The share of the planet's fresh water accounts for about 28 million km3, of which 4.2 million km3 is available for human use, representing 0.3% of the total volume of the hydrosphere. Common freshwater resources are unevenly distributed: most of them are in the underdeveloped regions, creating a shortage of fresh water in the developed regions.
Groundwater represents 14% of the global fresh water supply. Due to the increasing pollution of surface waters and their role as water supply source will increase.
The world's oceans is virtually inexhaustible water reservoir, in the future it could become one of the main sources of fresh water, but this requires a powerful and reliable desalination plants.
Water quality in nature is determined by the combination of different factors:
the climate, terrain, soil, character of riparian vegetation, area of flow, a feature of its structure, woodiness;
biological processes in the pond;
human activities (regulation of river runoff, wastewater discharge, shipping).
The composition of natural waters is assessed by physical, chemical and sanitary-hygienic indicators.
Physical parameters — temperature, suspended solids, color, odor and taste.
The temperature of groundwater is relatively stable during the year: 8 — 12°C, the temperature of surface waters varies according to the seasons of the year in the range of 0.1 - 30°C. Transparency and turbidity characterize the presence in water of suspended solids (particles of sand, clay, silt, plankton, algae). Colour of water is due to the presence of organic substances (humus, tannins, protein, uglevodorodnykh, fats, organic acids included in the composition of zoo - and phytoplankton of waters and the products of their metabolism or decay).
Tastes and odors in natural waters can be natural and artificial origin. There are four basic taste of water: salty, bitter, sweet and sour. Shades, folding of the basic taste sensations are called flavors. To odors of natural origin are earthy, fish, swamp, putrid, sulfurous, aromatic, clay, muddy, artificial — chloride, camphor, pharmaceutical, phenol, chlorine-Fe-Nonny, ammonia, odors of petroleum products.
Water chemical composition is characterized by ion composition, hardness, alkalinity, biochemical oxygen demand, the active reaction of hydrogen ions (pH), solids, total salt content, dissolved oxygen, hydrogen sulfide, chlorine, free carbonic acid. Toxic substances (arsenic, strontium, beryllium, lead, mercury and other heavy metals), and radionuclides are mainly anthropogenic products.
Water-dissolved gases — oxygen, carbon dioxide, hydrogen sulfide, methane, ammonia cause the odors and corrosiveness of water towards piping and equipment.
The importance of water is not confined to its physiological role, a large amount of water is necessary for the enterprises of various industries, household needs, create adequate sanitation for medical institutions, public catering enterprises, for carrying out recreational and physical activities. In many cities, water is consumed for washing streets and watering gardens.
Intensive development of industry, transport, overpopulation of several regions of the world have led to significant pollution of the hydrosphere. According to the world health organization (who), about 80% of all infectious diseases in the world is due to poor quality of drinking water and violations of sanitary-hygienic norms of water supply. Pollution of surface water films, oil, grease, lubricants prevents the exchange of water and atmosphere, which reduces the water saturation with oxygen and has a negative impact on the state of phytoplankton and leads to mass death of fish and birds.
According to the UN, the world produces up to 1 million products, of which 100 thousand are chemical compounds, including 15 thousand — potential toxicants. According to expert estimates, up to 80% of all chemical compounds entering into the environment, sooner or later enter water sources.
It is estimated that annually in the world dumped more than 420 km3 of wastewater that is able to make unfit for consumption there are about 7 million km3 of pure water, which is 1.5 times more total river runoff of the CIS countries.
Unfortunately, the science is not yet able to give a full picture of inflicted water damage. For example, according to the Council of the National Academy of Sciences of the United States, toxicologists have relatively complete information on the impact on human health, only 10% of the used pesticides and 18% used drugs. At least 1/3 of pesticides and medicines had not undergone toxicity tests.
In respect of chemicals that are used the problem is even worse: 80% of them did not pass the test. This situation, combined with the frequent leaks, emissions and man-made accidents potentially lead to serious pollution of the hydrosphere of the planet and the possibility of harmful effects on the health of the population.
Currently the largest consumer of water in rivers and reservoirs agriculture (60 — 70% of all resources). In second place are industry and energy, the third utilities. A special place in the use of water resources is the water consumption of the population. On household water use in our country accounted for 10% of total water consumption.
The Basics of operating in the Russian Federation water legislation emphasizes that the rivers are used to meet drinking and domestic needs of the population. It is unique in the huge physiological and hygienic value of water, its exceptional role in the normal complex physiological processes in the human body, creating the most favorable conditions of life.
The situation with drinking water in Russia is characterized as critical, which poses a direct threat to the health of the population. In this regard, the State Duma developed a draft Federal law "On drinking water", in which for the first time in our country, the attempts of legal regulation in the sphere of drinking water supply. The law provides state guarantees of provision of citizens and legal entities with drinking water and the conditions of implementation of these guarantees. The highest value of quality issues become so-called drinking water running man for drinking, domestic and cultural needs. This is because water may be the cause of different changes in the body and contribute to communicable and non-communicable diseases.
Impurities that affect the safety of drinking-water resources are divided into three categories:
inorganic chemicals, including mercury, cadmium, nitrates, lead and their compounds, and chromium compounds, copper;
organic chemicals — oil and petroleum products, pesticides, polychlorinated biphenyls;
pathogens, parasites.
A huge amount of pollutants introduced to surface water with sewage of the enterprises of ferrous and nonferrous metallurgy, chemical, petrochemical, oil, gas, coal, wood, pulp and paper industry, businesses, agriculture and utilities, as well as surface runoff from adjacent areas. A significant amount of nutrients and organic substances enter the water from agricultural land, pastures and cattle farms.
The possibility of transferring water carriers acute intestinal infections is very large, which threatens health and causes massive nature of the disease. Proved the possibility of transmission through water are cholera, typhoid fever and salmonellosis, dysentery, tularemia, brucellosis, viral hepatitis (Botkin's disease) and rotavirus enteritis. Water sources can contain viruses of poliomyelitis, various adenoviruses and enteroviruses.
Pathogenic microbes get into water sources with excreta of humans and animals. The most susceptible to bacterial pollution of surface waters, especially in densely populated and urbanized areas. Extremely dangerous in this respect neobespechenie drains of infectious hospitals and veterinary, urban household wastewater and the wastes of the enterprises for processing animal raw materials. Pathogenic microbes penetrate into the open water reservoirs in dumping of sewage with river boats, with the pollution of coasts and flushing contaminants from the soil surface precipitation, for watering cattle, washing clothes and bathing.
Water can also be a source of human infection by animal parasites - helminths or worms. With contaminated faeces, water to person can get their eggs in the intestine and grow into adult parasites skaridov, vlasoglav, pinworms, etc. human Infection animal parasites occurs and more complex way, through the so called with heater intermediate host (crustacean-Cyclops, fish with diphyllobothriasis and opisthorchiasis).
Infectious morbidity associated with water supply up to 500 million cases per year. Therefore water quality is one of the most important problems.
A serious danger to the health of the population is also associated with the chemical composition of water. In nature, water is never found in the form of chemically pure compounds; possessing the properties of the universal solvent, it carries constantly a large number of different elements and compounds, the ratio of which is determined by the conditions of the formation water, composition of aquifer rocks.
A great influence on the composition of natural waters, both surface and underground is having their industrial pollution. Therefore, the role of water in development of diseases of noninfectious nature is determined by the content in drink chemical contaminants, the presence and amount of which is caused by technogenic and anthropogenic factors. Experimental and clinical medical research has established an adverse effect on the body hardness of water, caused by a total content of salts of calcium and magnesium. High stiffness may play an etiological role in the development of kidney stones person. Urologists emit so-called "stone" areas — areas in which urolithiasis may be considered endemic. In recent years suggested that water with a low content of hardness salts contribute to the development of cardiovascular diseases.
Currently, it is widely known appearance of pathological changes in the body associated with an increased number in the water of nitrates. The latter (at their restoration to nitrite) contribute to the formation in blood of methemoglobin, preventing normal oxidative process in the body. The result is methemoglobinemia (cyanosis toxic), a very serious illness. Especially suffer from megamega-binemia of infants eating food milk mixture, prepared by water with a high content of nitrates. In recent years the attention of scientists attract nitrosamines — substances formed by the interaction of nitrates with aliphatic and aromatic amines. These compounds are widely used in industry, proved the possibility of their synthesis in natural reservoirs and in the human body. Nitrosamines are highly active carcinogens, a variety of pathways in their drinking water, good solubility and high stability make water one of the main sources of nitrosamines in the human body.
The importance of micronutrients for human life and animals is determined by their biological role, as they participate in mineral metabolism and influence General metabolism in nature as catalysts in biochemical processes. Water found up to 65 trace elements.
The most studied effect on the human body of fluoride. The lack of fluoride in the diet contributes to the development of dental caries which breaks the link between organic and inorganic elements of enamel and dentin of the teeth. When excessive intake of fluoride developing dental fluorosis, characterized by discoloration and erosion of the enamel on the teeth, increasing their abrasion and brittleness. Large amounts of fluoride can disrupt the metabolism in the body, cause changes in the bones (type of osteosclerosis) and joint stiffness. Other trace elements which can cause pathological changes in the human body, can be called lead, arsenic and strontium.
Over the past decade, the world celebrated the intensive growth of anthropogenic chemical contamination of the water used by the population. The development of the chemical industry, chemicals used in agriculture, the widespread use of new drugs in the home and at work has aggravated the problem of preventing the ingress of high concentrations of these substances in the human body with water.
The main sources of chemical pollution of water — industrial enterprises, primarily in chemical production, the enterprises of oil refining and petrochemical industry, production of new synthetic materials, chemicals, detergents, plants for thermal treatment of solid and liquid fuels. Their discharges of untreated or poorly treated wastewater can represent a significant threat to public health.
The level of water pollution determined by the presence of organic waste (pesticides, nitrates, phosphates, PCBs). Sources of such waste can be factories, cities, agriculture. Known cases of acute poisoning by heavy metals resulting from industrial pollution of natural waters. Mass cadmium poisoning was observed in Japan among the people of the coast R. Initi — ill about 200 people, and half of the cases with a fatal outcome. The cause of poisoning was the waste water cadmium mine
polzovatsja for irrigation of rice fields. Described cases of dermatitis in the use of underground water contaminated with salts of chromium in Hungary. Mass mercury poisoning in Japan was caused by the dumping of industrial sewage into Yokohama Bay and the R. Agano, which led to the accumulation of mercury in commercial fish is the main staple food of the local population.
About 1/3 of the total mass of pollutants entered into the water sources of surface and stormwater from areas that do not meet sanitary requirements, with agricultural facilities and land that affects the deterioration of the quality of drinking water, especially during the spring floods. Pollution affects not only surface but also groundwater. By the mid-1990s, has identified more than 1,000 of the centers of pollution of underground waters, 75% of which occur in the most populated part of Russia. In General, the groundwater is estimated as critical and has a dangerous tendency to further deterioration.