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 through 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 or scatter light in various directions, making the water appear turbid.

Turbidity is usually measured in NTU - Nephelometric Turbidity Units. However, NTU does not directly show 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 may have different particle compositions and sizes.

Why does well water become turbid?

In the case of a well, the most common reason is sand, silt, clay, and other mineral particles entering 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. The function of these is to allow water to pass through and retain sand and coarse particles. According to the North Carolina State University 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 appears constantly in large quantities in the water, the reason may not only be 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 such 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's composition. Cases where groundwater is directly affected by surface water are particularly important.

State technical manuals note that some groundwater sources can change seasonally due to heavy rain, flooding, earthworks, and other environmental factors.

If well water is usually clear but suddenly becomes turbid after rain, it is particularly important to determine the cause, as in such cases, simple filtration of precipitation may not be sufficient.

Are sediment and turbidity the same thing?

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 the water's transparency.

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

This difference determines what type of filtration will be needed.

Does all turbid water mean sediment?

No.

Sometimes 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 bottom to top in a few seconds or minutes, it is most likely 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, and after contact with oxygen, they convert into solid compounds and form sediment.

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

The state water system technical manual notes that iron often forms a red-brown precipitate, and manganese - a darker or black precipitate; both can leave stains on plumbing and, over time, reduce water flow in pipes.

This is important because in such a case, simply installing a small micron mechanical filter does not always solve the problem. If iron is still in a dissolved state, 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 dangerous for health?

Turbidity itself is not a specific contaminant.

The cause of turbidity may simply be natural mineral particles. But it is impossible to determine its safety by visual assessment of the water alone.

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 hinder the effective operation of the disinfection process. WHO's technical recommendations state that low turbidity is desirable for effective disinfection, and for effective chlorine disinfection, turbidity less than 1 NTU, and preferably even lower, is indicated.

This number should not be taken as a replacement for specific Georgian drinking water norms - it is a WHO technical guideline regarding disinfection effectiveness.

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 should be assessed separately.

How to find out what creates turbidity?

Initial observation also gives a lot of information:

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

However, visual assessment cannot be a final diagnosis.

Water analysis is particularly important for well water. 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 according to local conditions and changes found in the water. Changes in water color, taste, or smell are also cited as reasons for re-testing.

In 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 is sand and mechanical sediment filtered?

If analysis and water condition determine that the problem is mechanical particles, the main 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 within it.

But this is where the correct selection of the system becomes important.

Directing water with a large amount of sand directly to a very fine cartridge is technically a poor approach - the filter will quickly become loaded, pressure loss will increase, and frequent replacement will be required.

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

Why is a single micron filter not always correct?

Because the size and quantity of particles present 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 rapid clogging 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 rapidly fouls membrane systems, and pre-treatment 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 there is very fine clay or colloidal particles in the water?

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 ordinary sedimentation. Such water may permanently retain a milky, grayish, or brownish turbidity.

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 clump together and are transformed into more easily removable particles.

WHO's 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 household wells, the need for such a solution depends on the specific turbidity of the water and the type of particles.

Filter or well repair?

This is one of the most important questions.

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

But if the well suddenly starts bringing up a large amount of sand, the problem may be in the well itself.

The function of the well screen is precisely to allow water to pass through and to 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 placement, or other well components.

In such a case, simply installing a larger filter cannot eliminate the root 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 turbidity → what size are 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 after this can it be decided whether simple mechanical filtration is sufficient, whether several stages are needed, or if 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 automatically be correct for all sources.

Proper treatment of turbid water begins with identifying the cause

Upon seeing sediment in well water, the first reaction is often to install the finest filter.

In reality, an effective system begins 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 → determining the source of the problem → selecting 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 load.

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

→ Well Water Treatment
→ Get a consultation

Sources

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

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