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4DEVELOPMENT OF METHODS OF TREATMENT OF OBSOLETE MINERAL-
CONTAINING WASTE WATER
ABDULLAYEVA KAMALA S., HAJIEVA LEILA V.
Azerbaijan State University of Oil and Industry, Baki , AZ 1010 , Azerbaijan
Abstract: Water is the main raw material for various industries, agriculture and utilities. The increase in the amount of polluted water and the lack of clean water is already one of the urgent problems of today, and the lack of this resource will be even more dangerous in the future. One of the most important environmental tasks is the treatment of waste water from various industrial enterprises. The main sources of pollution of water bodies with mineral substances are oil, chemical, galvanic production, metallurgy and mining enterprises. The technologies of wastewater treatment with mineral substances allow creating water purification and water circulation systems for many industrial facilities.
In recent decades, a significant increase in the content of heavy metals, petroleum products, hard-to-oxidize organic compounds, synthetic surfactants, pesticides, and other pollutants in the waters of open water reservoirs has been observed due to the discharge of insufficiently treated substances. industrial and communal enterprises. waste water. Cleaning of water from harmful impurities requires significant costs, but they are not always implemented at an adequate level, which damages the ecology of human, animal and plant habitats. An ecological and economic approach to solving this problem allows to reduce the costs of wastewater treatment by using the wastes of some industries as reagents or by co-processing several types of wastes to be disposed of. The main goal is to determine the mineral content of the used waste water and to use effective treatment methods corresponding to it.
Key words: Mineral content, Quantum 2A spectrometer, waste water, purification, industrial water, nitrogen, phosphorus, fluoride ions.
Introduction
Deterioration of water quality in surface sources is mainly caused by substances of anthropogenic origin: oil products, surfactants, organic and biogenic elements, etc. This suggests that the technology and structures designed in the 60s and 70s of the last century cannot cope with the modern anthropogenic load. Every day, the content of biogenic elements (nitrogen, phosphorus, fluorine, magnesium) is increasing, which is why in the industry they are used to protect heating elements in devices, improve washing of polluted water, etc. new types of tools are being developed. In modern conditions, serious attention is paid to the intensification of wastewater treatment processes, the improvement of existing treatment technologies and the development of new effective treatment methods, the application of resource-saving technologies for the modernization of existing methods and constructions of water treatment facilities.
Some methods are used to increase the efficiency of wastewater treatment from mineral and colloidal pollutants. Physico-chemical methods, in particular, the considered method of using activated solutions of coagulants for the removal of nutrients from domestic wastewater, as well as for the treatment of drainage water, are becoming more and more important [1].
This makes it possible to intensify wastewater treatment processes, reduce the costs of reagents used in wastewater treatment without degrading the quality of treated water, reduce the operating costs of treatment plants, and reduce treatment costs. According to its nature, sewage pollution is divided into organic, mineral and biological.
-Organic pollutants: they are impurities of plant and animal origin.
-Mineral contaminants: acids and their salts, mineral oils, etc.
Biological and bacterial contaminants are different organisms:
-including yeasts and molds, small algae and bacteria
- pathogenic (pathogens of typhus, paratyphoid, dysentery, etc.).
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All wastewater can be divided into four groups based on particle size.
The first group of particles includes coarse impurities that are not soluble in water. Impurities of organic or inorganic nature can be insoluble. This group includes microorganisms (protozoa, algae, fungi), bacteria and helminth eggs. These impurities form unstable systems with water. Under certain conditions, they can sink or float to the surface of the water. A significant part of this group of pollutants can be separated from water as a result of gravity sedimentation [2].
The second group of waste consists of substances with a colloidal dispersion degree, the particle size of which is less than 10-6 cm. Hydrophilic and hydrophobic colloidal impurities of this group form systems with water with special molecular kinetic properties. This group also includes high molecular weight compounds because their properties are similar to colloidal systems. Depending on the physical conditions, the wastes of this group are able to change the state of fusion. The small size of their particles makes it difficult to collapse under the influence of gravity. When the aggregative stability is disturbed, the debris collapses.
The third group includes waste with a particle size of less than 10-7 cm. They have a degree of molecular dispersion. When interacting with water, solutions are formed. Biological and physico-chemical methods are used to clean wastewater from the third group of wastes [3].
The particles of the fourth group have particle sizes less than 10-8 cm, which corresponds to the ionic degree of dispersion. These are solutions of acids, salts and bases. Some of them, especially ammonium salts and phosphates, are partially removed from water during biological treatment. However, domestic waste water treatment technology (full biological treatment) does not allow to change the salinity of the water. To reduce the concentration of salts, the following physico-chemical cleaning methods are used: ion exchange, electrodialysis, etc.
Depending on its origin, wastewater is divided into three main categories: domestic, industrial and atmospheric. Domestic waste water enters the drainage network from residential buildings, domestic rooms of industrial enterprises, catering facilities and medical institutions. The composition of such waters includes various domestic wastes and sewage contaminated with detergents and domestic sewage. Domestic wastewater always contains a large number of microorganisms, some of which may be pathogenic, which are products of human activity. A characteristic of domestic wastewater is the relative stability of its composition. The main part of organic pollution in such waters is proteins, fats, carbohydrates and their decomposition products. Inorganic substances consist of particles of quartz sand, clay and salts formed during human activity. Mineral content includes phosphates, bicarbonates and ammonium salts. Organic substances make up 45-58% of the total mass of domestic sewage [4].
Industrial wastewater is produced as a result of technological processes. The quality of mineral-containing wastewater and the concentration of pollutants are determined by the following factors: the type of industrial production, raw materials, technological process modes, etc. In most enterprises, both mineral and organic wastewater are polluted in varying proportions. The concentration of wastewater pollution from different enterprises is not the same and varies within very wide limits, depending on the water consumption per production unit, the perfection of the technological process and production equipment.
The concentration of pollutants in industrial wastewater can vary greatly over time and depends on the course of the technological process in individual industries or in the enterprise as a whole.
Uneven concentration and flow of mineral-containing wastewater in all cases worsens the performance of treatment plants and complicates their work. Atmospheric wastewater is formed as a result of precipitation. This category of wastewater includes melt water as well as street irrigation water. Atmospheric waters contain a high concentration of quartz sand, clay particles, garbage and petroleum products washed from city streets. Pollution of the territory of industrial enterprises leads to the formation of impurities in rainwater that are characteristic of this production [5]. Based on the hydrogeological conditions of the area, the nature of production processes in a certain region, water consumption for domestic and industrial needs, one or another drainage system and the scheme of the drainage network are selected accordingly. The quality composition of domestic and industrial
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wastewater directly affects the choice of water treatment technology and, as a result, the environmental situation in a certain area.
Methods.
To determine the mineral content of waste water, it is analyzed by the Spectrometer method. In the studied samples, Mg2+, Na+, Ca+, Cl-, F-, etc. The concentration of mineral-containing wastes was measured by atomic absorption method. Spectroscopy (measurement error ± 0.001 mg/l) using a Quantum-2A spectrometer (Fig. 1) with a plasma atomizer manufactured by KORTEK LLC.
Figure 1. Quantum 2A spectrometer.
Substances are converted into atomic vapors by high-temperature vaporization of the sample using a flame or electrothermal atomizer to obtain free gaseous atoms. Most chemical compounds decompose. Atoms of matter exist in a free state. A hollow cathode lamp made of defined metal is used as a radiation source [6]. The wavelength interval between the spectral line emitted by the light source and the absorption line of the same element in the flame is very narrow, 0.001 nm, so interference with the absorption of other elements has practically no effect on the analysis results.
The measured quantity is the optical density of the flame determined in a narrow spectral range in the atomic absorption line. Atomic absorption wavelengths and mineral concentration limits optimal for determination by atomic absorption spectroscopy are given in table 1.
Table 1.
Substances Index, mq
Mg+ 25,2
Ca+ 32,7
Na+ 22,3
Cl- 23
F- 29
J- 12,5
As can be seen from the table, the content of Ca ions is high in waste water. Taking these into account, it is necessary to choose an effective method for cleaning mineral-containing waste [7]. Solutions.
Mechanical filtration is a separation process that removes or retains large suspended solids from liquids on the surface or inside a filter element. Filtration efficiency is determined by taking into account both particle (size; density; concentration) and fluid (viscosity; corrosion; pH value; temperature) properties and filter element properties (pore size; thermal resistance; chemical resistance). The following driving forces affect the rate of filtration: -hydrodynamic,
-gravity, -molecular, - electrostatic.
The characteristics and properties of both mechanical and membrane filtration were studied in the work. Filtration performance is strongly influenced and possible by the interaction between the retained components and the media being treated. Thus, in the study, the process of cleaning process liquid (CaCO3) using a microfiber filter was studied and the great potential of this type of equipment for cleaning water containing small particles of mechanical impurities was shown.
The advantages of mechanical filtration are the simplicity of the equipment, minimum energy consumption, and the ability to effectively remove suspended particles, for example, in the stage of pretreatment of wastewater from heavy metals in membrane installations. The main disadvantage is that filtration does not remove both inorganic and organic dissolved waste from solutions.
Among the mineral components, iron, potassium, sodium, calcium, magnesium, barium, chlorine, carbonates and sulfate ions remain in the filtrate.
Indicators of the composition of mineral-containing compounds in wastewater can be the detected residue, the electrical conductivity of the solution, and the salt content. On the basis of the study of the decomposition processes of mineral particles and the comprehensive analysis of data on the typical composition of filtered water, it is possible to try to predict the most likely composition of organic impurities in drainage water at different stages of biochemical destruction of waste. In addition to substances formed during anaerobic fermentation of the organic component of mineral waste, dissolved substances also enter the solution, in some cases forming new compounds with new properties, often more dangerous than the original ones. The higher the percentage of organic matter and water-soluble salts in mineral waste, the more pollutants will be in the filtrate [8].
A typical method of cleaning waste containing minerals is the nanofiltration method. The main and most important task of nanofiltration research is to determine the characteristics of nanofiltration membranes during purification of wastewater from mineral-containing ions.
Membrane properties - the selectivity of the membrane and its specific productivity. Selectivity is the percentage of solute retained by the membrane. A distinction is made between true and observed selectivity. True selectivity is the percentage of a substance retained by the membrane in the absence of concentration polarization. The observed selectivity is the percentage of the substance retained by the membrane in the presence of concentration polarization (equation 1):
R = (ci - c2/ci) • 100% (1)
Here c1 is the initial concentration of the solute in the separated solution, c2 - solute concentration.
The pH value plays a major role in the electrostatic mechanism when separating NFs. Therefore, studies of the effect of the pH value of the initial solution on the selectivity of the NF membrane were also carried out [9].
The selective layer of the investigated nanofiltration membrane (ZAO STC "RM-Nanotech") consists of piperazinamide. When the membrane is placed in an aqueous solution with a pH close to neutral, the membrane acquires a negative charge due to the dissociation of the carboxyl groups of the polymer. As the pH of the solution decreases, the dissociation of the carboxyl groups is suppressed and the amino groups of piperazinamide are protonated, which leads to an increase in the positive charge of the active centers on the membrane surface. At the isoelectric point (IEN), the positive and negative charges of the selective layer are compensated, resulting in a neutral membrane surface. In this region, there is no electrostatic interaction between the membrane and the dissolved ions due to the decrease in the membrane surface potential. The contribution of the electrostatic mechanism to the total nanofiltration capacity is reduced. Concentration polarization is the phenomenon of increasing the concentration of the substance retained by the membrane in the layer close to the surface of the membrane during the membrane separation process. The principle of the method is to
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pass a liquid containing finely dispersed impurities through a filter material that does not pass liquid and solid particles. Oils, petroleum products, resins, etc. is removed. The driving force of filtration is the pressure difference before and after the filter partition. Nanofiltration is used for deep mechanical purification of water from solid and liquid particles that are insoluble in water, in most cases it is the last stage of water purification and is carried out after its initial sedimentation in settling tanks, diluters or other structures. This is due to the fact that the filter resource is limited and it is most rational to use it to remove particles that do not settle. However, nanofiltration removes up to 80% of waste [10].
Conclusion
In this article, the analysis of experimental data shows that the characteristics of the effectiveness of NF for water treatment of mineral-containing solutions by the nanofiltration method have been determined - selectivity of the membrane, specific productivity, etc. NF membranes were found to have high selectivity (-98%) at concentrations greater than 100 mg/l. The most commonly used methods of wastewater treatment in the Republic of Azerbaij an, their treatment efficiency, place in the technological process, and ways of possible improvement of these methods to improve the quality of water resources are analyzed. It can be summarized that the effectiveness of traditional wastewater treatment methods does not allow purification up to standard values. Nevertheless, there are a significant number of variations for improving existing methods, as well as fundamentally new methods of wastewater treatment. These methods are gradually included in technological schemes and allow to increase the degree of wastewater treatment. In modern conditions, special attention is paid to various ways of intensification of wastewater treatment processes, improvement of existing treatment technologies, including the application of new methods and technological techniques that improve the quality of wastewater treatment and reduce the anthropogenic impact on the ecosystem; for these purposes, it is appropriate to use resource-saving wastewater treatment technologies that allow saving materials and natural resources.
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