The activities of man, like any other living being, are invariably accompanied by the allocation of a considerable amount of waste life. In modern conditions, almost all of them are carried away by the waters of sewer rivers. Finally, it is almost impossible for our civilization to imagine without a huge number of factories and other enterprises that also produce a lot of sewage in a multitude.
About process of neutralization of drains
Wastewater treatment is a process after which the drains are suitable for use for technical purposes or return to the environment without prejudice to the latter. In a word, the method depends on the further use of the liquid. For example, wastewater from shells is not the same as the contents of the drain pits where the contents of the toilet bowl come down.
Why is it so important?
In April 1993, more than 400 thousand people in Milwaukee were on a hospital bed as a result of getting into the drinking water of cryptosporidium. After this event, which received a powerful resonance in WHO, the world community has become much more cautious about the fluid that flows from under the faucets in the guise of "drinking water." This view was only strengthened after the publication of some cases of epidemics in India, as a result of which hundreds of people died. But it was in the usual E. coli, which got into the water pipe from poorly treated drains! So, wastewater treatment is an extremely important process that preserves the life and health of people.
Any pollutants radically change the taste, color and smell of the liquid, not to mention its suitability for use in food or technical purposes. Industrial wastewaters are the most dangerous, as they often contain concentrations of heavy metals and other substances that are tens and hundreds of times higher than the most "optimistic" MPCs. Of course, in this case everything depends on the specific production that discharges the sewage. The canalization of the average city in comparison with them may seem like a "spring", since in it, at least, there are no radioactive isotopes or a huge amount of heavy metals.
Classification of drains
Dangerous pollution that makes water unsuitable for drinking and use for domestic purposes can be qualified as physical, chemical, biological factors. The emission of radioactive isotopes stands apart. Accordingly, the classification of pollution will be identical to the causes that cause them:
- Mechanical factors. Characterized by a sharp increase in the smallest mechanical suspension in a liquid.
- Chemical. The water content of any chemical compounds is increased. It does not matter whether these substances can have a negative impact on the health of the human body.
- Biological and bacteriological (domestic waste water). A very dangerous type of pollution, as in this case the water content of microorganisms is exceeded. At the very beginning of the article, we already said, what is fraught with this.
- Thermal pollution. This is the so-called discharge into the rivers and other water bodies of water from pond-coolers at the thermal power plant and nuclear power plant. It is not necessary to treat this variety lightly, since such phenomena lead to mass death of endemics adapted to low water temperatures, which are typical for our area.
- Radioactive. Radioactive isotopes are found in water and bottom sediments. This happens when a sewage system is faulty in some industrial plants or nuclear power plants.
Characteristics of the main types of waste
In our conditions, the most common drainage is of three types:
- Inorganic origin impurities, including even nontoxic compounds.
- Substances of organic origin.
- Mixed sewage.
It is very dangerous waste metallurgical industries, because they contain a huge amount of heavy metals and other toxic compounds. They change the physical properties of water. In those reservoirs, where this poison falls, all life dies, including trees and other vegetation along the coast. Organics also drop oil refineries and similar production. There is not only relatively safe oil in effluents, but also extremely toxic phenols and similar substances. In addition, we should not discard the livestock-type enterprise.
They throw out a huge amount of organic matter. The latter causes a sharp deterioration in the organoleptic properties of water. In reservoirs, where the sewage waters of enterprises enter, there is a sharp development of microscopic algae, flowering, in the liquid to a minimum, the oxygen content falls. Fish and other hydrobionts are dying. The production of electronics, including the etching of printed circuit boards and the release of radio engineering products of various types, produces mixed-type effluents. They contain dyes, heavy metals, acetone, phenols and other compounds.
The risk of oil products falling into the water
Now scientists around the world are sounding the alarm, as a huge amount of oil enters the World Ocean. It forms a thin film on the surface of water, which can sometimes be seen only from iridescent divorces. This not only leads to a significant deterioration in the organoleptic properties of the liquid, but also to a sharp decrease in the supply of oxygen, which enters the ocean by diffusion. Again, the hydrobionts suffer, especially the shortage of this substance in corals, the number of which in the seas and oceans catastrophically decreases every year. Only 10 mg of oil and oil products make water absolutely unsuitable for drinking and living creatures.
Extremely dangerous phenols, of which we have repeatedly mentioned above. They are present in the drains of almost all industrial enterprises. This is especially true of those that are engaged in the production of coke. In the presence of these substances, there is a mass death of inhabitants of ponds, rivers, seas and oceans, and the water itself acquires an extremely unpleasant, putrid smell.
What are the substances in them?
The wastewater treatment plant receives sewage of the following composition:
- Proteins - 28%.
- Carbohydrates - 17,5%.
- Fatty acids - 10%.
- Oils, fats - 27%.
- Detergents - 7%.
As you can see, the main share of pollutants is organic. In industrial conditions, it is pointless to discuss any composition of wastewater, since in each case it is different. In particular, in some cases, allegedly purified "water" is dumped directly into the river (!), Which in appearance and composition resembles the used engine oil.
The main sources of pollution
As a rule, industrial and social objects, as well as livestock and poultry farms are to blame for environmental pollution. Very dangerous solid wastes, which are formed when the open development of mineral deposits, as well as waste, formed in the process of wood processing. Water and rail transport give a lot of biological waste. If they get into water sources, they cause their colonization with E. coli or eggs of worms. It is especially dangerous when a medical institution is higher upstream.
General information about the cleaning process
Processing includes the following methods:
- Mechanical. This includes filtration, which is used by all wastewater treatment plants, as well as sedimentation.
- Physical. This is electrolysis, aeration, treatment of effluents with ultraviolet radiation.
- Chemical methods. Special formulations are used for the deposition and disinfection of substances that may be contained in effluents.
- Biological wastewater treatment. In this case, plants that metabolize organic matter, as well as certain types of protozoa, snails and fish are used.
Preparatory work is carried out before processing. More precisely, the analysis of sewage. Specialists of chemical laboratories determine which pollutants are contained in them. This helps to choose the best strategy for their neutralization. The general procedure for wastewater treatment includes screening out: particulate matter, bacteria, seaweed, plants, inorganic impurities and organic substances. Removing solid particles is the simplest step. It includes filtration and precipitation by settling. It is much more difficult to clean sewage from thin suspensions, which are not retained by usual filter materials.
One of the simplest and cheapest methods, which, nevertheless, provides a high degree of purification, is the use of activated carbon. Filters with this material are used practically at all enterprises, whose management takes seriously the protection of the environment.
How does activated carbon work?
The main advantage of coal is its high absorption capacity. Simply put, there are so many pores on the surface of the particles of this substance that they can trap so many water-polluting compounds that several times exceeds the volume of the coal itself. It is the process of trapping, binding of polluting reagents and is called absorption. It should be noted that for the purpose of purifying drinking water, coal was used before our era. Active research and production of this material began during the two world wars. Factors affecting absorption are the particle size, surface area, the structure of the substance to be bonded, the acidity of the medium (pH), the temperature that wastewater has.
Which substances can bind activated carbon?
Charcoal absorbs many substances, ranging from non-ferrous metals and ending with complex organic compounds (for example, phenols). Of course, it will not protect against radioactive compounds, but it is possible to remove the main types of inorganic and organic impurities with it.
Coagulation of pollutants
In some cases, special liquids can be used for purification, which contain particles of colloidal substances. What are they needed for? Everything is simple - microscopic particles, combining with molecules of pollutants, cause them to precipitate. The phenomenon is known as coagulation. In some treatment plants, the electrolysis method is also used. The method is similar to the previous one, since the ions formed in this process also contribute to the deposition of contaminants.
On the contrary, modern researchers are increasingly proposing methods that use massive molecules that can more effectively bind and precipitate pollutants. This process is called flocculation.
Used chemical compounds
As we have already said, wastewater treatment may involve the use of negatively charged ions. Historically, aluminum sulfate is used for these purposes, as well as lime. These compounds cause a sharp change in the pH of the water, which leads to the death of pathogenic microorganisms, which are found in many in effluent. In some cases, substances based on ferric iron can be used. Some chemists believe that similar methods could be used by Egyptians for two thousand years before our era. The potassium permanganate also perfectly precipitates the organic matter.
More on the method of settling
Whatever it was, but the bound organic falls out in the form of flakes or gel. These sewage sludges can be easily captured with a simple mechanical filter. This method works best with relatively dense particles (for example, silt and other heavy organic impurities), while lighter particles (eg, microscopic algae) are best removed by settling. The sludge tank must be large enough that its filling should proceed as slowly as possible. This is due to the fact that the normal course of the process requires at least four hours. After organic and inorganic impurities settle on the bottom, water can be considered conditionally purified, suitable for use for technical purposes. This method is often used in the preliminary treatment of effluents.
Then comes the aeration sequence. Water enters the giant vats where compressed air enters under high pressure, which is discharged into the liquid by means of nebulizers. Have you ever seen how a compressor works in a conventional aquarium? In this case, almost the same thing happens. Aeration allows you to saturate the water with oxygen and to precipitate the remaining organic impurities. After such treatment, the liquid is most often supplied to special ponds planted with higher aquatic vegetation (biological treatment of wastewater). And only then water is considered suitable for use for technical purposes. It can be watered planting vegetables and fruits, and also dumped in natural water.