რატომ არის ჭაბურღილის წყალი მღვრიე და როგორ იფილტრება ნალექი?

Why is well water cloudy and how is sediment filtered out?

What is water turbidity?

Turbidity is an optical property of water that shows how much the particles in the water prevent light from passing freely.

In other words, the more fine suspended particles there are in the water, the more its transparency is lost.

Turbidity can be caused by clay, silt, fine mineral particles, organic matter, and microscopic material. According to the USGS technical definition, such particles absorb light or scatter it in different directions, making the water appear turbid.

Turbidity is usually measured in NTU - Nephelometric Turbidity Units. However, NTU does not directly indicate how many milligrams of sand or other solid material are in the water. Turbidity is an optical measurement, while the concentration of suspended solids is a separate parameter. Therefore, two waters with the same NTU can have different particle compositions and sizes.

Why does well water become turbid?

In the case of a well, the most common cause is sand, silt, clay, and other mineral particles that enter the water from underground layers.

A well draws water from a water-bearing geological layer – an aquifer. If this layer contains sand, gravel, silt, or other loose material, small particles of it can enter the well along with the water under certain conditions.

In properly constructed wells, a well casing, a special well screen, and in some cases, a gravel pack are used to reduce this, with the function of allowing water to pass through while retaining sand and larger particles. According to North Carolina State University's Cooperative Extension, one of the primary functions of a well screen is to limit the entry of sand and sediment into the well.

If sand constantly appears in the water in large quantities, the reason may not be solely the natural quality of the water. Damage to the screen, enlargement of its openings, or other technical problems with the well can also increase the amount of sand in the water. Penn State Extension notes that corroded or enlarged well screen openings can cause similar contamination.

Therefore, a constant and large amount of sand should not be considered merely a filtration problem – sometimes, the condition of the well itself needs to be checked first.

Why does turbidity change with rain or season?

The quality of well water is not always absolutely constant.

Heavy precipitation, flooding, earthworks, changes in groundwater levels, or other hydrological processes can affect the water composition. Cases where groundwater is directly influenced by surface water are particularly important.

State technical manuals note that some groundwater sources can change seasonally as a result of heavy rain, flooding, earthworks, and other environmental factors.

If well water is normally clear but suddenly becomes turbid after rain, it is especially important to determine the cause, as in such a case, filtering out just the sediment may not be sufficient.

Are sediment and turbidity the same?

No - they are related, but not exactly the same.

Sediment is specific solid material, such as sand, silt, or other particles, that moves in water and may eventually settle at the bottom.

Turbidity, on the other hand, is a measure of water's transparency.

For example, coarse sand in water can quickly settle and appear at the bottom of a container. Very fine clay or colloidal particles, however, remain suspended in water for much longer, giving the water a completely turbid appearance.

This difference determines what type of filtration will be needed.

Does all turbid water mean sediment?

No.

Sometimes the water coming out of the tap looks milky or cloudy white but becomes completely clear in a few seconds.

This may not be sediment at all.

According to USGS, a common cause of such an effect is microscopic air bubbles in the water. If you fill a glass with water and the water gradually clears from the bottom up in a few seconds or minutes, it is highly likely that you are dealing with air bubbles and not solid sediment.

If particles settle at the bottom of the glass or the water remains turbid after several minutes, another cause needs to be investigated.

What is the connection between iron and manganese and turbid water?

The cause of turbidity and color in well water is not always sand or clay.

Groundwater may contain iron and manganese. Under certain conditions, they are found dissolved in water, but after contact with oxygen, they transform into solid compounds and form sediment.

As a result, the water may turn yellow, orange, reddish-brown, or dark.

State technical guidance for water systems notes that iron often forms red-brown sediment, while manganese forms darker or black sediment; both can stain plumbing fixtures and, over time, reduce water flow in pipes.

This is important because in such cases, simply installing a small micron mechanical filter does not always solve the problem. If iron is still dissolved, it may first be necessary to oxidize it and only then filter the resulting particles. EPA technical materials describe filtration of sediment after oxidation as one approach to treating iron and manganese.

Is turbid water hazardous to health?

Turbidity itself is not the name of a specific contaminant.

The cause of turbidity could simply be natural mineral particles. However, it is impossible to determine its safety solely by visual assessment of the water.

WHO (World Health Organization) notes that turbidity can have both aesthetic and water safety implications, as it can be caused by various chemical and biological particles.

Furthermore, high turbidity is important from the perspective of water disinfection. Suspended particles can make the disinfection process less effective. WHO's technical recommendations state that low turbidity is desirable for effective disinfection, and for effective chlorine disinfection, turbidity of less than 1 NTU, and preferably even lower, is recommended.

This figure should not be taken as a replacement for specific Georgian drinking water standards – it is a WHO technical guideline related to the effectiveness of disinfection.

Therefore, "we removed the sediment, the water is safe" is not a correct conclusion. In the case of well water used for drinking, its microbiological and chemical parameters must be assessed separately.

How to find out what creates turbidity?

Even initial observation provides a lot of information:

  • If sand grains are visible in the water and they settle quickly – it is likely that we are dealing with relatively coarse mechanical particles;
  • If the water remains uniformly turbid for a long time – the presence of very fine silt, clay, or colloidal particles is possible;
  • If the water is initially clear and then turns reddish or brownish – one possible cause is iron;
  • If the water is milky and quickly clears from the bottom up in a glass – it is most likely air bubbles and not sediment.

However, visual assessment cannot be a definitive diagnosis.

For well water, water analysis is particularly important. The CDC recommends that private well water be tested periodically, including for coliform bacteria, nitrates, pH, and total dissolved solids; additional parameters should be determined based on local conditions and changes found in the water. Changes in water color, taste, or odor are also cited as reasons for retesting.

In the case of turbidity problems, it is practically useful to determine Turbidity/NTU, and depending on the specific situation, also iron, manganese, and other relevant parameters.

How are sand and mechanical sediment filtered?

If analysis and water condition determine that the problem is mechanical particles, the primary principle of their removal is physical filtration.

Water passes through a filtration medium that separates solid particles from the water flow.

The EPA describes filtration as a process where water passes through a porous filtration medium, and solid particles are physically retained in it.

But this is where selecting the correct system becomes important.

Directly running water with a large amount of sand through a very fine cartridge is technically a poor approach – the filter will quickly become clogged, pressure loss will increase, and frequent replacement will be necessary.

Therefore, during high mechanical load, staged filtration is often used: initially, relatively coarse particles are removed, then finer sediment, and if necessary, more precise water purification is performed at the final stage.

Why isn't a one-micron filter always the right choice?

Because the size and quantity of particles in well water can be completely different.

In one water, sand may dominate, in another - silt, and in a third, such fine clay particles that they do not settle for hours.

The smaller the filter pores, the finer the particle it can retain, but at the same time, in highly turbid water, the risk of it rapidly becoming clogged increases.

In state technical manuals, microfiltration technology is described as a technology for removing sand, silt, and clay-sized particles, but it is also noted that high suspended solids content quickly clogs membrane systems and pretreatment may be necessary.

Therefore, there is no correct answer to the question "What micron filter do I need?" without knowing the water's condition.

What happens if the water contains very fine clay or colloidal particles?

This is a more complex case.

Some particles are so fine that they remain in the water for a long time and are practically not removed by conventional settling. Such water can maintain a milky, grayish, or brownish turbidity indefinitely.

When treating highly turbid water, it may be necessary to use not only cartridge filtration but also media filtration, sedimentation, and in certain cases, coagulation/flocculation, during which very small particles agglomerate and transform into more easily removable particles.

WHO technical guidelines for drinking water describe combinations of sedimentation, coagulation, media filtration, and membrane processes in multi-stage approaches to reducing turbidity.

In the case of a household well, the need for such a solution already depends on the specific water's turbidity and particle type.

Filter or well repair?

This is one of the most important questions.

If there is a small amount of mechanical sediment naturally in the water, properly selected filtration is a completely logical solution.

But if the well suddenly starts to bring up large amounts of sand, the problem may be with the well itself.

The function of a well screen is precisely to allow water to pass through and retain a large portion of sand and gravel from the formation. Accordingly, constant sand pumping may indicate a need to inspect the screen, gravel pack, pump location, or other well components.

In such a case, simply installing a larger filter will not eliminate the cause of the problem.

How is the correct filtration system selected?

There is no universal system for well water.

To make the right decision, first of all, it is necessary to determine:

What creates the turbidity → What is the size of the particles → How high is their quantity → Does the problem change seasonally → Is there iron or manganese in the water → Is the water microbiologically safe → How much water needs to be treated.

Only then can it be decided whether simple mechanical filtration is sufficient, whether several stages need to be used, or whether the water requires additional treatment.

The EPA also notes that the choice of water treatment technology depends directly on the chemical composition and turbidity of the raw water – the same technology cannot be automatically correct for all sources.

Proper treatment of turbid water begins with identifying the cause

The first reaction when seeing sediment in well water is often to install the finest filter.

In reality, an effective system starts with another question:

What is this sediment?

Sand, silt, clay, iron compounds, and turbidity associated with microbiological problems may require completely different treatments.

Therefore, the correct sequence is:

Water condition assessment → Necessary analysis → Identifying the source of the problem → Selecting the appropriate filtration technology → Correct installation and periodic maintenance.

With such an approach, filtration not only makes the water visually cleaner but also protects subsequent filtration stages, plumbing, and water-related equipment from excessive mechanical stress.

At AQUAREA, well water systems can be selected according to specific water quality and required capacity – from mechanical sediment removal to multi-stage water treatment.

→ Well Water Treatment
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Sources

The following authoritative sources were used in the preparation of this article:

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