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.

Basic Heavy Duty Whole House Cartridge Filters

Tough, versatile 20-inch “Big Blue” housings can be used alone or in a variety of combinations to meet virtually any “whole house” filtration situation. They are simple, durable, easy to install, and easy to service. They use standard-sized cartridges so replacements are easy to find. Parallel installation, as pictured below, make them suitable for even large homes.  Installing in parallel greatly reduces pressure loss, enhances the effectiveness of the unit,   and extends the life expectancy of the cartridges.

Cartridge filters are much easier to maintain than tank-style filters.  As for installation, they care compact in size and do not require electricity or connection to a drain.  Most require only an annual cartridge change, which can usually be done by the homeowner.

The  chart below shows sizing suggestions for whole house filtration for water that is treated with chlorine or chloramine.

Basic Housing and Bracket Setup. The Housing is available for 3 pipe sizes–3/4″, 1″, or 1.5″.  This very versatile “Big Blue” housing will accept any standard 4.5″ X 20″ cartridge. It can be used for sediment cartridges, carbon cartridges, or “media” cartridges for special purposes like iron removal or pH increase.

Typical Sediment Carbon Arrangement  (System 1 above.)

Sediment filter with parallel carbons  (System 2 above.)

Sediment filter with three carbons  (System 3 above.)

System 1, pretreating for a TAC unit

Sediment, Triple Carbon (System 3) , pre-treating for a TAC unit. 

Upending A Decades-Long Theory Of Reverse Osmosis Water Desalination

The process of reverse osmosis has proven to be the state-of-the-art method for removing salt from seawater and increasing access to clean water. Other applications include wastewater treatment and energy production.

Now a team of researchers reveal in a new study that the standard explanation for how reverse osmosis works — one that has been accepted for more than five decades — is fundamentally wrong. In the process, the researchers offer an alternate theory. Besides correcting the record, these insights could lead to more effective uses of reverse osmosis. The results of the study, led by the lab of Prof. Menachem Elimelech, are published in Science Advances.

Reverse osmosis — a technology first put to use in the 1960s — removes salt and impurities from water by passing the water through a semipermeable membrane, which allows the water to go through while blocking the contaminants. To explain exactly how it works, researchers have used the theory of solution-diffusion. This theory assumes that the water molecules dissolve and diffuse through the membrane by way of their concentration gradient — that is, the molecules move from areas of high concentration to wherever there are fewer molecules. Although this theory has been widely accepted for more than 50 years and is even taught in textbooks, Elimelech said he has long had questions about it.

“Some of the assumptions do not make any sense,” said Elimelech, the Sterling Professor of Chemical and Environmental Engineering. For instance, he said, the theory is based in part on the idea that pressure across the membrane is constant. “Whenever you have water flow through any porous material, there is always a pressure drop.”

To get a better sense of the physics involved, the research team — which included scientists from the University of Wisconsin-Madison and Texas Tech University — did a combination of experiments and computer simulations. Specifically, they used simulations of the molecules’ movements, which revealed that water transport is driven by changes in pressure within the membranes. They further show that water molecules travel as clusters through a network of pores in the membrane. This contrasts with the conventional theory based on the solution-diffusion model, which assumes that the water molecules separate from each other in the membranes. Supplementing the computer simulations, the scientists performed experiments that allowed them to observe water passing through membranes. The results showed that the way that water permeates the membrane depends on the membrane pore size, the size of the water molecules, and viscosity of the water. This was also inconsistent with the solution-diffusion model.

Overall, the simulations and experiments demonstrated that, rather than being driven by the concentration of molecules, reverse osmosis is driven by pressure changes within the membrane.

Because previous measurements related to reverse osmosis were based on a faulty understanding of it on a molecular level, Elimelech said, many attempts to advance the field have met a dead end. Having a more accurate theory to explain reverse osmosis, he said, could open the way toward developing more effective materials and techniques to improve the process.

Other authors of the study include Li Wang, Mohammad Heiranian, Hanqing Fan (all from Yale); Jinlong He and Ying Li from University of Wisconsin-Madison; and Lianfa Song from Texas Tech University.

This work was supported by the National Alliance for Water Innovation (NAWI), funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE), Advanced Manufacturing Office, under Funding Opportunity Announcement Number DE-FOA-0001905 through a subcontract to Yale University and University of Wisconsin-Madison.

Source: Yale School of Engineering & Applied Science via Water Online.

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Source: University of Rhode Island via Water Online.

Water News Briefs for April 2023

Lead Pipe Replacement Moves at a Snail’s Pace

In 2018, almost 30 cities across New York state received federal money to carry out a specific, urgent task: removing lead service lines that poison drinking water. The city of Troy – which sits across the Hudson River and just north of Albany – was among them, receiving $500,000. But five years later, city leaders have failed to spend a single dollar of that money, and have yet to remove a single lead pipe. The revelation emerged at a city council meeting this winter, raising all sorts of questions. Chief among them is why the city hasn’t spent the money. Troy’s failure illustrates the challenges small cities face when trying to address environmental injustices like lead pipes.  Full article from The Guardian.

World’s Ocean Temperature Hits All-Time High

The temperature of the world’s ocean surface has hit an all-time high since satellite records began, leading to marine heatwaves around the globe, according to US government data. Climate scientists said preliminary data from the National Oceanic and Atmospheric Administration showed the average temperature at the ocean’s surface has been at 21.1C since the start of April – beating the previous high of 21C set in 2016. “The current trajectory looks like it’s headed off the charts, smashing previous records,” said climate scientist Prof Matthew England. Hotter oceans provide more energy for storms, as well as putting ice sheets at risk and pushing up global sea levels, caused by salt water expanding as it warms. Marine heatwaves can also have devastating effects on marine wildlife and cause coral bleaching on tropical reefs. The Guardian.

Railroads Follow Rivers.

Decisions made more than 150 years ago about where to run railroad tracks have significant consequences today when trains derail. That’s because rail lines usually follow rivers. At a time when climate change is altering rainfall and flooding patterns increasing the risk of washouts and mudslides on tracks, it is increasingly risky and irresponsible to run large trainloads of petroleum and hazardous chemicals along the banks of rivers. The Colorado River, for example, furnishes water for 40 million people.  A significant derailment along the Colorado could be devastating. USA Today.

Industry Knew about the Dangers of PFAS Decades Ago, but Kept It Secret

Industry sponsored studies documented PFAS toxicity in 1978 but this information was not shared with the US EPA until 2000. PFAS have been linked to a range of health problems, including testicular and kidney cancers, decreased birth weight, and thyroid disease. While most companies have stopped producing two forms of PFAS— perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS)—the chemicals persist in drinking water systems, and new forms of PFAS are raising concerns. This revelation underlines the basic truth that allowing industry to voluntarily regulate itself does not work. Strong governmental oversight is essential.

Ice Sheets Are Shrinking Much Faster Than Predicted

New research shows that the massive ice sheets at the top and bottom of our planet are shrinking much faster than previously thought. The international study compiled satellite measurements over time and depicts what one researcher described as a “devastating trajectory.” PBS News.

Garden Hose Art Like the Decorative  Basket Above  Was Once Featured in National Garden Hose Day Events

National Garden Hose Day Is On the Ropes Because of the Political Climate

National Garden Hose Day,  a lusty national holiday celebrated in June, reached peak popularity as an early summer good time event in the years preceding the pandemic.  Garden Hose Day festivities were curtailed beginning in 2020 due to public health concerns, and, unfortunately, efforts to bring the holiday back have faltered because of the divisive political climate.

Many US cities have already cancelled Garden Hose celebrations this year because of fears of transgender participation in the Garden Hose Tug, a tug of war event that is often the center of Garden Hose festivities. Critics also point out that the garden hose is not mentioned either in the Bible or the US Constitution and that the shape of the garden hose itself has sexual implications and should not be seen by children under 18. In Texas and Mississippi there are now bills before the state legislature to remove books from libraries that have pictures of garden hoses.

(Since fake news has become so common that it’s hard to recognize these days, the Pure Water Gazette wishes to advise that the article above is completely phony. Please do not sue or write abusive letters. While we’re at it we’ll confess to having invented and shamelessly promoted a non-existent holiday for a number of years. To our credit, we did not try to sell you a Monkey Pox tee shirt or a NFT depiction of Garden Hose Superman blasting the enemies of the Second Amendment with a high powered fire hose. Here’s a Garden Hose Day article from 2013, back in the good old days before politics got so nasty that you couldn’t enjoy a good old summer Garden Hose Tug or Hose Blast competition.)

Can Water Cause Weight Gain?

Important research published in the journal Obesity establishes a definite link between weight gain and PFAS in drinking water. “Our study adds new evidence that being overweight isn’t just about a lack of physical activity and unhealthy eating habits – PFAS are increasingly suspected to be a contributing factor.”  The PFAS exposures in the European participants are quite comparable to levels in America, so my concern is that our exposures to PFAS are making it difficult for us to avoid getting overweight.”  Full article in Pure Water Gazette.

Camp Lejeune Toxic Water Case Payout Could Top $21 Billion

by Peter Chawaga

Camp Lejeune served its soldiers and their families highly contaminated water over a period of 24 years

“Hundreds of thousands of veterans and their relatives exposed to cancer-causing drinking water on the North Carolina Marine base are expected to file claims,” Bloomberg Law reported. “The bill lawmakers passed last summer acknowledged the government’s culpability and had an estimated price tag of $6.1 billion. The Congressional Budget Office says that total could balloon in later years by another $15 billion.”

The issues with Camp Lejeune’s water date back decades, with some speculating that chemicals leaking from a dry-cleaning operation nearby were originally to blame. Service members and their families were exposed to the dangerous effluent for more than three decades, and the recent Congressional act gave anyone who spent more than 30 days on the base between 1953 and 1987 the chance to file a civil claim. As a result, law firm advertisements offering to represent victims have proliferated.

Camp Lejeune served its soldiers and their families highly contaminated water over a period of 24 years

“Law firms and legal marketing agencies spent more than $145 million on advertising last year in a bid to recruit them,” according to Bloomberg Law.

But despite the federal clearance and eagerness of legal representatives, victim health claims have been slow to resolve.

“Even though Congress passed a law last August giving Camp Lejeune victims two years to sue for damages in federal court, the process of compensating the thousands of people affected by the contamination is moving at a snail’s pace,” according to Roll Call. “The Navy and Marine Corps, which have denied responsibility for causing health problems at the base since the contamination was first discovered in 1982, have taken no action on about 20,000 damage claims filed with the Navy Judge Advocate General after the legislation was signed into law.”

As the claims pile up and legal firms continue to push toward resolution per the Congressional approval, it’s clear that this decades-long saga over one of the most shocking drinking water contamination issues in American history is far from over.

“Here we are six-plus months since the bill was passed and to my knowledge not one claim has been settled, not one offer has been made,” Mike Partaine, a man who was born at Camp Lejeune and has since been diagnosed with breast cancer, told Roll Call. “Why is it taking so long? That’s what the community has been saying too.”

To read more about how water systems address harmful chemicals, visit Water Online’s Drinking Water Contaminant Removal Solutions Center.

Water Online

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Water News Briefs for March 2023

New studies reveal that toilet paper can be a serious contributor to PFAS levels found in wastewater. Phys.org. For information about the origin of PFAS in toilet paper and significance, see the excellent Guardian report.

Lake Mead continues to shrink and is now at the lowest level it has been since it was first filled. “Lake Powell, the nation’s second-largest reservoir and one that provides water and power to millions of people in southern California, has reached its lowest levels since its first filling in the 1960s,” USA Today reported. “If the lake’s level falls much lower, it won’t be possible to get water out of it … If the lake falls another 32 feet — about the amount it fell in the past year — power generation concerns become more urgent.”  Pure Water Gazette. Ironically, as many areas suffer with record drought, recent storms have filled some California lakes to their highest level in years. Newsweek.

Alarmingly high levels of PFAS have been found in lakes in Alaska’s two largest cities,  Fairbanks and Anchorage.  Some lake water has PFAS levels 1000 times what is considered safe for drinking water. “Use of PFAS compounds began in the 1950s, and there are thousands of them. Most famously, they are found in flame-suppressants. Most of the environmental PFAS contamination in Alaska and many other places is believed to have been caused by use of those firefighting foams at airports, where their use is mandated by the Federal Aviation Administration. Military sites are also known for using such foams. But the PFAS compounds are widespread in consumer and industrial products like nonstick cookware, clothing, upholstery and personal-care goods such as shampoos. They are called “forever chemicals” because they do not degrade.”  Alaska Beacon.

An estimated 8,100 gallons of latex finishing material, a water-soluble acrylic polymer solution, was released into Otter Creek in Bristol, Pennsylvania, on March 25. Boil water alerts are expected. Yahoo.

The EPA has determined that US military bases with cancer-linked PFAS-contaminated drinking water have been significantly undercounted. “Data obtained from the Department of Defense (DOD) by the Environmental Working Group (EWG), under the Freedom of Information Act, show that locations with notably high levels of total PFAS include Fort Leavenworth, in Kansas; the Joint Forces Training Base, in California; Belmont Armory, in Michigan; McChord Air Force Base, in Washington; Fort Hunter Liggett, in California; and the Sierra Army Depot, in California.” When water at military bases is contaminated, communities in their vicinity are usually at risk as well.  Water Online.

The EPA has released new draft Maximum Containment Levels (MCL) for PFOA and PFOS (collectively part of the group of chemicals known as PFAS) permissible in drinking water at a national level.  The new allowable levels are 4 ppt for PFOA and 4 ppt for PFOS.  For context, one part per trillion is one drop per 21 million gallons of water.  See the full article below from Environmental Health News for details.

Chinese archaeologists discovered what may be one of the world’s oldest manual flush toilets — dating back 2,200 to 2,400 years, per Live Science.

A massive 5,000-mile seaweed bloom is approaching the Florida coast and threatening water quality. The seaweed, known as sargassum, can tangle up boats and other marine machinery, release dangerous hydrogen sulfide, and inundate beaches. The seeweed is laced with heavy metals like arsenic which make disposal and reuse extremely difficult. Research suggests the causes for this massive bloom are related to climate change and are similar to those that have been driving increases in source water algal bloom, which threatens drinking water quality, across the country.  Water Online.

Are We Slowly Dying of Thirst?

The world is facing an imminent water crisis, with demand expected to outstrip the supply of fresh water by 40% by the end of this decade, experts have said on the eve of a crucial UN water summit. Governments must urgently stop subsidising the extraction and overuse of water through misdirected agricultural subsidies, and industries from mining to manufacturing must be made to overhaul their wasteful practices, according to a landmark report on the economics of water. Nations must start to manage water as a “global commons”, because most countries are highly dependent on their neighbors for water supplies; and overuse, pollution and the climate crisis threaten water supplies globally, the report’s authors say.  — The Guardian.  Lkewise, the U.N. issued a warning that “vampiric overconsumption” is rapidly depleting the world’s water supply. BC Water News.

Plasticosis

The world’s oceans are permeated with plastic waste, from surface waters to some of their deepest reaches. And we know from numerous studies that fish, turtles, seabirds and smaller sea creatures are ingesting bits of plastic when they feed. Now, scientists are starting to pin down the effects of a plastic diet.

Marine scientist Matthew Savoca explains findings from a recent study that identified a new illness, which the authors call plasticosis, in seabirds. Scarring in the birds’ digestive tracts resembles effects in humans who are longtime smokers or have been exposed to asbestos. As Savoca sees it, plasticosis “could be a sign that a new age of disease is upon us because of human overuse of plastics and other long-lasting contaminants, and their leakage into the environment.” The Conversation.

Only Fleck 5600  on Our Website Now

By far our most popular backwashing filters over the years have been those built with the reliable and very user friendly Fleck 5600 control. Now only 5600 filters are shown on our website. We made the change to 5600 only for water softeners a couple of years ago and it has worked out well.

The 5600 has size limitations. It works only on filters that need a backwash rate of 7 gallons per minute or less.  If a larger filter than those shown on our site is needed, we can usually supply it, but it can’t be ordered from the shopping cart. We still stock and support the Fleck 2510 models that were recently taken down, but they are available by phone only so that we can assure that they are properly sized. We also sell much larger filters and softeners with Fleck and Nelsen C-Series (Clack) controls that are not shown on the website.

The very popular Fleck 5600 SXT (simple electronics) control, pictured above, is ideal for customer-maintained filters.  No special tools are needed for repairs and parts are easy to find.  We program the control before it is shipped, and changes in programming are easy. We still supply the time-clock version of the 5600 as well for those who prefer it.

Our Fleck 5600 backwashing  filters.