Color of water. Transparency of water according to the Secchi disk, according to the cross, according to the font. Turbidity of water. The smell of water. Color of water Odors of natural origin
Turbidity is an indicator of water quality, caused by the presence in water of undissolved and colloidal substances of inorganic and organic origin. Turbidity in surface waters is caused by silt, silicic acid, iron and aluminum hydroxides, organic colloids, microorganisms and plankton. In groundwater, turbidity is caused primarily by the presence of undissolved minerals, and when it penetrates into the ground Wastewater– also by the presence of organic substances. In Russia, turbidity is determined photometrically by comparing samples of the test water with standard suspensions. The measurement result is expressed in mg/dm3 when using a basic standard suspension of kaolin or in TU/dm3 (turbidity units per dm3) when using a basic standard suspension of formazin. The last unit of measurement is also called Formazine Turbidity Unit (FTU) or in Western terminology FTU (Formazine Turbidity Unit). 1FTU=1EMF=1EM/dm3. Recently, the photometric method for measuring turbidity using formazin has become established as the main method throughout the world, which is reflected in the ISO 7027 standard (Water quality - Determination of turbidity). According to this standard, the unit of measurement for turbidity is FNU (Formazine Nephelometric Unit). US Environmental Protection Agency (U.S. EPA) and World Organization The World Health Organization (WHO) uses the turbidity unit NTU (Nephelometric Turbidity Unit). The relationship between the basic units of turbidity is as follows: 1 FTU=1 FNU=1 NTU.
WHO does not standardize turbidity based on health effects, but from the point of view appearance recommends that turbidity be no higher than 5 NTU (nephelometric turbidity unit) and, for disinfection purposes, no more than 1 NTU.
A measure of transparency is the height of the water column at which one can observe a white plate of a certain size lowered into water (Secchi disk) or distinguish a font of a certain size and type on white paper (Snellen font). Results are expressed in centimeters.
Characteristics of water by transparency (turbidity)
Chroma
Color is an indicator of water quality, mainly due to the presence of humic and sulfic acids, as well as iron compounds (Fe3+) in 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 areas of peat bogs and swampy forests have the highest color, and the lowest color in steppes and steppe zones. In winter, the content of organic substances in natural waters is minimal, while in spring during the period of high water and floods, as well as in summer during the period of mass development of algae - water blooms - it increases. Groundwater, as a rule, has less color than surface water. Thus, high color is an alarming sign indicating trouble in the 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 are different. The presence of organic matter not only worsens the organoleptic properties of water and 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, in principle, 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.
Color is measured in degrees on the platinum-cobalt scale and ranges from units to thousands of degrees - Table 2.
Characteristics of waters by color
Taste and smack
The taste of water is determined by substances of organic and inorganic origin dissolved in it and varies in character and intensity. There are four main types of taste: salty, sour, sweet, bitter. All other types of taste sensations are called tastes (alkaline, metallic, astringent, etc.). The intensity of taste and aftertaste is determined at 20 °C and assessed using a five-point system, according to GOST 3351-74*.The qualitative characteristics of shades of taste sensations - taste - are expressed descriptively: chlorine, fishy, bitter, and so on. The most common salty taste of water is most often caused by sodium chloride dissolved in water, bitter by magnesium sulfate, sour by excess free carbon dioxide, etc. The threshold of taste perception of salty 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 their effect on the taste organs, ions of some metals are arranged in the following rows:
O cations: NH4+ > Na+ > K+; Fe2+ > Mn2+ > Mg2+ > Ca2+;
O anions: OH->NO3->Cl->HCO3->SO42-.
Characteristics of waters by taste intensity
|
Intensity of taste and aftertaste |
The nature of the appearance of taste and aftertaste |
Intensity rating, point |
|
Taste and aftertaste are not felt |
||
|
Very weak |
Taste and aftertaste are not perceived by the consumer, but are detected during laboratory testing. |
|
|
Taste and aftertaste are noticed by the consumer if they pay attention to it |
||
|
Noticeable |
Taste and aftertaste are easily noticed and cause disapproval of water |
|
|
Distinct |
Taste and aftertaste attract attention and make you refrain from drinking |
|
|
Very strong |
The taste and aftertaste are so strong that they make the water unfit for consumption. |
Smell
Odor is an indicator of water quality, determined by the organoleptic method using the sense of smell based on the odor strength scale. The smell of water is influenced by the composition of dissolved substances, temperature, pH values and a number of other factors. The intensity of the odor of water is determined by experts at 20 ° C and 60 ° C and measured in points, according to the requirements.The odor group should also be indicated according to the following classification:
By nature, odors are divided into two groups:
- natural origin (organisms living and dying in water, decaying plant debris, etc.)
- artificial origin (impurities of industrial and agricultural wastewater).
Natural scents
|
Odor designation |
Character of the smell |
Approximate type of smell |
|
Aromatic |
Cucumber, floral |
|
|
Bolotny |
Muddy, muddy |
|
|
Putrefactive |
Fecal, waste |
|
|
Woody |
The smell of wet wood chips, woody bark |
|
|
Earthy |
Rotten, smell of freshly plowed earth, clayey |
|
|
moldy |
Musty, stagnant |
|
|
Fish oil smell, fishy |
||
|
Hydrogen sulfide |
Rotten egg smell |
|
|
Grassy |
The smell of cut grass and hay |
|
|
Uncertain |
Odors of natural origin that do not fall under the previous definitions |
The intensity of the odor according to GOST 3351-74* is assessed on a six-point scale - see the next page.
Characteristics of water by odor intensity
|
Odor intensity |
Character of the odor |
Intensity rating, point |
|
The smell is not felt |
||
|
Very weak |
The smell is not perceived by the consumer, but is detected during laboratory testing |
|
|
The smell is noticed by the consumer if you draw his attention to it |
||
|
Noticeable |
The smell is easily noticed and causes disapproval of the water |
|
|
Distinct |
The smell attracts attention and makes you refrain from drinking |
|
|
Very strong |
The smell is so strong that it makes the water unfit for consumption. |
Hydrogen value (pH)
Hydrogen index (pH) - characterizes the concentration of free hydrogen ions in water and expresses the degree of acidity or alkalinity of water (the ratio of H+ and OH- ions in water formed during the dissociation of water) and is quantitatively determined by the concentration of hydrogen ions pH = - IgIf the water has a reduced 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.
Determination of pH is carried out using a colorimetric or electrometric method. Water with a low pH reaction is corrosive, while water with a high pH reaction tends to foam.
Depending on the pH level, water can be divided into several groups:
Characteristics of water by pH
Control over the pH level is especially important at all stages of water treatment, since its “change” in one direction or another can not only significantly affect the smell, taste and appearance of water, but also affect the effectiveness of water treatment measures. The optimal pH value required varies for different water treatment systems according to the composition of the water, the nature of the materials used in the distribution system, and depending on the water treatment methods used.
Typically, the pH level is within the range at which it does not directly affect the consumer quality of water. Thus, in river waters the pH is usually in the range of 6.5-8.5, in precipitation 4.6-6.1, in swamps 5.5-6.0, in sea waters 7.9-8.3. Therefore, WHO does not propose 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 characteristic soapiness, bad smell, may cause irritation to eyes and skin. That is why the optimal pH level for drinking and domestic water is considered to be in the range from 6 to 9.
Acidity
Acidity is the content of substances in water that can react with hydroxide ions (OH-). The acidity of water is determined by the equivalent amount of hydroxide required for the reaction.In ordinary natural waters, acidity in most cases depends only on the content of free carbon dioxide. The natural part of acidity is also created by humic and other weak organic acids and cations of weak bases (ammonium ions, iron, aluminum, organic bases). In these cases, the water pH does not fall below 4.5.
Polluted water bodies may contain large amounts of strong acids or their salts due to the discharge of industrial wastewater. In these cases the pH may be below 4.5. Part of the total acidity that reduces pH to values< 4.5, называется свободной.
Rigidity
General (total) hardness is a property caused by the presence of substances dissolved in water, mainly calcium salts (Ca2+) and magnesium (Mg2+), as well as other cations that appear in much smaller quantities, such as ions: iron, aluminum, manganese (Mn2+) and heavy metals (strontium Sr2+, barium Ba2+).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 consists 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 water, the second by the presence of sulfates, chlorides, silicates, nitrates and phosphates of these metals.
In Russia, water hardness is expressed in mEq/dm3 or 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 (constant) - caused by the presence of calcium chlorides, sulfates and silicates dissolved in water (they do not dissolve and do not settle in the solution when the water is heated).
Characteristics of water by value overall hardness
|
Water group |
Unit of measurement, mmol/l |
|
Very soft |
|
|
Medium hardness |
|
|
Very tough |
Alkalinity
Water alkalinity is the total concentration of weak acid anions and hydroxyl ions contained in water (expressed in mmol/l), which react during laboratory tests with hydrochloric or sulfuric acids to form chloride or sulfuric acid salts of alkali and alkaline earth metals.The following forms of water alkalinity are distinguished: bicarbonate (hydrocarbonate), carbonate, hydrate, phosphate, silicate, humate - depending on the anions of weak acids that determine the alkalinity. 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.
Iron, manganese
Iron, manganese - in natural water appear mainly in the form of hydrocarbons, sulfates, chlorides, humus compounds and sometimes phosphates. The presence of iron and manganese ions is very harmful to most technological processes, especially in the pulp and textile industries, and also worsens the organoleptic properties of water.In addition, the content of iron and manganese in water can cause the development of manganese bacteria and iron bacteria, colonies of which can cause clogging of water supply networks.
Chlorides
Chlorides – The presence of chlorides in water can be caused by the leaching of chloride deposits, or they can appear in the water due to the presence of effluent. Most often, chlorides in surface waters appear in the form of NaCl, CaCl2 and MgCl2, and always in the form of dissolved compounds.Nitrogen compounds
Nitrogen compounds (ammonia, nitrites, nitrates) arise mainly from protein compounds that enter the water along with wastewater. Ammonia present in water can be organic or inorganic. In the case of organic origin, increased oxidation is observed.Nitrites arise mainly due to the oxidation of ammonia in water; they can also penetrate into it along 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.
Hydrogen sulfide
O at pH< 5 имеет вид H2S;
O at pH > 7 appears as the 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 leaching of sedimentary rocks, leaching of soil 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.
Carbon dioxide
Hydrogen sulfide gives water an unpleasant odor, leads to the development of sulfur bacteria and causes corrosion. Hydrogen sulfide, predominantly present in groundwater, can be of mineral, organic or biological origin, and in the form of dissolved gas or sulfides. The form under which hydrogen sulfide appears depends on the pH reaction:
- at pH< 5 имеет вид H2S;
- at pH > 7 it appears as an HS- ion;
- at pH = 5: 7 can be in the form of both H2S and HS-.
Sulfates
Sulfates (SO42-) – along with chlorides, are the most common types of contaminants in water. They enter the water due to the leaching of sedimentary rocks, leaching of soil 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.Carbon dioxide
Carbon dioxide (CO2) – depending on the reaction, the pH of water can be in the following forms:- pH< 4,0 – в основном, как газ CO2;
- pH = 8.4 – mainly in the form of bicarbonate ion HCO3-;
- pH > 10.5 – mainly in the form of carbonate ion CO32-.
Dissolved oxygen
Oxygen enters a body of water by dissolving it upon contact with air (absorption), as well as as a result of photosynthesis by aquatic plants. The content of dissolved oxygen depends on temperature, atmospheric pressure, the degree of water turbulization, water salinity, etc. In surface waters, the content of dissolved oxygen can range from 0 to 14 mg/l. There is practically no oxygen in artesian water.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 using the formula: M = (ax0.1308x100)/NxP, where
M – degree of water saturation with oxygen, %;
A – oxygen concentration, mg/dm3;
P – atmospheric pressure in a given area, MPa.
N is the normal oxygen concentration at a given temperature and total pressure of 0.101308 MPa, given in the following table:
Oxygen solubility depending on water temperature
|
Water temperature, °C |
|||||||||
Oxidability
Oxidability is an indicator characterizing the content of organic and mineral substances in water that are oxidized by a strong oxidizing agent. Oxidability is expressed in mgO2 required for the oxidation of these substances contained in 1 dm3 of the tested water.There are several types of water oxidation: permanganate (1 mg KMnO4 corresponds to 0.25 mg O2), dichromate, iodate, cerium. The highest degree of oxidation is achieved by dichromate and iodate methods. In water treatment practice, permanganate oxidation is determined for natural, slightly polluted waters, and in more polluted waters, as a rule, dichromate oxidation (also called COD - chemical oxygen demand). Oxidability is a very convenient complex parameter that allows one to assess the overall contamination 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 influx of surface and groundwater, atmospheric precipitation, industrial and domestic wastewater. The amount of oxidizability of natural waters can vary widely 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 substances compared to underground waters. Thus, mountain rivers and lakes are characterized by oxidability of 2-3 mg O2/dm3, lowland rivers - 5-12 mg O2/dm3, rivers fed by swamps - tens of milligrams per 1 dm3.
Groundwater has an average oxidizability at a level of from hundredths to tenths of a milligram of O2/dm3 (exceptions include water in areas of oil and gas fields, peat bogs, heavily swampy areas, and groundwater in the northern part of the Russian Federation).
Electrical conductivity
Electrical conductivity is a numerical expression of the ability of an aqueous solution to conduct electricity. The electrical conductivity of natural water depends mainly on the degree of mineralization (concentration of dissolved mineral salts) and temperature. Thanks to this dependence, the value of electrical conductivity can be used to judge the mineralization of water with a certain degree of error. This measurement principle is used, in particular, in fairly common instruments for operational measurement of total salt content (so-called TDS meters).The fact is that natural waters are solutions of mixtures of strong and weak electrolytes. The mineral part of the water consists mainly of sodium (Na+), potassium (K+), calcium (Ca2+), chlorine (Cl–), sulfate (SO42–), and hydrogen carbonate (HCO3–) ions.
These ions mainly determine 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 (provided, of course, that these ions are not contained in the water in significant quantities, as, for example, this can be in industrial or domestic wastewater). 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 modern level of technology makes it possible to minimize these errors, thanks to pre-calculated and stored dependencies.
Electrical conductivity is not standardized, but a value of 2000 µS/cm approximately corresponds to a total mineralization of 1000 mg/l.
Redox potential (redox potential, Eh)
The oxidation-reduction potential (a measure of chemical activity) Eh, together with pH, temperature and salt content in water, characterizes the state of stability of water. In particular, this potential must be taken into account when determining the stability of iron in water. Eh in natural waters varies mainly from -0.5 to +0.7 V, but in some deep zones Earth's crust can reach values of minus 0.6 V (hydrogen sulfide hot waters) and +1.2 V (superheated waters of modern volcanism).Groundwater is classified:
- Eh > +(0.1–1.15) V – oxidizing environment; water contains dissolved oxygen, Fe3+, Cu2+, Pb2+, Mo2+, etc.
- Eh – 0.0 to +0.1 V – transitional redox environment, characterized by an unstable geochemical regime and variable content of oxygen and hydrogen sulfide, as well as weak oxidation and weak reduction of various metals;
- Eh< 0,0 – восстановительная среда; в воде присутствуют сероводород и металлы Fe2+, Mn2+, Mo2+ и др.
The transparency of Lake B. Miassovo for most of the ice-free period fluctuates within 1-3-5 m and only shortly before freeze-up it increases to 6.5 m. In May, after the ice melts, and in the fall, starting from the end of August, the lowest water transparency is observed. The minimum transparency in spring and autumn depends on the massive development and death of phytoplankton and the entry of allochthonous suspensions into the water during ice melting and intense precipitation. An important role is played by spring and autumn homothermy, which promotes mixing and removal of sediments into the water column.[...]
The transparency of water depends on its color and the presence of suspended matter. . nnx substances.[...]
Water clarity is determined using a glass cylinder with a ground bottom (Snellen cylinder). The cylinder is graduated in height in centimeters, starting from the day. The height of the graduated part is 30 cm.[...]
Water clarity for ultraviolet rays is one of its most important properties, thanks to which the decomposition of chemicals in all areas of the environment is possible. Effective wavelengths (approximately 290 nm) entering the atmosphere quickly lose energy and become almost inactive (450 nm). However, such radiation is sufficient to break a number of chemical bonds.[...]
The transparency of water depends on the amount of mineral and organic substances suspended and dissolved in it, and in the summer - on the development of algae. The color of water, which often reflects the content of dissolved substances in it, is also closely related to transparency. Transparency and color of water are important indicators of the state of the oxygen regime of a reservoir and are used to predict fish kills in ponds.[...]
The transparency of the water determines the amount sunlight, entering the water, and, consequently, the intensity of the photosynthesis process in aquatic plants. In turbid waters, photosynthetic plants live only at the surface, but in clear water they penetrate to great depths. The transparency of water depends on the amount of mineral particles suspended in it (clay, silt, peat), on the presence of small animals and plant organisms. [...]
Water transparency is one of the indicative signs of the level of development of life in water bodies and, along with thermals. chemistry and circulation conditions constitute the most important environmental factor.[...]
Clear water and bright sun require the use of baits with a matte surface or dull color. The fish-repellent shine of the bait can be easily and quickly extinguished by holding it over a piece of burning birch bark.[...]
Water transparency ranges from 1.5 m in summer to 9.5 m in winter, and in deep lakes it is much higher. [...]
The transparency of water depends on the amount and degree of dispersion of substances suspended in water (clay, silt, organic suspensions). It is expressed in centimeters of water column, through which lines 1 l m thick are visible, forming a cross (defined by the “cross”) or lead No. 1 (by Snellen or by the “font”). [...]
Water transparency is one of the main criteria for judging the condition of a reservoir. It depends on the amount of suspended particles, the content of dissolved substances and the concentration of phyto- and zooplankton. Affects the transparency and color of water. The closer the color of the water is to blue, the more transparent it is, and the yellower it is, the less transparent it is.[...]
Water transparency is a measure of the self-purification of open reservoirs and a criterion for the efficiency of treatment facilities. For the consumer, it serves as an indicator of the good quality of water.[...]
The color of the lake's water varies seasonally and is not uniform in different parts of the lake, as is its transparency. So, in the open part of the lake. Lake Baikal, with its high transparency, has dark water Blue colour, in the Selenga shallow water area it is grayish-green, and near the river. Selenga is even brown. In Lake Teletskoye, in the open part, the color of the water is green, and near the shore it is yellow-green. The massive development of plankton not only reduces transparency, but also changes the color of the lake, giving it the color of the organisms in the water. During flowering, green algae color the lake green, blue-green algae give it a turquoise color, diatoms give it a yellow color, and some bacteria color the lake crimson and red.[...]
Less transparent water heats up more at the surface (in the case when there is no intense mixing of water due to wind or current). More intense heating has serious consequences. Since warm water has a lower density, the heated layer seems to “float” on the surface of cold and therefore heavier water. This effect of water stratification into almost non-mixing layers is called stratification water body(usually a body of water - a pond or lake).[...]
Typically, water transparency is correlated with biomass and plankton production. In the conditions of different natural zones of temperate pops, the lower the transparency, the better, on average, the plankton is developed, i.e. there is a negative correlation. Researchers pointed this out at the end of the last and beginning of this century. Further, the study of water transparency allows us to delineate the distribution water masses of various genesis and indirectly judge the distribution of currents in reservoirs of slow water exchange [Butorin, 1969; Rumyantsev, 1972; Bogoslovsky et al., 1972; Vologdin, 1981; Ayers et al, 1958].[...]
Particulate matter and plankton suspended in the water, as well as snow and ice in winter, make it difficult for light to penetrate the water. Only 47% of light rays penetrate through a meter-thick layer of distilled water, and almost no light passes through dark water (for example, swamp lakes) to a depth of more than one meter. Approximately 50 cm of ice allows less than 10% of light to pass through. And if the ice is covered with snow, then only 1% of the light reaches the water. Of the light rays, green and blue penetrate deepest into clear water.[...]
Research on lake water transparency. B. Miassovo were carried out in 1996-1997, the results are presented in Fig. 11. Transparency measurements were carried out on the main measuring vertical using the standard Secchi disk method. The frequency of measurements is monthly.[...]
To determine the transparency of water directly in a reservoir, the Secchi method is used: a white enamel disk is lowered on a string into the reservoir; The depth in centimeters is noted at the following moments; a) when the visibility of the disk disappears and b) when it becomes visible when raised. The average of these two observations determines the transparency of the water in the reservoir.[...]
Lighting conditions in water can be very different and depend, in addition to the strength of illumination, on the reflection, absorption and scattering of light and many other reasons. A significant factor determining the illumination of water is its transparency. The transparency of water in different bodies of water is extremely varied, ranging from the muddy, coffee-colored rivers of India, China and Central Asia, where an object immersed in water becomes invisible as soon as it is covered with water, and ending with the transparent waters of the Sargasso Sea (transparency 66.5 m), the central part Pacific Ocean(59 m) and a number of other places where the white circle - the so-called Secchi disk, becomes invisible to the eye only after diving to a depth of more than 50 m. Naturally, the lighting conditions in different bodies of water, located even at the same latitudes at the same same depth, are very different, not to mention different depths, because, as is known, with depth the degree of illumination quickly decreases. Thus, in the sea off the coast of England, 90% of the light is absorbed already at a depth of 8-9 M. [...]
Seasonal fluctuations in the transparency of lake waters include winter and autumn maximums and spring and summer minimums. Sometimes the summer minimum shifts to the autumn months. In some lakes, the lowest transparency is caused by a large amount of sediment delivered by tributaries during high water and rain floods, in others - by the massive development of zoo- and phytoplankton (“blooming” of water), in others - by the accumulation of organic substances. [...]
The amount of coagulant introduced into water (mg/l, mg-eq/l, g/m3 or g-eq/m3) is called the coagulant dose. The minimum concentration of a coagulant that corresponds to the best clarification or discoloration of water is called the optimal dose. It is determined experimentally and depends on the salt composition, hardness, alkalinity of the water, etc. The optimal dose of the coagulant is considered to be its minimum amount, which during test coagulation gives large flakes and maximum water transparency after 15-20 minutes. For aluminum sulfate, this concentration usually ranges from 0.2 to 1.0 mEq/l (20-100 mg/l). During a flood, the dose of the coagulant increases by approximately 50%. At water temperatures below 4 ° C, the dose of aluminum coagulant is increased almost twice.[...]
When the source water contains suspended substances up to 1000 mg/l and a color value of up to 150 degrees, clarifiers ensure water transparency of at least 80-100 cm along the cross and a color value of no higher than 20 degrees of the platinum-cobalt scale. In this regard, in some cases, clarifiers without: filters are used. Clarifiers are designed to be round (diameter no more than 12-14 m) or rectangular (area no more than 100-150 m2). Typically, clarifiers operate without flocculation chambers.[...]
An important factor determining the transparency of water in stagnant bodies of water is biological processes. Water clarity is closely related to biomass and plankton production. The better developed the plankton, the less transparent the water. Thus, water transparency can characterize the level of development of life in a reservoir. Transparency has great importance as an indicator of the distribution of light (radiant energy) in the water column, on which photosynthesis and the oxygen regime of the aquatic environment primarily depend.[...]
Most of our planet is covered with water. Water environment is a special habitat, since life in it depends on physical properties water, primarily on its density, on the amount of oxygen and carbon dioxide, dissolved in it, from the transparency of the water, which determines the amount of light at a given depth. In addition, the speed of its flow and salinity are important for the inhabitants of water.[...]
For thousands of years, people have been trying to get clean water. Several centuries ago, the main efforts of people were aimed at obtaining clear water. For example, water purification in the early US water supply systems consisted mainly of removing sludge, and in many cases the reason for creating the first public water supply systems was simply the desire to eliminate dirty channels along streets and roads. Thus, almost until the beginning of the 20th century. the danger of infection through water was not the main argument in favor of creating public water supply systems. Before 1870, there were no water filtration plants in the United States. In the 70s of the 19th century, coarse sand filters were built on the river. Poughkeepsie and R. Hudson New York, and in 1893 the same filters were built in Lawrence, pcs. By 1897, more than 100 fine sand filters had been built, and by 1925 - 587 fine sand filters and 47 coarse sand filters, providing treatment for 19.4 million m3 of water.[...]
Primary production of phytoplankton correlates with water transparency (Vinberg, 1960; Romanenko, 1973; Baranov, 1979, 1980, 1981; Bouillon, 1979, 1983; Voltenvveider, 1958; Rodhe, 1966; Ahlgren, 1970]. Correlation coefficients d) between the transparency value , phytoplankton biomass and chlorophyll a content are quite reliable and amount to g = -0.48-0.57 for reservoirs of the BSSR [Ikonnikov, 1979]; Estonia - r = -0.43-0.60 [Milius, Kieask, 1982], Poland - r - -0.56, ponds in Alabama r = -0.79 [Alman, Boyd, 1978]. The average indicators of chlorophyll "a" content and water transparency according to the white disk for deep lakes are given in Table. 64.[...]
The indirect method of determining water transparency (optical density) is widely used. Optical density is determined by optoelectric devices - colorimeters and nephelometers, using calibration graphs. A number of photocolorimeters for general industrial use are produced (FEK-56, FEK-60, FAN-569, LMF, etc.), which are used at water treatment plants. However, this type of instrumental monitoring of the content of suspended substances in water is associated with large expenditures of labor and time for collecting and delivering water samples.[...]
A comparison of zooplankton biomass per unit area with transparency shows that in reservoirs of the tundra, northern and middle taiga, with increasing transparency, zooplankton biomass per unit area decreases. In lakes of the northern taiga, zooplankton biomass from 7.5 g/m1 with water transparency less than 1 m to 1.4 g/m3; with water transparency of more than 8 m, in lakes of average size from 5.78 g/m2 to 2.81 g/m2, respectively. [...]
Primary lakes, which arose when natural basins were filled with water, are gradually populated by plants and animals. Young lakes have clean, transparent water, their bottom is covered mainly with sand, and overgrowth is insignificant. Such lakes are called oligotrophic (from the Greek words oligos - “small”, and trophe - “nutrition”), i.e. low in nutrition. Gradually these lakes become saturated with organic matter. Dying aquatic organisms sink to the bottom, forming muddy bottom sediments, and serve as food for animals living on the bottom. Organic substances released by animals and plants and remaining after their death accumulate in water. An increase in the amount of nutrients stimulates further development life in a pond.[...]
The upper pool of the Uglich hydroelectric power station turned out to be polluted. Despite the high water transparency of 130 cm, invertebrate filter feeders had a very low density; zebra mussels were absent.[...]
For preparing masonry mortar High Quality 1 Water hardness is of great importance. In order to determine the hardness or softness of water at home: by heating it, dissolve a small amount of crushed soap in it, after cooling the solution remains clear - the water is soft, in; When cooled, the solution becomes covered with a film when cooled. Except in hard water lather does not whip.[...]
Average values of ichthyomass in lakes of the middle taiga zone and in lakes of the zone mixed forests with increasing transparency they decrease (Table 66).[...]
Characteristic of rhodanium compounds is a very insignificant effect on the organoleptic properties of water. Even at concentrations of substances greater than 100 mg/l, none of the testers indicated any noticeable change in the odor of the water; There was no change in color or transparency of the water. The ability of thiocyanates to impart flavor to water is somewhat more pronounced.[...]
Ukhta River: depth on average 5 m, channel with a large number of riffles on which communities of the genus Sparganium develop. Water transparency is up to 4 m, the bottom is silted sand, pebbles, silted pebbles. The temperature in July-August reaches 18°C. Kolva River: depth up to 7 m, water transparency up to 0.7 m, sandy bottom, temperature in July-August does not exceed 12°C. [...]
A photoelectronic installation for monitoring filter washing (index AOB-7) operates on the principle of weakening the light flux in a layer of water containing suspended substances. The absorption of light is recorded by a photocell connected to an indicating electrical measuring device of the MRSchPr type. The use of a simple phototurbidimetric technique for measuring water transparency is acceptable in this case, since filters are always washed with purified water with a low, almost constant water color. The primary sensor consists of a flow cell, a sealed chamber for a photocell, a chamber with an electric light bulb, and an electromagnet with hair brushes that periodically wipe the cell window. Secondary device indicating type MRShchPr or EPV. Their position regulators are used to stop washing the filters when the specified water transparency is reached.[...]
In general, it is impossible to put an end to the definition of the concept of a small river. Some works are based on studying the level of development of aquatic organisms. So, Yu.M. Lebedev (2001, p. 154) wrote: “The Small River is a watercourse with water transparency to the bottom, the absence of true phytoplankton and adult fish, except for slow-growing local populations of roach, perch, gudgeon (trout for mountain rivers and grayling for Siberian ones), and the predominance of scraper animals in the benthos.”[...]
Number of falling solar radiation absorbed by the earth's surface is a function of the absorptive capacity of that surface, that is, it depends on whether it is covered by soil, rock, water, snow, ice, vegetation, or something else. Loose, cultivated soils absorb much more radiation than ice or rocks with a highly reflective surface. The transparency of water increases the thickness of the absorbing layer, and thus, a given layer of water absorbs more energy than the same thickness of opaque land.[...]
Natural E.e. occurs on a scale of millennia; it is currently suppressed by anthropogenic energy associated with human activity. EUTROFICATION (E.) - a change in the state of an aquatic ecosystem as a result of an increase in the concentration of nutrients in water, usually phosphates and nitrates. With E.v. Cyanobacteria and algae develop in very large quantities in plankton, water transparency sharply decreases, and the decomposition of dead phytoplankton consumes oxygen in the bottom zone. This sharply impoverishes the species composition of the ecosystem, almost all fish species die, plant species adapted to life in clean water(salvinia, amphibian buckwheat), and duckweed and hornwort are growing massively. E. is the scourge of many lakes and reservoirs located in densely populated areas.[...]
Photosynthetic release of oxygen occurs when carbon dioxide is absorbed by aquatic vegetation (attached, floating plants and phytoplankton). The process of photosynthesis proceeds more intensely, the higher the water temperature, the more biogenic (nutrients) substances (phosphorus compounds, nitrogen compounds, etc.) in the water. Photosynthesis is possible only in the presence of sunlight, since it, along with chemicals Photons of light are involved (photosynthesis occurs even in non-sunny weather and stops at night). The production and release of oxygen occurs in the surface layer of the reservoir, the depth of which depends on the transparency of the water (it can be different for each reservoir and season - from several centimeters to several tens of meters).[...]
This happened with the problem of the color of the sea: in 1921, the origin of the color of the sea was explained simultaneously by both Shuleikin (in Moscow) and Ch. Raman (in Calcutta). The area of work of both authors was reflected in the interpretation of the issue: Raman, who dealt with the crystal clear waters of the Bay of Bengal, gave a theory of sea coloring based on the idea of purely molecular scattering of light in water. Therefore, his theory is not applicable to seas that exhibit strong scattering of light in water.[...]
Vaamochka belongs to the estuary type of lakes, its depth does not exceed 2-3 m, water transparency is low. Pekulneyskoye is of fiord type, in the central part the depth varies from 10 to 20 m, and in the hall. Kakanaut fluctuate within 20-30 m. Lakes Vaamochka and Pekulneyskoye are connected to each other by channels, and through a common mouth, usually washed out in winter, to the Bering Sea. Compared to the lake. Vaamochka’s role in regulating the flow of Pekulneisky is much greater, since its area exceeds the area of the lake. Vaamochka more than four times, and the catchment area is more than half of the total basin area of the system. In this regard, from the beginning of the spring flood to the opening of the mouth, the flow in the channels is directed from the lake. Vaamochka to Pekulneyskoye, and after the opening of the mouth of Pekulneyskoye Lake is more susceptible to the influence of sea tides.[...]
In general, environmental safety management requirements water resources are based on the implementation of water use plans developed taking into account the specified factors and processes that describe the state of aquatic ecosystems. The determining indicators of the state of aquatic ecosystems are: water purity class, saprobity index, species diversity index, as well as gross phytoplankton production [State Assessment..., 1992]. Parameters related to water quality also include such indicators as water transparency, pH value, content of nitrate ions and phosphate ions in water, electrical conductivity, biochemical oxygen consumption, etc. [...]
The need for fertilizer in ponds is determined by biological, organoleptic and chemical methods. Biological method consists in determining the intensity of photosynthesis in algae by observing the growth of algae in flasks into which different quantities fertilizers and take into account the development of algae in them. More simply, the need for fertilizers can be determined by the transparency of the water. Fertilizers are applied when the water transparency is more than 0.5 m. The most accurate method is to chemically analyze the water for nitrogen and phosphorus content and bring them to a certain standard. [...]
As a result of these factors upper layer The ocean is usually well mixed. That's what it's called - mixed. Its thickness depends on the time of year, wind strength and geographical area. For example, in the calm summer, the thickness of the mixed layer on the Black Sea is only 20-30 m. And in the Pacific Ocean near the equator, a mixed layer with a thickness of about 700 m was discovered (by an expedition on the research vessel "Dmitry Mendeleev"). From the surface to a depth of 700 m there was a layer of warm and clear water with a temperature of about 27 °C. This area of the Pacific Ocean is similar in its hydrophysical properties to the Sargasso Sea in Atlantic Ocean. In winter on the Black Sea, the mixed layer is 3-4 times thicker than the summer one, its depth reaches 100-120 m. Such a big difference is explained by intense mixing in winter time: how stronger wind, the greater the disturbance on the surface and goes stronger mixing. Such a jump layer is also called seasonal, since the depth of the layer depends on the season of the year.[...]
For hydrobiology, it is important that the classification of streams by size reflects ecosystem components. From this point of view, foreign studies are extremely interesting, demonstrating that the transit nature predominates in low-order watercourses, and the accumulative nature predominates in larger rivers. This approach to classification, although attractive, is not very operational. It has been established that in the upper sections of the river network scrapers predominate among benthic animals, and below they are replaced by gatherers. It is also known that if water transparency exceeds maximum depth rivers, then periphyton algae develop in such watercourses, and true plankton is poorly represented. With increasing depths, the ecosystem acquires a planktonic character. Apparently, the last criterion can be chosen as the boundary between small and larger watercourses. Unfortunately, it is necessary, but not sufficient. So, for example, the Zeya in the upper reaches, according to its hydro-optical characteristics, can be classified as small, and its tributary in this section of the Arga, due to the high color of the water, is not transparent to the bottom. Therefore, the criterion must be supplemented. As you know, fish live in watercourses whose depth exceeds a certain minimum. For trout it is 0.1 m, for grayling - 0.5, for barbel - 1 m.
The main pollutants present in wastewater from municipal wastewater treatment plants are grouped and presented in Diagram 1
Organic substances in wastewater in their physical state can be in undissolved, colloidal and dissolved states, depending on the size of their constituent particles (Table 1). As the particle size of pollutants changes, they are consistently removed at all stages of biological treatment (Scheme 2).
Table 1 Composition of organic substances in untreated wastewater by particle size
Scheme 1
Water clarity
The transparency of wastewater is due to the presence of undissolved and colloidal impurities in it. A measure of transparency is the height of a column of water at which a font of a certain size and type can be read through it. Municipal wastewater entering for treatment has a transparency of 1-5 cm. The treatment effect is most quickly and simply assessed by the transparency of the treated water, which depends on the quality of treatment, as well as on the presence in the water of small activated sludge flakes that do not settle in two hours and dispersed bacteria. The grinding of sludge flakes can be a consequence of the disintegration of larger, older flakes, the result of their rupture by gases, or under the influence of toxic wastewater. Small flakes can stick together again, but, having reached a certain small size, they do not enlarge further. Transparency is the most efficient, responsive to violations, indicator of the quality of cleaning. Any, even minor, unfavorable changes in the composition of wastewater and in the technological mode of its treatment lead to the dispersion of sludge flakes, disruption of flocculation, and, consequently, to a decrease in the transparency of purified water.
Biological wastewater treatment must provide at least 12 cm of purified water transparency. With complete, satisfactory biological treatment, transparency is 30 centimeters or more, and with such transparency, all other sanitary indicators of contamination, as a rule, correspond to a high degree of purification.
Transparency is determined in shaken (characterizes the presence of suspended and colloidal substances) and settled (presence of colloidal substances) samples. Transparency in a settled sample characterizes the operation of aeration tanks, transparency in a shaken sample characterizes the operation of secondary settling tanks.
Examples. If the transparency of purified water in a shaken sample is 19 cm, and in a settled sample it is 28 cm, we can conclude that the aeration tanks are operating satisfactorily (colloidal substances are well removed) and secondary settling tanks (we can expect that the removal of suspended substances in purified water will not exceed 15 mg/dm3 ),
Scheme 2 Sequential removal of organic particles (depending on their size) at different stages of wastewater treatment
If, according to the test results, the transparency in the shaken sample is 10 cm, and in the settled sample 30 cm, this means that colloidal substances are well removed from wastewater in aeration tanks, but secondary settling tanks work unsatisfactorily and provide low transparency of purified water.
A change in the transparency of the silt water can serve as a prompt signal of changes in the purification process even when other methods of physical and chemical control do not yet detect deviations, since all violations are accompanied by grinding of activated sludge flakes, which is immediately recorded by the reduced transparency of the silt water.
The transparency of water depends on the amount of mechanical suspended substances and chemical impurities it contains. Turbid water is always suspicious from an epizootic and sanitary point of view. There are several methods for determining water transparency.
Comparison method. The test water is poured into one colorless glass cylinder, and distilled water into the other. Water can be rated as clear, slightly clear, slightly opalescent, opalescent, slightly turbid, turbid and very turbid.
Disk method. To determine the transparency of water directly in a reservoir, a white enamel disk is used - a Secchi disk (Fig. 2). When a disc is immersed in water, the depth at which it ceases to be visible and at which it becomes visible again when removed is noted. 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.
Type Method (Snellen). More accurate results are achieved when using a glass calorimeter with a flat bottom (Fig. 3). The calorimeter is installed at a height of 4 cm from standard font No. 1:
After shaking, the water to be tested 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 is 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 turbid, from 10 to 20 cm - cloudy, up to 10 cm is unsuitable for drinking purposes. Good clear water does not produce sediment after standing.
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 it by the handle, the wire ring is lowered into a cylinder with the water being tested until its contours become invisible. Then use a ruler to measure the depth (cm) at which the ring becomes clearly visible when removed. An indicator of acceptable transparency is considered to be 40 cm. The obtained data “by ring” can be converted into readings “by font” (Table 1).
Table 1
Converting water transparency values “by ring” to values “by font”
Water transparency in hydrology and oceanology is the ratio of the intensity of light passing through a layer of water to the intensity of light entering the water. Water transparency is a value that indirectly indicates the amount of suspended particles and colloids in water.
The transparency of water is determined by its selective ability to absorb and scatter light rays and depends on the conditions of surface illumination, changes in the spectral composition and attenuation of the light flux, as well as the concentration and nature of living and non-living suspended matter. With high transparency, water acquires an intense blue color, which is characteristic of open ocean. In the presence of a significant amount of suspended particles that strongly scatter light, the water has a blue-green or green color, characteristic of coastal areas and some shallow seas. At the confluence of large rivers carrying large amounts of suspended particles, the color of the water takes on yellow and brown shades. River runoff, saturated with humic and fulvic acids, can cause the dark brown color of sea water.
The transparency (or light transmission) of natural waters is determined by their color and turbidity, i.e. their content of various colored and suspended organic and mineral substances.
Determining water transparency is a mandatory component of monitoring programs for the state of water bodies. Transparency is the ability of water to transmit light rays deep into it. A decrease in light flux reduces the efficiency of photosynthesis and, consequently, the biological productivity of watercourses.
Even the purest waters, free of impurities, are not absolutely transparent and in a layer of sufficiently large thickness they completely absorb light. However, natural waters are never completely clean - they always contain dissolved and suspended substances. Maximum transparency is observed in winter. When the spring flood passes, transparency noticeably decreases. Minimum transparency values are usually observed in summer, during the period of mass development (“blooming”) of phytoplankton.
For lakes in Belarus with a natural hydrochemical regime, transparency values (based on the Secchi disk) vary from several tens of centimeters
up to 2-3 meters. In places where wastewater enters, especially with unauthorized discharges, transparency can decrease to several centimeters.
Depending on the degree of transparency, water is conventionally divided into clear, slightly turbid, medium turbid, turbid, and very turbid (Table 1.4). A measure of transparency is the height of the cable of a Secchi disk of certain dimensions lowered into the water.
Table 1.4
Characteristics of water transparency
Conclusion: Lakes are bodies of water occupying a natural depression on the earth's surface. There are a number of classifications of reservoirs with stagnant water, the main indicators of pollution of which are the degree of saprobity and trophic status. To classify lakes as water bodies of one kind or another in terms of saprobity and trophicity, they are studied physical indicators and species composition of macrozoobenthos.