Water in the hot water supply system (DHW) must comply with the quality regulated by SanPiN 2.1.4.1074-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control". At the same time, the working conditions and the organization of hot water supply systems are different than in the case of cold drinking water supply. A number of specific requirements for the design and operation of these systems are associated with this. They are formulated in such regulatory documents as SanPiN 4723-88 “Sanitary rules for the installation and operation of centralized hot water supply systems”, RD 34.37.506-88 “Methodological instructions for water treatment and the chemical regime of water-heating equipment and heating networks”, SP 41- 101-95 “Designing of heat points”, etc.

DHW water issues

Water heating for hot water supply occurs on equipment having an open circuit. As needed, make-up water enters it.

An important feature of hot water supply is that the hot water at the distribution point must have a certain temperature. When opening the faucet, the consumer should not wait for the cooling water to drain. This problem is usually solved by organizing a constant circulation of water through heat exchangers in order to maintain its temperature in the networks in a given interval.

In addition, the occurrence of stagnant zones with relatively low temperature in hot water systems leads to the multiplication of microorganisms, including pathogens; deposits of biological origin adversely affect the performance of networks and equipment.

On the other hand, the operation of systems at elevated temperatures is associated with the activation of metal corrosion processes. Corrosion products together with biomass particles and other insoluble impurities form deposits on the surface of pipelines and heat exchangers, narrowing the water passage and making it difficult to heat.

Basically, the presence of insoluble impurities is associated with the low quality of make-up water, which in many cases determines the condition of the source, as well as the deterioration or low power of the water treatment equipment.

For the preparation of water for hot water systems, the same methods are used as in all other cases, which have already been repeatedly described in the pages of the Aqua-Therm magazine.

Non-chemical treatment

Most often, a violation of the current standards for water quality for hot water supply concerns the content of dissolved oxygen: usually it is 0.1-0.17 mg / l, although the permissible concentration is 40-60 μg / l. At the same time, the presence of dissolved oxygen in water causes more severe pipe corrosion in domestic hot water systems than in cold drinking water supply.

The required concentration of residual oxygen can be achieved by deaeration. And the air present in water in the form of microbubbles is removed using separators of various designs. In addition to enhancing corrosion, air, accumulating in various parts of the system and forming the so-called air plugs, interferes with the normal flow of water.

Corrosion of metals is also facilitated by the fact that in mass construction in hot water supply systems, black steel pipes are often used together with pipes having a galvanized surface. With their mixed installation, due to the formation of galvanic pairs, accelerated destruction of the anticorrosion coating occurs. We also note that domestic-made galvanized pipes produced according to GOST 3262-75 * have a zinc coating thickness of 30 microns, the service life of which is only 1.5-2 years. As a rule, the coating thickness of foreign-made galvanized pipes is 70-80 microns.

A serious problem for DHW systems is the formation of mineral deposits on the surface of water-heating equipment, pipes and plumbing.

To prevent this, in some cases, ultrasonic emitters are installed on the water-heating equipment, which prevent the deposition of sludge on the surface of the equipment and pipelines. It is then removed from the system by filtering. One of the types of such equipment is “Zeusonic” devices, designed to protect low and medium capacity hot water boilers, as well as various heat-exchange equipment, from scale. The action of these devices is based on the excitation of intense acoustic pulses. Used in the DHW system and electrochemical anti-scale devices, protective cathodes. For example, the AEA-T apparatus manufactured by Azov OJSC (Dzerzhinsk, Nizhny Novgorod Region).

Inhibitors and decalcifiers

Dosing of chemical reagents has become widespread to prevent the formation of deposits and sludge in hot water systems. However, there are restrictions on their use, regulated by the values \u200b\u200bof maximum permissible concentrations of these reagents in hot water. It should be guided by the “List of materials, reagents and small-sized treatment devices authorized by the State Committee for Sanitary and Epidemiological Surveillance of the Russian Federation for use in the practice of drinking water supply”.

Thus, according to the List, the residual content in the water used to protect the DHW systems from corrosion and scale formation of the zinc complexonate hydroxyethylidene diphosphonic acid (OEDPK) should not exceed 5.0 mg / l. And the maximum permissible residual content of hydroxyethylidene diphosphonic acid used for the same purpose is 0.6 mg / l.

Among the chemicals for treating hot water there are both reagents that have a narrowly targeted - anti-corrosive or anti-scale - effect, and complex ones that improve water quality in several ways at once.

For example, the reagent for correcting the preparation of water for Advantage K 350 boilers from Ashland (Finland) eliminates metal corrosion, reduces the rate of formation of deposits, binds oxygen dissolved in water and absorbs carbon dioxide.

The complex effect of the reagent is due to the fact that it contains amines (diethyl hydroxylamine and 2-amino, 2-methyl-propanol), alkali (potassium hydroxide) and synthetic polymers. When dosed in water, the alkali binds free carbon dioxide, amines regulate the pH level and absorb dissolved oxygen, and the present polymers, creating a coating of a thin film, prevent the formation of deposits on the inner surfaces of the system elements.

Another Ashland reagent, Drewgard 120, is based on a mixture of pyrophosphate and potassium hydroxide. This system also forms films that impede the occurrence of negative processes on the internal surfaces of pipelines and equipment.

As in closed circuits, in open-type systems, sodium silicate reagents are used as corrosion inhibitors and mineral deposits. Basically, these preparations contain sodium salt of silicic acid and sodium hydroxide. The action of this composition is also based on its film-forming properties.

For water with high corrosivity, silicate treatment can only be used if the saturation index is less than 0 and greater than -1.5, and the total content of sulfates and chlorides is in the range of 50-75 mg / l. With higher corrosion activity, the use of silicate water treatment is not productive, especially in cases of high sulfate content.

Complexons are widely used as antiscales - substances that, due to the contained polar groups, interact with precipitates, converting them into solution. These include the already mentioned zinc complexonate OEDFK.

As a result of the action of many types of chemicals during water treatment in the DHW system, light suspensions and easily removable sediments are formed. However, they can cause damage to equipment and participate in the formation of deposits on the inner surface of pipes and equipment.

Filters

To remove insoluble impurities from hot water, mechanical filters and hydrocyclones are used. Basically, these devices are similar to those used in cold water supply systems (of course, adjusted for a higher temperature), but the features of cleaning hot water after entry points should be considered separately.

Usually, a coarse filter with a mesh size of 400-500 microns is placed directly at the consumer. Its main purpose is the protection of water meters and fittings. Thinner filters in this place are not practical, as they will clog very quickly. But after water meters, as a rule, wash filters are installed, the purpose of which is to remove most of the suspended solids. Most often, filters with a retention threshold of 20 to 100 microns are used for this purpose. They reliably protect valves and mixers, but also require periodic cleaning. Filters with programmable automatic flushing can be used, but they are much more complicated and expensive.

A more affordable option for organizing the removal of the smallest mechanical impurities is filters with replaceable cartridges with pore sizes in the range of 1-20 microns. They have different performance, and their service life varies from 3 to 12 months. It should be noted that such small pore sizes make it possible to retain iron impurities in various degrees of oxidation (Fe3 + and Fe2 +), protecting faience and enamel plumbing from red smudges. DHW cartridge filters are similar to those used for the purification of cold drinking water; the difference is only in the case materials and the filter itself.

Biosafety

In addition to removing mechanical impurities, the quality of water in the hot water supply is characterized by the absence of biological contamination. Legionella are the most dangerous, which multiply especially quickly in storage tanks, stagnant zones of pipelines, as well as with the periodic use of hot water and shutdown of hot water. A favorable environment for their reproduction is stagnant water with a temperature of 25-45 ° C.

Usually, an effective disinfection of water is under preparation. However, any violations in the operation of hot water supply increase the risk of infection. The most common way to combat legionella is to heat water: heating water to a temperature of 70-80 ° C instantly leads to complete disinfection of water from this type of bacteria. With decreasing temperature, the processing time should accordingly be increased. So, at 65 ° C, the water treatment time should be at least 10, and at 60 ° C - 20 minutes. The disadvantage of this method is that the hot water supplied to the consumer has a lower temperature, and heating in the places where the heaters are installed does not exclude the formation of stagnant zones.

To combat the Legionella, various technical solutions are offered. Accumulative boilers are increasingly equipped with the function of automatic periodic heating of water to a temperature that ensures disinfection; pipelines are designed so that there is no place for stagnant zones; special thermostatic valves are installed in the circulation lines, which do not allow a dangerous decrease in temperature, etc.

A common method of disinfection is the use of UV radiation. In the course of such processing toxic products do not form, organoleptic indicators of water do not worsen. Various water disinfecting systems of domestic and foreign production have been considered more than once in the journal Aqua-Term.

In relation to the topic of this article, it is advisable to touch on the GenoBreak model manufactured by Grunbeck (Germany). This unit simultaneously processes water with ultraviolet and ultrasonic radiation. The value of this combination lies in the fact that the cavitation effect of ultrasonic signals allows you to destroy not only Legionella, but also their carriers - amoebas, whose presence allows Legionella to avoid damage during some other types of water treatment.

There are other ways to combat legionella, for example, electrochemical anodic generation of ions that have a pronounced antiseptic effect of silver or copper. According to some experts, it reduces the risk of Legionella infection and the use of copper pipelines.

In the fight against Legionella, the use of chemicals, in particular bleaching liquor in the concentration of free chlorine of at least 10 mg / l, with a treatment duration of 1-2 hours should not be ruled out. However, it is necessary to strictly observe the current standards for the presence of such reagents. In this regard, the combined use of sodium hypochlorite and UV irradiation, which can reduce the concentration of a chemical reagent, is especially valuable.

Shvab V.V., BioBird LLC, Moscow

The energy strategy of Russia for the period up to 2030, approved by order of the Government of the Russian Federation of November 13, 2009 N 1715-r, defines the goals and objectives of the long-term development of the country's energy sector for the coming period, priorities and guidelines, as well as mechanisms of state energy policy on individual stages of its implementation, ensuring the achievement of the intended goals.

Strategic goals for the development of heat supply are:

· Achieving a high level of comfort in residential, public and industrial premises, including quantitative and qualitative growth in the range of heat supply services (heating, cold supply, ventilation, air conditioning, hot water supply), a high level of provision of the population and sectors of the country's economy with this set of services, corresponding to leading European countries at an affordable cost;

· Dramatic increase in the technical level of heat supply systems based on innovative, highly efficient technologies and equipment;

· Reduction of unproductive heat losses and fuel consumption;

· Providing manageability, reliability, safety and efficiency of heat supply;

· Reduction of negative environmental impact.

Ensuring the rational and efficient operation of hot water supply systems is an important task to improve energy efficiency in the light of the implementation of Federal Law No. 261-FZ of November 23, 2009.

The operation of hot water systems is associated with a large consumption of heat and energy. So, for example, in residential apartment buildings, the cost of hot water supply (water heating) exceeds the cost of heating.

Improving the efficiency of hot water supply systems is impossible without ensuring the quality of hot water and without developing measures to prevent the formation of deposits (sludge) in heat exchangers and distribution pipelines.

The need to develop these measures is caused by the fact that for many natural waters used for hot water supply containing aggressive carbon dioxide, carbon dioxide equilibrium (state of stability) is achieved when they are heated to 55-65 0 C.

At a higher temperature, the carbon dioxide balance is disturbed, which leads to the precipitation of calcium carbonate from the water. In heat exchangers, calcium carbonate is deposited in the form of solid crystalline deposits, in the pipelines of hot water systems - mainly in the form of fine crystalline sludge. The higher the temperature of heating the water, the more heat exchangers overgrow and the more sludge is deposited in the pipelines of the system. The greatest amount of sludge falls in the distribution pipelines. Such deposits, in addition to reducing the throughput of pipelines, cause corrosion due to differential aeration (uneven aeration of covered and uncovered pipe sections). As a result of this, corrosion damage to the horizontal highways of DHW systems is more intense in the lower part of pipes covered with deposits. When water cools down as it passes through the system, a precipitate of calcium carbonate is released from it, the carbon dioxide equilibrium shifts in the opposite direction, as a result of which part of the carbon dioxide dissolved in water becomes aggressive and contributes to corrosion of pipelines. The higher the initial temperature of water heating, the greater the amount of aggressive acid is formed when the water cools.

The combination of the above processes leads to the fact that the corrosion rate of pipelines increases by about 1.5-2 times for every 10 0 C increase in water temperature. The presence in the water of suspended particles of colloidal iron, formed as a result of corrosion of steel pipelines, intensifies the process of precipitation of sparingly soluble compounds, because solid particles become crystallization centers. All this leads to a deterioration in water quality and to a violation of the operational characteristics of centralized hot water supply systems.

Unfortunately, in practice, this factor is not taken into account when designing and operating heat power systems (boiler houses, central heating, heating and domestic hot water), or is rarely considered. The adopted ITP schemes do not take into account the requirements for stabilization treatment of hot water (paragraph 3.3 of SanPiN 2.1.4.2496-09 “Hygienic requirements for ensuring the safety of hot water supply systems”). Namely, in violation of the requirements of subsection. 3.3.1. the schemes do not provide for special water treatment (anti-scale, anti-corrosion), due to technological requirements. In addition, according to clause 11.16 of SNiP 2.04.07-86 “Heat Networks”, protection against corrosion and scale formation shall be provided, clause 5.2 of SP 41-101-95 “Design of heating points” requires the provision of water treatment depending on the quality of the water, supplied from the networks of domestic drinking water supply, pipe material and equipment of the STsGV adopted in the project, as well as the results of feasibility studies.

The reference to the fact that hot water, after the heat exchanger, meets the regulatory requirements is incorrect. Heating of water, a solution consisting of many chemicals of technogenic and natural, usually mineral, origin, as well as substances entering water sources as a result of human activities, leads to an increase in the rate of a chemical reaction by 140-4000 times. And this leads to a significant deterioration in water quality. Moreover, the reaction, as a rule, starting in heat exchangers, passes and ends in the pipelines associated with them.

Our proposed technology for the use of non-reagent water purification / purification devices and the protection of heat exchangers and associated pipelines against corrosion and scale formation based on the use of WEITZ-WASSERWELT biobird water vitalizers (Germany) allows to eliminate many problems that adversely affect the functioning of the above systems and, above all, DHW systems, in particular:

· The presence of corrosion in pipelines leads to a deviation from the norms and rules of composition and the deterioration of the properties of water (turbidity, odor, etc.). According to new The rules for the provision of utilities to owners and users of premises in apartment buildings and residential buildings (APPROVED by the Decree of the Government of the Russian Federation of May 6, 2011 No. 354) deviation of the composition and properties of hot water from the requirements of the law  Russian Federation technical regulation not allowed ;

· The presence of scale formation leads to "overgrowth" of heat exchangers and pipelines, which leads to a decrease in the efficiency of heat exchangers (in the presence of deposits, heat removal decreases, i.e., more heat is needed to reach the required temperature) and pressure (pipe capacity), t .e. in multi-storey buildings, the upper floors will not be provided with the necessary pressure. According to new The rules … pressure deviation in the hot water system is not allowed.

Devices clean water in closed cycles and return it to its original form. Within 1-25 days after installation, the water in the system becomes transparent, and calcium salts begin to break down and are converted to aragonite, which becomes an integral part of the water and does not adversely affect water users, heat power plants and associated pipelines. And, importantly, there is no need to drain this water into the sewer during flushing and fill the system again. Almost as such, leaching can be eliminated. The use of this technology will save millions of cubic meters of pure water in this case.

So, for example, when performing reagentless flushing of the hot water system with the subsequent installation of a biobird water vitalizer (photo No. 3) in the building of the Mytishchi District Drama and Comedy Theater “FEST” using the proposed technology, a positive result was achieved 24 hours after the start of work. Those. after 24 hours, the water from brown (photo No. 1) turned into transparent without visible elements of pollution (photo No. 2). It should be noted that the supply of hot water to consumers did not stop.

Photo No. 1 Hot water condition in make-up rooms No. 5 and 6 before the start of work on washing and installing the biobird water vitalizer (February 2011)		Photo No. 2 Hot water condition in make-up rooms No. 5 and 6 after washing and installing biobird water vitalizer (August 2011)
Photo No. 3 Water vitalizer biobird BWV 100 installed in the ITP of the MRTDK building "FEST" on the pipeline in front of the heat exchanger after mixing cold water with reverse hot water (August 2011)

Since 2006, biobird water vitalizers, the main component of the proposed devices, have been successfully used in many regions since 2006: Volgograd, Leningrad, Moscow (Mytishchi, Sergiev Posad) and Saratov regions, the Republic of Tatarstan, Udmurtia, Khakassia and other regions of the Russian Federation, and also in the CIS countries: Belarus and Kazakhstan.

· Non-profit partnership “Russian Heat Supply”, about which a corresponding entry was made in the “Register of modern affordable energy-efficient technologies in the field of heat supply” (Certificate No. 03 of 12/14/2010);

· The Ministry of Industry and Energy of the Saratov Region, about which an appropriate decision was made to include in the “List of innovative energy-efficient technologies and measures possible (appropriate) for implementation in the territory of the Saratov Region” (letter No. 05.01 / 246 of January 25, 2011).