Water Conditioning & Purification Magazine

Safe City Water Made Even Better

By Greg Reyneke, MWS

In the era of COVID-19, many people have an acute interest in bacteria, mold, fungus and, of course, virus. While the COVID-19 pandemic created significant fear and concern, our drinking water supply was relatively immune from this threat, due to the hard-working men and women who comprise our essential municipal water treatment sector. US EPA ranks drinking water pollution as one of the top environmental threats to health. Credible estimates suggest that only half of waterborne disease outbreaks in community water systems (and about one third of those in non-community systems) are ever detected, investigated or even reported. Microbes in tap water may actually be responsible for as many as 30 percent of gastrointestinal illness in the US and recent studies indicate that there is a far greater waterborne transmission pathway for viral activity than previously believed.

One hundred-fifty years ago, much of the US water supply was teeming with various forms of aquatic organisms including coliforms, bacteria, viruses and protozoa. Cholera, typhoid and dysentery were a serious public health problem and they are still major concerns in third-world nations where over a billion people lack clean drinking water and almost two billion lack adequate sewage distribution and processing systems. Waterborne microorganisms range in size from extremely small viruses in the submicron range to relatively large cysts than can approach 50 micron in diameter. Pathogenic microorganisms can occur naturally in lakes, streams, reservoirs and most surface water sources. Even groundwater supplies are not immune since the existence of subterranean bacteria has been definitively proven, along with the ability of enteric viruses and other organisms to leach into groundwater from the land application or burial of sewage sludge and other residential and industrial wastes.

Americans expect cheap, clean, safe drinking water from every faucet in their home, but America’s water treatment and delivery infrastructure is aging and outdated. Central plant operators are doing the very best they can within the confines of limited budgets, outdated equipment and sometimes, unreasonable regulations. Considering catastrophic water quality failure events that are so frequently highlighted in recent news, more and more Americans are realizing that they need to take responsibility to improve the taste, odor, appearance and sometimes, even the safety of centrally supplied water.

Municipal disinfection is crucial
There are nearly 250,000 public water supply systems in the US, serving everywhere from the smallest towns to major metropolitan areas. Approximately 90 percent of the US population currently receives their water through community water systems, with everyone else using private wells or other individually controlled supplies. Chlorine and chloramine are currently used by over 98 percent of all US water utilities that disinfect their drinking water.

The typical municipal water treatment process involves a series of different steps. Some of the major steps include flocculation and coagulation, sedimentation, filtration and disinfection. Chlorination is often performed at several stages of the treatment process. On surface water supplies, chlorination may be performed in the initial stages to combat algae and other aquatic life that will interfere with treatment equipment and subsequent stages in the process. The chlorination stage that we are particularly interested in occurs as the final treatment step, after the completion of the other major cleaning processes, where the concentration and residual content of the chlorine can be closely monitored. Chlorine remains in the water as it is distributed to homes and businesses, thereby retaining some of its ability to continue killing.
Chlorination can deactivate microorganisms through a variety of mechanisms, such as damage to cellular membranes, inhibition of enzymes, destruction of nucleic acids and various other currently unknown/undocumented mechanisms. The effectiveness of the chlorination process depends upon a variety of factors, including chlorine concentration, contact time, water temperature, pH value and level of turbidity.
Chlorination is undoubtedly the cheapest, most effective way to disinfect water that is stored, processed and distributed to homes and businesses at a municipal level. Chlorination is not 100-percent effective against all waterborne contaminants and has the potential to create several undesirable byproducts, but it is still the cheapest, most efficient killer to help protect from potentially deadly waterborne contaminants. Chlorine and its DBPs can be addressed through a variety of processes, such as metallic redox media and activated carbon catalysis.

Chloramine as an option
Chloramine has been used as a drinking water disinfectant in the US since 1929. In 1998, a US EPA survey estimated that 68 million Americans were drinking water disinfected with chloramine. Several major US cities (such as Philadelphia, San Francisco, Tampa Bay and Washington, DC) use chloramine to disinfect their drinking water. Chloramines are derived from the combination of chlorine and ammonia, where chlorine is substituted for hydrogen. There are three known species:

  • Monochloramine (Chloroamine, NH2Cl) – the very best biocide
  • Dichloramine (NHCl2)
  • Nitrogen trichloride (NCl3)

The various species of chloramine can rapidly shift from one form to another. The predominant species depends on pH, temperature, dissolved oxygen, carbon dioxide, organics in the water and the instantaneous chlorine-to-ammonia ratio. Chloramines can form spontaneously in water or be deliberately formed at the municipal level, since many localities actively choose chloramine as their disinfectant technology. Chloramines are chosen because monochloramine is more stable (less reactive) with other organics in water than free chloramine, meaning that it will stay active for longer in the supply and form significantly fewer trihalomethanes and other undesirable chlorine-related byproducts. Other DBPs can form though, such as toxic halonitriles (cyanogen chloride), halonitromethanes (chloropicrin) and other nitrogen-rich compounds. Some of these compounds can potentially endanger human health.

All chloramines are respiratory irritants, with trichloramine being the most severe. Chloramines also contribute to corrosion of metals as well as degradation of rubber. Due to their inherent stability, chloramines can be difficult to address with regular activated carbon. Catalytic or surface-treated activated carbon typically yields the fastest and most comprehensive results depending on what other contaminants are in the water.

DBPs—an overlooked threat
Epidemiological studies have related exposure to chlorination byproducts with birth defects, pregnancy complications, certain cancers like bladder, rectal and kidney (some studies also suggest that there might also be a causal relationship between chlorine byproducts and breast cancer in men and women), respiratory stress, eye irritation, skin damage, headaches and fatigue. Traditionally, the risk of chlorine DBPs has been downplayed since the risk of non-chlorination is far greater. In fact, the World Health Organization (WHO) in their Disinfection Guidelines state: “the risk of death from pathogens is at least 100 to 1000 times greater than the risk of cancer from disinfection by-products (DBPs) {and} the risk of illness from pathogens is at least 10,000 to 1 million times greater than the risk of cancer from DBPs.” Later in the paper, the position is asserted even more strongly: “The estimated risks to health from disinfectants and their by-products are extremely small in comparison to the real risks associated with inadequate disinfection, and it is important that disinfection should not be compromised in attempting to control such by-products. The destruction of microbial pathogens through the use of disinfectants is essential for the protection of public health.”

One might think that consumers must choose between illness and/or death from waterborne disease and microorganisms or a steady decline in quality of life from the permanent damage caused by chlorine compounds and the inevitable byproducts of disinfection. Today’s affordable water quality improvement technologies give consumers a much better option: disinfect and protect the water with chlorine or chloramine at the municipal level to keep it as safe as possible until it reaches the home, then reduce or completely remove the chlorine, DBPs and other contaminants, effectively enjoying the best of both worlds. Not unlike how packaging protects foods in transit, disinfectants keep our water safe until we are ready to use it.

Anatomy of a whole-house carbon filter
There are numerous carbon-based options available to protect your clients from chlorine tastes and odors, pesticides, herbicides, emerging contaminants and various DBPs. The simplest and cheapest option is a replaceable POE carbon cartridge, but it has a major downside: reduced flow and pressure. It has its place, but is rarely the best solution for whole-house use. Professionals will recommend a whole-house (POE) system that meets consumers’ budgets and performance requirements and can provide necessary flow and longevity. Whole-house carbon filters can be self-backwashing, non-backwashing upflow or non-backwashing downflow. Each has distinct advantages and disadvantages.

Non-backwashing downflow. A simple tank with in/out head and distribution system. Usually loaded with gravel and carbon media, water enters at the top of the tank, moves downwards through the media column and then up the riser. This compacts the bed, traps certain sediment and maximizes contact time with the media. The disadvantage is that the media column will be without adequate prefiltration; it will eventually become fouled with sediment and carbon fines, resulting in unacceptable pressure-drop and even channeling of the media, allowing passage of untreated water downstream.

Non-backwashing upflow. A simple tank with in/out head and distribution system. Usually loaded with gravel, metallic redox media and carbon media. Water enters downward through the riser, moves upward through the media column and then exits at the top of the tank. While the upflow service protects the media from sediment fouling, it minimizes the effective contact time with the media and often allows for bleed-through of contaminants.

Backwashing. A simple tank with a self-backwashing control head (preferably computerized and with a flowmeter) and distribution system. Usually loaded with gravel, metallic redox media, sediment filtration media and carbon media. Water enters at the top of the tank, moves downward through the media column and then up the riser. This compacts the bed, traps sediment through depth-filtration and maximizes contact time with the media. After a certain number of gallons have been processed, or after a certain calendar interval, the system backwashes to reclassify the media and purge trapped sediment or media fines.

Completing the treatment train
Whole-house carbon systems are frequently installed along with other treatment technologies, such as water softeners, ultrafilters and ultraviolet disinfection systems. Since I typically specify water softeners with highly chlorine-resistant resin, I usually recommend a whole-house carbon filter be installed after the water softener and before ultrafiltration or UV to ensure the highest quality of water downstream. Naturally, there are exceptions to every rule, so consult with your local Master Water Specialist and your equipment manufacturer when selecting any water quality improvement solution and deciding on the order of treatment/filtration.

Maintenance and best practices
Regardless of the system(s) that you install for your client, always be sure to properly disinfect the treatment equipment and downstream plumbing infrastructure after installation. Replace or augment the carbon and other media on a regular schedule as recommended by the equipment manufacturer and according to industry best practices.

Sustainability and certification
End-users are particularly interested in ensuring that every aspect of their lives is as environmentally responsible and sustainable as possible. Established standards, such as WQA/ASPE/ANSI S-802: Sustainable Activated Carbon Media for Drinking Water Treatment, cover raw activated carbon media products. Certification to this standard covers the sustainability of material sourcing, transportation, processing, distribution and end-of life planning to ensure a minimal environmental impact. In addition to the sustainability of products, the actual performance of systems can be measured against consensus-based standards such as NSF 42 for aesthetic effects. Often, dechlorination systems are customized for a specific project and will not necessarily be certified as an actual system.

Conclusion
As a water treatment professional, your primary responsibility is to provide your clients with the very best water at an affordable price in an environmentally responsible manner. Modern activated carbon and catalytic carbon-based filtration systems should be a prominent tool in your water quality management tool chest.

About the author
Greg Reyneke, Managing Director at Red Fox Advisors, has two decades of experience in the management and growth of water treatment dealerships. His expertise spans the full gamut of residential, commercial and industrial applications, including wastewater treatment. In addition, Reyneke also consults on water conservation and reuse methods, including rainwater harvesting, aquatic ecosystems, greywater reuse and water-efficient design. He is a member of the WC&P Technical Review Committee, currently serves as President of the PWQA Board of Directors and chairs the Technical and Education Committee. You can follow him on his blog at www.gregknowswater.com

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