We recommend no more than 10 gpm/ft² (square foot); five gpm/ft² or less is recommended for the best performance.
3. Make sure the carbon it is properly rinsed before it goes into service.
4. Check peroxide residuals into and out of the filter to verify proper settings. Some dealers use peroxide test kits for this procedure, and others use ORP) meters to verify settings. Some use a simple bubble test, which is simply drawing a clear glass of water and verifying the micro bubbles leftover clear up rapidly (20 seconds or less) and will adjust feed rates accordingly. The best methods are testing the peroxide or ORP.
5. As always, be sure to test for iron and sulfide after the filter to verify it is performing properly.

With proper steps taken prior to installation, peroxide can offer a great alternative to other solutions when handling difficult iron and hydrogen sulfide problems. Despite peroxide’s power, it is safe and versatile to use and decomposes into water and oxygen. It will provide iron- and sulfur-free water naturally, without using harmful chemicals.

Article Source:  WCP Online. Dec. 14, 2009.

Pure Water Gazette Fair Use Statement

3M Knew that PFAS Was Hazardous to Humans in 1950. It Is Still Being Produced.

Should 3M be required to pay for cleaning up the evironmental disaster created by its products?

In 1947, 3M began producing perfluorooctanoic acid (PFOA) by electrochemical fluorination.

In 1951, DuPont purchased PFOA from then-Minnesota Mining and Manufacturing Company for use in the manufacturing of teflon, a product that brought DuPont a billion-dollar-a-year profit by the 1990s. DuPont referred to PFOA as C8. The original formula for Scotchgard, a water repellent applied to fabrics, was discovered accidentally in 1952 by 3M chemists Patsy Sherman and Samuel Smith. Sales began in 1956, and in 1973 the two chemists received a patent for the formula. As far back as 1950, studies conducted by 3M showed that the family of toxic fluorinated chemicals now known as PFAS could build up in our blood. By the 1960s, animal studies conducted by 3M and DuPont revealed that PFAS chemicals could pose health risks. But the companies kept the studies secret from their employees and the public for decades.

Here is a timeline of some important events.

1950 – 3M mice study reveals that PFAS builds up in blood.

1956 – Stanford University study finds that PFAS binds to proteins in human blood.

1961 – DuPont toxicologist warns that PFAS chemicals enlarge rat and rabbit livers.
1962 – Volunteers who smoke PFAS-laced cigarettes get “polymer fume fever.”

1963 – 3M technical manual deems PFAS toxic.

1965 – DuPont rat study shows liver damage and increased spleen size.

1966 – The Food and Drug Administration rejects a DuPont petition to use PFAS chemicals as a food additive, citing liver studies. 1966 – 3M study finds that PFAS causes “acute oral toxicity” in rats.

1970 – 3M warns Fire Journal, the magazine of the National Fire Protection Association, that PFAS is toxic to fish. 1970 – DuPont scientists say PFAS is “highly toxic when inhaled.”

1973 – DuPont finds there is no safe level of exposure to PFAS in food packaging. 1975 – 3M is informed that PFAS builds up in human blood samples. 1975 – DuPont warns 3M about “toxic effects” of PFAS in food packaging.

1977 – 3M tests workers and animals to measure PFAS in blood. 1977 – 3M finds PFOS, the PFAS chemical in the company’s Scotchgard fabric treatment, “more toxic than anticipated.”

1978 – 3M animal tests find lesions on spleen, lymph nodes and bone marrow.

1978 – 3M concludes that PFOS and PFOA, a PFAS chemical used to make DuPont’s Teflon, “should be regarded as toxic.”

1979 – DuPont survey of employees in its Parkersburg, W.Va., Teflon plant finds possible evidence of liver damage.

1981 – 3M and DuPont reassign female workers after animal studies reveal PFAS damages the eyes of the developing fetus.

1983 – 3M identifies PFAS’ potential harm to the immune system as a cause for concern.

1984 – 3M documents rising fluorine levels in workers’ blood.

1984 – DuPont detects PFAS in the tap water in Little Hocking, Ohio, but does not alert the local water utility.

1987 – 3M PFOA animal study finds tumors.

1989 – 3M study finds elevated cancer rates among PFAS workers.

1990 – 3M study finds risk of testicular cancer from exposure to PFOA, also known as C8.

1992 – DuPont study finds elevated cancer rates among workers.

1992 – Former 3M scientist finds male PFOA workers more likely to die from prostate cancer.

1995 – DuPont scientist expresses concern over long-term PFAS health effects.

1997 – DuPont study finds heightened cancer rates among workers at the Parkersburg plant.

1998 – 3M scientists report that PFAS moves through the food chain.

1998 – 3M provides EPA evidence that PFAS accumulates in blood.

1998 – 3M animal study finds liver damage from PFAS exposure.

1999 – 3M scientist describes PFOS as “the most insidious pollutant since PCB.”

2000 – 3M animal study finds liver damage from PFOS exposure

Information Sources

EWG

Wisconsin Dept. of Health Services

Wikipedia

Water News — June 2023

In spite of much publicized environmental consequences, bottled water use is growing rapidly in the UK. “Big water brands are expected to grow more than 10% in the next four years – an equivalent of more than 280m extra plastic bottles. ”  Calling plastic bottled water “a scar on our society,” David Hall, the UK managing director of Brita, noted:  “Plastic bottled water takes about five seconds to make, five minutes to use, and a staggering 500 years to break down in landfill. It’s one of the main culprits of the worldwide plastic pollution crisis.”  The Guardian

3M to stop producing PFAS chemicals by 2025

3M started winding down PFAS production in the 2000s under pressure from the EPA. The company recently announced that it will cease production of forever chemicals entirely by 2025. But the hundreds of millions of pounds of the chemicals the company produced for more than half a century still persist, indefinitely, in the environment. They’re also lingering inside of us: in our blood and our excrement, primarily via the foods we eat and the water we drink.  Reference — Grist  —  3M polluted drinking water with PFAS for decades. Will it have to pay for the clean up? | Grist

Texas Nixes Water Breaks for Construction Workers

In spite of record breaking temperatures and the fact that Texas leads the nation in worker deaths because of heat, Texas Governor Greg Abbott just signed a broad new law that will nullify a wide range of local regulations, including mandated water breaks for construction workers.  Dallas and Austin currently require workers to be given at least 10 minutes to cool down and hydrate every four hours.  Yahoo News.

Could Predatory Bacteria Replace Chlorine?

Research from Lund University in Sweden indicates that harmless predatory bacteria can be introduced into water to eat most other bacteria. This could become a replacement for chlorination.   Interesting Engineering.

The Boring Company, a tunnel-building company founded by Elon Musk, plans to dump 142,500 gallons of wastewater per day into the Colorado River in Texas.  Local residents and food producers are alarmed at the plan and have pushed back strongly against the company’s wastewater permit application. The company plans to do the wastewater treatment itself until a new wastewater treament plant is completed at Bastrop, TX. Yahoo News.

A bridge crossing the Yellowstone River in Montana collapsed on June 24, sending a freight train carrying potentially hazardous materials into the swirling waters below. The derailment forced the shutdown of several drinking water intakes downstream and emergency measures at water treatment plants in neighboring Yellowstone County.  New York Daily News.

Chemical manufacturing giant 3M has agreed pay up to $10.3 billion over 13 years to help municipalities test for and clean up toxic PFAS chemicals in public water supplies. The settlement is trivial compared to the company’s profits from the chemicals and the actual cost of cleanup.

Removal of Groundwater Has Changed the Tilt of the Earth

How safe is America’s drinking water?

There are still millions of Americans without access to clean tap water

by Justin Klawans

While it is generally fine to consume tap water in the United States, there are still millions of Americans who suffer from a lack of safe drinking water. The situation in Flint, Michigan, probably comes to mind, but there are many other areas around the country where drinking water can be hazardous.

Is tap water in America safe to drink?

For the most part, yes. The United States has “one of the safest water supplies in the world,” according to the U.S. Centers for Disease Control and Prevention (CDC). More than 90% of Americans get their tap water from public water systems, the CDC reported, all of which are subject to safe water standards. These standards are enforced by both the U.S. Environmental Protection Agency (EPA) and the Safe Drinking Water Act. The latter “requires many actions to protect drinking water and its sources — rivers, lakes, reservoirs, springs, and groundwater wells” and sets “national health-based standards for drinking water to protect against both naturally-occurring and man-made contaminants that may be found in drinking water.” This includes testing for the presence of dangerous contaminants like E. coli, salmonella, and cryptosporidium.

The CDC admits, though, that contamination can still occur. The most common safety violations are “illegal levels of pathogens (bacteria and viruses), nitrates, arsenic, and harmful byproducts from disinfectants like chlorine,” Maura Allaire, a water quality expert at UC Irvine, told National Geographic. Then there is the commonly held fear of lead exposure from old pipes.

Contamination from lead pipes leeching into the water supply is an ongoing risk, and “the U.S. currently holds approximately 9.2 million lead service lines underground,” ABC News reported. They are a “silent and deadly consequence.” Lead is not the only chemical that has people worried about their water supply. There have been renewed concerns over harmful “forever chemicals,” called PFAs, that can make their way into water systems, some of which have been linked to cancers and reproductive diseases in women.

How many Americans don’t have access to clean water?

In a nation of approximately 335 million, “more than two million Americans live without basic access to safe drinking water and sanitation,” according to the U.S. Water Alliance, and at least 1.4 million of these Americans don’t have access to indoor plumbing at all, the Alliance added.

How Often Should Carbon Filter Cartridges Be Changed?

MatriKX Chloraguard Filter Cartridge, 2.5″ X 9.75″ — Standard Drinking Water Size

The simple and probably the best answer for residential applications is that carbon filter cartridges should be changed at least once a year. The more complicated answer is that it all depends on what you expect of the cartridge, how  much you know about your water, and how willing you are to monitor such things as the amount of water used and the flow rate.

Carbon filters are a very versatile tool that can be applied to many different problems. What they do best and easiest is remove chlorine and improve taste and odor. But they are also the most practical treatment for many more difficult problems, like chemicals in general (see how many times carbon appears as the treatment of choice in this contaminant removal chart),  and very hard to treat items like VOCs and PFAS.

Below is the manufacturer’s lifespan recommendation for the high quality coconut shell carbon block filter pictured above.

• Chlorine: 45,000 @ 1 gpm,
• Chloramine: 4,000 @ 0.5 gpm,
• PFAS: 3,500 @ 0.5 gpm,
• VOC: 750 @ 0.5 gpm,

Note that if your requirement is only the removal of chlorine from drinking water the cartridge should last until you die of old age.  However, if your city uses chloramine rather than chlorine as its disinfectant, it will last only about 1/10 as long, and you’ll have to be sure to run the water half as fast. Running the cartridge at “chlorine speed” will greatly reduce its service life as well as its effectiveness when treating chloramine or difficult contaminants like PFAS and VOCs.

In most cases the once-a year-rule works well and assures excellent performance with most contaminants. If more than a couple of people are using the water and VOCs are a known issue, changing the cartridge twice a year is a good idea.

And then, of course, there are variables to be considered like multi-cartridge filters, position of the cartridge within the unit (a reverse osmosis pre-filter treats much more and much dirtier water than a reverse osmosis post filter), water temperature, pH, etc.  But, for simplicity, the once-a-year cartridge change works pretty well.

Proposed Water Regulations May Not Help The People They Are Supposed To

by Ike Brannon

Gazette Introductory Note: Before you read this article, let me explain what it is about.  The EPA has spent several years trying to decide how much of the “forever chemicals” grouped under the name PFAS can be allowed in US drinking water. This is hard to figure out, especially since they have to find a number that can be more or less acceptable to the interested parties: consumer advocates, environmentalists, public health officials, water utilities, the manufacturers of the offending substance and other business interests that profit from its use, plus loud and often obnoxious elected and unelected officials and lobbyists who represent and take donations from all of the above. Although the EPA will try to rely on science in setting its allowable, the number finally chosen will be a negotiated compromise.

The four parts per trillion PFAS allowable recently announced by the EPA is unlikely to be final. Manufacturers and public water suppliers, who will be pressed to pay for cleanup or face litigation, prefer a higher number. The higher the better. The article below is from Forbes magazine and cites evidence from the Wall Street Journal. This may give a hint about the the concern over the EPA’s low allowable figure. It really isn’t your water bill that Forbes is concerned about.  It is the “existential threat to the companies responsible for these chemicals”  and “the enormous impact that the EPA’s actions have on businesses.” Not even mentioned are your daughter’s miscarriage or your aunt’s liver cancer.  Nor do they bring up the billions upon billions of dollars that 3M and other companies have taken in during the seven decades that they sold these products while knowing that they had devastating public health consequences.–Gene Franks.

Late last year the Environmental Protection Agency proposed a new set of rules that would designate perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) – two types of per- and polyfluoroalkyl substances (PFAS) – as hazardous substances, and other regulations that would reduce the allowable level of these substances in the drinking water to just four parts per trillion.

These stringent limits—which go beyond the UN recommendations of twelve parts per trillion as well as those of any other country and approach or exceed what state-of-the-art technology can currently detect—would dramatically increase costs for water treatment facilities, requiring most of them to make new investments in equipment both to detect and remove the substances. The lower threshold would provide a new impetus for future lawsuits.

However, the EPA’s rules could result in unintended consequences and would not necessarily result in a better outcome. For instance, people living in communities both with and without the chemical in their water supply at detectable limits will find themselves paying much higher water bills for the more stringent testing as well as the removal of the chemicals from the water.

While some may argue that we should not let cost deter us from removing potential health costs, it has not yet been established that the EPA threshold is, in fact, the appropriate threshold to establish safe drinking water. If the higher U.N. standard or the even higher standards in place in Europe are sufficiently safe, then the additional costs to get our standard below theirs will have bought us little or no additional protection.

These artificially lower levels will also leave many companies exposed to lawsuits seeking compensation for potential damages from these pollutants. Given that many of these companies have already faced lawsuits that have resulted in them having to pay hundreds of millions of dollars, establishing even lower limits would doubtless subject them to further litigation from community groups, local governments, and class-action lawsuits instigated by tort lawyers seeking a higher payday.

These lawsuits have already begun: The Wall Street Journal reports that over 300 utilities are seeking to recover the cost of filtering the chemicals out of their water, and that the lawsuits seeking damages represent an “existential threat” to the companies responsible for these chemicals, much of which entered the water table via their use in producing a foam used to put out fires.

There are now rumblings of a potential $10 billion settlement between 3M and municipal providers of consumer drinking water. This litigation and potential settlement illustrates the enormous impact that the EPA’s actions have on businesses.

Article Source: Forbes

Pure Water Gazette Fair Use Statement

Understanding Chlorine: How It Works to Disinfect Water

Introductory Note:  The article below is adapted from information from Blue-White Industries.  It provides a good explanation for the frequently misunderstood terms free chlorine, total chlorine and combined chlorine.

For over a century, chlorine has been used to provide clean drinking water to communities in the U.S. and across the world. In the correct doses, chlorine can kill a broad range of pathogens while remaining safe for people and animals to consume. The key is dosage, as too little chlorine will not have the disinfecting power required to eliminate the most critical pathogens. Too much chlorine can cause water to taste and/or smell unappealing, or worse, have long-term negative impact.

Measuring chlorine isn’t a simple matter of saying, “I have X parts per million in my water.” After all, once chlorine enters water, it begins to change, and when it interacts with pathogens and other matter, it changes again.  There are technically three measurements that must be considered: free chlorine, combined chlorine, and total chlorine.

How Chlorine Works

In water, chlorine breaks down into smaller chemicals such as hypochlorite ion and hypochlorous acid. It is these substances that kill bacteria, viruses, and other microorganisms. They do this by either collapsing proteins in bacterial cells or damaging the outer membrane of viruses and similar pathogens. Not every pathogen is equally vulnerable to chlorine, however. Protozoa such as Giardia lamblia and Cryptosporidium are chlorine-resistant. Fortunately such pathogens are large and can be easily removed via filtration.

Free Chlorine

“Free chlorine” is the amount of chlorine that is available to combine or oxidize contaminants in water. The greater the amount of free chlorine, the greater the disinfection potential. In a drinking water system, the amount of free chlorine should generally be kept between 2 ppm and 4 ppm. When free chlorine levels rise above 4 ppm, the water may take on a strong “swimming pool” smell or taste.  However, too little chlorine means there may not be enough chlorine available to disinfect pathogens.

Combined Chlorine

When hypochlorite ions and hypochlorous acid interact with contaminants, they form new compounds. Generally speaking, these new compounds are no longer available for disinfection. The amount of combined chlorine measures how many pathogens or other contaminants have been using chlorine, which helps to understand how dirty the water is (or was).

Of course, not all combined chlorine chemicals are inert. When chlorine combines with nitrogen, it can form chloramines. These compounds do have some disinfection power, but they are not likely present in high enough quantities to be considered in disinfection potential (unless operators deliberately added ammonia to the system with the intent of forming chloramines).

Other types of combined chlorine include disinfection byproducts (DBPs), such as trihalomethane and haloacetic acid. These substances occur when chlorine reacts with natural organic matter in the water. DBPs can be harmful to human health and are regulated by th the U.S. EPA.

Water News for May, 2023

Home of the EPA in Washington, DC

Certainly the biggest water news of the month was the breakthrough agreement of water managers in Arizona, California and Nevada to cut back water use from the Colorado River to keep the river from falling to a level that could endanger the water supply of farms and cities that depend on the river.  The federal government will pay some $1.2 billion dollars to cities, irrigation districts and Native American tribes if they temporarily use less water. National Public Radio.

The US Environmental Protection Agency is taking unprecedented enforcement action over PFAS water pollution by ordering the chemical giant Chemours’ Parkersburg, West Virginia, plant to stop discharging extremely high levels of toxic PFAS waste into the Ohio River. The river is a drinking water source for 5 million people, and the EPA’s Clean Water Act violation order cites 71 instances between September 2018 to March 2023 in which Chemours’ Washington Works facility discharged more PFAS waste than its pollution permit allowed.

The agency also noted damaged facilities and equipment that appeared to be leaking PFAS waste onto the ground. The chemicals are ubiquitous and linked at low levels of exposure to cancer, thyroid disease, kidney dysfunction, birth defects, autoimmune disease and other serious health problems.  The step by the EPA drew praise from some environmental groups, but at least one noted the permit still allows high levels of PFAS pollution and may not adequately protect the environment and human health.  The Guardian.