How to properly analyze water from a well and disinfect it after testing

Content

So, no matter how deep the well is, and no matter where it is located, the groundwater that enters it can seriously deviate from the norms for the content of certain substances in them. And there may be several reasons for this:

• Proximity to the location of heavy industry enterprises, livestock farms;
• Nearby landfills where concentrations of nitrates, heavy metals, iron, ammonia, salts and organic matter may be elevated
• Getting into the well itself of various debris and foreign objects: leaves, branches, caterpillars - as a result of which dirt and mucus accumulate in the well over time, and the water in it deteriorates.

Sources of groundwater pollution

And the water treatment system in the well is completely different from the method of wastewater treatment for industrial enterprises. Completely different norms and requirements are already quoted here.

Content

So, no matter how deep the well is, and no matter where it is located, the groundwater that enters it can seriously deviate from the norms for the content of certain substances in them. And there may be several reasons for this:

• Proximity to the location of heavy industry enterprises, livestock farms;
• Nearby landfills where concentrations of nitrates, heavy metals, iron, ammonia, salts and organic matter may be elevated
• Getting into the well itself of various debris and foreign objects: leaves, branches, caterpillars - as a result of which dirt and mucus accumulate in the well over time, and the water in it deteriorates.

Sources of groundwater pollution

And the water treatment system in the well is completely different from the method of wastewater treatment for industrial enterprises. Completely different norms and requirements are already quoted here.

Sample transfer methods to the laboratory:

1. Self-delivery of the sample to our office.
2. Sample delivery to one of the official Ecodar Order Receiving Centers.
3. Free departure of a specialist of the water treatment department (free departure is valid for Clients who want to install a water treatment system within Moscow and the Moscow region)

Choose the best research option by the number of indicators and cost.
Having familiarized yourself with the price list in detail, you will see for yourself that our offer is one of the most
attractive in the target market. If you need more detailed advice or recommendations on the choice
research option, you can always count on the help of our specialists. Within its competence
they will answer all your questions.

Features of analysis from a well

Well water testing is longer and more expensive than well water analysis, since this source is subject to various types of pollution (substances of biological origin, surfactants, pesticides, etc.). This is due to the fact that this source is located close to the surface of the earth.

In this regard, a laboratory analysis of water from a well should contain data on the following indicators of the aquatic environment:

• Data on the presence or absence of Escherichia coli, protozoa, Giardia and other microorganisms.
• Indicators of the concentration of inorganic components of water (mercury, lead, copper particles, zinc components).
• Concentration data for all types of pesticides.
• The concentration of components of organic origin is also studied.
• Radionuclides are analyzed.
• During the test, the concentration of herbicides is analyzed.

Important: if your well is shallow (up to 10 m), then you need to carefully control the microbiological indicators of the aquatic environment, since under such conditions various bacteria and protozoa multiply very quickly in stagnant water.In addition, well water must be checked for the concentration of petroleum products, detergent surface components and fertilizers, because all these substances can easily penetrate into the well aquatic environment during heavy rainfall.

In addition, well water must be checked for the concentration of petroleum products, detergent surface components and fertilizers, because all these substances can easily penetrate into the well water environment during heavy rainfall.

Research methods and what indicators are checked

Water analysis is divided into:

1. organoleptic;
2. chemical;
3. microbiological.

In addition, by the number of parameters and the combination of these three main types of testing, they can be called:

• standard;
• extended;
• optimal;
• full.

The first ones provide for the diagnosis of basic parameters:

1. organoleptic;
2. pH;
3. rigidity;
4. chloride content;
5. sulfates;
6. iron, etc.

It is practiced in relation to wells with a depth of more than 30 m, that is, those in which the water is less susceptible to pollution.

An extended test is carried out in the most accessible wells with a depth of less than 30 m. In this case, a test is added to the standard test for:

• microorganisms;
• nitrites;
• nitrates;
• silicon;
• copper;
• magnesium, etc.

Organoleptic method

An organoleptic study is one that is obtained with the help of the human senses - sight, taste, smell.

The following parameters are examined:

1. Transparency. This is the ability of water to transmit light and make objects at depth visible.

   It is determined by the presence and quantity of chemical and mechanical suspensions. Normally, transparency should not be less than 30 cm.

   

   

   

2. Color.Normally, the water should be colorless. The laboratory method of determination involves comparing the color of the sample with the scale.
3. Smell. Should be missing. Depending on its nature, it may indicate the presence of pathogenic microorganisms, an excessive amount of sulfuric acid compounds, chlorine, pollution by industrial effluents, etc.
4. Taste. In good water should be absent. Temperature dependent. There are four main tastes (bitter, sweet, sour, salty) and tastes - metallic, astringent, chlorine-alkaline, etc. The taste test is carried out only with guaranteed safe water, after disinfection or, in extreme cases, after 5 minutes of boiling.

Microbiological

Microbiological analysis is a set of tests that determine the presence of microorganisms (viruses, bacteria and fungi) in water. They get into the water, as a rule, as a result of human activities. Can lead to infection and disease.

In addition, the presence of microorganisms changes the organoleptic parameters:

• taste;
• color;
• smell.

The main danger of microbiological contamination is for sandy shallow wells.

The essence of microbiological diagnostics consists in placing water samples on nutrient media for microorganisms and determining their species composition based on the results of reproduction.

The main parameters of microbiological research include:

1. TMC (total microbial count). Normally there should be no more than 50
2. TKB (total number of coliform bacteria). Under normal conditions, it should be absent.
3. TKB (number of thermotolerant coliform bacteria). Should also be missing.

It must be borne in mind that their presence does not always lead to intestinal diseases.

Chemical

Chemical (physico-chemical) analysis of water is the main one and involves not only the study of the presence and quantity of a single element or their compounds, but also their groups responsible for some general properties of water - hardness, acidity, redox potential ( Eh), permanganate index.

The most important are the following parameters:

1. Acidity (pH). It characterizes the activity of hydrogen ions, which determine the rate of various biochemical reactions, as well as the corrosive aggressiveness of water.

   A high pH indicates an alkaline environment, a low pH indicates an acidic one. For humans, the most acceptable pH values ​​are 6.5-8.5.

2. General hardness. This is the total content of calcium and magnesium salts. It is measured in degrees of hardness (°F). The normal value is 7-10 mg-eq / l or 350 mg / l. High rigidity disables plumbing and kitchen equipment, creates problems when washing and bathing, changes the taste of drinks and soups in a negative direction.
3. The content of specific elements and compounds that affect the drinking properties of water. It is measured in Mg/Dm3. The allowable rate for each element is different. Checked:
   • Iron.
   • Fluorine.
   • Chlorides.
   • sulfates.
   • Nitrates.
   • Nitrites etc.

Each element gives water specific properties that affect water quality. The number of controlled elements and parameters can reach two hundred.

Hygienic requirements for drinking water

For drinking water in centralized water supply systems, the quality criterion is the standards set out in SanPiN 2.1.4.1074-01.In addition to hygiene requirements, the document also indicates the rules for determining water quality, some of its provisions:

a). Sanitary rules and norms (SanPiN) apply to water resources from the central water supply systems used by the population for household needs and drinking. The standard is not mandatory for water intake from individual water sources.

b). Drinking water must be epidemically and radioactively safe, chemically harmless and have acceptable organoleptic properties.

in). The epidemic safety of water is determined by its compliance with the standards of microbiology and parasitology according to the table in Fig. one.

G). When analyzing the state of water resources, the abstraction is made from ground sources before they are fed into the network.

e). The safety of drinking water in terms of its chemical composition is established according to the following standards:

1. A general indicator that includes harmful chemical elements most common in the waters of the Russian Federation (table in Fig. 2), as well as anthropogenic (included in the geological sphere of human activity) globally common substances. The last group consists of a number of organic and inorganic reagents (table in Fig. 3)
2. By the presence of harmful components in the water, which are the result of water treatment (chlorination, fluorination, ozonation) (table in Fig. 4)
3. By the presence in the water of chemically harmful elements that have entered the source during human activities. The list of harmful substances from industrial enterprises includes about three hundred items, divided into eight groups, some of which are listed in the tables in Fig. 5 and fig. 6.

Fig.3 Safety standards for anthropogenic substances

e).All substances found in water and subjected to analysis are divided according to signs of harmfulness into the following groups:

and). s.-t. – sanitary and toxicological

h). -org. - organoleptic, having the following decoding of harmful changes in water properties:

• app. - affect the smell;
• env. – paint the medium in different colors;
• Pen. - promote foaming;
• sq. – create a surface film;
• inoculation - bring flavor
• op. - cause colloidal opacification (opalescence).

Rice. 4 Standards for the content of harmful impurities after water treatment

and). According to the danger to human health, substances are divided into the following classes:

• 1 - having extreme danger;
• 2 - having a high danger;
• 3 - dangerous;
• 4 - with moderate danger.

Hazard classification takes into account:

• when conducting analyzes, determining priority studies;
• when planning the sequence of measures for the protection of water sources in case this requires financial investments;
• to justify the need to replace hazardous reagents in technical processes with less harmful ones.
• to determine the priority of methods for controlling harmful substances in water intake sources.

Rice. 5 MPC norms in water for hydrocarbons obtained from industrial waste

to). High-quality water must comply with organoleptic and radiation safety standards, the data are given in the table in fig. 7.

l). The water should not contain films or organisms that are visible to the human eye.

m). If chlorine is simultaneously present in the water in a free and bound state, their combined mass should not exceed 1.2 mg per liter.

n).Chemical analysis of drinking water for the presence of pathogenic microorganisms should be carried out in laboratories that have a license and a conclusion on compliance with the conditions for conducting research with SanPiN.

about). When establishing the maximum concentration limit for harmful reagents, the recommendations of the World Health Organization (WHO) were taken into account.

In addition to the considered standard, for individual water supply, they are guided by the SanPiN 2.1.4.1175-02 regulatory document, which regulates hygienic requirements for the quality of water from non-centralized sources.

The document provides a limited number of standardization criteria for organoleptic and chemical composition. In the first case, the color, turbidity, smell and taste of water are considered, the main criteria for the chemical composition are the pH, total hardness, mineralization, permanganate oxidizability and nitrate content (table in Fig. 10).

Fig.6 MPC norms in water for organoelement compounds obtained from industrial production

Self water analysis

If you do not have time to take fluid samples to the laboratory or there is no such institution nearby, then you can do the water analysis yourself. However, it can only be used as a temporary measure and you should not rely on the results obtained completely. It is better to get to the laboratory afterwards.

Conclusions about water quality are made on the basis of such observations:

1. Turbid contents in the well may be due to the ingress of particles of sand and clay into it. In this case, you will need to arrange a new bottom filter, since the old one does not cope with its tasks. Also, the cause of cloudy water can be depressurization of the seams. Through them, dirty groundwater enters the structure.
2. The rusty color of the water and the taste of iron indicate an excess of this element in the composition of the water. To combat the problem, use a special filter.
3. The rotten smell of the contents of a hydraulic structure indicates an increased content of hydrogen sulfide in it. This substance appears as a result of the vital activity of bacteria and the decomposition of organic compounds. Usually, the active reproduction of bacteria is associated with stagnant water and siltation of the source. The well must be cleaned and used regularly.
4. The smell of oil products indicates the ingress of sewage into the well. You can't drink from this source.

Sampling for analysis

To take a sample from the source and determine the quality of the water, choose the off-season period. During the spring and autumn months, surface waters are the most polluted. If they have the opportunity to penetrate the mine, then they will definitely affect the composition.

To check the quality of water from a newly built well, water for analysis should be taken no earlier than 3-4 weeks after its commissioning.

Water control is carried out only after a 3-week period of operation of the hydraulic structure. During this period, the pollution of the mine, which arose during the construction work, will subside, and the water will be partially cleared.

To obtain reliable results from a well water test, it is important that the sample is taken correctly. To do this, you need to follow a number of simple rules:

To do this, you need to follow a number of simple rules:

1. The container for fluid intake should be made of transparent colorless glass or plastic. It can be a bottle of mineral or distilled water with a volume of 2 liters, or a glass two-liter bottle.It is unacceptable to use eggplants from sweet and low-alcohol drinks for these purposes, if they have not been previously washed without the use of detergents.
2. When taking water from a well with a bucket, try to let it go a little lower than usual. This decision is explained by the fact that closer to the surface, the water may turn out to be stagnant, and at the very bottom it may include impurities of silt. Therefore, the best option would be the "golden mean".
3. Before filling the dishes, they are rinsed with selected water. Well water is poured into the bottle in a thin stream so that it flows smoothly along the inner wall of the container. Non-pressure supply will prevent the saturation of water with oxygen from the air, thereby preventing the occurrence of chemical processes.
4. The bottle is filled with liquid up to the very neck so that an air lock does not form in the container. If you are using a plastic bottle, squeeze the sides of the container slightly before closing the cap tightly, squeezing out the air.
5. Water taken from the well should be delivered to the laboratory within the next 2-3 hours. The faster the liquid gets to the laboratory, the more reliable the results will be. If this is not possible, place the container on a shelf in the refrigerator - this will reduce the reaction rate.

The maximum shelf life of a sample is up to two days. Temperature fluctuations should be avoided during sample storage.

Image gallery

A reverse osmosis system equipped with a semi-permeable membrane or filters is able to purify water from iron in high concentrations without the use of chemical oxidants.

The aeration method has also proven itself well.It is carried out by introducing air into the water using a compressor that creates atmospheric pressure drops. To do this, the water in the well is sprayed with special installations by means of spouting or showering.

Removal of hydrogen sulfide from liquid

Hydrogen sulfide is a waste product of anaerobic bacteria. Sulfuric bacteria live at the bottom of the well, where oxygen does not enter.

Experts offer two ways to solve the problem:

1. Physical
   - assumes saturation of the liquid with air. Forced aeration helps to destroy sulfur bacteria and additionally oxygenate the water, making it more beneficial to health. To implement this method, you will have to purchase expensive equipment.
2. Chemical
   - involves the use of disinfectants and oxidizing agents: sodium hydrochloride, hydrogen peroxide or ozone. It provides the most complete degassing. Under the action of oxidizing agents, hydrogen sulfide compounds are converted into less active forms.

The liquid, which has undergone chemical cleaning, must undergo additional filtration through active carbon. For water purification, both carbon filters equipped with activated carbon and filters with granular filler are used.

Treatment of water with a solution of potassium permanganate helps to eliminate the problem. Potassium permanganate powder is first diluted in a three-liter jar to obtain a concentrated solution of a saturated purple color, and then poured into a well.

In the future, in order to prevent the formation of colonies of bacteria that produce hydrogen sulfide, it is recommended to periodically “purge” with compressed air.

What to do in case of bad results?

If the analyzes showed the presence of organic or chemical contaminants, it is necessary to treat the water.

The following work is being carried out:

• Mechanical cleaning of the well shaft. They pump out water and remove all dirt, plaque, mud and other layers from the walls. Change the bottom filter (stones and sandy backfill soaked with silt).
• Eliminate mine leaks. Detected cracks or holes are carefully sealed. This allows you to exclude the ingress of unwanted components from the soil.
• Wall disinfection. A chlorine solution is applied with a brush or roller.
• Water disinfection. Use bleach, which is collected in a bucket. Then they scoop up water and pour it back, mixing the liquid with bleach.
• Use of specialized water treatment compounds that are commercially available.
• Installation of filters that trap foreign components.

Usually they produce a full range of works, paying special attention to the most developed types of pollution.

Our advantages

High quality work.
EKVOLS specialists who analyze water from wells and other sources have more than ten years of experience. Their professionalism, the use of modern equipment and proven reagents are a guarantee of the thoroughness of the study and obtaining a reliable result. All work, from taking water from a source to testing it in a laboratory, fully complies with the regulatory requirements of SNiP and SanPiN. The basis of the analysis is the main chemical-technological institution of Russia - RKhTU im. D. I. Mendeleev.

Free sampling.
After the order is placed in the EKVOLS company, our specialists go to the customer.Sampling works from the source are carried out free of charge, the client pays only for laboratory analysis of water from a well or other source. The total cost of the study depends on the number of indicators that will be monitored. You can order only a chemical, only a bacteriological test or a study in all respects.

Package of services.
The main advantage of EKVOLS is that the company is ready to provide each customer with the entire package of services related to the organization of autonomous water supply. Based on the analysis of water from the source, the optimal equipment is selected, the type of purification (one-, two-, three-stage), a scheme for connecting pipes to the main filter is created. In addition, we provide delivery of systems and components to the right place with their subsequent installation and commissioning. After the conclusion of the relevant service contract, we carry out regular service activities.

To order an analysis of water from a natural or artificial source at EKVOLS, use the services of the site. For advice and assistance, please contact our specialists: contact them in an online chat, request a call back or send a request to the proposed email address.

Country houses are often supplied with water from a well or well, which can contain a wide range of impurities hazardous to health. Well water analysis is an effective way to get rid of them. This is a modern solution to the problem of water treatment. The equipment has optimal weight and size characteristics that simplify installation, and has a long working resource. Therefore, by purchasing it, you will provide yourself with high-quality water for a long time.Contact our specialist, and he will tell you everything about the capabilities of this system and the features of its operation.

As you know, water is the source of all life. It is the water resource that is considered the most demanded and in need of protection. Water helps to function not only for humans, but for our entire planet. Therefore, one of our most important tasks is to keep water sources clean, suitable for our needs and completely safe. To assess the state of water, we are accustomed to using the services independent laboratories for water analysis
. After the assessment, it is already possible to draw certain conclusions and develop a further plan of action.

Analysis of drinking water in Moscow, analysis of waste water in Moscow
- all this is necessary to consider how that source of water can be used, from which the sample was taken.

Why else do you need make an analysis of drinking water in Moscow
? Our high pace of life, the development of industry, construction, manufacturing and other sectors of the economy, causes indelible damage to the environment. That is why it is necessary to ensure that the quality of the water is acceptable so that the water can be used safely. Waste water analysis laboratories
allows you to solve the problem of choosing the necessary filters for water purification and determine for what purposes this water is generally suitable, that is, whether it can be drunk or used only for domestic tasks.

If you don't know where to take water for analysis in Moscow
, then you are lucky, you have already found the very organization involved in the analysis wastewater in a laboratory in Moscow
. The Moscow SES laboratory provides services to the population and companies for water analysis in Moscow, cost
which is not overpriced and will not hit your budget.

Well water analysis options

• Mini water analysis:
  pH, odor, turbidity, electrical conductivity, iron, hardness, sulfides.
• Standard research:
  pH, smell, color, turbidity, electrical conductivity, permanganate oxidizability, hardness, alkalinity, ammonium ion, sulfate ion, chloride ion, hydrogen sulfide, iron.
• Base rate:
  pH, smell, color, turbidity, electrical conductivity, permanganate oxidizability, hardness, alkalinity, ammonium ion, sulfate ion, chloride ion, hydrogen sulfide, iron, manganese.
• Comprehensive analysis:
  pH, smell, color, turbidity, electrical conductivity, permanganate oxidizability, hardness, alkalinity, ammonium ion, sulfate ion, chloride ion, hydrogen sulfide, iron, manganese, fluoride ion.
• Extended research:
  pH, smell, color, turbidity, electrical conductivity, permanganate oxidizability, hardness, alkalinity, ammonium ion, sulfate ion, chloride ion, hydrogen sulfide, iron, manganese, fluoride ion, nitrate ion, nitrite ion, phosphate ion, calcium, silicon, copper , magnesium, suspended solids.

cost

2 How to sample water for analysis?

It is worth remembering that the results of water analysis depend not only on the professionalism of the laboratory staff, but also on whether the selection for a general (complete) analysis of water from the well was made correctly and this selection was delivered to the site.

The process of taking water from a well for analysis

So that no third-party factors affect the final indicators of the study, the selection of water composition must be carried out in accordance with the following rules:

• the container in which you make the selection of the composition must be sterile - for this, boil it first, if it is a plastic bottle - just pour boiling water over it;
• the minimum volume of containers for laboratory selection of the composition is at least 1 liter;
• the use of plastic bottles of non-carbonated drinking water is allowed. You can not take bottles from carbonated drinks or cocktails, as the dyes in their composition will affect the final analysis;
• the selection of the composition of water in the laboratory must be delivered within a day.

To date, the most common are such methods of water analysis, each of which allows you to check the selection of the composition of water for the content of certain types of contaminants.

Water analysis methods:

• chemical general analysis;
• microbiological analysis (aka bacteriological).

2.1 Chemical analysis

Chemical complex (general) analysis of water from a well or express analysis of water is the most complex method of analysis, which is recommended to be done at the slightest suspicion of deterioration in water quality. To find out the chemical and quantitative composition of water in the laboratory, its organoleptic and chemical-physical parameters are checked.

There are two types of analysis: standard chemical complex analysis, and advanced chemical analysis. Standard analysis involves checking the composition of water by 14 points, extended - by 25 points.

For sources whose depth exceeds 25 meters, a standard test is sufficient, however, for shallow sources, which are wells, it is better to do an extended chemical complex analysis, since the water from them is more contaminated with inorganic compounds and metals.

Tap water with a high concentration of iron impurities

An extended analysis must necessarily be carried out before putting a new source into operation, regardless of its depth.

Chemical analysis allows you to find out the following indicators:

• hardness of water;
• iron content;
• the cause of the bad smell of water;
• oxidizability;
• alkalinity of water;
• pH
• turbidity of water;
• the content of chemical impurities: fluorides, aluminum, chlorides, sulfates, manganese, ammonium, nitrites, mercury, copper, lead, ammonium.

The market average cost of chemical water analysis today is from 50 to 75 dollars, depending on the laboratory.

2.2 Microbiological analysis

It is necessary to carry out a microbiological analysis for all wells, the depth of which is less than 15 meters, this type of analysis allows you to determine the content of pathogenic bacteria and other microorganisms in the water.

The presence of such organisms very often becomes a factor that makes water undrinkable: it not only stinks, but can also cause a person to become infected with very unpleasant diseases, such as diarrhea, dysentery and hepatitis A.

Modern apparatus for water analysis

Microbiological analysis reveals such indicators as the total microbial count, the content of temperature-resistant microorganisms in the water, and the number of colimorphic bacteria.

The main factor in the microbiological quality of water is the content of colimorphic bacteria, since they are the easiest to detect, but at the same time, they have the most negative impact on the human body.

Water sampling must be carried out as carefully and quickly as possible, which ensures that third-party bacteria enter the water sample to a minimum.It is best to purchase a container for such an analysis directly in the laboratory, it must first be boiled and rinsed with alcohol.

How does the type of study affect sampling rules?

Selection rules vary depending on the purpose and type of analysis. The amount of water needed for research and the sampling methodology are also changing.

Chem. test

For chemical analysis, the most important thing is the use of clean containers that would not contain impurities. Therefore, the use of oil bottles, carbonated drinks, household chemicals, juices and mineral (salt) water is prohibited.

Another condition for the correct intake is the preliminary discharge of stagnant water, as well as settling in the presence of silt, sand, clay or other mechanical impurities in the water.

Bacteriological

For bacteriological analysis, the faucet must be thoroughly disinfected before sampling. This is done with a special swab dipped in alcohol.

After the material of the tampon is soaked in alcohol, it is set on fire, and the flame is passed over the surface of the faucet until a characteristic hiss occurs when the faucet is opened.

Such an analysis is carried out in disposable sterile gloves, while the hands are also exposed to an antiseptic before sampling. Samples are taken in special sterile half-liter containers, which are taken in research laboratories.

The jet for collecting samples for bacterial analysis should be as thin as possible in order to contact the faucet and other surfaces as little as possible.

If it is not possible to treat the tap with a flame, then it is placed in an alcohol solution for several minutes.

Read more here.

Radiological

For radiological analysis, two samples are taken: one in a 5-liter container, the other in a 1.5-liter bottle.

One of them (5 l) is intended for a detailed full radiological examination, the second (1.5 l) for determining the specific activity of radon.

Another condition is that these samples must be transported upside down.

Physico-chemical

Before taking samples, the water is first drained, after which two containers are filled with a thin stream of water. In the case of analysis for 10 indicators, a container of 1.5 liters is used, for 20 or more - at least three liters.

An important condition is the complete absence of air under the cap of the container. The samples taken must be submitted for analysis within a day, later the results of the studies lose their accuracy.

Laboratory

General water analysis involves a set of several samples to determine certain indicators. First of all, samples are taken for bacteriological examination, then for chemical or physicochemical. Therefore, disinfection of the tap in this case is also necessary.

If the purpose of the analysis is to determine the quality of the consumed water, then sampling is carried out without first draining the water.

parasitological

For parasitological analysis, 50 liters of drinking water or 25 liters of water not intended for drinking are taken.

Before sampling, a preliminary drain is performed for 2 minutes, the use of extension hoses or nozzles is allowed.

When sampling from reservoirs and wells, 2 liters are taken every 2-5 minutes.

Sanitary virus

The tap is also disinfected with fire using a burning swab or cotton wool, after which water is drawn into a clean half-liter container for 10-15 minutes even after overflow.

Then one third of the water is drained and a special cotton-gauze plug with a cap made of paper is installed.