Perspectives of Using of Ultrasonic Cavitation in Water Treatment Technology for the Food Productions

Water is one of the main raw materials in the production of most foods; on its composition and quality greatly affect the quality of the finished product. In food production, water is used as a system of potable water supply, and is extracted from underground water sources. At the today’s highly anthropogenic water pressure purification systems in the food industry do not always cope with the difficult task of water treatment, and manufacturers are often faced with the need for additional water treatment. In this connection, the search for new approaches to adjusting the properties and composition of the water is important. The article notes the use of ultrasonic cavitation for water treatment processes for the food industry.


Introduction
As we know, the quality of the water plays a significant role in food production technology is strictly regulated by the sanitary-epidemiological requirements -safety, safety in chemical composition, organoleptic properties. Under the water quality to understand the characteristics of the composition and properties of water, determining its suitability for specific types of water.
Analysis of water status reports data in the Russian Federation showed that the share of water supply systems that do not meet sanitary and epidemiological requirements, was 18.4% in 2012. The proportion of unsatisfactory water samples from the water networks of distribution for the of surface waters of first category of samples do not meet hygienic standards for chemical indicators in recent years has averaged 25.5%, according to microbiological indicators -8,9% (10, 6, 7).
A comparison of the water quality standards in Russia, the European Union, the World Health Organization showed that the same water quality in different regulations differ greatly from each other. In Russia, too low in terms of the requirements of total hardness, total bacterial count, the content of sulfate, ammonia nitrogen, turbidity, color, pH. (Table. 1).
It should also be noted that the feature of the Russian standards is that for some of the indicators set maximum permissible concentration (MPC), which are used beyond the sensitivity of the procedures. With such a high analysis accuracy can handle only a few well-equipped laboratory in Russia (10,14,15). The tightening requirements for water quality for producers inevitably associated with the search for new opportunities and affordable mechanisms to intensify and improve the efficiency of manufacturing processes, the special importance at this stage of the process becomes a cycle as the water treatment.
For the organization of an effective water treatment businesses need to keep track of the main critical water quality parameters used by them for production.
At the food production, water is used as a system of potable water supply, and is extracted from underground water sources.
To determine indicators measuring system discrepancy to its purpose and its lack efficacy, we analyzed the water quality within the framework of one of the leading enterprises in the food industry of the Ural region ("Vitex" company). The studies were conducted on the season during 2010-2017. (Table. 2) Was found that the test water samples two indicators: total hardness and iron content, are symptoms, it is a systematic deviation from the norm was observed for them.
The data indicate that acute facing the enterprises of food industry task efficient cleaning, disinfection, correction of organoleptic characteristics and conditioning mineral composition of the water used for food production.
The selection and combination of the method of water treatment is defined as the appearance and the type of food production, as well as the properties and the quality of the incoming water. The analysis proposed in the literature of water treatment methods allowed them to systematize the subject carried out the purposes (Fig. 1). To solve these problems, using physical, physico-chemical and chemical processing methods. In practice, there is often the combination of physical factors of influence that accelerates water purification processes. In particular, the application of an electric field accelerates the processes of flocculation and sedimentation of coagulated slurry increases the degree of purification of water from organic and inorganic impurities filtration; improved separation of algae. The required safety criteria are more correspond to physical (reagentless) water treatment methods. In accordance with modern requirements for food production and the development of science as a water treatment consists in cleaning contaminants from a variety of factors, and to improve the properties of drinking water quality without altering their composition.
To solve the problem of water quality parameters in order to adjust the total content of iron and stiffness, contact exposure was chosen to water ultrasonic cavitation.
Regarding the effect of ultrasonic treatment on the structure and properties of the water there is many conflicting data, explains the different theories. However, it is undeniable that the ultrasonic exposure to water causes changes in its structure, which in turn is reflected in varying degrees the properties and performance of water quality. Changes in the structure and properties of water are determined by a number of effects caused by sonication. According to the data (4), one of the most powerful effects is the cavitation disintegration, causing the dissociation of water molecules and destruction of the substances present therein.
Ultrasonic vibrations (frequency above 20 kHz) lead to the formation of zones in an aqueous medium of high and low pressure, wherein the distance between adjacent areas of compression (or stretching) is wavelength. This snapshot is moved to the medium speed of sound (1 -3, 9 -12), which can not but affect the component composition and structure of water. Deep study of ultrasound given in the works of IE Elpinera, L. Bergman, I. Peirsol, R. Knapp, LD Rosenberg and many others, indicate its ability to concentrate the sound energy, causing a number of specific effects (4, 16 -20).
For applied research Ultrasound technology "wave" model UZTA-0.4 / 22-OM (operating principle is based on the properties of high intensity ultrasound in liquid environments).
Ultrasonic cavitation treatment mode: 2 kW at a frequency of 22 kHz ± 1.65. Tap water in a volume of 250 ml sonicated device power 30%, 45% and 60% (120 W, 180 W, 240 W), the exposure time of 1, 3 and 5 minutes. Monitoring was carried out according to the nomenclature of the critical targets set in the previous stage of the research.
As a result, the most effective set of ultrasonic treatment regimes for adjusting water quality (reduced index relative to the initial value): General hardness Iron content 180 W, 5 min 24,6% 240 W, 3 min 24,7% 180 W, 3 min 15,0% 180 W, 5 min 23,0% ultrasound + filtration It has been found that the use of sonication to reduce the water hardness. When processing power of 180 W and 240 W for 3 minutes, -an average of 20 -24%, ultrasound exposure for 5 minutes under these facilities to reduce the stiffness value still only 5% -7. The resulting effect is based on the destruction of propagating pressure pulses in the water of hydration shells by cavitation and the dissolved ions existing in the form of calcium and magnesium bicarbonates and thereby stimulate the transition of the hardness salts in amorphous colloidal form carbonates, which can exist in water without crystallizing. Interactions of calcium and magnesium salts, ultrasonic treatment promotes the precipitation of sediment in them, thereby softening the water. Evaluation results of water hardness in function of time and power affecting factors are plotted (Figure 1).  These figures make it possible to note the positive trend of the impact of ultrasonic vibrations to reduce water hardness. When mechanical effects is the destruction of hardness, reduced concentration, which has a positive effect on food production technologies.
The trend is that different power ultrasound destroys various salt water, less power ultrasound destroys calcium salts, with the allocation of the water of calcium ions, which increases its share in the overall reduction of water hardness. Sonication power greater effect on increasing the magnesium salts with magnesium ions also shares at lower total water hardness.
To ensure effective water purification from iron was necessary to set the initial state of the element in the test water samples and the effect of ultrasonic treatment on him. Monitoring was performed using Purbe diagram. It was found that ultrasonic treatment accelerates the oxidation of Fe 2 + to Fe 3 + with subsequent formation of Fe(OH)3.
Because of the insolubility of Fe(OH)3 for water purification from iron it was nice on the need to further filter the water samples studied.
As a result, it was found that ultrasonic treatment followed by filtration reduced the iron content in water (with respect to the filtered water) in the processing mode power 180 W, exposure time 5 minutes and 3 -15 and 23%, respectively.
Ultrasonication 180 watts for 3 min, allowed to reduce the total count value, but this mode can not be acknowledged effective. The increase in power as sonication exposure possible to achieve the best results, the effect of ultrasonic impact of 180 W, 5 minutes, and 240 watts, 3 minutes and 5 differed slightly. Using the mode sonication power of 180 W for 5 minutes and 240 watts power for 3 and 5 minutes, allowed to reduce the value of 6 TMC of water -7 times.
Comprehensive analysis of the results allowed us to determine the most effective regimen of ultrasonic influence -180 W, the exposure time of 5 minutes.
To determine the degree of effectiveness of the modified water treatment technology comparative analysis of water quality was performed, produced using traditional and updated technology.
The results of these studies have shown that using a modified technology using sonication allows to adjust the values of indicators beyond the standard values, and ensure that the water quality standard.
The results of the indicator of total hardness of the test water samples are provided in Figure 2. As seen from the data presented below, the ultrasonic treatment of the water reduces the overall stiffness index values. The nature of the dependency of the total hardness of the power of ultrasonic influence is somewhat different. Similar curves were obtained by ultrasonic treatment 180 and 240 watts of power. Reducing the overall rigidity is most active in the processing 1 and 3 minutes -an average of 20%, the effect of ultrasound for 5 minutes under these facilities to reduce the value of this indicator is still only 5 -7%.
Considering the effect of ultrasonic treatment of water in the values of total hardness, depending on the power of the ultrasound, we can say that similar values reduce the effects of this indicator observed for 1 minute treatment. The intensity of total hardness reduction in the processing capacity of 30% for 3 and 5 minutes, significantly inferior to the results of the water treatment capacity of ultrasound 180 and 240 watts.
Studies have shown that the ultrasonic water treatment is also possible to reduce the total content of iron in it, the most pronounced reduction effect was noted when processing in the power mode -180 W, 3 min exposure. Obviously ultrasonic impact accelerates the oxidation of Fe 2 + to Fe 3 + with subsequent formation of Fe(OH) 3 .
Thus, in our view, the use of ultrasonic cavitation in water treatment technology in the production of food is justified reception solve unconditioned quality of tap water used manufacturing enterprises.
The most effective mode of combination of power and 180 watts accepted exposure time 3 min. In the literature, there is quite a lot of evidence on the effect of ultrasound disinfecting fluids, including water.
According to data (13), the death of microorganisms in a liquid medium under the influence of ultrasound, occurs mainly due to the destruction of cell membranes secondary sound. The destruction occurs instantly or almost instantly -over several periods or periods of tens of forcing oscillator.
Lethal threshold sound field characteristics different for different microorganisms and depends on the shape of the shell and its mechanical strength. We know that Rod and flagellated bacteria are killed in the acoustic field likely than coccoid. It is also associated with a difference limit mechanical stresses arising in the envelopes under the influence of deformation, which arises with deformation of the medium through which the pressure disturbance spreads. It was established that the lethal effect of decreases in inverse proportion to the square of the distance of the biological object to the point of collapse of cavitation bubble (8).
Does not exclude other mechanisms ultrasonic disintegration. So, the hypothesis is known about the possibility of the destruction of material wedging pressure fluid forced into micro-relief of the interface in high-pressure phase after the transition to a low-pressure phase (Paultera effect).
Known hypothesis about the participation in the destruction of highly monovalent and divalent hydroxyl materials (Taylor effect) resulting from cavitolisation water. There mechanisms to achieve the result may be merely chemical character. In the process of sterilization it can be disinfectant action of hydroxyl ions and hydrogen peroxide (5).
But, one way or another, an exceptional role in the occurrence and effect of all these effects is the presence of mechanical forces associated with the emergence of shock waves resulting from collapse of the cavitation bubbles, that is, the acoustic cavitation fields or secondary audio.
As the most effective modes of disinfection in the literature indicated: frequency above 20 kHz power greater than 150 W, and the duration of exposure of 3 minutes or longer.
In this connection, we carried out a series of experiments on the effect of ultrasonic treatment on the value of the index total bacterial count of water. Samples were sonicated in water mode: frequency 22 kHz, power 180 W and 240, the duration of exposure to 3 and 5 min.
The results of these studies have shown that 180 watt sonication for 3 minutes, allowed a few to reduce the value of the total count, but this cannot be considered an effective treatment.
The increase in power as sonication exposure significantly reduced the TMC, and the effect ultrasound exposure of 180 W for 5 minutes and 240 W 3 and 5 min differed slightly.
In general, the ultrasonic treatment modes Power 180 W effects and 5 minutes and 240 watts of power 3 and 5 minutes, allowed to reduce the value of TMC of water in 6 -7 times.
The findings suggest the possibility and high efficiency of the use of ultrasonic processing, water disinfection within the food production.

Conclusion
Thus, in our view, the use of ultrasonic cavitation in water treatment technology in the production of food is justified reception solve unconditioned quality of tap water used by food industry.
As the most effective water disinfection regime was installed sonication frequency of 22 kHz to 180 watts exposure time of 5 minutes and 240 watts for 3 minutes exposure time; for reducing the iron content and the water hardness -a combination of 180 watts of power and exposure time 3 min.