Water Treatment Basics 101

If you get your water from a municipal source, it will have undergone treatment before entering your home.

However, municipal suppliers don’t completely remove contaminants from drinking water, and there are hundreds of impurities found in public water in trace amounts all across the U.S. You may want to look at private water treatment options for this reason.

If you’re a well owner, you’ll need to privately treat your water because, unlike municipal water, it doesn’t get treated for you before arriving at your home.

This article will look at the basics of water treatment, including public water treatment and the methods of water treatment at home.

🏙️ Community Water Treatment

Community water treatment is the process of filtering, disinfecting, and purifying water to make it suitable for drinking.

Community water treatment takes place on a big scale, using methods that are affordable for constant daily use.

The purpose of community water treatment is to keep the public supplied with safe, clean drinking water.

The U.S. Environmental Protection Agency (EPA) is responsible for ensuring this.

Community water treatment facilities are required to have their source water tested several times each week to ensure that it’s up to EPA standards.

Public water treatment plants have a duty to ensure that the water going out through their taps is safe for drinking, and anyone found not to be meeting EPA standards will be investigated and potentially fined.

What Are the 5 Stages of Water Treatment?

If you’re getting your water from a municipal supply, it will most likely go through the following treatment steps:

Screening – The first step in the community water treatment process, before any other surface water treatment, is screening. This removes large objects like sticks and leaves from raw water; solid matter is later removed during filtration.

Coagulation/Flocculation – The next two stages of surface water treatment are coagulation and flocculation. Coagulants aid in the removal of small particles like dirt and bacteria by causing them to bond together.  Once they do, these coagulated particles (or flocs) become heavy and sink; once the solids are removed, the water is ready for filtration.

Sedimentation – After flocculation, the process of flocs sinking to the bottom of the water supply is known as sedimentation.

Filtration – The next step in community water treatment is filtration, which removes any remaining pollutants using a physical barrier or biological process. The floc-free water passes through several filter types, including slow sand filtration, gravel filtration, and charcoal filtration.

Different filters have different pore sizes. For example, slow sand filtration typically has a pore size of less than 5mm, while charcoal filtration has a pore size of 0.045 mm-0.18 mm. This allows for particles of all sizes to be removed, including dust, chemicals, and bacteria.

Disinfection – The final stage of the community water treatment process is disinfection, which makes the water safe to drink by removing pathogens.

A disinfectant such as chlorine or chloramine is used in a water treatment plant to remove impurities that are difficult to remove by filtration, such as bacteria and viruses. These disinfectants, added in safe amounts to water, remain in water as it travels to our homes, ensuring potable water from our faucets.

The World Health Organization has more information on the water treatment process, found here.

Water Fluoridation

An additional public water treatment stage in many states is water fluoridation.

Water fluoridation is the process of adding fluoride, a mineral proven to prevent dental decay, to public water.

Most U.S. states add fluoride to water systems that serve communities, and few fluoridate individual wells and springs that supply water throughout the state.

You can check whether your local public drinking water systems fluoride your water here.

🏘️ Private Water Treatment

Private water treatment, or treating your own water at home, is becoming a more popular choice nowadays.

The average public water supply might be safe to drink, but our drinking water quality could still be a lot better. Most water supplies contain trace amounts of organic chemicals, disinfection byproducts, suspended solids, heavy metals, and other stuff that you wouldn’t want to drink.

The public water treatment process doesn’t purify raw water; it just filters it and removes disease-causing agents via filtration and chemical disinfection. We know enough from the Flint, Michigan disaster to know that public treated water isn’t always as safe as it should be.

If you’re worried that conventional treatment from your water distribution system isn’t enough, you can arrange for your own household water treatment.

Well Water Treatment Vs Municipal Water Treatment

For private well owners, there is no option but to filter their water at home using household water treatment. Private wells aren’t linked to a water distribution system, and don’t benefit from the water treatment technologies that public water receives.

If you own a well, it’s your responsibility to test your ground water quality and determine the appropriate treatment to ensure you have access to safe drinking water.

The biggest and most obvious difference between well water treatment and municipal water treatment is this: well water treatment is carried out at home, using a dedicated point of entry or point of use filter, while municipal water treatment is carried out on a large scale in a water distribution system.

📰 Common Water Treatment Methods

Some of the most common at-home filtered water treatment methods are listed below.

Point of Entry Water Treatment

Water softeners

What are they? Water softeners are single or dual-tank systems that are used to prevent hardness minerals – calcium and magnesium – from causing limescale issues.

How do they work? There are two common types of water softening systems: salt-based systems and salt-free systems. Salt-based systems use ion exchange to physically remove hardness minerals and replace them with sodium ions, while salt-free systems crystallize these minerals, preventing them from sticking to surfaces and forming scale.

What do they remove? Water softeners offer targeted calcium and magnesium removal. Some softeners can also remove low levels of iron.

How much do they cost? The average cost of a water softener is $1,200-$1,800. The annual running cost of a salt-based softener is about $150-$200.

Need to treat hard water? Read reviews of the best water softening systems here.

ion exchange water softener in basement

Whole-home cartridge filters

What are they? Whole-home cartridge filters are designed to filter water at the point of use by removing a variety of substances.

How do they work? Cartridge filters have a series of filter cartridges, each with its own purpose. Sediment filters and activated carbon filters are usually involved in a cartridge filter system. When water flows through these filter stages, different contaminants are trapped in the media.

What do they remove? Cartridge filters remove or reduce a range of impurities, from chemical contaminants to organic materials, natural organic matter, heavy metals, volatile organic compounds (VOCs), and more.

How much do they cost? The average upfront cost of a whole-home cartridge filter is $300-$700, with a maintenance spend of $250 to $550 annually.

Whole House Filter with Several Stages

Whole-home tank-based filters

What are they? There are numerous types of tank-based filters. Some are used to treat public water, while others are used in households that get their water from a private well. They typically contain one to two filter tanks, each with its own set of filter media.

How do they work? These filters use various filter stages to remove harmful contaminants from water. A tank-based system for municipal water usually has a carbon tank that removes particulates and some chemicals, while well water tank-based filters use air injection/oxidation to remove a handful of well contaminants.

What do they remove? Carbon tank-based systems can remove sediment, chlorine, VOCs, inorganic chemicals, and other harmful contaminants. An air injection tank removes iron, manganese, and sulfur.

How much do they cost? The average upfront cost of a whole-home tank-based water filter is about $1,100-$3,200, with an annual maintenance cost of $100-$300.

See our picks of the best whole home water filters, or the best systems for well water if you are on a private well.

Springwell whole house water filter system

Sediment filters

What are they? Sediment filters are designed to remove sediment from whole-home drinking water. They’re either installed as standalone filters or as first filter stages for systems like reverse osmosis, water softeners, and whole-home cartridge filters.

How do they work? There are different types of sediment filters that work uniquely depending on their design. Some sediment filters trap contaminants in their pores, while others hold onto contaminants until they can be manually flushed out of the filter.

What do they remove? Sediment filters remove larger particles like rust, dirt, sand, dust, and any physical material from water. Municipal water doesn’t typically contain sediment, so sediment filters are commonly used for treating well water supplies.

How much do they cost? The average cost of a point of entry sediment filter is $80-$200. Annual maintenance costs $20 to $70, depending on how frequently the filter needs to be changed.

sediment water filter

UV filters

What are they? UV filters use ultraviolet (UV) light to kill microorganisms, such as bacteria and viruses. These filters can be installed as standalone filters or added as a final stage to other whole-home water filter applications.

How do they work? A UV filter emits ultraviolet light at specific wavelengths that can kill microbes and prevent them from reproducing, without damaging other water components.

What do they remove? UV filters kill bacteria, viruses, protozoans, cysts, and other pathogens in water. UV purification is typically used by households who get their drinking water from a surface water or well water source, which is more likely to contain microbes than city water.

How much do they cost? The average upfront cost of a residential UV filter is $600-$1,200. Annually, you can expect to spend between $100 and $150 on UV filter maintenance.

viqua uv disinfection system

Point Of Use Water Treatment

Under-sink filters

What are they? Under-sink filters are installed underneath your kitchen sink to filter your drinking water before it leaves your faucet. There are several types of under-sink filters, including cartridge filters and reverse osmosis filters.

How do they work? Cartridge under-sink filters use a number of filter stages, including sediment and activated carbon filters, to remove different contaminants from water. Reverse osmosis filters follow the same concept, but these systems also feature a semi-permeable membrane, which removes up to 99.99% of contaminants larger than water particles.

What do they remove? It depends on the filter, but most under-sink filters can remove suspended particles, chemicals like chlorine, and heavy metals like lead, improving water quality. Reverse osmosis under-sink filters can also remove microbial pathogens, such as pathogenic bacteria.

How much do they cost? The cost of an under-sink filter is $150-$500, and up to $800-$1,000 for a reverse osmosis system. The annual cost, depending on filter replacement cost, is around $100-$400.

Undersink reverse osmosis system

Faucet mounted filters

What are they? Faucet mounted filters are installed directly onto your kitchen faucet, to filter water as you use it. When you turn on your faucet, water will pass through the filter before leaving the spout.

How do they work? A faucet mounted filter typically uses a carbon filter, like activated carbon, to treat water with adsorption. Adsorption is one of the most effective physical processes to improve drinking water quality.

What do they remove? Most faucet mounted filters can remove chlorine and other contaminants that affect water’s taste and odor. Some faucet mounted filters can also remove heavy metals like lead.

How much do they cost? Faucet mounted filters are affordable, costing around $40-$60, with an annual cost of $50-$100.

faucet filter

Countertop filters

What are they? There are two types of countertop filters: those that attach to your kitchen faucet via a hose and filter water as you use it; and standalone countertop filters that use electricity or gravity filtration to send water through filters.

How do they work? Countertop filters use filter cartridges to filter drinking water. Most countertop filters use several stages of filtration to remove both larger and smaller particles.

What do they remove? Standalone countertop filters typically remove the same particulates as faucet-mounted and under-sink filters, including chemical disinfectants like chlorine, heavy metals like lead, and other chemicals and impurities that affect water quality. Reverse osmosis countertop filters offer water purification and can remove or reduce disease causing agents that are unsafe for human consumption.

How much do they cost? Depending on the complexity of the system, a countertop filter can cost anything between $70 and $400, with an annual spend of $40-$150.

aquatru review

Water filter pitchers/dispensers

What are they? These types of water filters are most common, and most affordable. A simple filter pitcher or dispenser can be filled with water and produces a batch of filtered water within minutes.

How do they work? Water filter pitchers and dispensers typically use a filtration cartridge, such as activated carbon or ion exchange resin, to filter water. The filters use gravity filtration to improve water quality, and some pitchers can remove hundreds of impurities.

What do they remove? Water filter pitchers and dispensers can remove chlorine, volatile organics, metals like lead and copper, pesticides, herbicides, and industrial chemicals. They also remove water contaminants associated with cloudiness or color.

How much do they cost? Water filter pitchers cost around $20-$80 upfront. The annual cost of owning a water filter pitcher is about $30-$60.

Clearly Filtered water filtration pitcher