Turbidity is an indicator of water quality due to the presence in water of undissolved and colloidal substances of inorganic and organic origin. Turbidity in surface waters is caused by silts, silicic acid, iron and aluminum hydroxides, organic colloids, microorganisms and plankton. In groundwater, turbidity is caused mainly by the presence of undissolved mineral substances, and when sewage penetrates into the soil, also by the presence of organic substances. In Russia, turbidity is determined photometrically by comparing samples of the studied water with standard suspensions. The result of the measurement is expressed in mg/dm3 when using the basic kaolin standard suspension or in MU/dm3 (turbidity units per dm3) using the basic formazin standard suspension. The last unit of measure is also called the Formazine Turbidity Unit (FMU) or in Western terminology FTU (Formazine Turbidity Unit). 1FTU=1EMF=1EM/dm3. AT recent times The photometric method for measuring turbidity by formazin has been established as the main one all over the world, which is reflected in the ISO 7027 standard (Water quality - Determination of turbidity). According to this standard, the turbidity unit is FNU (Formazine Nephelometric Unit). Agency for Protection Environment USA (U.S. EPA) and World Organization The World Health Organization (WHO) uses the Nephelometric Turbidity Unit (NTU) for turbidity. The relationship between the basic turbidity units is as follows: 1 FTU(NUF)=1 FNU=1 NTU.
WHO does not standardize turbidity according to indications of health effects, however, from the point of view of appearance recommends that turbidity be no higher than 5 NTU (nephelometric turbidity unit) and, for decontamination purposes, no more than 1 NTU.
A measure of transparency is the height of a water column at which one can observe a white plate of a certain size lowered into the water (Secchi disk) or distinguish a font of a certain size and type on white paper (Snellen font). The results are expressed in centimeters.
Chroma
Color is an indicator of water quality, mainly due to the presence of humic and fulvic acids, as well as iron compounds (Fe3+) in the water. The amount of these substances depends on the geological conditions in the aquifers and on the number and size of peatlands in the basin of the river under study. Thus, the surface waters of rivers and lakes located in the zones of peat bogs and swampy forests have the highest color, the lowest - in the steppes and steppe zones. In winter, the content of organic matter in natural waters minimal, while in spring during floods and floods, as well as in summer during the period of mass development of algae - water bloom - it increases. Groundwater, as a rule, has a lower color than surface water. Thus, high color is an alarming sign indicating the trouble of water. In this case, it is very important to find out the cause of the color, since the methods for removing, for example, iron and organic compounds differ. The presence of organic matter not only worsens the organoleptic properties of water, leads to the appearance of foreign odors, but also causes a sharp decrease in the concentration of oxygen dissolved in water, which can be critical for a number of water treatment processes. Some basically harmless organic compounds, entering into chemical reactions(for example, with chlorine), are capable of forming compounds that are very harmful and dangerous to human health.
Chromaticity is measured in degrees of the platinum-cobalt scale and ranges from units to thousands of degrees - Table 2.
The qualitative characteristics of the shades of taste sensations - aftertaste - are expressed descriptively: chlorine, fish, bitter, and so on. The most common salty taste of water is most often due to sodium chloride dissolved in water, bitter - magnesium sulfate, sour - an excess of free carbon dioxide, etc. The threshold of taste perception of saline solutions is characterized by the following concentrations (in distilled water), mg/l: NaCl - 165; CaCl2 - 470; MgCl2 - 135; MnCl2 - 1.8; FeCl2 - 0.35; MgSO4 - 250; CaSO4 - 70; MnSO4 - 15.7; FeSO4 - 1.6; NaHCO3 - 450.
According to the strength of the effect on the taste organs, the ions of some metals line up in the following rows:
O cations: NH4+ > Na+ > K+; Fe2+ > Mn2+ > Mg2+ > Ca2+;
O anions: OH-> NO3-> Cl-> HCO3-> SO42-.
Intensity of flavor and taste |
The nature of the appearance of taste and taste |
Intensity score, score |
Taste and taste are not felt |
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Very weak |
Taste and taste are not perceived by the consumer, but are detected in the laboratory |
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Taste and taste are noticed by the consumer, if you pay attention to it |
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Noticeable |
Taste and taste are easily noticed and cause disapproval of water. |
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distinct |
Taste and taste attract attention and make you refrain from drinking |
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Very strong |
The taste and flavor is so strong that it makes the water unfit for drinking. |
The odor group should also be indicated according to the following classification:
Odors are divided into two groups:
Odor designation |
The nature of the smell |
Approximate type of smell |
Aromatic |
Cucumber, floral |
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Bolotny |
muddy, muddy |
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Putrefactive |
Fecal, sewage |
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Woody |
The smell of wet chips, woody bark |
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Earthy |
Pretty, the smell of freshly plowed land, clayey |
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moldy |
Musty, stagnant |
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The smell of fish oil, fishy |
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hydrogen sulfide |
The smell of rotten eggs |
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Grassy |
The smell of cut grass, hay |
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Uncertain |
Odors of natural origin that do not fall under the previous definitions |
Odor intensity |
The nature of the odor |
Intensity score, score |
The smell is not felt |
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Very weak |
The smell is not felt by the consumer, but is detected in the laboratory test |
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The smell is noticed by the consumer, if you pay attention to it |
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Noticeable |
The smell is easily noticed and causes disapproval of water. |
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distinct |
The smell attracts attention and makes you refrain from drinking |
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Very strong |
The smell is so strong that it makes the water unusable |
If the water has a low content of free hydrogen ions (pH> 7) compared to OH- ions, then the water will have an alkaline reaction, and with an increased content of H + ions (pH<7)- кислую. В идеально чистой дистиллированной воде эти ионы будут уравновешивать друг друга. В таких случаях вода нейтральна и рН=7. При растворении в воде различных химических веществ этот баланс может быть нарушен, что приводит к изменению уровня рН.
pH determination is carried out by colorimetric or electrometric method. Water with a low pH is corrosive, while water with a high pH tends to foam.
Depending on the pH level, water can be divided into several groups:
Typically, the pH level is within the range at which it does not directly affect the consumer qualities of water. Thus, in river waters pH is usually in the range of 6.5-8.5, in atmospheric precipitation 4.6-6.1, in swamps 5.5-6.0, in sea waters 7.9-8.3. Therefore, WHO does not offer any medically recommended value for pH. At the same time, it is known that at low pH, water is highly corrosive, and at high levels (pH>11), water acquires a characteristic soapiness, bad smell may cause eye and skin irritation. That is why for drinking and domestic water, the pH level in the range from 6 to 9 is considered optimal.
In ordinary natural waters, acidity in most cases depends only on the content of free carbon dioxide. The natural part of the acidity is also created by humic and other weak organic acids and cations of weak bases (ions of ammonium, iron, aluminum, organic bases). In these cases, the pH of the water is never below 4.5.
Polluted water bodies may contain a large number of strong acids or their salts by discharging industrial wastewater. In these cases, the pH may be below 4.5. The part of the total acidity that lowers the pH to values< 4.5, называется свободной.
But general content in natural waters, calcium and magnesium ions are incomparably greater than the content of all other listed ions - and even their sum. Therefore, hardness is understood as the sum of the amounts of calcium and magnesium ions - the total hardness, which is made up of the values of carbonate (temporary, eliminated by boiling) and non-carbonate (permanent) hardness. The first is caused by the presence of calcium and magnesium bicarbonates in the water, the second by the presence of sulfates, chlorides, silicates, nitrates and phosphates of these metals.
In Russia, water hardness is expressed in mg-eq / dm3 or in mol / l.
Carbonate hardness (temporary) - caused by the presence of calcium and magnesium bicarbonates, carbonates and hydrocarbons dissolved in water. During heating, calcium and magnesium bicarbonates partially precipitate in solution as a result of reversible hydrolysis reactions.
Non-carbonate hardness (permanent) - caused by the presence of chlorides, sulfates and calcium silicates dissolved in water (they do not dissolve and do not settle in solution during heating of water).
Water group |
Unit of measure, mmol/l |
Very soft |
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medium hardness |
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Very tough |
The following forms of water alkalinity are distinguished: bicarbonate (hydrocarbonate), carbonate, hydrate, phosphate, silicate, humate - depending on the anions of weak acids, which determine alkalinity. The alkalinity of natural waters, the pH of which is usually< 8,35, зависит от присутствия в воде бикарбонатов, карбонатов, иногда и гуматов. Щелочность других форм появляется в процессах обработки воды. Так как в природных водах почти всегда щелочность определяется бикарбонатами, то для таких вод общую щелочность принимают равной карбонатной жесткости.
In addition, the content of iron and manganese in water can cause the development of manganese bacteria and iron bacteria, the colonies of which can cause overgrowth of water pipes.
Nitrite arises mainly due to the oxidation of ammonia in water, but can also penetrate into it together with rainwater due to the reduction of nitrates in the soil.
Nitrates are a product of the biochemical oxidation of ammonia and nitrites, or they can be leached from the soil.
O at pH< 5 имеет вид H2S;
O at pH > 7 acts as an HS- ion;
O at pH = 5:7 can be in the form of both H2S and HS-.
Water. They enter the water due to the washing out of sediments. rocks, soil leaching and sometimes due to the oxidation of sulfides and sulfur - protein breakdown products from wastewater. A high content of sulfates in water can cause diseases of the digestive tract, and such water can also cause corrosion of concrete and reinforced concrete structures.
Hydrogen sulfide gives water an unpleasant odor, leads to the development of sulfur bacteria and causes corrosion. Hydrogen sulfide, predominantly present in groundwater ah, may be of mineral, organic or biological origin, and in the form of dissolved gas or sulfides. The form in which hydrogen sulfide appears depends on the pH reaction:
The relative content of oxygen in water, expressed as a percentage of its normal content, is called the degree of oxygen saturation. This parameter depends on water temperature, atmospheric pressure and salinity level. Calculated by the formula: M = (ax0.1308x100)/NxP, where
М is the degree of water saturation with oxygen, %;
А – oxygen concentration, mg/dm3;
R - Atmosphere pressure in the area, MPa.
N is the normal oxygen concentration at a given temperature and a total pressure of 0.101308 MPa, given in the following table:
Water temperature, °С |
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There are several types of water oxidizability: permanganate (1 mg KMnO4 corresponds to 0.25 mg O2), dichromate, iodate, cerium. The highest degree of oxidation is achieved by bichromate and iodate methods. In the practice of water treatment for natural slightly polluted waters, permanganate oxidizability is determined, and in more polluted waters, as a rule, bichromate oxidizability (also called COD - chemical oxygen demand). Oxidability is a very convenient complex parameter for assessing the total pollution of water with organic substances. Organic substances found in water are very diverse in nature and chemical properties. Their composition is formed both under the influence of biochemical processes occurring in the reservoir, and due to the inflow of surface and ground waters, precipitation, industrial and domestic wastewater. The value of the oxidizability of natural waters can vary over a wide range from fractions of milligrams to tens of milligrams of O2 per liter of water.
Surface waters have a higher oxidizability, which means they contain high concentrations of organic matter compared to groundwater. So, mountain rivers and lakes are characterized by oxidizability of 2-3 mg O2/dm3, flat rivers - 5-12 mg O2/dm3, swamp-fed rivers - tens of milligrams per 1 dm3.
Groundwater, on the other hand, has an average oxidizability at the level of hundredths to tenths of a milligram of O2/dm3 (exceptions are waters in areas of oil and gas fields, peat bogs, in heavily swamped areas, groundwaters in the northern part of the Russian Federation).
The fact is that natural waters are solutions of mixtures of strong and weak electrolytes. The mineral part of the water is predominantly sodium (Na+), potassium (K+), calcium (Ca2+), chlorine (Cl–), sulfate (SO42–), hydrocarbonate (HCO3–) ions.
These ions are responsible mainly for the electrical conductivity of natural waters. The presence of other ions, for example, ferric and divalent iron (Fe3+ and Fe2+), manganese (Mn2+), aluminum (Al3+), nitrate (NO3–), HPO4–, H2PO4–, etc. does not have such a strong effect on electrical conductivity (of course, provided that these ions are not contained in water in significant quantities, as, for example, it can be in industrial or household sewage). Measurement errors arise due to the unequal specific electrical conductivity of solutions of various salts, as well as due to an increase in electrical conductivity with increasing temperature. However, the current level of technology allows minimizing these errors, thanks to pre-calculated and stored dependencies.
The electrical conductivity is not standardized, but the value of 2000 μS/cm approximately corresponds to a total mineralization of 1000 mg/l.
Groundwater is classified:
Transparency of sea water- an indicator characterizing the ability of water to transmit light rays. Depends on the size, quantity and nature of suspended solids. To characterize the transparency of water, the concept of "relative transparency" is used.
For the first time, the degree of transparency of sea water was able to determine the Italian priest and astronomer named Pietro Angelo Secchi in 1865 using a disk with a diameter of 30 cm, lowered into the water on a winch from the shady side of the ship. This method was later named after him. AT this moment exist and are widely used. electronic devices for measuring water transparency (transmissometers)
There are three main methods for measuring water transparency. All of them presuppose the definition optical properties water, as well as taking into account the parameters of the ultraviolet spectrum.
First of all, water transparency calculations are an integral part of research in hydrology, meteorology and oceanology, the transparency / turbidity index determines the presence of undissolved and colloidal substances of inorganic and organic origin in water, thereby affecting pollution marine environment, and also allows you to judge the accumulation of plankton, the content of turbidity in the water, the formation of silt. In shipping, the transparency of sea water can be a determining factor in the detection of shallow water or objects capable of causing damage to the vessel.
Transparency of water according to the Secchi disk, according to the cross, according to the font. Turbidity of water. The smell of water. Water color.
There are suspended solids in the water, which reduce its transparency. There are several methods for determining the transparency of water.
Water has increased turbidity due to the content of coarse inorganic and organic impurities in it. The turbidity of water is determined by the gravimetric method, and by a photoelectric colorimeter. The weight method is that 500-1000 ml of turbid water is filtered through a dense filter with a diameter of 9-11 cm. The filter is preliminarily dried and weighed on an analytical balance. After filtering, the filter with sediment is dried at a temperature of 105-110 degrees for 1.5-2 hours, cooled and weighed again. The amount of suspended solids in the test water is calculated from the difference between the masses of the filter before and after filtration.
In Russia, the turbidity of water is determined photometrically by comparing samples of the studied water with standard suspensions. The measurement result is expressed in mg / dm 3 using the main standard suspension of kaolin (turbidity for kaolin) or in MU/dm 3 (turbidity units per dm 3) when using formazin stock standard suspension. The last unit of measurement is also called the Turbidity Unit. according to Formazin(EMF) or in Western terminology FTU (formazine Turbidity Unit). 1FTU=1EMF=1EM/dm 3 .
Recently, the photometric method for measuring turbidity by formazin has been established as the main one all over the world, which is reflected in the ISO 7027 standard (Water quality - Determination of turbidity). According to this standard, the unit of measure for turbidity is FNU (formazine Nephelometric Unit). The United States Environmental Protection Agency (U.S. EPA) and the World Health Organization (WHO) use the Nephelometric Turbidity Unit (NTU).
The relationship between the basic turbidity units is as follows:
1 FTU(EMF)=1 FNU=1 NTU
WHO does not standardize turbidity for health reasons, however, from the point of view of appearance, it recommends that turbidity be no higher than 5 NTU (nephelometric turbidity unit), and for decontamination purposes - no more than 1 NTU.
Odors in the water may be associated with vital activity aquatic organisms or appear when they die - these are natural smells. The smell of water in a reservoir can also be caused by sewage effluents entering it, industrial effluents are artificial odors. First, a qualitative assessment of the smell is given according to the relevant features:
The strength of the smell is evaluated on a 5-point scale. The flask with a ground stopper is filled 2/3 with water and immediately closed, shaken vigorously, opened and the intensity and nature of the odor are immediately noted.
A qualitative assessment of the color is made by comparing the sample with distilled water. To do this, separately investigated and distilled water is poured into glasses made of colorless glass, viewed from above and from the side against a white sheet in daylight, color is evaluated as an observed color, in the absence of color, the water is considered colorless.
The temperature in water sources is determined by a scoop or conventional thermometer wrapped in several layers of gauze. The thermometer is kept in water for 15 minutes at the sampling depth, after which readings are taken.
The most favorable temperature for drinking water is 8-16°C.
The transparency of water depends on the amount of mechanical suspended solids and chemical impurities contained in it. Turbid water is always suspicious in epizootic and sanitary terms. There are several methods for determining the transparency of water.
comparison method. The test water is poured into one cylinder made of colorless glass, and distilled water is poured into the other. Water can be rated as clear, slightly transparent, slightly opalescent, opalescent, slightly turbid, turbid, and highly turbid.
Rice. 2. Secchi disk.
disk method. To determine the transparency of water directly in the reservoir, a white enameled disk is used - the Secchi disk (Fig. 2). When the disk is immersed in water, the depth at which it ceases to be visible is noted and at which it becomes visible again when removed. The average of these two values shows the transparency of the water in the reservoir. In clear water, the disk remains visible at a depth of several meters: in very muddy water it disappears at a depth of 25-30 cm.
Rice. 3. Calorimeter.
The investigated water after shaking is poured into the cylinder. Then they look down through the column of water at the font, gradually releasing water from the calorimeter tap until it becomes possible to clearly see font No. 1. The height of the liquid in the cylinder, expressed in centimeters, is a measure of transparency. Water is considered transparent if the font is clearly visible through a column of water of 30 cm. Water with a transparency of 20 to 30 cm is considered slightly cloudy, from 10 to 20 cm - cloudy, up to 10 cm is unsuitable for drinking purposes. Good clear water after standing does not give a deposit.
Rice. 3. Determination of water transparency by the ring method.
Table 1
Translation of water transparency values "on the ring" to the value "on the font"
The transparency of water depends on the amount of mechanical suspended solids and chemical impurities contained in it. Turbid water is always suspicious in epizootic and sanitary terms. There are several methods for determining the transparency of water.
comparison method. The test water is poured into one cylinder made of colorless glass, and distilled water is poured into the other. Water can be rated as clear, slightly transparent, slightly opalescent, opalescent, slightly turbid, turbid, and highly turbid.
disk method. To determine the transparency of water directly in the reservoir, a white enameled disk is used - the Secchi disk (Fig. 2). When the disk is immersed in water, the depth at which it ceases to be visible is noted and at which it becomes visible again when removed. The average of these two values shows the transparency of the water in the reservoir. In clear water, the disk remains visible at a depth of several meters; in very turbid water, it disappears at a depth of 25-30 cm.
Font method (Snellen). More accurate results are achieved using a glass calorimeter with a flat bottom (Fig. 3). The calorimeter is installed at a height of 4 cm from the standard font No. 1:
The investigated water after shaking is poured into the cylinder. Then they look down through the column of water at the font, gradually releasing water from the calorimeter tap until it becomes possible to clearly see font No. 1. The height of the liquid in the cylinder, expressed in centimeters, is a measure of transparency. Water is considered transparent if the font is clearly visible through a column of water of 30 cm. Water with a transparency of 20 to 30 cm is considered slightly cloudy, from 10 to 20 cm - cloudy, up to 10 cm is unsuitable for drinking purposes. Good clear water after standing does not precipitate.
ring method. Water transparency can be determined using a ring (Fig. 3). To do this, use a wire ring with a diameter of 1-1.5 cm and a wire cross section of 1 mm. Holding the handle, the wire ring is lowered into the cylinder with the investigated water until its contours become invisible. Then the ruler measures the depth (cm) at which the ring becomes clearly visible when removed. An indicator of acceptable transparency is considered to be 40 cm. The data obtained “by the ring” can be converted into indications “by the font” (Table 1).
Table 1
Translation of water transparency values "on the ring" to the value "on the font"
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