FEDERAL SUPERVISION SERVICE
IN THE SPHERE OF NATURE MANAGEMENT

QUANTITATIVE CHEMICAL ANALYSIS OF WATER

MASS MEASUREMENT TECHNIQUE
CONCENTRATIONS OF SUSPENDED SUBSTANCES AND
INCINED SUSPENDED SUBSTANCES IN
SAMPLES OF DRINKING, NATURAL AND WASTE WATER
GRAVIMETRIC METHOD

PNDF 14.1:2:4.254-2009

The technique is approved for the purposes of the state
environmental control

MOSCOW 2009
(Edition 2012)

The methodology has been reviewed and approved by the Federal budget institution « federal center Analysis and Assessment of Technogenic Impact” (FBU “FTsAO”).

Developer:

Analytical Center CJSC ROSA

1 AREA OF USE

Real normative document establishes a methodology for quantitative chemical analysis various types waters, with a chain for measuring the content of suspended and calcined suspended solids by the gravimetric method. The methodology applies to the following objects of analysis: drinking water; natural waters, including surface and underground sources of water supply; industrial, domestic, storm water and treated wastewater. The technique can be used to analyze samples of snow cover and melt water.

The measurement range of the content of suspended and calcined suspended solids is from 0.5 to 5000 mg/dm 3 .

The duration of the analysis of one sample for the content of suspended solids is 14 hours, a series of 10 samples - 15 hours.

The duration of the analysis of one sample for the content of calcined suspended solids is 17 hours, a series of 10 samples - 18 hours.

The block diagram of the analysis is given in the appendix.

Significant amounts of oils and fats interfere with the determination, therefore, when taking a sample, it must be excluded that a surface film or pieces of fat get into it. If, nevertheless, in the sample delivered to the laboratory, visible fat or oil is present on the surface, then they are removed before analysis. Fat is removed from the surface of the sample taken with a spoon or spatula, and oil with a piece of filter paper.

They also remove impurities in the form of single inclusions, for example, small sticks, grass, etc.

2 REGULATORY REFERENCES

4 MEASUREMENT METHOD

The method for determining suspended solids is based on their separation from the sample by filtering water through a pre-weighed paper or membrane filter and determining the weight of the sediment on the filter, dried to constant weight at (105 ± 2) °C.

The method for determining calcined suspended solids is based on their separation from the sample by filtering water through a pre-weighed paper or membrane filter, drying to constant weight at (105 ± 2) °C, and then determining the weight of the sediment on the filter, calcined to constant weight in a muffle furnace at (600 ± 15) °С.

5.1.2 Laboratory balance with a maximum load of 210 g of a high accuracy class according to GOST R 53228.

5.1.3 Laboratory funnels, V-56-80 XC, V-75-110 XC according to GOST 25336.

5.1.4 Homogenizer, for example, brand IKA from Labortechnic (Germany), model Ultra-Turrax T 25 or any other.

5.1.5 Distiller or installation of any type for obtaining distilled water in accordance with GOST 6709 or water for laboratory analysis of purity 2 in accordance with GOST R 52501.

5.1.6 Conical flasks with a capacity of 500 and 1000 cm 3 according to GOST 25336.

5.1.7 Muffle furnace with working chamber lined with a ceramic muffle, providing a temperature of (600 ± 15) °C.

5.1.8 Metal tweezers with sharp ends.

5.1.10 Filtering unit with a vacuum pump.

5.1.11 Vials with a ground stopper (for storing reagent solutions).

5.1.12 Refrigerator household, providing storage of samples at a temperature of (2 - 10) °C.

5.1.13 Measuring cylinders with a capacity of 500 and 1000 cm 3 according to GOST 1770, 2 accuracy classes.

5.1.14 Drying cabinet for general laboratory purposes, providing a temperature of (105 ± 2) °С.

5.1.15 Crucible tongs.

5.1.16 Any spatula or spoon.

It is allowed to use measuring instruments, auxiliary equipment, laboratory glassware with similar or better metrological and technical characteristics.

5.2 Reagents and materials

5.2.1 Distilled water in accordance with GOST 6709 or for laboratory analysis in accordance with GOST R 52501 (2nd degree of purity), (hereinafter distilled water).

5.2.3 Iron (III) chloride (ferric chloride), 6-aqueous according to GOST 4147, h., saturated solution (for labeling bottles).

5.2.4 Paper filters "blue tape" with a diameter of 15 cm, with an ash mass of (0.0016 - 0.0020) g according to TU 6-09-1678 or according to TU 2642-001-42624157.

5.2.5 Membrane filters with a pore diameter of 0.45 µm.

Reagents of a higher qualification, as well as materials with similar or better characteristics, may be used.

6 CONDITIONS FOR SAFE WORK

6.1 When performing analyzes, it is necessary to comply with safety requirements when working with chemical reagents in accordance with GOST 12.1.007.

6.2 When working with the equipment, it is necessary to comply with the electrical safety requirements when working with electrical installations in accordance with GOST R 12.1.019 and the safety requirements when working with muffle furnace in accordance with the instruction manual.

6.3 The organization of training for workers in labor safety should be carried out in accordance with GOST 12.0.004.

6.4 The laboratory room must comply with the fire safety requirements in accordance with GOST 12.1.004 and have fire extinguishing equipment in accordance with GOST 12.4.009.

7 OPERATOR QUALIFICATION REQUIREMENTS

Persons who own the technique of gravimetric analysis are allowed to perform measurements and process their results.

8 MEASUREMENT CONDITIONS

When performing measurements in the laboratory, the following conditions must be met:

All documents presented in the catalog are not their official publication and are intended for informational purposes only. Electronic copies of these documents can be distributed without any restrictions. You can post information from this site on any other site.

MINISTRY OF HOUSING AND UTILITIES OF THE RSFSR

Order of the Red Banner of Labor
Academy of Public Utilities them. K.D. Pamfilova

RECOMMENDATIONS
TO IMPROVE CONTROL METHODS
QUALITIES NATURAL AND WASTE WATER
USING VLADIPOR MEMBRANES
TYPE MFA-MA

Department of scientific and technical information of AKH

Moscow 1990

Recommendations for the use of filtering membranes "Vladipor" of the MFA-MA type in determining the color, turbidity, dry residue, dissolved and suspended solids, the content of aquatic organisms, iron bacteria and viruses in water are outlined.

The recommendations were developed by the Research Institute of Municipal Water Supply and Water Purification of the ACS named after. K.D. Pamfilova (Candidate of Medical Sciences N.A. Rusanova, Candidates of Chemical Sciences I.V. Seryakova and O.Ya. Antonova) and are intended for the laboratories of PUVKH and SES.

Development and organization of industrial production of filtering membranes "Vladipor" grades MFA-MA No. 1-10 and filtering apparatus for microbiological water analysis opened up the prospect of widespread use in the country progressive method membrane filters.

AT last years The Research Institute of Public Water Supply and Water Purification developed "Recommendations for the use of Vladipor filter membranes of the MFA-MA brand for sanitary and bacteriological analysis of water", which were included in Amendment No. 1 to GOST 18963-73 "Drinking water. Methods of sanitary-bacteriological analysis. In addition, NII KVOV together with the trust Rosvodokanaladka and I Moscow medical institute them. THEM. Sechenov developed "Recommendations for improving the method of sanitary and bacteriological control of wastewater quality."

However, sanitary-bacteriological analysis does not exhaust the possibilities of using the membrane method in the study of water quality. The method is suitable for the study of non-sanitary indicative bacteria, at the stages of physical-chemical, organoleptic, hydrobiological and virological analyzes of water quality.

Based on the work carried out at the institute during 1985 - 1987, recommendations were developed for the use of Vladipor membranes of the MFA-MA type in determining color, turbidity, which were included in Amendment No. 1 to GOST 3351-74 “Drinking water. Methods for determining taste, smell, color and turbidity”; recommendations have also been developed for the use of these membranes in determining the dry residue, dissolved and suspended solids, the content of aquatic organisms, iron bacteria and viruses in water.

The laboratories of the Northern and Western waterworks of Moscow, the central laboratory of the PUVKH of Yaroslavl, the laboratory of the wastewater treatment plant of the city of Khodorova and the laboratory of the physical and chemical wastewater treatment plant of the city of Radvilishkis (LitSSR) participated in approbation of the recommendations.

GENERAL PROVISIONS

1. Vladipor membranes of grades MFA-MA No. 1-10 are produced by the Kazan Production Association Tasma named after. V.V. Kuibyshev (TU 6-05-1903-81).

To study the quality of water, membranes with a disk diameter of 35± 2 mm.

2. The filtering device in which the membrane is mounted is selected taking into account the purpose of filtering. If a suspension released from a water sample is being investigated, it is most convenient to use a filter apparatus for microbiological water analyzes (AF index), manufactured by the factories of the Ministry of Housing and Communal Services of the RSFSR. Similar apparatus available in waterworks laboratories can be used, as well as filter systems assembled from a Bunsen flask, a Seitz funnel (or other suitable funnel), a water jet (or other vacuum-producing) pump. If the leachate is to be examined, the filter device must have a container to collect it. The aforementioned Bunsen flask system can be used. Just like a Seitz funnel, you can mount a filter section with it, removed from the common collector of the filter apparatus for microbiological water analysis (the hole where it was attached to the apparatus should be closed with a rubber stopper).

3. The membranes are prepared for operation by boiling as follows: at the bottom of the vessel in which boiling is performed (a beaker, an enamel pan, etc.), a "milk watchman" or a stainless steel mesh is placed to limit violent boiling. Distilled water is poured into this vesselin a small volume that limits the free rotation of the filter membranes in it, but sufficient for the filter membranes to be covered with water when immersed. The temperature of distilled water in the vessel is brought to 80 - 90 ° C and the heat is reduced. After that, filter membranes are placed one by one on the surface of the water, visually checked for cracks, holes, bubbles, etc. Water with membranes placed in it is slowly brought to a boil and boiled over low heat for 10-15 minutes. This water is then drained and replaced with a small amount (to cover the filter membranes) of distilled water. The filter membranes are then ready for use. Reboiling of filter membranes is not required.

If the work does not require sterility, the duration of boiling can be reduced to 3 - 5 minutes. In this case, there is less shrinkage of the filters, their ovality is somewhat less pronounced. When using membranes in handicraft, home-made filtering apparatuses, made according to the Rublevsky type, this can have a positive value.

COLOR DETERMINATION

The color of water is determined photometrically - by comparing samples of the test liquid with solutions that mimic the color of natural water.

One of the stages of analysis is the filtration of the test water and control distilled water through a membrane filter. Boiled filter membranes "Vladipor" MFA-MA No. 5, 6, 7 and 8 (any of the above numbers) are used with filter devices in which the filtrate can be collected.

Other stages of preparation for analysis and determination of color are carried out in accordance with GOST 3351-74 "Methods for determining taste, smell, color and lightness" (p.).

DETERMINATION OF TURBIDITY

The turbidity of water is determined photometrically - by comparing samples of the investigated water with standard suspensions.

One of the stages of analysis is the filtration of the test water in order to obtain a filtrate used as a control liquid in determining the optical density of the test water sample.

Boiled filter membranes "Vladipor" grades MFA-MA No. 5, 6, 7 and 8 (any of the above numbers) are used with filter devices in which the filtrate can be collected.

Other stages of preparation for analysis and determination of turbidity are carried out in accordance with GOST 3351-74 "Methods for determining, taste, smell, color and turbidity" (p. 5).

DETERMINATION OF SUSPENDED SUBSTANCES

Suspended solids are water-insoluble contaminants. They are determined gravimetrically after a delay on the filter.

The choice of method for the retention of suspended solids depends on their nature. The method using membrane filters is used in the presence of sewage or natural water fine suspension, which is not retained by ashless filtrates, and in cases where the amount of suspended solids in the water is below 10 mg/l. This method guarantees the retention of suspended solids whose particles have a particle size of 1 µm and above.

A contraindication to the use of the membrane filter method for the determination of suspended solids is the presence of hygroscopic suspended solids in the studied wastewater and less often natural water, the retention of which on membrane filters prevents the membranes from reaching a constant mass during drying, which is required in the analysis process.

Boiled membranes "Vladipor" brand MFA-MA No. 9, 10 are used. Excess moisture from the membranes after boiling is removed by blotting them on filter paper. The membranes are transferred to numbered bottles and dried to constant weight at 105± 2 °C for 30 - 45 min. The numbered lid of the bottle is placed next to the bottle during drying. After 45 minutes, the bottle is closed with an appropriate lid, transferred for 20-30 minutes to cool in a desiccator and weighed.

The sample is analyzed no later than 1 day without preservation. Thoroughly mixed test water is transferred in several steps into a measuring container.

When the content of suspended solids is 5 - 10 mg/dm 3 the volume of the filtered sample is 0.2 - 0.4 dm 3 ; if suspended solids are in the range of 10 - 50 mg/dm 3 , the sample volume is 0.2 - 0.5 dm 3 . The error of such a determination is in the allowable great-grandfathers: it does not exceed 20% (at p = 0.095). When the concentration of suspended solids is more than 50 mg/dm 3 , the sample volume is 0.05 dm 3 . In this case, the error of determination is even smaller: 5 - 10%.

Before filtration, the dried filter is moistened in distilled water and put into the filter device. The measured volume of water is filtered under vacuum. If necessary, the process can be accelerated by filtering the sample through several sequentially replaceable membranes; it is possible to fill the sample from the cylinder without additional mixing into the filter funnel in small portions. The last portion is shaken well, and then filtered. The cylinder and walls of the funnel are rinsed several times with small volumes of distilled water; the resulting suspension is filtered.

At the end of filtration, the membrane filter with the precipitate is dried in an open bottle for 45–60 minutes, cooled,having closed the bottle with a lid, in a desiccator, weighed. After that, re-drying is carried out for 15 - 20 minutes and re-weighing after cooling. Drying to constant weight is considered to be achieved if the difference between the masses during weighing after the first and after repeated drying (both filters without sediment and filters with sediment) does not exceed 0.0002 g.

The calculation is made according to the formula

where X - the content of suspended solids, mg/dm 3 ;

m 1 - weight of the weighing bottle with filter and sediment, mg;

m2 - weight of the bottle with a clean filter, mg;

V - the volume of the analyzed sample, cm 3 .

Example . A sample of 500 cm 3 of water was filtered. The weight of the weighing bottle with a filter and suspension is 21065.8 mg, the weight of the weighing bottle with a clean filter is 21054.4 mg. Suspended solids content

mg / dm 3.

DETERMINATION OF DRY RESIDUE, SOLVED SUBSTANCES

The term "Dry residue" is used in the study of natural (GOST 17.1.3.03-77 "Rules for the selection and assessment of the quality of sources of centralized domestic drinking water supply") and drinking water (GOST 18164-72 "Drinking water. Method for determining the content of dry residue"). The term "Dissolved substances" is used in the study of wastewater ("Method technological control work treatment facilities city ​​sewer. - M.: Stroyizdat, 1977). These terms denote the same generalized indicator of water quality, which determines the content of non-volatile dissolved and colloidal impurities of an inorganic and organic nature. This is the residue obtained by evaporating to dryness the filtered test water, dried at a temperature of 103 ° C, investigated gravimetrically.

The first stage of the analysis is the filtration of the water sample under study, which is carried out through a paper or membrane filter in order to free the sample from suspended impurities. The use of membrane filtration is indispensable if there is a fine suspension in the water.

Boiled filter membranes "Vladipor" grades MFA-MA No. 9, 10 are used with filtering devices in which the filtrate can be collected. The volume of the studied sample of drinking water is not less than 300 cm 3 , the volume of purified urban waste liquid is not less than 100 cm 3 . Samples are not preserved, they are examined immediately or not later than in a day.

The resulting filtrate should be visually transparent. It is evaporated, dried and examined gravimetrically according to current rules(GOST 18164-72 "Drinking water. Method for determining the content of dry residue", "Method of technological control of the operation of urban sewage treatment facilities").

HYDROBIOLOGICAL ANALYSIS

When analyzing water, sediments from structures and loading filters for the content of algae cells (phytoplankton, phytobenthos, phytoperiphyton), small forms of zooorganisms (ciliates, rotifers, etc.), in most cases, preliminary concentration of organisms is required.

Filtering membranes “Vladipor” of grades MFA-MA No. 9, 10 prepared by boiling are used.

The volume of filtered samples is dictated by the objectives of the study.

During the flowering period, samples should be filtered without pouring the entire test volume into the filter funnel, but proportionally (50-100 ml each), draining first of all the upper settled part of the sample. The last 1 - 2 portions are filtered after shaking well. The container is rinsed with 10 ml of water, which is also filtered. If filtration through one filter slows down during operation, the next portion of the sample can be filtered through a new filter. Delayed aquatic organisms are washed out in the volume of water required for the study from all filters used to filter this sample.

In the resulting concentrate, the qualitative and quantitative composition of hydrobionts is studied using microscopy.

DETERMINATION OF IRON BACTERIA

Direct microscopy of iron bacteria concentrated on a filter membrane is one of the simplest and most operational methods assessment of the qualitative composition and concentration of iron bacteria in natural and drinking water, in sediments and fouling of water supply systems.

Boiled filter membranes "Vladipor" grades MFA-MA No. 5, 6, 7 and 8 are used.

The volume of the test sample depends on the concentration of iron bacteria and other suspensions in it (1 - 1000 cm 3).

Having finished filtration, the membranes are dried and inscribed. If necessary, stain the retained iron bacteria. The whole membrane or a separate segment is mounted on a glass slide.

Vaseline oil is used to clear the membranes. This is followed by microscopy of iron bacteria.

VIROLOGICAL STUDY

In virological studies of drinking, natural, waste water, conducted on cell cultures, prerequisite is the elimination (limitation) of the negative impact on the cells of bacteria contained in the same water samples as viruses.

Filtering membranes "Vladipor" brand MFA-MA No. 1 sterilized by boiling are used to remove bacterial suspension from samples.

The volume of the filtered sample is 5 - 10 cm 3 . Processing larger samples is difficult due to the length of the filtration process through these membranes.

The contamination with bacterial flora can be significantly reduced by filtering water samples through sterilized boiling filtering membranes "Vladipor" grades MFA-MA No. 2, 3, 4.

The membranes are used with filtering devices in which the filtrate can be collected. At the same time, the filter funnel, the container for collecting the filtrate, its plug must be pre-sterilized.

The use of membranes does not exclude the need to use antibiotics when seeding samples in cell culture.

suspended solids- These are water-insoluble particles remaining on the filter when the analyzed sample is passed through the filter. Their determination is carried out either immediately after filtering the sample, drying the residue on the filter to constant weight at 105-110 ° C and weighing it, or indirectly by the difference between the total content of impurities and the amount of dissolved substances. Filtration, centrifugation or indirect calculation can be used to determine suspended solids. The choice of method depends on the purpose, the composition of the laboratory equipment, the amount and nature of suspended solids. For exact definition small-

Large quantities (less than 50 mg/dm) are filtered through a membrane filter. For the analysis of waters with a high content of suspended solids, it is advisable to use a paper filter.

Performing analysis

Samples for determination are taken in glass or polyethylene bottles. The determination is best done immediately, but not later than after 1 day. Canning them is unacceptable.

it is necessary to take a sample with a volume of at least 1000 cm3; at high contents of suspended solids, one can limit oneself to a smaller

volume - 500 cm3 (although when using a sample with a volume of

1000 cm results will be more accurate).

Ashless filters are preliminarily prepared and checked before the determination. To do this, they are numbered with a simple pencil or ballpoint pen, placed in weighing bottles and dried in an oven for about 1 hour at 105-0 ° C to constant weight. Then the bottles with filters are closed with lids, placed in a desiccator and after cooling they are weighed with an accuracy of 0.0002 g. After that, the bottles, having opened the lids, are again placed in an oven for 30 minutes and weighed after cooling. If the weight of the filter bottles differs by no more than 0.0002 g, drying can be completed.

Dried filters should be checked for soluble impurities. To do this, they are put into glass funnels and washed with demineralized water, spending about 200 cm 3 on each filter. The washed filters are placed in bottles and dried again to constant weight. If the mass of the filter before and after washing changes by less than 0.001 g, then the filters of this batch can be used without preliminary washing immediately after drying. Otherwise, it is necessary to pre-wash them with demineralized water or use filters from another batch. This check should be carried out for each new batch of filters.

A 1000 cm 3 cylinder of a thoroughly mixed sample is measured (or a smaller volume, but such that it contains at least 100-250 mg of suspended solids) and filtered through a dried and pre-weighed paper filter.

Before starting filtration, the filter should be moistened with a few drops of demineralized water and carefully put into the funnel. The first portions of the filtrate (100-200 cm 3 ) may contain filtrate fibers, so they should be returned to the analyzed sample. At the end of filtration, the walls of the vessel in which the sample was located are washed with demineralized water to wash off the adhering particles of suspended solids, and pour it onto the same filter. Then the filter is washed 1-2 times with small portions (10-15 cm 3 each) of demineralized water, placed in the same weighing bottle in which they were weighed, and dried in an oven at 105-110 ° C to constant weight. After drying, the filter bottle is weighed again.

When filtering the sample and washing the filter, in order to avoid losses, it is filled with liquid no more than % of its volume.

Results processing

where t is the weight of the weighing bottle with the dried filter and sediment of suspended solids, g; t 0- weight of the same bottle with dried filter up to

filtering operations, g; K pr - the volume of water samples taken for analysis

If a sample of 1000 cm3 is taken for analysis, the formula is simplified.

Suspended solids present in natural waters consist of particles of clay, sand, silt, suspended organic and inorganic matter, plankton and various microorganisms. Suspended substances enter open water bodies together with melt or rain water, as a result of erosion of river channels, with sewage. In large reservoirs, the turbidity of the water increases near the banks due to sediment resuspension during strong wind. Suspended particles reduce the transparency of water, thereby reducing the penetration of light into it, which in turn reduces the photosynthesis of aquatic plants and aeration of the aquatic environment. Suspended substances affect the temperature and composition of the dissolved components of surface waters, they contribute to the silting of the bottom in areas with a low flow rate, and have an adverse effect on the vital activity of aquatic organisms. Various pollutants can be sorbed on suspended particles; settling to the bottom, they can become a source of secondary water pollution.

The concentration of suspended particles is related to seasonal factors and runoff regime, depends on the rocks that make up the channel, as well as on anthropogenic factors such as agriculture, mining, etc.

The concentration of suspended matter in surface watercourses can reach significant values ​​- up to 3000-10000 mg / dm 3, the usual content is 100-1500 mg / dm 3.

In accordance with the requirements for the composition and properties of water in water bodies at points of household and drinking and cultural and community purposes, the content of suspended solids as a result of wastewater discharge should not increase, respectively, by more than 0.25 mg / dm 3 and 0.75 mg / dm 3 .

Determination of the concentration of dissolved substances

The method for measuring the mass concentration of dissolved substances is based on evaporating to dryness 5-1000 cm 3 of a filtered water sample in a pre-calcined and weighed porcelain cup, drying the dry residue for 3 hours at a temperature of 105 ° C and weighing it on an analytical balance. The mass of the dry residue should be in the range of 50-500 mg, otherwise a larger volume of water is taken for analysis.

Mass of dry residue orsolute concentrationcharacterizes the total content of mineral substances in water; usually expressed in mg / dm 3 (up to 1000 mg / dm 3) and ‰ (ppm or thousandth with a mineralization of more than 1000 mg / dm 3). MPC - no more than 1000 mg / dm 3.

Water with a high salt content adversely affects plant and animal organisms, production technology and product quality, causes scale formation on the walls of boilers, corrosion, and soil salinization.

Hardness of water

Hardness of water- this is a combination of water properties due to the presence of multiply charged cations in it, primarily Ca 2+ and Mg 2+ cations. Distinguish between general, temporary and permanent water hardness.

General hardness consists of hydrocarbonate (temporary or removable) and non-carbonate (permanent) water hardness. The first is caused by the presence of calcium and magnesium bicarbonates in water, the second - by the presence of water-soluble sulfates, chlorides, silicates, nitrates and hydrogen phosphates of these metals. Quantitatively, the total hardness of water is expressed as the total number of millimoles of equivalents of Ca 2+ and Mg 2+ ions contained in 1 liter of water (mmol equiv / dm 3). To determine the hardness of water, a titrimetric (complexometric) method is used.

AT vivo calcium and magnesium ions enter the water as a result of the interaction of dissolved carbon dioxide with carbonate minerals and other processes of dissolution and chemical weathering rocks. The source of these ions is also microbiological processes occurring in soils in the catchment area, in bottom sediments, as well as wastewater from various enterprises.

Hydrocarbonate hardness is easily removed by boiling water, and therefore it is called temporary rigidity: calcium and magnesium bicarbonates, when boiled, turn into calcium and magnesium carbonates and settle on the walls of the vessel in the form of scale

Ca (HCO 3) 2 CaCO 3  + CO 2  + H 2 O,

Mg (HCO 3) 2
MgSO 3  + CO 2  + H 2 O

Hydrocarbonate hardness can be eliminated by adding slaked lime

Ca (HCO 3) 2 + Ca (OH) 2  2CaCO 3  + 2H 2 O

Mg (HCO 3) 2 + 2Ca (OH) 2  Mg (OH) 2  + 2CaCO 3  + 2H 2 O.

Permanent hardness boiling cannot be removed. In this case, sodium carbonate or phosphate is added to the water to remove Ca 2+ and Mg 2+ ions. In this case, the following reactions will take place:

CaCl 2 + Na 2 CO 3  CaCO 3  + 2NaCl,

3СаCl 2 + 2Na 3 PO 4  Ca 3 (PO 4) 2 + 6NaCl.

Currently, ion-exchange resins - ion exchangers - are widely used to eliminate water hardness, with the help of which it is possible to carry out complete desalination of water.

Water hardness varies widely. Water with a total hardness of less than 2 mmol equiv / dm 3 is considered soft, from 2 to 10 - medium hardness, more than 10 mmol equiv / dm 3 - hard. Hydrocarbonate hardness is up to 70–80% of the total hardness.

High hardness worsens the organoleptic properties of water. Water with a hardness of more than 10 mmol equiv/dm 3 has a bitter taste and has an effect on the digestive organs, affects the kidneys, and contributes to the appearance of dermatitis. Hard water does not digest meat and vegetables well. For drinking purposes, water of medium hardness is recommended. Hard water does not foam with soap, since the soluble sodium salts of fatty acids contained in the soap are converted into insoluble calcium salts of the same acids. When boiling hard water, scale forms on the walls of steam boilers, which makes it difficult to heat water, causes an increase in fuel consumption, and accelerates the wear of boilers. Soft water is recommended for household and industrial purposes.

Wastewater is a complex heterogeneous system containing pollution of various nature. Substances are presented in soluble and insoluble, organic and inorganic form. The concentration of compounds varies, in particular, organic pollution in domestic wastewater are presented in the form of proteins, carbohydrates, fats and biological products. In addition, effluents contain rather large impurities - waste of vegetable origin, such as paper, rags, hair and synthetic substances. Inorganic compounds are represented by phosphate ions, the composition may include nitrogen, calcium, magnesium, potassium, sulfur and other compounds.

Domestic waste always includes biological substances in the form of molds, eggs, worms, bacteria, viruses. It is because of the presence of pollutants that wastewater is considered dangerous for humans, plants and animals in epidemiological terms.

To determine the composition and amount of suspended particles in the discharge water, it is necessary to conduct many analyzes of the chemical and sanitary-bacteriological type. The results will show the level of concentration of pollutants in the water, and therefore the most best option cleaning. But a complete analysis is not always possible, so it is easier to use a simplified version that gives an incomplete characterization of water, but provides information about transparency, the presence of suspended particles, the concentration of dissolved oxygen and the need for it.

The analysis is carried out according to the following indicators:

1. Temperature . The indicator indicates the rate of sedimentation from suspensions and the intensity of processes species affecting the efficiency and quality of cleaning.
2. Colour, coloration. Domestic wastewater rarely has a pronounced color, but if there is such a factor, the quality of the wastewater is very poor and requires strengthening the work of treatment facilities or complete replacement cleaning method.
3. Smells. As a rule, a high concentration of organic decomposition products, the presence of phosphates in the wastewater and nitrogen, potassium, and sulfur included in the composition give the streams a sharp unpleasant odor.
4. Transparency. This is an indicator of the level of contaminants contained, determined by the font method. For domestic water, the standard is 1-5 cm, for flows that have undergone purification methods with biological compounds - from 15 cm.
5. The pH level is used to measure the reaction of the medium. Permissible indicators 6.5 - 8.5.
6. Sediment. It is the dense sediment, determined by the sample filtrate, that is measured. According to SNiP standards, no more than 10g/l is allowed.
7. suspended solids make up no more than 100-500 cg / l in urban waters with an ash content of up to 35%.

Phosphorus and nitrogen, as well as all their forms, are studied separately. 4 forms of nitrogen are taken: total, ammonium, nitrite and nitrate. AT sewage the general and ammonium types are more common, nitrite and nitrate only if cleaning methods were used by means of aerotanks and biofiltrates. Establishing the concentration of nitrogen and its forms is an important component of the analysis, since nitrogen is necessary for the nutrition of bacteria, like phosphorus.

Typically, nitrogen in domestic wastewater is found in in full, but there are not enough phosphates, therefore, often with a lack of phosphates, they are replaced by lime (ammonium chloride).

• sulfates and chlorides are not subject to changes during treatment, the removal of suspended solids is possible only with the complete processing of wastewater, however, the content of substances in low concentrations does not affect biochemical processes, therefore, the permissible parameters remain within 100 mg/l.
• Toxic elements- these are also suspended substances, however, even a small concentration of compounds has a negative impact on the life and activity of organisms. That is why suspended solids of a toxic type are classified as especially polluting and are separated into a separate group. These include: sulfides, mercury, cadmium, lead and many other compounds.
• Synthetic surfactant suspended solids is one of the most serious threats. The content of elements in wastewater negatively affects the state of water bodies, and also reduces the functionality of treatment facilities.

Only 4 groups of surfactants differ:

1. Anionic - compounds account for ¾ of the world production of synthetic surfactants;
2. Non-onogenic - occupy the second place in terms of concentration in urban wastewater;
3. Cationic- slow down the cleaning processes occurring in the sedimentation tanks;
4. Amphoteric - rare, but significantly reduce the efficiency of removing waste from the water.

Dissolved oxygen is contained in drain waters no more than 1 mg / l, which is extremely small for normal operation microorganisms that are responsible for removing suspended particles from wastewater. Maintaining the vital activity of bacteria requires from 2 mg / l, therefore, it is important to control the content of dissolved oxygen in domestic waste water, especially those that are discharged into artificial or natural reservoirs - failure to comply with acceptable standards for the content of dissolved oxygen will lead to the appearance of polluting particles in lakes and disruption of natural natural balance. And this already means the extinction of natural resources.

As for the biological compounds that make up the drain waters, the purification process copes with them by 90% or more. This is especially true for helminth eggs found in streams in great variety. The concentration of eggs reaches up to 92% of the total composition of pollutants, so the removal of elements is one of the most important tasks.

Treatment options for domestic and industrial waste water

The most practical and popular is the method in which removal is carried out biologically. Functionally, the process is the processing by active biological components of polluting particles that have entered domestic wastewater. There are two options for removal:

1. Anaerobic - the process of destruction of substances without access to air / oxygen;
2. Aerobic - the destruction and removal of suspended particles by beneficial microorganisms with the supply of oxygen.

In addition, artificial conditions are created for better processing of organics, but sometimes bacterial colonies are enough for the treatment of domestic waste streams to take place in natural conditions, and it is only important to monitor the flow of a sufficient amount of organics.

Artificially created conditions are called filter fields. These are special areas with sandy or loamy soil prepared for natural flow biological treatment contaminants in waste water through filtration through the soil layers. In this way, the permissible levels of the content of substances are achieved. The process proceeds with the help of aerobic and anaerobic bacteria contained in the soil, so the removal of polluting particles is considered more complete. However, the method cannot always eliminate phosphates and nitrogen in the treated waters, and is also considered inconvenient due to large areas, seasonal use and bad smell.

The use of septic tanks and aeration biological treatment plants can also cope with wastewater treatment. The advantages of artificial sewage treatment plants are in the possibility of intensifying cleaning processes, retrofitting equipment such as biofilters, as well as the ability to use structures throughout the year. Of great importance is the ability to clean without an unpleasant odor. while maintaining favorable climate and the receipt of a sufficient amount of organic matter, the cleaning process takes place continuously, and the most serious polluting compounds, the concentration of which is exceeded, are removed. But it's important to remember that general composition incoming drains should not contain many elements, such as:

• Chemical acids;
• Gasolines and solvents;
• Biologically active substances;
• antibiotics;
• Compounds of washing powders, detergents;
• Abrasives.

With all the possibilities of removal, cleaning in domestic septic tanks cannot cope with the compounds of phosphates, nitrates, and nitrogen also does not neutralize, however, a significantly reduced concentration allows the accumulation of purified streams in reservoirs, from where to take water for irrigation or technical needs.

Suspended substances that are part of the drain streams are removed by a biological treatment method, that is, by cultivating microorganisms in the waters that destroy the compounds of polluting particles. Organics can be of both plant and animal origin, with carbon being the main component of plant debris, and nitrogen being the main component of animal debris. That is why the total composition of beneficial bacteria for wastewater treatment must contain all types of microorganisms in order to successfully cope with the removal of contaminants.

In order to remove aggressive chemical compounds, phosphates, toxic substances, which are part of industrial effluents, are used centralized systems cleaning, which shows the use of strong reagents and chemicals. And in order to deal with pollution in domestic waters, where the water comes from for irrigation, washing the car and other household needs, enough high-quality septic tanks.