Water Quality and Treatment

Then and Now

By Ed Butts, PE, CPI

The processes and equipment associated with potable and industrial water treatment have without a doubt seen some of the greatest technological changes and expansion in the water supply industry over the past 50 years.

The history of water quality regulation and treatment is extensive and comprehensive. For example, the standard methods used in 1975 for removing or correcting the primary aesthetic problems from well water (i.e., iron, calcium carbonate/hard water, and manganese) generally used conventional ion exchange (water softening) or the multistep process of oxidation/reduction/filtration for iron and manganese.

Many improvements have been made to both these processes in the last 50 years, mostly with better grades of oxidative filter media and water softener resins. In addition, many new and sometimes exotic chemicals and contaminants are now regulated by the U.S. Environmental Protection Agency and included in public health water quality standards—some of which weren’t even known in 1975.

So, let’s examine the changes that have occurred in water treatment during the past five decades and look ahead with emphasis in the following eight general groups:

• Pathogenic viral, bacterial, fungal, and parasitic contaminants
• Non-pathogenic and potentially pathogenic contaminants
• Impact of the Groundwater Rule
• Inorganic and synthetic and volatile organic contaminants
• Aesthetic contaminants
• Radionuclides Rule
• Lead and Copper Rule
• Emerging contaminants.

Background

The Safe Drinking Water Act of 1974 celebrated its 50th anniversary last year. Along with its amendments authorized by the EPA in 1986 and 1996, it enforces national regulatory standards to protect public health through monitoring and regulation of drinking water and its sources against naturally occurring or human-made contaminants.

The SDWA standards included health-based maximum levels for microbiologic, inorganic, chemical, and other contaminants in drinking water supplied from regulated public water systems (Figure 1).

A public water system (PWS) is any water system serving 15 or more connections or an average of 25 or more people per day for at least 60 days per year. Water systems are further classified as community water systems, transient-noncommunity water systems, and nontransient-noncommunity water systems.

The list of Interim Primary Drinking Water Standards was released in 1975. It featured 21 contaminants including arsenic, lead, mercury, nitrates, radionuclides, turbidity, and coliform bacteria.

The SDWA directs the EPA to consider the health effects and occurrence information for unregulated contaminants as well as making decisions to place contaminants on the list at five-year review phases, culminating in the current release of a Contaminant Candidate List 5 (CCL5) in 2022.

Phase I became effective in 1989 and consisted of the original eight volatile organic contaminants. Phase II became effective in 1993 and included 10 additional volatile organic contaminants, 14 original synthetic organic contaminants, and the original eight inorganic contaminants. It roughly doubled the number of drinking water standards.

The chemical contaminants were thereafter promulgated in 1993 into phases collectively called the Phase II/V Rules or the Chemical Contaminant Rules.

These rules regulated more than 65 contaminants in the three contaminant groups. Over the five-year review period, the EPA gathered and analyzed occurrence and health effects data. Through the Phase II/V Rules, the EPA established the following:

• Maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs)
• Monitoring requirements
• Best available technologies for removal of the 65 listed chemical contaminants.

Subsequent lists and testing requirements have been released over the intervening years with progressively more regulated and unregulated contaminants.

The current CCL list includes 66 chemicals; three chemical groups: per- and polyfluoroalkyl substances, cyanotoxins, and disinfection byproducts; and 12 microbes that were selected from a universe of chemicals used in commerce, pesticides, biological toxins, disinfection byproducts, and waterborne pathogens.

In fact, it is becoming increasingly difficult to adequately track new and emerging contaminants, for as of this writing, the EPA is considering expanding the list of regulated and unregulated contaminants.

Most states have adopted the EPA rules with minor modifications for regional and local deviations.

Testing and monitoring requirements vary with the size of the served water system or population, water system classification, and type of source with a repeat cycle of every three years for groundwater sources being the most common.

Reduced monitoring of certain contaminants is possible with consistent non-detectable or below MCL levels after an initial series of tests. Most aesthetic standards, including iron, manganese, and hardness, continue to be unregulated contaminants on the federal level although some states issue MCLs and regulate and enforce the levels.

Pathogenic Viral and Bacterial Contaminants

Most of the pathogenic contaminants we currently deal with were already present, identifiable, and enforceable in 1975, but their potential risk to human health was often not as well known. Pathogens are organisms that can cause a rapid onset of illness or disease. They can be transmitted through human-to-human contact, bodily fluids, and food or water transmission.

There are different types of pathogens, and they can cause a wide variety of different diseases, with some being more severe than others. As human bodies are warm and rich in nutrients, they can provide a pathogen with an ideal environment as a host in which to grow and multiply. There are several different
types of pathogens, but we’re going to focus on the four most common types found in water supplies: viruses, bacteria, fungi, and parasites.

The Total Coliform Rule (TCR) was originally implemented by the EPA in 1989. Its purpose was public health protection by identifying and reducing levels of pathogens in water, primarily fecal and E. coli bacteria. This was accomplished through enhanced monitoring and control of total coliforms in all public water systems.

Generally, the TCR established a maximum contaminant level based on the presence or absence of total coliforms; modified monitoring requirements including testing for fecal coliforms or E. coli; required use of a sample site plan; and routine sanitary surveys for systems collecting fewer than five water samples per month. The TCR has since undergone several updates and revisions since its release.

Another type of bacteria, Legionella, causes a malady known as Legionnaires’ Disease, which acquired its name in 1976, when an outbreak of pneumonia occurred among people attending a convention of the American Legion at a hotel in Philadelphia. More than 32,000 cases of Legionnaires’ Disease and more than 600 outbreaks occurred between 1995- 2005. The disease is particularly associated with hotels, fountains,cruise ships, and hospitals with complex potable water systems and cooling systems.

Although the risk of Legionnaires’ Disease being spread by large-scale water systems cannot be eliminated, as it is often spread through air, it can be greatly reduced by writing and enforcing a highly detailed systematic water safety plan appropriate for the specific facility involved. Some of the preventive measures include proper system design, reducing the production of aerosols, regular line flushing, prevention of water stagnation and buildup of biofilms, and adequate chlorine doses.

Fungal and Parasitic Contaminants

Unquestionably, some of the greatest impact to water quality since 1975 occurred with the increased presence and identification of fungi and parasites.

Fungi are ubiquitous, heterotrophic organisms present in oceans, freshwater, and drinking water. They can be divided based on their ability to colonize different environments into three groups: mesophilic fungi, generalists, and specialists.

The occurrence of fungi in drinking water has received increased attention in the past few decades and they are now generally and universally accepted as drinking water contaminants. Knowledge about the occurrence and diversity of fungi in water has increased considerably from a low knowledge base to one of increased importance.

The emergence of parasites Giardia Lamblia and Cryptosporidium has significantly changed surface water treatment, and in some cases, groundwater treatment. These two parasites are known to cause gastrointestinal diseases in humans and are readily transmitted through water supplies.

Due to their tough outer coating, they are resistant to normal doses of chlorine and can be deactivated using enhanced methods of filtration accompanied by ultraviolet exposure or adequate chlorine or chlorine dioxide doses with sufficient contact time.

Although the parasites are uncommon in properly constructed deep groundwater sources, they can and often do occur in water supplies subject to the influence of surface water. This type of water source is regulated by the EPA as a “Groundwater Under the Direct Influence of Surface Water” source. These sources must generally adhere to the same stringent filtration and disinfection standards as surface water supplies.

Non-Pathogenic and Potentially Pathogenic Contaminants

In addition to pathogenic contaminants, there are several non-pathogenic constituents that can impact water quality within the distribution system or treatment processes. Many of them are harmless, while some are a nuisance and others are potential pathogens. Many of these are being examined for eventual addition to water quality regulations as emerging contaminants. The list in Table 1 comprises the most common ones.

The Groundwater Rule

The Groundwater Rule is one of the many outcomes from the 1996 amendments to the 1974 Safe Drinking Water Act. The amendments required the EPA to develop regulations that require an adequate level of disinfection of public groundwater systems to a degree defined “as necessary” to protect public health.

Obviously, this wide-open term provided the EPA with a great deal of latitude it could use while formulating and developing proposed and final rules.

Initially, the Groundwater Rule was commonly referred to as the Ground Water Disinfection Rule, but the term was subsequently shortened to the current version to more closely align with the actual intent of the rule and the role that natural disinfection processes may play.

The rule was originally developed as the result of several groundwater studies and disease outbreak data that demonstrated that pathogenic viruses and bacteria can occur in public water systems that use groundwater, particularly groundwater delivered to consumers without treatment of any kind.

Viral and bacterial pathogens, often found in fecal contamination from animal and human feces, can readily reach groundwater, and in turn, drinking water supplies. This can occur through shallow or even deep wells via a route of inadequate or defective well depth, sanitary seal, broken or corroded well casings, wellhead flooding, failed septic systems, and wells constructed too close to a septic drainfield.

Waterborne disease caused from viral or bacterial pathogens usually results in gastrointestinal symptoms such as diarrhea or vomiting, which usually doesn’t require medical intervention for healthy adults but can be serious or even fatal to high-risk groups of the population such as young children, the elderly, and people with compromised immune systems.

Although available data does not indicate that any more than a small percentage of wells or aquifers contain fecal contamination, the severity of the possible health impacts and the number of affected water consumers potentially exposed to the pathogens indicate that some type of regulatory response is needed.

The Groundwater Rule applies to more than 150,000 public water systems serving more than 100 million water consumers in the United States and is also applicable to water systems where groundwater supplies are mixed with surface water supplies. The rule took effect on January 8, 2007.

Inorganic, Synthetic, and Volatile Organic Contaminants

The three groups encompassing inorganic, synthetic, and volatile organic contaminants have experienced the greatest growth since 1975 with more than 300% of additions. As more potentially harmful contaminants are discovered, the list of inorganic, synthetic, and volatile organic contaminants will likely continue to expand in the coming years.

Aesthetic Contaminants

Although problems with inorganic and organic contaminants, bacteria, or viruses represent a greater human health hazard, problems associated with the presence of hardness, iron, manganese, or hydrogen sulfide are usually more visible and impactful to the water consumer. And therefore, usually more of an immediate concern. This is due to the aesthetic and possible taste and odor effects these contaminants place on the water system and individual residences.

Water hardness is a condition caused from the excessive concentration of calcium (Ca) and magnesium (Mg) ions. The presence of elevated hardness is often evident and verified from the higher consumption of laundry and dishwater soap, a calcium scum buildup and encrusting scale on water heater elements, and the familiar white spots often seen on glassware, fixtures, and silverware.

While there is no defined maximum level of hardness, problems with groundwater start to typically be seen when hardness levels as calcium carbonate rise above 60 mg/l (equal to 3.50 grains per gallon or gpg).

Depending on other constituents in water, mainly iron and manganese, many water systems successfully operate using groundwater sources with hardness levels as high as 150-250 mg/l. The suggested maximum secondary level for hardness is 250 mg/l.

Water hardness is one of the only water contaminants where too little as well as too much can result in problems. Too soft of a water, normally below 20-40 mg/l, can cause its own problem by accelerating corrosion in many types of metallic pipe, notably copper, while too much, generally above 125- 150 mg/l, causes staining of glassware and fixtures as well as possible pipe plugging and water heater failure from scaledover elements. The best condition is to frequently try to find a balance between 60-100 mg/l.

Water delivered from any well can be subject to the possibility of entrained gases. The most common are hydrogen sulfide (H₂S), carbon dioxide (CO₂), methane (CH₄), ammonia (NH₃), nitrogen (N), and radionuclides, principally radon (Rn)

When measuring gases, the term “concentration” is used to describe the amount of gas by volume in the air or water. The two most common units of measurement are parts per million (ppm), which is equal to milligrams per liter (mg/l), as well as percentage of concentration expressed as %. Except for radon, gases are secondary contaminants in a water supply and considered to be an aesthetic nuisance in nature and impact.

Radionuclides Rule

Many people are surprised to learn that drinking water sources, especially groundwater, can contain radioactive elements, but radionuclides occur naturally in many rocks and minerals. Some radionuclides, such as uranium, have been present since the Earth formed. Others, such as radon and radium, are the product of the decay of those original radionuclides.

There are various forms and allowable levels of regulated radionuclides in water such as combined radium 226/228 and gross alpha. Radionuclides in water can be a concern for human health because several are known to be toxic or carcinogenic.

The EPA published the Radionuclides Final Rule on December 7, 2000. The new rule revised the original radionuclides regulation that had previously been in effect since 1977. The revisions set new monitoring requirements for community water systems and ensured customers receive water meeting the maximum contaminant levels for radionuclides in drinking water.

Lead and Copper Rule

The EPA published a regulation to control lead and copper in drinking water in 1991. This regulation is known as the Lead and Copper Rule and also referred to as the LCR.

Various revisions to the rule have been implemented since it was published. The 1991 rule established a maximum contaminant level goal (MCLG) of zero for lead in drinking water and a monitoring and treatment technique to reduce corrosion of lead and copper within the distribution system.

Although they are not typical of groundwater quality, the possible presence of lead and copper can have a negative impact on selection of a water source. Lead and copper enter drinking water primarily through a leaching or dissolving action occurring by prolonged water contact with plumbing materials such as service pipe, fixtures, and solder. It can also originate from materials in the water pumping, treatment, or distribution system, and more rarely, from the source itself.

Exposure to lead from leaching service lines can occur anywhere in the United States, but the presence of older lead service lines is more predominant in the Midwest and East Coast regions as heavy development preceded that on the West Coast by several decades.

Excessive exposure to lead and copper is known to cause health problems ranging from mild stomach distress for low copper levels to severe learning disabilities and irreparable brain damage for elevated lead levels. Beyond routine monitoring for the elements in the source, the treatment technique for the rule requires water systems to monitor drinking water at customer water taps. If lead concentrations exceed an action level of 15 parts per billion (15 ppb) or copper concentrations exceed an action level of 1.30 parts per million (1.30 ppm) in more than 10% of customer taps sampled, the system must undertake a number of additional actions to control corrosion. Schools and childcare facilities are under increased scrutiny due to the greater number of exposed individuals and the effects to younger brain formation being more detrimental.

Advancements to Online Water Treatment

The 50-year period between 1975 to today has seen significant growth and cutting-edge advances in drinking water and industrial water treatment for online (pump and treat) applications.

For example, the two methods typically used for iron and manganese removal in 1975 were either an oxidative process (chlorination followed by filter sand media to remove oxidized material) or manganese greensand with potassium permanganate feed. Today, there are many more methods capable of removing these constituents as well as many other pathogenic and non-pathogenic contaminants.

Enhanced and new methods of mechanical and media filtration and screening methods for macro, micro, ultra, and nano applications are just a few of these advancements. These include new cartridge and bag filters and specialty filter medias for oxidation of iron and manganese; ion (cation) exchange media for water softening; anion exchange media for arsenic, tannin, nitrate, and fluoride removal; and electrokinetic media, electrocoagulation, phytoremediation.

Groundwater treatment of coliform and iron-laden water has benefited from the use of dry chlorine feeders dropping chlorine pellets directly into the well. Powdered activated carbon (PAC) and adsorptive media have aided tastes and odors as well as granular activated carbon (GAC), mixed-media for multiple contaminants, and chlorine generators, ozone, and ultraviolet disinfection processes.

One of the greatest improvements to water treatment since 1975 has been the expanded use of reverse osmosis for desalinization and enhanced removal of heavy metals and microscopic constituents. These systems are now widely used for municipal, commercial, industrial, whole house, and point-of-ofuse
treatment applications.

Technologies such as packed tower aeration (air stripping) and significant improvements to pretreatment and membranes used for reverse osmosis have greatly expanded in use and application. Although this was a known technology in 1975, it was infrequently used for potable water systems at the time due to the need of adequate pretreatment, high incidence of membrane fouling, high operating pressure requirements, and
premature membrane failure.

Groundwater Contamination and In-Situ Remediation

Many natural constituents and human-induced contaminants are routinely found in groundwater, with the problem exploding in both incidence and degree throughout many regions since 1975.

However, hydrogeologists have made great strides in identifying, characterizing, modeling, tracking, and removing groundwater contaminants in soils and aquifers during the past 50 years.

The principal natural constituents include dissolved salts, iron, manganese, fluoride, calcium, arsenic, radionuclides, and trace inorganic metals.

In arid regions with limited and slow rates of recharge, the low levels of percolation may result in mineralized water of inferior quality, generally high in concentrated salts (for example, sodium chloride).

In more humid climates, the constant weathering of sedimentary rock leaches calcium and magnesium from the rock, creating excessively high hardness levels and increased levels of dissolved iron and manganese into groundwater.

The most common pollution sources are the result of human interaction and causes. This category generally includes disposal of wastewater and solid waste; disposal of industrial wastewater; use of fertilizers, pesticides, and insecticides; and disposal of byproducts and waste from mining activities and
nuclear energy waste.

Contamination from human-induced activity can be caused by several different operations and events: water well overpumping; excessive or improper use of fertilizers, pesticides, or herbicides; mining tailings; process tailwater; stormwater runoff; hazardous waste; extended and unfettered urban development; change of climatic conditions; misuse of chemicals; improper disposal of organic and inorganic chemicals; sewage or industrial waste storage, seepage, or pipe leakage; river network interruption; mineral processing of radioactive minerals; and cemeteries.

A common groundwater contaminant, solvents, can be found in aqueous or non-aqueous forms. Many pollutants, such as trace elements, are concentrated in the discharge material and water and occur from various anthropogenic activities that can be extremely toxic and lethal to humans and animals.

Additional contaminants that have been detected in groundwater and are a direct cause from human activities include hydrocarbons, halogens, biphenyls, industrial chemicals, and biological contamination (i.e., coliform bacteria, viruses, and parasites).

Groundwater contamination generally occurs when man-made, refined natural products or synthetic substances or compounds—petroleum products, heavy metals, surface water runoff, industrial chemicals—migrate into a groundwater system and cause it to become unsafe for direct human use and consumption. Current estimates of the extent of groundwater contamination suggest that 0.5% to 2% of the groundwater in the Lower 48 United States may be contaminated at any one time.

In-situ or direct dosing water treatment involves mixing and dosing chemical reagents or processes directly into the affected surface water body or aquifer for the treatment or remediation of a number and variety of issues instead of pumping water through a water treatment plant.

Much of this growth has been in groundwater treatment of affected aquifers. Superfund groundwater cleanup technologies and strategies have greatly evolved since the program’s inception in 1980. Initially, a groundwater pump-and-treat method was the primary technology and strategy used, as this was often the only viable groundwater remedial approach at the time.

However, over the subsequent years, new groundwater treatment technologies and approaches have become available, allowing flexibility in how aquifer cleanup goals can be achieved and measured. These include new and sometimes radical methods for removing heavy metals and inorganic, volatile, and synthetic organic contaminants from aquifers.

Depending on site conditions and cleanup goals, response actions may include active or less active treatment approaches. For certain sites, monitored natural attenuation, which relies on natural processes that decrease or attenuate soil and groundwater contaminant concentrations, may be used to complement or as an alternative to conventional pump-and-treat or other technologies.

In addition to attenuation, other in-situ processes primarily developed over the past 50 years such as adsorption, biodegradation, desorption, diffusion, dispersion, dilution, sorption, and aerobic (in oxygen) and anaerobic (free from oxygen) processes are used.

Emerging Contaminants

Per- and polyfluoroalkyl substances (PFAS) were regulated by the EPA on April 10, 2024, with the final National Primary Drinking Water Regulation for six PFAS.

Other emerging contaminants that could be considered for potential regulation include perchlorate, microplastics, pharmaceuticals, antibiotics, and hormones—which all are garnering increased attention from public health experts and the federal government.

Many of these emerging contaminants will be funded using the Drinking Water State Revolving Fund (DWSRF). In addition to surface waters, these contaminants have also been detected in a significant number of groundwater sources around the United States that are used for drinking water.

Undoubtedly, many of these emerging contaminants will be subject to future regulation and MCL levels. The EPA announced on December 14, 2023, that it is beginning the process to prioritize five additional toxic chemicals for risk evaluation under the Toxic Substances Control Act, one of which is vinyl chloride that is used in the manufacturing and processing of polyvinyl chloride (PVC).

Many of these are destined to be added to the regulated lists of inorganic, synthetic, and volatile organic contaminants.

Examples of potential DWSRF emerging contaminants include:

• Perchlorate
• Strontium
• Manganese
• 1,4-Dioxane
• Tungsten
• Naegleria fowleri (Brain-eating amoeba)
• Cyanotoxins
• Microcystins
• Cylindrospermopsin
• Anatoxins
• Saxitoxins
• Lithium
• Legionella pneumophila
• Disinfection byproducts
• Per- and polyfluoroalkyl substances
• Chlorate
• Formaldehyde.

This concludes this month’s installment of Engineering Your Business. We will continue our year-long look at changes over the past 50 years next month with an update on water wells, drilling rigs, and pump hoists.

Until then, work safe and smart.

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Ed Butts, PE, CPI, is the chief engineer at 4B Engineering & Consulting, Salem, Oregon. He has more than 40 years of experience in the water well business, specializing in engineering and business management. He can be reached at epbpe@juno.com.