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Is Tap Water Bad for Plants? Here Are the Facts

An Old Faucet Running Water Into The Garden.

As Victorious Gardeners, we want to keep our garden crops healthy so they can keep us healthy.  Since most living things are more water than anything else, it’s right to ask, “Is tap water bad for plants?” And if it is a problem, how do we make tap water safe for plants?

This article answers those questions and backs up the answers with hard data.  As with many things, there’s no firm “yes” or “no” answer.  It all depends on the circumstances.

The links in this article provide support for the information we’re discussing.  Some of these links also offer evidence of the effects of tap water on people.  We’re providing these links so you can start an investigation if you’re interested.

Video: Is Chlorine and Chloramine in Tap Water Harmful to Plants?

Here’s What We’ll Learn About Tap Water

We’ll discuss household tap water from municipal water supplies.  If you’re fortunate enough to have your own well or spring-fed water, this information won’t apply.  You might want to check our articles on how hard water and softened water affect plants.

Are you already watering your house plants and garden with tap water?  If they’re are healthy, then there’s nothing to worry about.  Keep using tap water without any concerns.

If your plants look unhealthy or have yellowed or spotted leaves, your water could be a problem. 

We’ll do a deep dive into the chemicals used to purify tap water.  These chemicals are necessary because we need a water source that is free of ugly disease bugs.  The problems arise when chemical levels are safe for people but not for plants.

Many people have concerns about chlorine in water, but we’ll discover it isn’t much of a problem for plants in soil.  The suspicious chemicals are chloramine and especially fluoride.  All of these are harmful chemicals at any level in hydroponics or aquaponics.

Continue reading to learn more about tap water and plants.

Where Does Municipal Tap Water Come From?

Water sources for municipal supplies are usually reservoirs, lakes, rivers, streams, springs, or wells.  Government regulations set the standards that make tap water safe for drinking.

The EPA claims tap water in the United States is safe for people.  Our environmental safety is their responsibility, but sometimes things can go wrong.

The recent problems in Flint, Michigan are only one example.  Here’s another article by the U.S. Geological Survey about the growing PFAS problem in tap water.

What’s in my Tap Water?

Most gardeners haven’t had any trouble using tap water on their plants.  But is there a point where it can become unsafe for plants?

Let’s start with some basic facts about tap water:

  • It has an average pH level of 7.5, which is more alkaline than rain water.  This is an average, so some areas are less alkaline, and others are more.  As the pH increases, the plants can’t efficiently absorb nutrients from the soil.  They prefer slightly acidic conditions for the best growth.
  • Municipal water is like any other water in nature.  Depending on the water’s origin, it has varying amounts of dissolved minerals.
  • The hardness caused by the minerals varies depending on where you live.  Water treatment plants usually don’t soften tap water.  That’s because hardness minerals are harmless and beneficial.
  • Water treatment removes nitrates.  This is because high nitrate concentrations can cause problems for babies.  The babies come first, but that makes tap water less desirable for plants.
  • Tap water contains disinfecting chemicals to prevent contamination.  Your state and local water authorities determine what chemicals they will use and EPA regulations set the standards.
  • Another possible addition to your tap water would be fluoride.  Contact your local water department to determine if they add it to your water supply.

The Tap Water Trio:  Chlorine, Chloramine, and Fluoride

First, we need to get some background information on these chemicals.  Then, we’ll dig into their effects on plants.

Chlorine and chloramine are the two chemicals used most often to disinfect water.  Mixing them makes them both less effective.  The mixture also lowers the water quality because it causes a bad taste and odor.

Fluoride is an additive to prevent tooth decay, but it’s also toxic enough to be a disinfectant.

The following chart shows the maximum allowable levels of these chemicals in water.  The EPA calls these numbers the Maximum Contaminant Level (MCL).

Please note that these numbers are the maximum safe levels for people, not plants.

MCL in mg/l (ppm)MCL in mg/gal
Chlorine4.015.5
Chloramine4.015.5
Fluoride4.0
Bottled water 0.8 – 2.4 mg/l.
15.5

These numbers are the maximum enforceable standard.  The EPA doesn’t want water treatment facilities to exceed these numbers.

Now, we can throw in some government confusion.  Infants and children still developing teeth shouldn’t get that much fluoride.  The EPA says they shouldn’t receive more than 2 ppm of fluoride daily.

But the EPA says this is a recommendation and isn’t enforceable.  Children who receive more fluoride could develop dental fluorosis.  So, why isn’t the enforceable fluoride standard set at 2.0 ppm?

And the government can complicate things even more.  The US Public Health Service has recommended since 2015 that fluoride in water shouldn’t exceed 0.7 ppm.

They claim this level will prevent tooth decay and avoid causing dental fluorosis.  So, why isn’t the fluoride standard set at 0.7 ppm?

These are more examples showing we need to take what experts say with a grain of salt.  They really don’t know the safe level of added fluoride.  What if it’s zero?

Are There Other Ways to Disinfect Tap Water?

Other effective ways to disinfect water include UV light and ozonation.  These methods work great at the water plant but can’t disinfect water moving through pipes.

Chlorine and chloramine can travel with the water and disinfect it all the way to your tap.

The chlorine remaining in the water at your faucet is the “chlorine residual.”  This residual ensures you receive disinfected water at your faucet.  The residual chlorine level usually varies from 0.2 to 1.0 mg/l (or ppm).

The residual level can vary greatly depending on whether you’re near or far from the water treatment plant.

Chlorine in Tap Water

Three forms of chlorine are most often used to disinfect tap water:

  • Chlorine Gas.  This is the least expensive and most effective way to disinfect water.  Those factors make chlorine the preferred disinfectant.  This greenish-yellow gas is heavier than air and is highly toxic.
  • Sodium Hypochlorite.  If you use bleach for your laundry, you’re using sodium hypochlorite.  This is the easiest of the three to handle but has a short shelf life.
  • Calcium Hypochlorite.  This is a white solid sold as pellets or granules.  It has a penetrating odor and will increase the pH of water (making it more alkaline).  By itself, it can create enough heat to explode.

Chlorine evaporates from tap water in one to five days.  The time needed depends on how much water needs dechlorinating.

You can speed up the evaporation by boiling the water for 20 minutes.  Please make sure the water is at room temperature before watering any plants.  Cooking them while they’re still in the ground isn’t a good idea!

Since water needs filtration before adding chlorine, every water plant filters before disinfecting. If any organic matter is in the water, chlorine combines with it.  This forms “disinfection byproducts,” which are toxic and may cause cancer

Tap Water Disinfected With Chloramine

Chloramine is a disinfectant in about 1/3 of US water supplies.  This mixture of chlorine and ammonia is more stable than chlorine but is also less effective.  Chloramine is more corrosive than chlorine.  Besides being corrosive, it also degrades rubber and leaches metals from pipes.

Chloramine can take three forms: mono-, di-, or trichloramine. These forms depend on the mineral content and pH of the water.  Monochloramine is the form that’s most often present in water.  It changes forms depending on the water condition.

They’re all respiratory irritants, with trichloramine being the worst.  Chloramine-treated water may irritate when used in tight spaces like showers.

Chloramine forms fewer disinfection byproducts than chlorine.  However, the ones that form are more toxic than those formed by chlorine.  This shouldn’t be a problem anyway after filtering all the organic matter from the water.

The extra stability of chloramine means it lasts much longer than chlorine.  It won’t evaporate from water; you can’t remove it by boiling or distilling it.  The best way to remove chloramine is by filtration.  The problem is even some reverse osmosis filters can’t do it.

For more information about chloramine, see Concerned Citizens About Chloramine.  Chloramine bans are in effect in most of Europe.

Fluoride in Tap Water

Fluoride is the ionized form of the element fluorine.  Chemists rate fluorine as the most chemically reactive element.  To quote from Lenntech’s website:

“Fluorine readily forms compounds with most other elements, even with the noble gases krypton, xenon and radon. It is so reactive that glass, metals, and even water, as well as other substances, burn with a bright flame in a jet of fluorine gas.

In aqueous solution, fluorine commonly occurs as the fluoride ion F. Fluorides are compounds that combine fluoride with some positively charged counterpart.”

Fluoride is a normal part of soil, water, and air.  We can’t escape it since fluorine is the 13th most abundant element in the earth’s crust.  Since fluorine is so reactive, it always combines with other elements.

Why is Fluoride Added to Tap Water?

Preventing tooth decay is the only reason for adding fluoride to water.  Fluoride is a questionable treatment for tooth decay.  Click on that link to start your trip down the rabbit hole to learn the truth about fluoride.  That website has a massive amount of information about fluoride’s effects.

Natural Fluoride Compounds

Calcium fluoride is the most prevalent fluoride compound in soil and water.  Fluoride compounds are also in foods, especially tea, coffee, and seafood.

Experts don’t consider fluoride a nutrient for people.  However, micro quantities help maintain the strength of bones and teeth.

Fluoride in living things becomes part of organic molecules.  That means the fluoride binds with carbon and other elements.  These compounds aren’t a significant part of soil and water.

Fluoride isn’t a nutrient for keeping plants healthy, either.  They’ll suffer harm when levels get too high.  Natural fluoride exposure for plants happens through water, air, and soil.

The natural fluoride levels range from almost nothing to 10 parts per million.  Most water in rivers, lakes, streams, etc., ranges from 0.1 to 0.2 ppm.  Ocean water ranges from 1.2 to 1.4 ppm.

Areas near active volcanoes can have extreme levels of natural fluoride.  This problem compounds further in third-world countries.  Many industries in these areas dump fluoride compounds straight into the air, water, and soil.

In those areas, fluoride can be at toxic levels for all living things.

Fluoride Compounds Used in Water Treatment

  • Sodium Fluoride.  This dry salt compound was the first chemical used to fluoridate water.  Small water systems still use it.  This fluoride is more dangerous than calcium fluoride.
  • Fluorosilicic Acid.  Most of the fluoridated water systems in the US use this liquid.  It replaced sodium fluoride as the preferred chemical.  Other names for it include hydrofluorosilicate, HFS, or FSA.
  • Sodium Fluorosilicate.  This is another dry salt.
  • The fluoride in water won’t evaporate.  Unless filtered out, it stays in the water.

Worldwide, fluoride use in water varies.  A few places mandate it, some prohibit it, and others leave it to the local government.

The Effects of Chlorine, Chloramine, and Fluoride on Plants

We will now investigate the possible plant problems caused by these chemicals.  Unfortunately, there aren’t many studies about their effects on plants.

How Chlorine Affects Plants

Chlorine Study #1

A study in 1987 at the Connecticut Agricultural Experimentation Station tested chlorine exposure on 11 species of potted plants.

Since we’re a website about growing our own food, we’ll look at the results for the four vegetables used in this study.  These vegetables were:

  • Calabrese broccoli (Brassica oleracea var. italica)
  • Salad bowl lettuce (Lactuca sativa)
  • California wonder peppers (Capsicum anuum)
  • Rutgers tomatoes (Lycopersicum esculentum)
Here are the critical points of this study:
  • All the plants germinated from seeds.
  • They divided the plants into six groups.
  • Then they gave the plants water with chlorine levels of 0, 2, 8, 18, 37, or 77 mg/l (ppm).
  • The vegetable seeds had normal sprouting regardless of the chlorine level.
  • All the plants were slow to show any damage from the chlorine.
  • After three weeks, the seedlings using 37 or 77 mg/l chlorine in water had visible signs of damage.  They lacked vigor and had chlorosis (yellowed leaves).
  • The pepper and tomato seedlings started showing damage at 8 mg/l of chlorine.
  • Lettuce showed signs at 18 mg/l of chlorine, and broccoli at 37 mg/l.
So, what did Study #1 show?
  • First, the chlorine level needed to harm a plant depends on the plant.
  • We can say that plants getting water with 37 mg/l or more of chlorine will suffer harm.
  • Plants grown in soil don’t appear to suffer chlorine damage at levels found in tap water.

Chlorine Study #2

The American Society for Horticultural Science published this study on January 19, 2023.  It looked at the effects of tap water on hydroponic Rex lettuce (Lactuca sativa).  Note below that this study used the same types of water as Study #1.

Here are the key points:
  • They used reverse osmosis (RO) water with the same chlorine levels as tap water.
  • The specific chlorine levels were 0, 0.5, 1, 1.5, 2, and 4 mg/l (ppm).  Adding any required fertilizers completed the set-up.
  • In three days, phytotoxicity occurred in the plants given water with 1 mg/l or more of chlorine.  Phytotoxicity is damage to plants caused by chemicals.
  • Another test was growing lettuce in sandy soil with 10mg/l of residual chlorine.  This lettuce suffered chlorosis, leaf necrosis (cell death), and stunted growth.
  • The plants treated with 0.5 mg/l or more of chlorine showed different degrees of phytotoxicity.  This was three days after transplanting the plants to the hydroponic system.
  • All plants treated with 4 mg/l of chlorine showed damage.  This happened three days after moving to the hydroponic system.
  • By day 10, all the leaves had symptoms of damage from any chlorinated water.
  • The plants treated with 0.5 mg/l water showed the least damage after day 10, and new leaves showed no symptoms.
  • Lettuce watered with 0 mg/l of chlorine showed no phytotoxic symptoms.
What can we learn from Study #2?
  • Plants raised in hydroponics systems are more sensitive to chlorine.  They’ll suffer damage from any chlorine in the water.

What can we conclude from these two studies?

  • Since the researchers used the same variety of lettuce in both studies, we can get a clearer picture.
  • If you’re growing plants with hydroponics, use dechlorinated water.  The safest approach with hydroponics is to call any chlorinated water dangerous.  This would also apply to aquaponics.
  • It appears that some chlorine binds to soil particles, leaving less for the plants to absorb.
  • If your tap water chlorine is within the EPA 4 mg/l limit, watering plants in the soil won’t cause a problem.

Chlorine’s Effect on Soil Organisms

Chlorine kills bacteria in soil and compost.  The chlorine has little effect because the bacteria reproduce so quickly.

In one study, researchers applied high-chlorine water to the soil.  This continued for 126 consecutive days. Two days after they stopped, soil microorganisms returned to their original levels.  They also found this happened at all soil depths.

Chlorine binds to the surface of soil particles.  Most of the chlorine binds to the surface soil, and little of it travels lower.

In one study, researchers tested water chlorinated at 5 ppm.  It only killed organisms in the top half-inch of soil. Organisms deeper than one-half inch were thriving.

Some Other Facts About Chlorine

  • Chlorine is a micronutrient for plants.
  • Plants use it in photosynthesis, osmosis, and plant growth.   It’s also necessary for turgor regulation.  That’s the rigidity of plant cells based on their internal cell pressure.
  • Internal chlorine concentration varies depending on the plant.
  • Chlorine toxicity reduces photosynthesis, growth, and yield.
  • Symptoms of chlorine toxicity are like other nutrient deficiencies.  The symptoms include yellowed leaves, brown or black spots, or burned leaf tips.

How Chloramine Affects Plants

A look at the EPA website reveals a lack of research about the effects of chloramine on people, let alone plants.

They have the typical official-sounding words that translate to “We don’t have a clue.”  Chloramine safety appears to be based on a lot of assumptions.

The EPA says chloramines have disinfected water for about 100 years.  Since “no one” suffered any harm, they’re safe.  OOOOOKay.

We only found two studies done at Kyoto Prefectural University.  They showed hydroponic leaf lettuce got brown roots one day after exposure to 0.2 ppm of chloramine.  The browning became intense at 0.3 mg/l.

The opinions about chloramine run from it being safe to harmful.  Since there’s so little research, none of these opinions offer any references for support.  Some sources say, “Chloramine is as safe as chlorine for plants.”

This statement might be accurate, but it doesn’t inspire much confidence.  We can restate it as “Chloramine is as dangerous as chlorine for plants.”  Do you see how the choice of one word, “safe” or “dangerous,” changes how you feel about that statement?

We’ve already shown how chlorine can affect plants.  We discovered the effect depends on the amount of chlorine and the type of plant.

What can we determine about chloramine’s effects?

Lacking any hard data, it’s wise to assume that chloramine at least has effects similar to chlorine.  But chloramine has some characteristics that can make it worse than chlorine:

  • It doesn’t evaporate like chlorine.  That means it stays in the water and soil much longer.
  • The longer “life” of chloramine gives it more time to affect soil organisms and plants.
  • Chloramine is a synthetic compound made by mixing chlorine and ammonia.  It doesn’t occur in nature, so living things don’t have any defenses against it.

Experts in hydroponics and aquaponics have found a consistent problem.  Even slight amounts of chemicals harm fish and water-grown plants.

We don’t have reliable information about chloramine’s harmful effects on plants.  That indicates we have to handle it with care.

We could start with the exposure levels we found with chlorine.  But chloramine’s dangers might begin at lower levels because of its stability.

The stability of chloramine lets it stay longer in soil and water.  That increases the exposure of plants to chloramine’s toxic effects.

How Fluoride Affects Plants

A study posted on ScienceDirect shows fluoride affects plants by oxidative stress.  Fluoride also reduces chlorophyll, nutrients, and sugar levels.

Another study comes from the West Pomeranian University of Technology in Poland.  This one looked at the effects of sodium fluoride on winter wheat.  They found that any level of fluoride harmed the germination and growth of the seedlings.

A study by scientists from several universities looked at fluoride in the soil.  They found it harms plants even at low levels.

What Can We Conclude About Fluoride’s Effects on Plants?

We could have mentioned several other studies.  Their combined conclusions are as follows:

  • Fluoride already exists in soil, air, and water.  Watering plants with fluoridated water increases fluoride above the natural levels.
  • Fluoride in soil has a normal range from 150 – 400 ppm.  Most of this fluoride binds to the soil and is insoluble (plant roots don’t absorb it).  Some soils go as high as 1000 ppm of fluoride, and contaminated soil can exceed 3500 ppm.
  • High levels of fluoride are toxic to all living things.
  • Because of its chemical nature, fluoride accumulates in plant tissues.
  • Studies have found that water with less than 3.1 mg/l of fluoride doesn’t accumulate in food plants.
  • Despite that, studies also show that the fluoride level in plants depends on two things.  Those are the plant type and the fluoride levels in the soil.

Even if you have low fluoride in your tap water, it can accumulate in your plants over time.  It doesn’t evaporate like chlorine, and it likes to combine with almost anything it touches.

Fluoride appears to be the main culprit when using tap water for your plants.  Chloramine is coming in as a close second.

How to Make Tap Water Safe for Plants

If you have a well-managed water department, you shouldn’t have a problem using tap water for plants.  If that isn’t the case, or you don’t want the chemicals in your water, here are some options for removing them:

Four Effective Ways to Remove Chloramine or Chlorine From Water

1. Filtration

The most effective filters have three parts:

  • A large particle filter to remove dirt and dust.
  • An activated charcoal filter to remove chlorine.  Chloramine needs catalytic charcoal to remove it.
  • A reverse osmosis filter to remove any dissolved solids or salts.

For a home system, you won’t need the particle filter.  The water plant took care of that part.

The charcoal filter is effective at removing chlorine, chloramine, and fluorine.  Be aware that it must be the right kind of charcoal.

  • Activated Charcoal.  Treating charcoal with oxygen at high temperatures creates activated charcoal.  This process changes its internal structure and gives the charcoal powder smaller pores.  This makes the charcoal more absorbent.  Activated charcoal is an excellent filter for chlorine.
  • Catalytic Charcoal.  Chloramine will pass through an activated charcoal filter.  This is because it doesn’t stay in the filter long enough for the ammonia to break down.  Catalytic charcoal works like activated charcoal, but it also promotes chemical activity.  That gives it the ability to break down the ammonia in chloramine.

2. Removal With Chemicals

Potassium metabisulfite is the most common way to neutralize chlorine and chloramine.  Suppliers sell this chemical as Campden tablets.  One tablet can neutralize 20 gallons of water.

Although it’s a cheap solution, you’re adding another chemical to the water.  Also, Campden tablets often contain sodium instead of potassium. That makes them less suitable for plants.

Breweries often use Campden tablets to dechlorinate water.

3. Evaporation

This method works with chlorine but not chloramine or fluoride.  This is a small-scale method suitable for bucket or barrel-sized quantities of water.

The chlorine evaporates from small quantities of water in 24 hours.  Larger quantities can take up to five days. Boiling tap water for a few minutes speeds up the process.

Always ensure the water is at room temperature before using it on plants.  If the water is too hot or cold, it could be a death sentence for plants.

4. UV Light

This is an effective method for removing chlorine and chloramine from water.  It has some drawbacks, though.  The equipment can be expensive, and you must be careful when working with UV light.  Overexposure can cause sunburn and eye damage.

Removing Fluoride From Tap Water

Filtration effectively removes fluoride, but filters like Brita and Pur can’t do it.  Four types of filters will remove about 90% of the fluoride:

  • Reverse Osmosis Filter.  These filters provide the purest tap water you can get.
  • Deionization Filter.  These filters remove ionized minerals and salts from water.  To remove fluoride, the filter has to contain an ion-exchange resin.  These filters are available with or without the resin.
  • Activated Alumina Filter.  This material removes arsenic and fluoride from water.  This type of filter has a possible issue.  A study cited on the ClearChoiceWater website states these filters will leach trace amounts of aluminum into the water.
  • Bone Char Filter.  These filters are the oldest way to remove fluoride from water.  They also remove chlorine, chloramine, and heavy metals.

Another way to remove fluoride is by distillation.  This is only convenient for smaller quantities of water.  Countertop distillation units run from $200 – $1000.

So, After All That, Is Tap Water Safe for Plants?

Let’s start this section with a reassuring statement.  If you’re watering your plants with tap water and not having any problems, do this:

Celebrate your good fortune with a hearty glass of your favorite adult beverage!  Your tap water is good for plants.

Filtering tap water is the best solution if you’re concerned about chemicals.

Unfiltered tap water should be safe to use on plants if:

  • Your local water department confirms low salt levels (dissolved solids less than 450 mg/L).  These can be natural salts in the water or salts left by softening the water.  For indoor plants, salts will wash away by occasional watering with distilled water.  Rainwater takes care of this problem for outdoor plants.
  • Your local water department confirms they don’t use chloramines.  Fluoride is another problem.  The United States is one of the few countries that still adds fluoride to the water supplies in most states.

Hydroponic or aquaponic systems shouldn’t have these chemicals in the water.  The plants and fish will get sick and die.

Chloramine is suspicious since there’s a lack of research on this chemical.  There isn’t any scientific proof of its safety.  All we have are claims that its long-term use means it’s safe.

Remember cigarettes, DDT, and Paris Green?  These are a few of many substances that had long-term use but turned out to be toxic.

Currently, 30% of communities in the US have water treated with chloramine.  Many other countries have an outright ban on it.

Chloramine consists of two toxic chemicals: ammonia and chlorine.  We need to consider that it’s harmful until proven otherwise by actual testing.

It appears that fluoride could be the forgotten chemical for plant damage.  Many people are concerned about chlorine in water, but it doesn’t hang around long enough to worry about.

Additional Information About Tap Water

Who Sets Water Quality Standards in the U.S.?

The Safe Drinking Water Act (SDWA) gives the EPA the authority to set the standards for water quality.  State and local governments and water suppliers must follow these standards.  The EPA then has to check their performance.

Before my retirement, I took many business trips throughout the U.S., Canada, and Mexico.  Whenever I drank tap water, it was in small quantities when I didn’t have bottled water nearby.

The tap water in Mexico is still a gamble, so I never drank it.  Canadian tap water seemed to have consistent quality across the country.  In the U.S., there were places where the odor and taste of the tap water were “off.”  In those places, I considered the tap water undrinkable.

A reason exists for the inconsistent water quality in the US.  We can find it in the “National Secondary Drinking Water Regulations.”  According to the CDC website:

“National Secondary Drinking Water Regulations (NSDWR) are guidelines to help public water systems manage their drinking water for issues not related to health, such as taste, color, and smell.  Water systems are not required to follow these water quality standards for the 15 contaminants listed.  Although these contaminants may not be harmful to public health, if they are in water at levels above the standards, they can cause the water to look cloudy or colored, or to taste or smell bad.”

So, the EPA water standards mandate that the drinking water supply is safe.  But they don’t mandate that safe water should be pleasant water.

You can get a copy of your local Consumer Confidence Report on the EPA website.  That will give you information about your local tap water.

How is Tap Water Treated?

This section includes information from the following:

Water treatment is another area where I’ve had some professional experience.  I supervised an electrical maintenance department.  Our responsibilities included maintaining the control system for an industrial water treatment plant.

Industrial water treatment uses a process similar to that used for drinking water.  The difference is that industrial water treatment cleans dirty water from a mill.  Pumps then send the clean water back to the river.

The recycled water ends up being far purer than the original river water.  Our treatment plant was about a quarter of a mile upstream of the city water plant.  That meant we had to follow high standards for our water.

The Five Major Steps for Purifying Drinking Water

1. Coagulation

This step adds chemicals to the water that have a positive charge.  These neutralize the negative charges from dissolved particles and dirt.  The result is the unwanted substances combine with the chemicals.

Coagulation can also remove a lot of organic substances.  The water treatment industry calls these Natural Organic Matter (NOM) or Dissolved Organic Carbon (DOC). Large amounts of DOC give water a brown discoloration and an unpleasant odor and taste.

2. Flocculation

This part of the process takes the coagulation particles and mixes them.  That action makes the particles larger.  The larger particles, called flocs, are easier to remove from the water.

3. Sedimentation

The heavy flocs settle out of the water to the bottom of the sedimentation tank.  Removing the floc particles also removes some bacterial and viral contaminants.

An international study published in 1998 found that sedimentation removes 27 – 84 % of viruses and 32 – 87% of bacteria.

The chemicals used in the coagulation step end up as part of the floc particles.  That makes it easy to remove them together.

4. Filtration

This step forces the water through several filters that remove more particles.  The filters consist of sand, charcoal, clay, or gravel and have pores of various sizes.

The filtration step could also include reverse osmosis (RO) filters.  They would remove almost all particles, including bacteria and viruses.

5. Disinfection

This is the final step to kill all remaining bacteria, viruses, and parasites in the water.  Many treatment plants use ultraviolet light or ozone to kill these pests at the plant.  As stated earlier in this article, this doesn’t keep the water pure as it travels through pipes.

Adding chlorine, chloramine, or chlorine dioxide to the water keeps it pure as it travels through pipes.  To be 100% effective, enough disinfectants must be present to keep the water pure all the way to the faucet.

The final steps include adjusting the water’s pH and adding fluoride.  All these steps vary by community depending on the condition of the untreated water.  Some communities could have specific toxins or contaminants that need special treatment.

Bob Styer

As a child, I hated gardening. That was mainly because Dad expected us to work in the garden every so often even though we thought play was more important. Over the years, though, I've developed a real appreciation for growing things. Whether you're growing plants for food or to enjoy their beauty, gardening can make your life better. Seize the moment!

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