Indicators of pollution indices (according to various parameters: eutrophication, toxication, mineralization, etc.) are low; the degree of change in water quality in this part of the lake is also quite low.[ ...]
Indicators, the degree of pollution of industrial wastewater are determined by the characteristics of the production process. Along with the above, the most important indicators are: pH, acidity, alkalinity, content of heavy metals and other toxic impurities, color, suspended solids and floating impurities, water smell, etc.[ ...]
The total saprobity index is 1.530 for 200 valves counted and 1.528 for 1000. This is one of the highest values for this lake. Indicators of pollution indices (according to other parameters: toxification, mineralization, thermofication), on the contrary, are low. The degree of change in water quality in this part of the lake is also quite low.[ ...]
Degree chemical pollution soils is determined by the deviation of pollutant concentrations from the standard indicator (MAC)1. The result of such an assessment may be a zoning scheme for the city territory (M 1:25 OOO) according to the degree of soil contamination with the allocation of areas of the most dangerous areas of pollution (gardens, kitchen gardens, playgrounds and other areas where there is the greatest contact of people with the soil). Zones of influence of polluted soil cover on vegetation and material and technical facilities of the city, in some cases - on surface and ground waters are also distinguished.[ ...]
Pollution of water bodies. As the main indicators for assessing the state of surface waters, toxic, priority pollutants, including those with the properties of accumulation in the organs and tissues of aquatic organisms, were chosen. The criteria for assessing the degree of chemical pollution of surface waters with stable preservation of chemical pollution for three years are given in Table. 6.4. PKhZ-10 is widely used - a formalized total indicator of chemical pollution of water. It is calculated as the sum of concentrations normalized to the MPC of fishery reservoirs for 10 pollutants with maximum excess of MPC.[ ...]
The degree of pollution of surface and ground waters, bottom sediments, soil covers and lithosphere is also based on a large number of normative indicators based on direct ecogeological (hydrogeochemical, geochemical and geophysical, etc.) assessment criteria.[ ...]
Indicators characterizing the pollution of water sources and drinking water by substances classified as hazard classes III and IV, as well as the physicochemical properties and organoleptic characteristics of water, are additional. These indicators are used to confirm the degree of intense anthropogenic pollution of water sources, determined by the main indicators.[ ...]
Pollution contained in wastewater is of mineral, organic and bacterial origin and can be in dissolved, colloidal and insoluble states. The degree of pollution of wastewater is determined by a number of indicators of sanitary-chemical analysis.[ ...]
The indicator of the concentration of hydrogen ions in industrial wastewater is one of the most important qualitative characteristics of the purification process. The pH value provides the most reliable information on the degree of contamination by acids and alkalis (or the degree of purification from them) of water discharged into the sewer or returned to production. The rate and direction of reactions occurring during the treatment of industrial waste with chemical reagents in many cases depend on the pH value. By maintaining the concentration of hydrogen ions in the treated effluents at a certain level, it is possible to create optimal conditions for the separation of many undesirable substances from the water. organic matter. Thanks to modern equipment for continuous measurement of the pH value in solutions and pulps, it has become very convenient to control various processes in chemical technology, energy and industrial wastewater treatment using this parameter.[ ...]
In the water of the river Ufa has a limited presence of technogenic pollution, which is associated with a high concentration of oil refining, petrochemical and chemical enterprises. The most dangerous among them, benz(os)pyrene (B(os)P), is a global pollutant characteristic of urban areas. In this regard, it seems appropriate to compare changes in natural contaminants characterized by turbidity and oxidizability with the content of B(os)P in water source and compare the degree of purification from B(os)P with the efficiency of purification from natural contaminants. The comparison was carried out on the deterministic components of turbidity, oxidizability, B(a)P concentration in the water source and in drinking water.[ ...]
“Polluted” waters are understood as waters that, in the course of their use, are polluted by various components and are discharged into water bodies without purification or the degree of their purification is lower than that established by local authorities for regulating the use and protection of waters of the system of the USSR Ministry of Water Resources and bodies of the USSR Ministry of Health. Mine, mine and other similar waters are also classified as polluted waters if their salinity and other pollution indicators exceed the standards established for water that is allowed to be discharged without treatment.[ ...]
TO general indicators wastewater pollution should include indicators characterizing general properties water (organoleptic, physical and chemical), undissolved impurities (content of suspended solids and their ash content), dissolved substances (total content of inorganic and organic impurities, “organic” carbon, determination of permanganate and bichromate oxidizability, biochemical oxygen demand, etc.) . These indicators make it possible to judge the general contamination of water, the degree of contamination with inorganic and organic substances, including biologically oxidizable substances, etc.[ ...]
Water quality is a characteristic of the composition and properties of water, which determines its suitability for specific types of water use. Water quality is assessed by a complex of various indicators. Most indicators are used to assess any origin and destination. However, depending on the degree of water pollution and the type of water use, the number and set of indicators sufficient to characterize its quality can vary significantly. The main indicators of water quality are ionic composition, total salt content, color, smell and taste, hardness, alkalinity, content of iron, manganese and some other elements.[ ...]
The total indicator of water pollution exceeds the MPC by 300 times. It is quite clear that the discharge of such mine waters greatly pollutes the river runoff and is environmentally dangerous for small rivers. The liquidated mine has a much greater impact on the environmental conditions of the environment, and on this basis it is concluded that it is necessary to organize the treatment of wastewater from flooded mines.[ ...]
The criterion for the degree of suitability of biochemical oxidation for the neutralization of organic pollutants in wastewater is a biochemical indicator. This indicator is defined as the ratio of total biochemical oxygen demand (BODtotal) to chemical oxygen demand (COD).[ ...]
So far, organisms that are indicators of saprobity have not lost their significance during monitoring (Schroevers, 1988), but such information is not sufficient to assess the state of water bodies in case of toxic, “thermal”, radiation pollution, and acidification. For example, there were more than 60 methods for assessing water quality by zoobenthos (Bakanov, 1994; Bakanov, 2000), each of which provides valuable information about a reservoir. Complex methods are time-consuming, require the participation of specialists of different profiles.[ ...]
All wastewater discharged into the sewer and then discharged into water bodies or underground horizons is divided into three types according to the degree of pollution: polluted, the discharge of which into the water intake can only be allowed after appropriate treatment; normative-purified, which have been cleaned to the required indicators of residual pollution in these specific conditions; standard-clean, which, according to the conditions of the receiver, can be discarded without cleaning. The assignment of wastewater to one or another type is carried out by the authorities for regulating the use and protection of water.[ ...]
Analysis of water samples taken at the site of the planned wastewater discharge should reveal the degree of water pollution in the reservoir as a result of possible existing wastewater discharges upstream. In addition, it allows you to set the values of those indicators of water composition (pH, alkalinity, dissolved oxygen, BOD, specific hazardous substances of industrial effluents), which are directly used in calculations for the discharge of wastewater in relation to the rules for the sanitary protection of water bodies.[ ...]
The required degree of wastewater treatment is determined by: calculations of dilution of wastewater in the reservoir; permissible load on a reservoir for individual indicators of pollution (dissolved organic compounds and suspended solids); allowable change in the reaction of the reservoir (pH value). Calculations are also applied on the neutralizing capacity of the reservoir, the content of dissolved oxygen in the water of the reservoir, on the temperature of the water in it.[ ...]
As a result of pollution of petroleum products, physical and chemical indicators of the quality of commercial products change: density, viscosity, water content, mechanical impurities, flash point, acidity, etc. Depending on the type and degree of pollution, it is proposed to subdivide them into contaminated and waste.[ .. .]
The detection of E. coli bacteria in water should be considered as an indicator of fecal contamination of water, and their number allows us to judge the degree of this contamination.[ ...]
In addition to the usual pollution, characterized by general sanitary indicators, industrial wastewater from many industries contains specific impurities that have a significant degree of toxicity, and the same substances are often found in wastewater from different industries. A particularly large variety of toxic impurities differ, for example, from water from the enrichment of non-ferrous metal ores, from etching of metals and from electroplating, water from enterprises of the chemical and chemical-pharmaceutical industries, etc.[ ...]
Transparency is an indicator of the degree of general contamination of water. The transparency of urban wastewater usually does not exceed 3 - 5 cm. Wastewater after biological treatment have a transparency of more than 15 cm. The transparency of wastewater is determined by the font.[ ...]
When determining the degree of reduction, one should proceed from the fact that the effect of the total effect of harmful substances of the same group on the limiting sign of harmfulness is summed up according to a simple numerical addition scheme. The correctness of this is supported by data from the physiology of the sense organs (A. I. Bronshtein) and the results of specially designed experiments on substances with an organoleptic sign of harmfulness (M. N. Rubleva, S. D. Zamyslova, N. V. Grin, etc.). ...]
After the equalizer, the water leaves with a concentration of contaminants in all respects significantly lower than in the original waste water. From this we can conclude that for the initial wastewater the values of maximum (rather than average) concentrations are shown, the fluctuations in the degree of water pollution are very large and the averaging method is certainly appropriate.[ ...]
Bacteriological indicators of water quality are part of the study of the properties of waters of any composition, origin and bacterial contamination. Bacteriological indicators are more sensitive in determining the degree of pollution of a reservoir with domestic wastewater than the results of a chemical study. So, according to the content of saprophytic bacteria, one can detect water pollution with organic biologically degradable compounds when diluted by tens and hundreds of thousands of times. The high sensitivity of microbiological research methods has great importance in the protection of the aquatic environment from pollution.[ ...]
Saprobic indices, indicators of phytoplankton production and its biomass characterize the state of water in terms of its biota. This direction of assessing the quality of water systems refers to bioindication. Its advantage is the possibility of a comprehensive assessment of the degree of water pollution (degree of toxicity) even in the absence of information on the structure of pollutants.[ ...]
The most characteristic indicator of the ecological state of the seas is the degree of their pollution. According to international terminology, marine pollution is the introduction by humans directly or indirectly into the marine environment of substances that are harmful to animals and plants, cause a hazard to human health, degrade the quality of the marine environment, reduce it. beneficial features. The degree of water pollution in the sea is characterized by the MPC of pollutants (PM). On the basis of MPC, control over the state and quality of the marine environment is carried out. Exceeding the MPC, especially multiple, means an unfavorable and even crisis state of the marine environment.[ ...]
The quality of surface waters in the territory of the Varandey oil field has relatively improved, while the classification category of the degree of water pollution has changed from the 3rd class (category A) "very polluted" to the 2nd class "slightly polluted". In comparison with the survey results obtained in 1999, in 2001, the contamination of OHC, PAH, copper, zinc, cobalt and lead in the surface waters of the deposit area significantly decreased. Water quality improved in terms of BOD, COD and surfactant content. Pollution with phenols, iron, manganese, tin, nickel, cadmium and mercury remained almost at the same level. At the same time, an increase in phosphate levels was noted in the waters of a number of tundra lakes.[ ...]
Deep wastewater treatment can prevent the ingress of N and P into water bodies, since the content of these elements is reduced by 8–10% during mechanical treatment, by 35–50% with biological treatment, and by 98–99% with deep treatment. In addition, a number of measures have been developed to combat the process of eutrophication directly in water bodies, for example, an artificial increase in oxygen content using aeration installations. Such installations are currently in operation in the USSR, Poland, Sweden and other countries. To reduce the growth of algae in water bodies, various herbicides are used. However, it has been found that for UK conditions, the cost of deep wastewater treatment from nutrients will be lower than the cost of herbicides spent to reduce the growth of algae in water bodies. Essential for the latter is the reduction in the concentration of nitrates, which are hazardous to human health. The World Health Organization has adopted the maximum allowable concentration of nitrates in drinking water as 45 mg/l or 10 mg/l in terms of nitrogen, the same value is adopted according to sanitary standards for water bodies. The amount and nature of nitrogen and phosphorus compounds affect the overall productivity of water bodies, as a result of which they are included among the main indicators in assessing the degree of pollution of water sources.[ ...]
The number of bacteria in wastewater can be quite significant. It can reach many millions in 1 ml. The volume of the bacterial mass (containing 85% water) with the amount of 100 million bacteria in 1 ml is 0.04% of the wastewater volume. The presence of a large number of bacteria in wastewater characterizes the degree of contamination. However, this figure is not exhaustive. Firstly, there can be very polluted waters that do not have bacteria, but contain toxic substances, and secondly, in addition to pathogenic bacteria, there are also saprophytic, that is, beneficial ones. Therefore, in addition to determining the number of bacteria per ml of wastewater, it is important to know how many E. coli (coli bacteria) are present in wastewater. The presence of Escherichia coli in water does not mean that it is infected with infectious agents, such as typhoid fever. But the fact of the discovery of Escherichia coli indicates the presence of human and animal secretions in the water, which is a negative sanitary indicator. Bacterial contamination of wastewater is characterized by the amount of coli-titer, i.e., the smallest volume of water in ml, which contains one Escherichia coli. So, if the titer is 10, then this means that 1 E. coli was found in 10 ml; with a coli-titer equal to 0.001, 1000 Escherichia coli are found in 1 ml. Coli index means the number of Escherichia coli in 1 liter of liquid. In wastewater, the coli-titer can be 0.000001 or even less.[ ...]
When conducting experiments on the effect of water from natural reservoirs on Daphnia magna, it should be taken into account that the resulting differences in the state of daphnia in different water samples depend not only on contaminants that may be present in the samples, but also on a number of other conditions, such as food supply in a given area, natural composition of the water, etc. On the other hand, D. magna feels best in the (ß-mesosaprobic zone, therefore, small and moderate degrees of water pollution with decomposing substances can cause an improvement in the main indicators of the state of daphnia. In the conditions of the European part of the USSR, most In lowland rivers, the water normally has a transitional character from oligosaprobic to ß-mesosaprobic.In the water of rivers and lakes of the North, conditions, as a rule, are typical oligosaprobic, D. magna, when kept in such water, turns pale and can even die of starvation after 5-10 days .[ ...]
Differentiated pollution charge rates are determined by multiplying the basic charge rates by coefficients that take into account environmental factors by territory and river basin. Odds environmental situation and ecological significance of the state of atmospheric air and soil were calculated according to the assessment of the laboratory for monitoring the natural environment and climate of the State Committee for Hydrostat of the Russian Federation and the Academy of Sciences. They are based on an indicator of the degree of pollution and degradation of the natural environment on the territory of the economic regions of the Russian Federation as a result of atmospheric emissions inherent in these regions and waste generated and disposed of on their territory. The coefficients of the ecological situation and the ecological significance of the state of water bodies are calculated on the basis of data on the amount of discharged polluted wastewater and the category of the water body.[ ...]
dissolved oxygen. Oxygen dissolved in water is involved in the biological decomposition of organic substances. In contaminated surface water sources, the amount of dissolved oxygen is much less than at the saturation limit shown in Table. 2.5. Since fish and most other living organisms and plants living in the water cannot exist without oxygen, the amount of oxygen dissolved in water is the most important indicator of the degree of pollution of the reservoir. During aerobic water treatment, in order to maintain optimal conditions and prevent energy losses due to excessive aeration, the degree of aeration is regulated, guided by the results of determining the amount of oxygen dissolved in water. Dissolved oxygen analyzes are also used to determine the biochemical oxygen demand (BOD) of wastewater. Small samples of wastewater are mixed with dilution water and placed in a flask for analysis of dissolved oxygen at various intervals.[ ...]
Sanitary and hygienic assessment of water quality in water bodies is based on the data of physicochemical, bacteriological and hydrobiological analyzes of water samples. In order to characterize the degree of water pollution, the most important and specific indicators of water quality are selected, taking into account the production profile of the city-forming base not only in the city under study, but also in the suburban area.[ ...]
Thus, according to the value of the UKWIS, the surface waters of the surveyed area belong to the 3rd class of classification of the degree of water pollution - category B, “very polluted”.[ ...]
Notes: 1. Temporarily, until the development of special sanitary indicators and standards for the domestic and drinking and therapeutic use of sea water, the requirements and standards of these Rules apply to the composition and properties of sea water at the locations of water intakes of desalination plants, hydropathics and baths. In the places of water intakes of swimming pools with sea water, the number of bacteria of the group of Escherichia coli and Enterococci should not exceed 100/l and 50/l, respectively. 2. In case of systematic seasonal development and accumulation of algae, measures should be taken to clear the area of water use from them. 3. In case of organic pollution exceeding the established standard, the assessment of the degree and nature of pollution is carried out taking into account the sanitary situation and other direct and indirect sanitary indicators of sea water pollution (including total BOD). 4. To determine pathogenic microorganisms in sea water, the methods recommended by the “Guidelines for the detection of pathogens of intestinal infections in water” No. 1150-74 are used. 5. In places of mass bathing, an additional indicator of pollution is the number of staphylococci in the water. A signal value for regulating the load on the beaches is an increase in their number of more than 100 per 1 liter. 6. The conditions for the disposal, the degree of purification and disinfection of wastewater when they are discharged within the 1st belt of the sanitary protection zone should ensure that the wastewater coli index is not more than 1000 at a free chlorine concentration of at least 1.5 mg / l. When wastewater is discharged from the shore outside the I zone of the sanitary protection zone, the microbial pollution of sea water at the border of the I-II belts of the zone should not exceed I million according to the coli index. protection of surface waters from pollution by sewage" No. 1166-74, temporarily apply to water intakes for household and drinking and health-improving and therapeutic use of sea waters and areas of sea water use until the development of special standards for coastal waters of the seas.[ ...]
The data of hydrochemical analysis indicate the exceptional pollution of the waters of this lake with heavy metals (Ni - 2818, Cu - 53 µg/l, etc.). The degree of mineralization of the lake is average. The pH value of the bottom waters is close to neutral (7.01). Surface sediments of the lake are mesotrophic in nature.[ ...]
The role of aquatic fungi is known as indicators of various types and degrees of water pollution in water bodies.[ ...]
Aerobic saprophytes make up only a part of the total number of microbes in water, but they are an important sanitary indicator of water quality, since there is a direct relationship between the degree of contamination with organic substances and the microbial number. In addition, it is believed that the higher the microbial count, the more likely the presence of pathogenic microorganisms in the water. The microbial number of tap water should not exceed 100. In natural waters, this indicator varies over a very wide range for different reservoirs and for the seasons of the same reservoir. In clean water bodies, the number of aerobic saprophytes can be in the tens or hundreds, and in polluted and dirty water bodies it can be ten thousand and millions.[ ...]
One of the indicators for assessing the pollution of various media (food, water, air) is the amount of pesticides that can enter the human body upon contact with these media. Soil occupies a special place among other media. The hazard of the content of one or another pesticide in the soil is assessed taking into account the degree of transition to the media in contact with the soil - plants, water and air, as well as the impact on the general sanitary indicators of the soil. The results of the studies made it possible to recommend the following maximum permissible levels of the studied pesticides in the soil (in mg / kg): sevin - 1.05, PCP and PCA - 0.5, HCCH and γ-HCCH - 1.[ ...]
The main strategy for reducing water consumption in industry is to increase the degree of water turnover in the production cycle. Note that in the end, after many cycles of use in the technological process, extremely polluted water remains, and the question of what to do with it is far from trivial and has no other choice; this is very expensive water, because the construction and operation of very complex water supply systems is very expensive. Despite this, the typical value of water losses in urban networks is 50%. IN major cities developing countries, water losses are: Manila (Philippines) - 55-65%, Jakarta (Indonesia) - 50%, Mexico City (Mexico) - 50%, Cairo (Egypt) - 47%, Bangkok (Thailand) - 32%.[ . ..]
In urban industrial areas, where problems associated with water pollution inevitably arise, it is necessary to carry out rational planning activities on a broad basis. The EPA requires each state to develop regional plans to control water quality. To obtain government permission to build any object, its owners must link their plans with the plans of the entire area (locality). This involves preparing information on the environmental impact of the facility to determine whether the proposed facility will adversely affect the health and well-being of people, as well as the environment. In addition, state standards have a so-called “anti-degradation” clause, according to which, in order to preserve the high quality of some natural waters, their indicators can be set higher than those corresponding to this class of water sources. This purity of natural waters must be maintained unless it can be shown that other uses of water and other standards are justified for economic and social development. Therefore, in order to maintain high water quality at all facilities that may be sources of pollution, the necessary degree of wastewater treatment must be provided.[ ...]
Based on life experience, people have known for a long time that the greatest danger to drinking water is pollution by sewage and human and animal faeces [1]. Poor quality of drinking water is a source of morbidity of the population with intestinal infections and viral hepatitis. Agricultural enterprises are the main source of water pollution. During floods and heavy rains, manure from fields, roads and farm areas is washed into ravines and streams. IN Lately in the water protection zone major cities dacha construction has intensified, causing uncontrolled pollution of drinking water sources. So, in the Moscow River in spring, all sanitary and bacteriological indicators exceed the permissible and background values. Intensive degree of water pollution was characterized by fresh faecal pollution. This is a consequence of the entry of domestic and manure-containing surface runoff into water sources. More than 2.5 million tons of manure is accumulated in the Moscow region alone in spring. Due to the lack of manure storages of sufficient capacity, special mechanized means of applying manure for plowing, manure is taken out to the fields in winter, and as a result of snowmelt, it is washed away in large quantities and enters water sources. All these factors contribute to an increase in the epidemiological danger of drinking water.[ ...]
Practice has established that in the system of measures aimed at preventing or reducing pollution of water bodies with wastewater, the most desirable and effective are measures to rationalize technological processes, accompanied by a reduction in the discharge of harmful substances and the disposal of valuable wastewater substances or the use of wastewater in the circulating water supply system. When these measures turn out to be insufficient in terms of the degree of neutralization or unavailable for technical or economic reasons, there is a need for special sanitary measures for the treatment and disposal of wastewater. Therefore, the problem of reducing the discharge of wastewater into a reservoir, as a technological and sanitary problem, is inextricably linked with the problem of protecting water bodies from pollution in the sanitary and national economic interests of the population. In this regard, studies have acquired great importance, giving an idea of those indicators of the composition and properties of the water of a reservoir, by which it was possible to judge the degree of pollution of reservoirs. , should not be exceeded so as not to violate the normal conditions for water use and not to damage the sanitary and household and economic interests of the population.[ ...]
The dominant group in terms of quantity and diversity at all stations are chironomid larvae. It is based on a change in the species composition of chironomids and a regular change in the ratio of the abundance of larvae belonging to the subfamilies Orthocladiinae, Chironominae, Tanypodinae, which occurs due to an increase in the level of pollution. As a result of data processing, the following values of the Balushkina index were obtained: Metelevo - 1.53, Lesobaza district - 2.40, village Malkovo - 1.92. According to literature data, the index value, which lies in the range of 1.08-6.5, characterizes surface waters as moderately polluted. Thus, all three stretches of the river fall under this category. However, the village Metelevo has the smallest index, which characterizes it as the cleanest section of the presented. At the same time, the site in the Lesobaza area has the highest chironomid index, which indicates a stronger anthropogenic pollution in this area. The section of the river in the area of the village of Malkovo lies downstream. The index value decreases here, which is probably due to self-purification processes. For a more objective assessment of water quality, the Woodiwiss biotic index and the Naglschmidt method were also used in this work. The first method is based on the regularity of simplification of the taxonomic structure of the biocenosis as the level of water pollution increases. At all stations, the values of the Woodiwiss index were equal to 5. According to the water quality classifier of Roshydromet, the obtained value corresponds to moderately polluted waters (the third quality class). Thus, in this case, the Woodiwiss index and the Balushkina index indicate the same degree of water pollution. It should be noted that the Balushkina index, compared with the Woodiwiss index, makes it possible to assess not only the water quality class, but also shows the gradation of the pollution level in numerical terms. Its difference lies in the fact that the total number of species is counted, and not groups of organisms, as in Woodiwiss. It also does not require an exact definition to the species, it is enough to determine how many species are present. The Naglschmidt method takes into account not only the qualitative, but also the quantitative composition of organisms.[ ...]
The study of this group of animals is also of great importance because tubificids are included in the system of saprobic organisms and, in the case of mass development, are excellent indicators of the degree of pollution of water and bottom sediments. However, it is known that the accepted system of saprobic organisms, which underlies the biological analysis of water, with the help of which it is sometimes necessary to solve extremely important and responsible issues of sanitary and technical practice, is far from perfect.[ ...]
Based on the processing of literature and experimental data, as well as modern requirements for the creation of environmentally friendly industries, it is recommended to evaluate various methods of neutralization taking into account indicators of the degree of impact on the environment (water bodies, soil, air); possibilities integrated use products obtained in the purification process; manufacturability of the process (degree of automation, use of standard equipment); degree of danger (explosiveness, toxicity of the reagents used); economic effect from the use of the obtained products. Moreover, small-tonnage, medium-tonnage and large-tonnage production is considered separately. So, for example, when using the thermal method of neutralizing sulfur-containing wastewater, the quality indicator "Degree of environmental impact" was evaluated in points in accordance with the mark on the desirability scale for the following reasons. As a result of applying the thermal method of waste disposal, gaseous and solid wastes are formed, the use of which is not possible, since a melt of various salts is formed, which are practically impossible to find application. Utilization of gas emissions is also a complex technical task. Therefore, waste is released into the environment and is a source of soil, air, and water pollution. The degree of environmental hazard increases with an increase in the tonnage of the target product of the plant. In this regard, the method of thermal disposal of wastewater from large-scale production of sulfur-containing additives according to this indicator corresponds to the assessment "Very bad on the scale of desirability.[ ...]
E. coli inhabits the intestines of domestic animals, as well as wild ones - mammals and birds, reptiles, amphibians, fish and many invertebrates living near human settlements, that is, within the zone of fecal pollution of nature by humans. Naturally, within the same zone, E. coli is constantly found in water and soil. Therefore, an indicator of the degree of fecal water pollution is not the very fact of the presence of E. coli, but its amount in a certain volume of water.
Nitrogen-containing substances (ammonium ions, nitrite and nitrate) are formed in water as a result of the reduction of nitrites and iron nitrates with hydrogen sulfide, humic substances, etc., or as a result of the decomposition of protein compounds introduced into a reservoir with wastewater. In the latter case, the water is unreliable in sanitary terms. In artesian waters, the content of nitrites reaches tenths of mg/l, and in surface waters - up to thousandths of mg/l. The forms of nitrogen-containing compounds present in water make it possible to judge the time of introduction of wastewater into the water. For example, the presence of ammonium ions and the absence of nitrite are indicative of recent water pollution.[ ...]
Nitrogen-containing substances (ammonium ions, nitrite and nitrate ions) are formed in water as a result of the decomposition of protein compounds that almost always enter it with domestic sewage, wastewater from coke-benzene, nitrogen-fertilizer and other plants. Protein substances under the action of microorganisms undergo decomposition, the final product of which is ammonia. The presence of the latter indicates water pollution by sewage.[ ...]
Among the nitrogen-containing pollution in wastewater, ammonia is one of the most dangerous. It is the main food source for nitrifying bacteria; by increasing the pH, it contributes to the vital activity of the latter. Biological oxidation of ammonia consumes the largest number oxygen. So, according to the data, the oxygen consumption is 4.57 kg/kg of ammonia, 1.14 kg/kg of nitrites and 2.67 kg/kg of hydrocarbons.[ ...]
The decomposition of nitrogen-containing substances to the stage of ammonia (occurs rather quickly, therefore, its presence in water indicates its fresh pollution. The presence of nitrous acid in it also indicates recent water pollution.[ ...]
The scale of pollution, its nature and the duration of the pollutants in the areas of activity of agro-industrial enterprises are different. They are characterized by both nitrogen-containing organic and biogenic compounds (ammonium, nitrites, nitrates, etc.), pathogenic microorganisms, and mineral fertilizers, pesticides, and their metabolites. Contaminated soils and groundwater in some cases can be localized within the area of the agro-industrial complex itself and adjacent areas (large livestock complexes, farms, etc.), in others they occupy large areas measured in thousands of square kilometers (irrigated and rain-fed lands with intensive technology for growing agricultural products). The duration of the presence of polluting ingredients is determined by the rate of decay of organic and mineral substances, the life time of microorganisms. As a result, when the source of pollution is eliminated, the lifetime of some polluting components is measured from several days to 1-3 years, while others reach tens and even hundreds of years.[ ...]
Optimization of soil regimes, creation of optimal C:N ratios favors the mineralization of oil waste and reduces the time for cleaning soils from pollutants. With very intense, deep soil contamination with oil and oil products (especially in the southern regions), it is recommended to remove oil-saturated horizons and bury them, followed by the creation of bulk artificial fertile horizons.[ ...]
By the presence of nitrogen-containing substances in water, one can judge the contamination of it with domestic sewage. If the contamination is recent, then all the nitrogen is usually in the form of ammonia. If along with ammonia there are nitrites, then this means that some time has passed since the infection. And if all nitrogen is represented by nitrates, then a lot of time has passed since the infection, and the water of the reservoir at the sampling site has self-purified. It has been experimentally established that at room temperature, 10 mg of nitrogen of ammonium salts is oxidized to nitrites after 15 days, and when nitrites are oxidized to nitrates, 40 days are required.[ ...]
To determine pollution from natural sources, the flow of a pollutant is recorded over a certain surface area or the amount of substances deposited on special collectors is measured (taking into account the products of their subsequent oxidation); in this case, the estimate will be correct only if the amount of natural emissions greatly exceeds the amount of anthropogenic pollution. It is in this way that nitrogen oxides generated by lightning in areas remote from industrial zones are determined. The amount of oxides is determined by the amount of nitrates precipitated with precipitation. Emissions of alkaline materials from so-called "open" sources (unpaved roads, atmospheric soil erosion, agrotechnical measures, etc.) are estimated from the deposition of solid alkaline particles. However, in some cases, emissions from natural sources are quite difficult to attribute to specific objects. Thus, when applying fertilizers to fields, the total amount of ammonia emitted both by plants and as a result of the transformation of nitrogen-containing chemicals is usually determined.[ ...]
By the presence of certain nitrogen-containing compounds, the time of water pollution by effluents is judged. Thus, the presence of NH in the water and the absence of nitrites indicate recent water pollution. Their simultaneous presence indicates that a certain period of time has already passed since the initial pollution. The absence of MN in the presence of nitrites and especially nitrates indicates that pollution has occurred a long time ago and the water has self-purified during this time.[ ...]
Of the indicators of chemical pollution of source water or domestic drinking tap water, the decomposition products of organic compounds in water of nitrogen-containing substances in the first place deserve attention. and N0; The presence of albuminoid ammonia MH+ in water, even in the form of traces, indicates fresh contamination; if there are at least traces of the nitrite ion NO in the water, the water is usually considered suspicious in sanitary terms; the presence of nitrates NO in the water in the absence of ammonia and nitrites indicates the presence of pollution and completed mineralization. Salt ammonia and traces of the nitrite ion can also be present in unpolluted water as a result of the processes of reduction of nitrate salts when they interact with humic substances. However, in the absence of ammonia and nitrite ion, with a large amount of nitrate ion, increased oxidizability, and the presence of large amounts of chlorides and sulfides, water is usually considered suspicious in sanitary terms. Thus, the presence of nitrogen-containing substances in the absence of other indicators of pollution does not serve as evidence of the poor quality of water, especially if the water is artesian.[ ...]
Wastewater from lubricant production. Waste water pollution from the production of lubricants is represented by paraffinic, cycloparaffinic and aromatic hydrocarbons, carboxylic acids (and their esters), aliphatic alcohols, phenols and other organic substances. The concentration of contaminants in wastewater fluctuates greatly. Organic contaminants also include components of the oil base of lubricants, esters glycols, glycerin and macromolecular fatty acids, organosilicon acids, resins, various substances used as thickeners (petrolatums, ceresins, paraffins, urea derivatives and other nitrogen-containing compounds). The biochemical characteristics of effluents are given in Table. 1.3.[ ...]
A solution of phosphorus- and nitrogen-containing compounds (phosphorus up to 3 and nitrogen up to 15 mg/l) is supplied to the mixer / if these compounds are not present in the industrial effluent. Further, wastewater is sent to the aerotank 2, in which organic pollution is oxidized by activated sludge microorganisms during intensive aeration. Activated sludge adsorbs and, in the presence of atmospheric oxygen, oxidizes a significant part of the pollution.[ ...]
The process of nitrification is the final stage of the mineralization of nitrogen-containing organic pollutants. The presence of nitrates in treated wastewater is one of the indicators of the degree of their purification; therefore, it is necessary to use such treatment facilities that would provide optimal conditions for the vital activity of nitrifying bacteria.[ ...]
Destructive schemes involve the destruction of ammonia and other nitrogen-containing compounds with the production of elemental nitrogen. The best option for destruction schemes is the decomposition of contaminants directly in the gas or liquid system being cleaned. This option is limited only by the volume of gas or liquid. With large volumes, capital and operating costs rise sharply, and the costs increase exponentially as the content of contaminants in the treated gas decreases.[ ...]
Nitric oxide (I) N20 (nitrous oxide, laughing gas) does not have a great effect on air pollution, but is of known interest due to its prevalence in low concentrations. At a concentration of about 0.3 ppm, Li20 is a normal component of the unpolluted atmosphere, and at about the same concentration it is found in dissolved form in sea water. Trace amounts of N20 were also found in tobacco smoke (40 μg per 1 g of tobacco). Due to the lack of specific detection methods and due to good solubility in water, the presence of 1
At specific loads of 80-150 mg/g, complete oxidation and nitrification of nitrogen-containing contaminants is ensured. Ecological conditions correspond to the p-mesosaprobic zone of the reservoir. With the complete oxidation of dissolved organic substances entering the treatment, an undisturbed balance of their sorption and oxidation, low loads on activated sludge and a developed nitrification process, the most ecologically perfect biocenosis is formed - nitrifying activated sludge.[ ...]
Chemical analysis allows you to detect water components that are indicators of its pollution; these chemicals, which are harmless to the human body in the quantities in which they are found in water, indicate, however, the connection of the reservoir with one or another source of its pollution. Of the indicators of chemical water pollution, first of all, the decay products of organic compounds in the form of nitrogen-containing substances MH4‘, N02 "and M03" deserve attention (the sanitary significance of these substances was clarified in detail during their study). However, when assessing the sanitary value of nitrogen-containing substances, great care is needed, since they are, as mentioned, of mineral origin. The presence of nitrogen-containing substances in the absence of other indicators of pollution does not serve as evidence of the poor quality of water, especially if underground deep waters are investigated (from artesian wells.[ ...]
Biochemical wastewater treatment is carried out mainly to remove organic contaminants.[ ...]
The presence of all three ingredients in water indicates, on the one hand, a relatively old pollution, and, on the other hand, also the presence of fresh pollution. However, the given data on the significance of the determination of nitrogen-containing substances for assessing water in a sanitary sense can only be taken as a scheme, since it is necessary to take into account a number of factors that are detailed when determining the sanitary significance of each individual element in the group of nitrogen-containing substances.[ ...]
The presence of only nitric acid in the water, while the absence of ammonia and nitrous acid, indicates water pollution in the past. In this case, from the moment of water pollution, a period sufficient for nitrogen-containing substances to be completely mineralized has passed; therefore, the death of pathogenic microorganisms must also occur, and the water can be considered satisfactory in epidemiological terms, which must be confirmed by bacteriological research data.[ ...]
When designing and implementing monitoring of natural waters and soils, first of all, there is a need for geochemical mapping of oil and gas fields contaminated with various chemical and organic substances, with the identification and ranking of pollution sources according to their role in the formation of polluting technogenic flows, as well as with the determination of regional background values of pollutants ( mainly heavy metals, hydrocarbons, nitrogen-containing organics, etc.).[ ...]
The ability to wash chemicals from the soil by surface runoff has been demonstrated in many compounds. Thus, the intensive use of nitrogen-containing mineral fertilizers has led to a sharp increase in nitrogen compounds in groundwater. Polluted waters pose an even greater danger as a habitat for living organisms used by humans for food. The tendency of exogenous chemicals to migrate through food chains and accumulate leads to the fact that fish, mollusks, crustaceans, which have concentrated significant amounts of harmful substances, can cause poisoning of people. Thus, the well-known Minamata disease (Japan) is caused by water pollution with organomercuric substances and their concentration in algae used by the population as food.[ ...]
Wastewater from coke plants and factories. Wastewater from coke hydrocutting plants contains cycloparaffinic and aromatic hydrocarbons, phenols and nitrogen-containing compounds. The content of these contaminants in the effluent depends on the composition of heavy oil residues: fuel oil, tars, extracts from the selective purification of oils and other raw materials.[ ...]
The communal services of settlements are currently considered as one of the most important destructors of the sustainability of anthropogenic ecosystems. A special danger of pollution from communal sources began to acquire in the conditions of megacities. The main hazard factor is the unreliability and obsolescence of equipment and structures of engineering networks: water supply, sewerage; filtrate from storages of municipal solid waste. Water treatment facilities with extensive silt maps, aerators and settling tanks at wastewater treatment plants, sewage sludge fields and linear sewerage facilities discharge dirty wastewater as losses into the first aquifer from the surface. In large, especially old historical cities that have a tendency to turn into a metropolis or have become a metropolis, such as Moscow, the exploitation, conservation and liquidation of cemeteries becomes an acute problem. Underground water with the wrong choice of location for the cemetery is heavily polluted with nitrogen-containing compounds.[ ...]
Denitrification - the process of biochemical reduction of nitrate and nitrite nitrogen into oxides and free nitrogen - is used as a step in the biological treatment of wastewater from nitrogen-containing compounds. The process of denitrification requires the presence in the treated water of a specific biochemically easily degradable organic substrate. It undergoes, as a rule, complete oxidation to CO2 and H20. Denitrifying bacteria (heterotrophs present in large numbers in wastewater) can oxidize a very wide range of organic substances: hydrocarbons, alcohols and organic acids. If the denitrification process is carried out with biologically purified water, practically devoid of initial organic substances, then methanol is most often used as a carbon feed. The latter is completely consumed in the process of denitrification and does not contribute to the secondary pollution of treated wastewater.[ ...]
Mixed waste 25 enters the denitrifier 26, where the process of reduction of nitrites and nitrates to free nitrogen takes place, as well as the oxidation of organic pollution by nitrogen-containing compounds by saprophytic microorganisms. The sludge mixture 27 enters the secondary settling tank 29, where the purified liquid 28 is separated from the activated sludge. Activated sludge from the secondary settling tanks 12, 20, 29 is partly returned to the corresponding stages of the biochemical treatment process as return sludge 10, 17, 31, and partly as excess sludge 13, 21, 30 is fed to the sludge treatment.[ ...]
For wastewater treatment, which takes place most successfully under aerobic conditions, as can be seen from the previous one, the presence of oxygen is necessary to oxidize the organic matter that is part of the wastewater pollution. The oxygen consumed for this is replenished again mainly due to its dissolution from atmospheric air. Thus, in sewage treatment plants, which serve to mineralize organic contaminants that make up wastewater, two processes simultaneously occur: oxygen consumption and its dissolution. It has been established that the mineralization of organic matter, which occurs as a result of its oxidation with the assistance of mineralizing microorganisms or the so-called biochemical oxidation, occurs in two phases: in the first phase, carbon-containing substances are oxidized, resulting in carbon dioxide and water, in the second phase, nitrogen-containing substances are oxidized, first to nitrites, and then to nitrates.[ ...]
About 93% of nitrogen oxides are released from anthropogenic sources, mainly in the form of nitrogen monoxide, which is converted into nitrogen dioxide as a result of atmospheric free radical reactions. Estimates of nitrogenous emissions are less accurate than estimates of sulfur dioxide emissions. According to various researchers, in 1982 in the United States 5.6-7.2 million tons of nitrogen oxides (in terms of NO2) were emitted into the atmosphere by thermal power plants; when burning fuel in industry 3.1-3.8; vehicles 7.0-7.9; from other sources 2.8-3.0; total 18.7-21.7 million tons of pollution. Data on BO2 and NO emissions by seasons are given in Table 1. 4.[ ...]
Valuable information in the analysis of PAS can be provided by detectors that react specifically to individual heteroatoms or certain functional groups. It is a nitrogen-sensitive thermionic detector suitable for detecting nitrogen compounds. PAS at the level of picograms. For example, simultaneous detection of PAHs and[ ...]
In pure groundwater, they are not more than 0.1 mg / l, but in places where mineral fertilizers are used, the concentration increases sharply. The content of nitrates in soil solutions reaches 300 mg/l and more. The detection of nitrates and nitrites in soils and underground waters indicates their contamination with nitrogen-containing organic substances. They enter the body with food, as they can accumulate in various agricultural plants, and cause methgenoglobinemia, irritate the skin, etc. The toxic effect of nitrites on the body is due to their effect on the vasomotor and respiratory centers of the central nervous system, as well as the formation in the body of strong carcinogens - nitrosamines. Nitrosamines are also found in engine oils (up to 3%!). MPC in water - 45 mg/l, MPC in water according to the sanitary-toxicological sign of harmfulness - 10 mg/l.[ ...]
Sodium hypochlorite is a selective oxidizing agent, it oxidizes mainly ammonia, urea, amino acids and other substances and, to a lesser extent, carbohydrates. If, in parallel with the determination of chlorine capacity, the determination of permanganate oxidizability is carried out, then this allows one to get some idea of the nature of wastewater pollution. The action of NaOC1 will be even more selective if the analyzed water is boiled for only 1 min and in the analysis of heavily polluted waters instead of 0.02 N. NaOS1 solution, use 0.1 N. solution. Under these conditions, the effect of hypochlorite on carbohydrates is weakened, and on nitrogen-containing compounds remains unchanged.[ ...]
In natural waters, nitrogen is found in the form of a number of inorganic and various organic compounds. The inorganic forms of this element include ammonium, nitrites and nitrates - all highly soluble. Protein-like compounds, polypeptides, humic substances, amino acids, amines, urea - this is not a complete list of nitrogen-containing organic substances that are present in water in suspension (organism residues), in the form of colloidal and true solutions. Mutual transitions are constantly carried out between inorganic and organic nitrogen compounds. An increase in the content of nitrates and nitrites in water indicates water pollution. In pure waters, nitrite ions are not analytically detected.[ ...]
Thus, eutrophication of water bodies can be prevented by removing at least one nutrient from the water. In practice, this comes down to the removal of phosphorus compounds from wastewater, since carbon in the form of bicarbonates, and nitrogen as a result of assimilation from the air by some types of aquatic vegetation are almost always present in natural waters. In addition, due to the high solubility of most mineral nitrogen-containing salts, finding effective and economical methods for their removal is very difficult. Nevertheless, recently the need for strict regulation of the content of ammonium salts and nitrates in the water of reservoirs has been revealed. The “Rules for the Protection of Surface Waters from Pollution by Waste Waters” (1975) in force in our country, on the basis of toxicological characteristics, in the water of reservoirs of fishery significance, the content of ammonium compounds is limited, and in the water of reservoirs for drinking and domestic use - the content of nitrates. The maximum permissible concentration of ammonium compounds is 0.5 mg / l, and for nitrates (in terms of nitrogen) - 10 mg / l.[ ...]
The fall of rain causes the air to be purified in yet another way besides the one just described. Earlier we have already said that droplets are formed inside the cloud as a result of condensation on small particles with a radius of 0.1-1.0 microns. Sea salt particles are effective condensation nuclei. According to scientists, the majority of even smaller condensation nuclei are sulfur-containing particles, which are emitted into the atmosphere by sources of industrial pollution. Certain nitrogen compounds can also serve as condensation nuclei. When it rains, the droplets inside the cloud, as a result of collision and merger, are combined with raindrops. When they fall to the ground, they carry sulfur and nitrogen-containing substances with them. Sometimes these two types of substances even fertilize the soil, as they add nutrients (for plants) to it.[ ...]
The proportion of easily oxidized organic matter in relation to the total varies considerably and depends on the limnological type of the reservoir, the season of the year, biological processes, surface runoff, etc. . G. G. Vinberg showed that in the section of the upper Dnieper BODtot was 37.3-44.1% of the COD in July, and in June and February 16.7-22.5 and 23.5-37.2%, respectively. The values given in the same book for other water bodies range from 4.6 to 50%. Thus, the BODtotal/COD ratio can increase not only due to the pollution of a water body with domestic wastewater, but also due to natural processes that need to be distinguished when taking into account the anthropogenic impact on the water body. If BODtotal/COD does not exceed 10% in river sections, this clearly indicates the presence in the reservoir of compounds that do not decompose during treatment at the city aeration station. According to T. Stones, 37% of carbon-containing organic matter in domestic wastewater is not subject to complete biochemical oxidation. In the second phase of oxidation (after 5–10 days), the nitrification process proceeds intensively, which is estimated by the consumption of oxygen after sowing into highly diluted wastewater of nitrifying microorganisms isolated from treated wastewater. The process of decomposition of nitrogen-containing compounds is most active after the 15th day of incubation.[ ...]
The degree of biochemical oxidation of many organic compounds polluting wastewater is low. The degree of biochemical oxidation of sulfur- and nitrogen-containing compounds is very different - from 0.02 to 0.95. Moreover, the analysis of the real composition of wastewater in the sewer collectors of a number of industrial areas indicates a high content of conservative pollutants in them (BODp/COD from 1/6 to 1/15) .[ ...]
Statistical methods can be conditionally divided into direct and indirect. Indirect methods1 include methods of correlation analysis based on the use of correlation coefficients and elasticity. In particular, the existence of a risk of morbidity can be indicated by a high value of the correlation coefficient between the level of pollutant concentration in a particular area of the environment and the level of morbidity in the population, calculated from information reflecting the corresponding indicators in the totality of territories. Correlation analysis, for example, confirms the existence of direct relationships between the concentration of CO in the atmosphere and the frequency of asthma, the concentration of lead in the atmosphere, water and blood diseases, the concentration of nitrogen-containing and chlorine-containing compounds in water and diseases of the stomach and kidneys, the level of bacterial pollution of water and intestinal diseases and etc.
the presence of organic matter in the water. The amount of dissolved oxygen depends on the temperature of the water. The lower the temperature o, the more dissolved oxygen in the water. In addition, the oxygen content depends on the presence of zoo- and phytoplankton in the water. If there are a lot of algae or a lot of animals in the water, then the oxygen content is less, since part of the oxygen is spent on the vital activity of zoo - and phytoplankton. The oxygen content also depends on the surface of the reservoir: there is more oxygen in open reservoirs. The oxygen content under all other conditions will depend on the barometric pressure and on pollution. The greater the pollution, the less oxygen is contained in the water, because oxygen will be spent on the oxidation of pollution (organic substances). In order to judge whether there is enough or not enough oxygen in a reservoir, there are Windler tables, which provide data on the limit of oxygen solubility at a given temperature. If we determine the amount of dissolved oxygen in our water sample and find that at 7 degrees we have 9 mg of oxygen in our sample, then these numbers do not give anything. We have to look at Windler's table: at 7 degrees, 11 mg should be dissolved. Oxygen per liter and this suggests that, apparently, the water contains a large amount of organic matter
Indicator of biochemical oxygen demand (BOD). BOD is the amount of oxygen that is necessary for the oxidation of easily oxidized organic substances in 1 liter of water. Conditions for this analysis: exposure 1 day, 5 days, twenty days. Technique: it takes time and a dark place: two jars are taken, filled with the investigated water. In the first jar, the oxygen content is determined immediately, and the second jar is placed either for a day, or for 5, or for 20 in a dark room and the oxygen content is determined. The more organic substances are contained in the water sample, the less oxygen will be detected, because part of the dissolved oxygen will be spent on the oxidation of organic substances (easily oxidized).
The oxidizability of water is the amount of oxygen that is necessary for the oxidation of easily and moderately oxidizable organic substances found in 1 liter of water. Conditions: oxidizing agent - potassium permanganate, 10 minute boiling. Not always a high oxidizability figure indicates a problem with the water source. A high oxidizability figure may be due to plant organic matter. For example, the water of Lake Ladoga and, in general, the water of northern reservoirs contains a greater amount of organic matter of plant origin and the oxidizability of our waters is quite high, but this does not mean that the water is harmful or polluted. In addition, a high oxidizability figure may be due to the presence of inorganic substances in water - strong reducing agents, which is typical for groundwater. These include sulfides, sulfites, ferrous oxide salts. Nitrites. A high oxidizability figure may be due to the presence of organic matter of animal origin in the water, and only in this case we say that the reservoir is polluted. Naturally, the question arises, how can we decide due to what we have a high oxidizability figure. To answer this question, there are the following methods: in order to differentiate oxidizability due to organic substances from oxidizability due to inorganic substances, you need to put a sample in the cold: inorganic substances (mineral) are oxidized in the cold. Suppose we had an oxidizability of 8 mg/l, put a sample in the cold, found out that the oxidizability in the cold is 1 mg/l. It turns out that due to organic substances 7 mg / l are accounted for. Now we must differentiate vegetable organics from animal origin. In this case, you need to look at bacteriological indicators. GOST does not standardize oxidizability, since it can be high both in normal and polluted water. However, there are guidelines. Indicative norms are as follows: for surface water bodies - 6-8 mg / l. For underground water sources, for mine wells 4 mg/l, for artesian waters 1-2 mg/l.
COD is also an indicator of the presence of organic matter in water - chemical oxygen demand. This is the amount of oxygen that is necessary for the oxidation of easily, moderately and difficultly oxidized organic substances in 1 liter of water. Analysis conditions: potassium dichromium as an oxidizing agent, concentrated sulfuric acid, two-hour boil. In any water, if analyzed correctly, the BOD will always be less than the oxidizability, and the oxidizability will always be less than the COD. The determination of COD, BOD and oxidizability is important for predicting the wastewater treatment system. If we take the wastewater - the household and fecal wastewater of our city and the wastewater of the pulp and paper mill, and determine these 3 factors, you will get that in the household and fecal wastewater, the bulk is made up of easily oxidized chemicals, therefore, a biological method must be used for cleaning. In the effluents of the pulp and paper mill, there are significantly more medium- and difficult-to-oxidize substances, therefore, it is necessary to use chemical treatment.
The study of organic carbon is an indicator for the presence of organic substances in water. The more organic carbon found, the more organics in the water. There are indicative standards for organic carbon. It is considered that if it is present in the range of 1-10 mg / l, this reservoir is clean, More than 100 - polluted.
CCE - carbo-chloroform extract. This indicator allows you to determine the presence in the water of difficult-to-detect substances: petroleum products, pesticides, surfactants. All these substances are adsorbed on carbon and then extracted. It is believed that if CCE is within 0.15 - 0.16, then this reservoir is clean, 10 or more - the reservoir is polluted.
Determination of chlorides and sulfates. Chlorides give a salty taste, sulfates give a bitter taste. Chlorides should not exceed 250 mg/l, and sulfates should not exceed 500 mg/l. Most often, chlorides and sulfates in water are of mineral origin, which is associated with soil composition, but in some cases, chlorides and sulfates can be indicators of pollution when they enter water bodies as pollution with sewage baths, etc. If the content of these substances changes in dynamics, then, of course, there is pollution of the water source.
dry residue. If you take 1 liter of water and evaporate, weigh the remainder, you will get the weight of the dry residue. The more mineralized water, the greater this dry residue will be. According to GOST, the dry residue should not exceed 1000 mg/l. Loss on ignition makes it possible to judge the amount of organic matter in the residue (this is how organic substances burn out). The greater the loss on ignition, the more organic substances are contained in the water. In pure water, losses on ignition should not exceed 1/3 of the dry residue, that is, 333 mg.
All these indicators are indirect, since they do not allow themselves to determine those substances that caused pollution. More direct are bacteriological indicators - the index and titer of bacteria of the Escherichia coli group. pollution hygienic pond bacterial
The composition of wastewater and their properties are evaluated according to the results of a sanitary-chemical analysis, which includes, along with standard chemical tests a number of physical, physico-chemical and sanitary-bacteriological definitions.
The complexity of the composition of wastewater and the impossibility of determining each of the pollutants lead to the need to select indicators that would characterize certain properties of water without identifying individual substances.
A complete sanitary-chemical analysis involves the determination of the following indicators: temperature, color, odor, transparency, pH value, dry residue, solid residue and loss on ignition (ppp), suspended solids, settling solids by volume and mass, permanganate oxidizability, chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrogen (total, ammonium, nitrite, nitrate), phosphates, chlorides, sulfates, heavy metals and other toxic elements, surfactants (surfactants) , petroleum products, dissolved oxygen, microbial count, bacteria of the Escherichia coli group (ECG), helminth eggs. The number of mandatory tests of a complete sanitary-chemical analysis at urban sewage treatment plants may include the determination of specific impurities entering the drainage network of settlements from industrial enterprises.
Temperature - one of the important technological indicators. A function of temperature is the viscosity of the liquid and, therefore, the force of resistance to settling particles. Temperature is of paramount importance for biological purification processes, since the rates of biochemical reactions and the solubility of oxygen in water depend on it.
Coloring - one of the organoleptic indicators of wastewater quality. Household and fecal wastewater is usually weakly colored and has a yellowish-brownish or gray tint. The presence of intense coloring of various shades is evidence of the presence of industrial wastewater. For colored wastewater, the color intensity is determined by dilution to colorless, for example 1:400; 1:250 etc.
Smell - an organoleptic indicator that characterizes the presence of smelling volatile substances in water. Usually, the smell is determined qualitatively at a sample temperature of 20 °C and described as faecal, putrid, kerosene, phenolic, etc. If the odor is not clearly pronounced, the determination is repeated by heating the sample to 65 °C. Sometimes it is necessary to know the threshold number - the smallest dilution at which the smell disappears.
Hydrogen ion concentration expressed as pH. This indicator is extremely important for biochemical processes, the rate of which can significantly decrease with a sharp change in the reaction of the environment. It has been established that wastewater supplied to biological treatment facilities should have a pH value in the range of 6.5-8.5. Industrial wastewater (acidic or alkaline) must be neutralized before being discharged into the sewerage network to prevent its destruction. Municipal wastewater is usually slightly alkaline (pH = 7.2-7.8).
Transparency characterizes the total contamination of wastewater with undissolved and colloidal impurities, without identifying the type of pollution. The transparency of urban wastewater is usually 1-3 cm, and after treatment it increases to 15-30 cm.
Dry residue characterizes the total contamination of wastewater with organic and mineral impurities in various aggregate states (in mg/l). This indicator is determined after evaporation and further drying at t- 105 °C wastewater samples. After annealing (at t= 600 °C) the ash content of the dry residue is determined. According to these two indicators, one can judge the ratio of organic and mineral parts of contaminants in the dry residue.
dense residue - this is the total amount of organic and mineral substances in the filtered wastewater sample (mg/l). It is determined under the same conditions as the dry residue. After calcination of the dense residue at T = 600 °C, it is possible to roughly estimate the ratio of the organic and mineral parts of soluble sewage contaminants. When comparing calcined dry and dense residues of urban wastewater, it was determined that most of the organic pollutants are in an undissolved state. At the same time, mineral impurities are mostly in dissolved form.
Suspended solids - an indicator that characterizes the amount of impurities that lingers on the paper filter when filtering the sample. This is one of the most important technological
water quality indicators, allowing to estimate the amount of precipitation formed in the process of wastewater treatment. In addition, this indicator is used as a design parameter when designing primary clarifiers. The amount of suspended solids is one of the main standards when calculating the required degree of wastewater treatment. Losses on ignition of suspended solids are determined in the same way as for dry and dense residues, but are usually expressed not in mg / l, but as a percentage of the mineral part of suspended solids to their total dry matter. This indicator is called ash content. The concentration of suspended solids in urban wastewater is usually 100-500 mg/l.
Settling substances - part of suspended solids settling to the bottom of the settling cylinder during 2 hours of settling at rest. This indicator characterizes the ability of suspended particles to settle, allows you to evaluate the maximum effect of settling and the maximum possible volume of sediment that can be obtained at rest. In urban wastewater, sediments average 50-75% of the total concentration of suspended solids.
Under oxidizability understand the total content of organic and inorganic reducing agents in water. In urban wastewater, the overwhelming majority of reducing agents are organic substances; therefore, it is believed that the oxidizability value is fully related to organic impurities. Depending on the nature of the oxidizing agent used, chemical oxidizability is distinguished, if a chemical oxidizing agent is used in the determination, and biochemical, when aerobic bacteria play the role of an oxidizing agent; this indicator is the biochemical oxygen demand (BOD). In turn, chemical oxidizability can be permanganate (KMn0 4 oxidizer), bichromate (K 2 Cr 2 0 7 oxidizer) and iodate (Kiu 3 oxidizer). The results of determining the oxidizability, regardless of the type of oxidizing agent, are expressed in mg/l 0 2 . Bichromate and iodate oxidizability is called chemical oxygen demand, or COD.
Permanganate oxidizability - oxygen equivalent of easily oxidized impurities. The main value of this indicator is the speed and simplicity of determination. Permanganate oxidizability is used to obtain comparative data. Nevertheless, there are substances that are not oxidized by KMn0 4 . Only after determining the COD, it is possible to fully assess the degree of water pollution with organic substances.
BOD - oxygen equivalent of the degree of contamination of wastewater with biochemically oxidizable organic substances. BOD determines the amount of oxygen required for the vital activity of microorganisms involved in the oxidation of organic compounds. BOD characterizes the biochemically oxidizable part of organic wastewater contaminants, which are primarily in the dissolved and colloidal states, as well as in the form of suspension.
Nitrogen found in wastewater in the form of organic and inorganic compounds. In urban wastewater, the bulk of organic nitrogenous compounds are substances of a protein nature - feces, food waste. Not organic compounds nitrogen are represented by reduced - and TN 3 and oxidized forms N0 ^ and N0 ^. Ammonium nitrogen is formed in large quantities during the hydrolysis of urea, a human waste product. In addition, the process of ammonification of protein compounds also leads to the formation of ammonium compounds.
In urban wastewater, nitrogen in oxidized forms (in the form of nitrites and nitrates) is usually absent before treatment. Nitrites and nitrates are reduced by a group of denitrifying bacteria to molecular nitrogen. Oxidized forms of nitrogen can appear in wastewater only after biological treatment.
Connection source phosphorus in wastewater are physiological excretions of people, waste from human activities and some types of industrial wastewater.
The concentrations of nitrogen and phosphorus in wastewater are the most important indicators of sanitary-chemical analysis, which are important for biological treatment. Nitrogen and phosphorus are essential components of the composition of bacterial cells. They are called biogenic elements. In the absence of nitrogen and phosphorus, the biological treatment process is impossible.
Chlorides and sulfates - indicators, the concentration of which affects the total salt content.
To the group of heavy metals and other toxic elements includes a large number of elements, which increases with the accumulation of knowledge about cleaning processes. Toxic heavy metals include iron, nickel, copper, lead, zinc, cobalt, cadmium, chromium, mercury; to toxic elements that are not heavy metals - arsenic, antimony, boron, aluminum, etc.
The source of heavy metals is industrial wastewater from machine-building plants, electronic, instrument-making and other industries. Wastewater contains heavy metals in the form of ions and complexes with inorganic and organic substances.
Synthetic surfactants (surfactants) - organic compounds consisting of hydrophobic and hydrophilic parts, causing the dissolution of these substances in oils and water. Approximately 75% of the total amount of surfactants produced is accounted for by anionic substances, the second place in terms of production and use is occupied by nonionic compounds. In urban wastewater, these two types of surfactants are determined.
Oil products - non-polar and low-polar compounds extractable with hexane. The concentration of oil products in water bodies is strictly regulated; and since the degree of their retention does not exceed 85% at city treatment facilities, the content of oil products in the wastewater entering the station is also limited.
Dissolved oxygen in the wastewater entering the treatment plant is absent. In aerobic processes, the oxygen concentration must be at least 2 mg/l.
Sanitary and bacteriological indicators include determination of the total number of aerobic saprophytes (microbial number), bacteria of the Escherichia coli group and analysis for helminth eggs.
microbial count evaluates the total contamination of wastewater with microorganisms and indirectly characterizes the degree of water pollution with organic substances - food sources for aerobic saprophytes. This figure for urban wastewater ranges from 10 6 -10 8 .
The concentration of contaminants in wastewater (mg/l or g/m 3) is calculated by the formula
In ep - the concentration of any of the pollutants in the wastewater entering the treatment; A - the amount of pollution, g/day, per person; q- water disposal rate, l / person, per day.
The amount of pollution in wastewater per person is given in Table. 8.1
Table 8.1
Number of pollutants per inhabitant
Notes: 1. The amount of pollutants from the population living in non-sewered areas should be taken into account in the amount of 33%.
2. When discharging domestic wastewater from industrial enterprises into the sewer locality the amount of pollutants from operating personnel is not additionally taken into account.
Turbidity is an indicator of water quality due to the presence of undissolved and colloidal substances of inorganic and organic origin in water. 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. 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 turbidity unit 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) for turbidity. The relationship between the basic turbidity units is as follows: 1 FTU(NUF)=1 FNU=1 NTU.
WHO does not standardize turbidity for health reasons, however, in terms of appearance, it 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 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.
Characteristics of waters in terms of transparency (turbidity)
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, and the lowest color in the steppes and steppe zones. In winter, the content of organic matter in natural waters is 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 extraneous 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.
Chromaticity is measured in degrees of the platinum-cobalt scale and ranges from units to thousands of degrees - Table 2.
Characteristics of waters by color
Taste and flavor
The taste of water is determined by the substances of organic and inorganic origin dissolved in it and differs in character and intensity. There are four main types of taste: salty, sour, sweet, bitter. All other types of taste sensations are called off-tastes (alkaline, metallic, astringent, etc.). The intensity of taste and taste is determined at 20 ° C and evaluated according to a five-point system, according to GOST 3351-74 *.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-.
Characteristics of waters according to the intensity of taste
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Intensity of flavor and taste |
The nature of the appearance of taste and taste |
Intensity score, score |
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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. |
Smell
Smell is an indicator of water quality, determined by the organoleptic method using the sense of smell, based on the odor strength scale. The composition of dissolved substances, temperature, pH values and a number of other factors influence the smell of water. The intensity of the smell of water is determined by an expert 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:
Odors are divided into two groups:
- natural origin (organisms living and dead in water, decaying plant residues, etc.)
- artificial origin (impurities of industrial and agricultural wastewater).
Smells of natural origin
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Odor designation |
The nature of the smell |
Approximate type of smell |
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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 |
The odor intensity according to GOST 3351-74* is evaluated on a six-point scale - see the next page.
Characteristics of waters by odor intensity
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Odor intensity |
The nature of the odor |
Intensity score, score |
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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 |
Hydrogen index (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 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:
Characteristics of waters by pH
Control over the pH level is especially important at all stages of water treatment, since its "leaving" in one direction or another can not only significantly affect the smell, taste and appearance of water, but also affect the efficiency of water treatment measures. The optimum pH 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 the water treatment methods used.
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, an unpleasant odor, and can 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.
Acidity
Acidity refers to the content in water of substances 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 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 can 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. The part of the total acidity that lowers the 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 (Ca2+) and magnesium (Mg2+) salts, as well as other cations that act in much smaller quantities, such as ions: iron, aluminum, manganese (Mn2+) and heavy metals (strontium Sr2+, barium Ba2+).But the total content of calcium and magnesium ions in natural waters is 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).
Characteristics of water by the value of total hardness
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Water group |
Unit of measure, mmol/l |
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Very soft |
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medium hardness |
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Very tough |
Alkalinity
The alkalinity of water is the total concentration of weak acid anions and hydroxyl ions contained in water (expressed in mmol / l), which react in laboratory studies with hydrochloric or sulfuric acids to form chloride or sulfate 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, 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.
iron, manganese
Iron, manganese - in natural water act mainly in the form of hydrocarbons, sulfates, chlorides, humic compounds and sometimes phosphates. The presence of iron and manganese ions is very harmful to most technological processes, especially in the pulp and textile industry, 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, the colonies of which can cause overgrowth of water pipes.
chlorides
Chlorides - The presence of chlorides in water can be caused by the washing out of chloride deposits, or they can appear in the water due to the presence of runoff. Most often, chlorides in surface waters appear in the form of NaCl, CaCl2 and MgCl2, and, moreover, 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 sewage. Ammonia present in water can be of organic or inorganic origin. In the case of organic origin, increased oxidizability is observed.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.
hydrogen sulfide
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 as a result of leaching of sedimentary rocks, leaching of the soil, and sometimes as a result of the oxidation of sulfides and sulfur, the breakdown products of protein 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 in which hydrogen sulfide appears depends on the pH reaction:
- at pH< 5 имеет вид H2S;
- at pH > 7, it acts 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 pollution in water. They enter the water as a result of leaching of sedimentary rocks, leaching of the soil, and sometimes as a result of the oxidation of sulfides and sulfur, the breakdown products of protein 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 pH reaction of water, it can be in the following forms:- pH< 4,0 – в основном, как газ CO2;
- pH = 8.4 - mainly in the form of the bicarbonate ion HCO3-;
- pH > 10.5 - mainly in the form of carbonate ion CO32-.
Dissolved oxygen
The flow of oxygen into the reservoir occurs 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 turbulence, water salinity, etc. In surface waters, the content of dissolved oxygen can vary from 0 to 14 mg/l. In artesian water, oxygen is practically absent.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;
P - atmospheric 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:
Solubility of oxygen as a function of water temperature
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Water temperature, °С |
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Oxidability
Oxidability is an indicator that characterizes 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 studied water.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, atmospheric 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. Thus, 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).
Electrical conductivity
Electrical conductivity is a numerical expression of the ability aqueous solution conduct electric current. The electrical conductivity of natural water depends mainly on the degree of mineralization (concentration of dissolved mineral salts) and temperature. Due to this dependence, it is possible to judge the salinity of water with a certain degree of error by the magnitude of the electrical conductivity. This principle of measurement is used, in particular, in fairly common devices for the operational measurement of total salt content (the 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 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 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 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.
Redox potential (redox potential, Eh)
Redox potential (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 (overheated 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 - a transitional redox environment, characterized by an unstable geochemical regime and a 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.
