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The Newest Technologies of Decentralized Water Treatment as Essential Condition for Sustainable Development of Cities and Conservation of Historic Urban Landscapes. Examples from construction practice in St. Petersburg.

Report on the Forum on Barcelona: "Sustainable urban
development. Strategic planning and problems of
conservation of historic urban landscapes”

      The strategic planning and decision of problems of steady development of historical cities and areas, both on regional, and on international (UNESCO) levels, encounters the serious obstacles created by imperfection and pastness of existing  engineering networks. Perhaps, the most difficult task of management in historical landscapes today is the organization of water supply for the population of such urban areas. Nowadays water coming to the town dwellers reflects not only the ecology of the region, but  technical level of centralized water treatment plants and, in very big degree, condition of pipelines, supplying buildings with water as well pipe fittings.

     As to ecology, water is one of vitally important substances of nature which, without recognizing the state borders, circulates freely in the earth and near-earth space and is able to unite people in creation of generally accepted values. But water may separate as well the neighboring regions if somebody of neighbors deals ecologically erroneously with water resources. The slightest distinction from water standard composition propagates very fast over the neighboring regions and creates problems for people, which have done nothing wrong to the water.

     It is no accident that at water usage in all countries of the Europe, including those ranking among the most developed countries in EC, there arise problems being similar in many aspects. And if powerful centralized water supply plants in big towns may for the time being cope with deterioration of the supplied water quality, then for small farms and individual users not being connected to the centralized water supply networks it is getting more and more difficult to cope with deterioration of situation in ecology.

       As to drinking and domestic water used in the most of the Russian and many Europe regions, unfortunately it is often becoming less and less safe as regards its sanitary-epidemiological condition, and not only in the rural areas but in towns and settlements as well.

       All above-mentioned is the result of interaction between a number of factors which are now typical for all of the Europe. On one side the anthropogenic, technogenic load on natural environment (which in many areas of Leningrad and other regions has already reached the limit of its recreation resource) is becoming stronger. On the other side, the rate of construction, repair and modernization of water treatment and sewage works is being more and more behind everyday needs by force of economical situation the ecological and sanitary-hygienic legislation is lagging to a considerable extent behind demands of the times.

       As far as quality of drinking water supplied from the municipal centralized water supply systems is almost everywhere considered as rather low both by specialists and population, a broad market functions of individual and collective decentralized facilities of water treatment (in the market segment of industrial goods), as well as of the bottled "ecologically sound" water (in the segment of food products). Nowadays a great number of apparatus and appliances carrying out tap water final treatment with various indices of efficiency are used for so-called "small water treatment". It is fulfilled on the basis of technological principles such as filtration of different types and sorption. Apparatus for electrical oxidation and reduction of harmful substances or for their coagulation, devices for water disinfection by ozonation and ultraviolet irradiation are spread much less.

     Abundance of types and subtypes of water treatment devices is not so much evidence of development of the present class of facilities, as of their lack of efficiency, durability and of the user dissatisfaction with real technical data of these devices. We may reveal objectives reasons for such dissatisfaction if we consider the results of tests run on models being available on the market and aimed at solution of really serious problems of water purification. Seriousness of these problems is stipulated by rather bad state (so to say by rather low technological level and decrepitude) of pipelines being in operation at public services, or by difficulties arising at water intake from natural sources. At this point a number of obstacles arises connected with short service life of filters which, moreover, are overgrown with microflora during operation and show their functioning quality dependence on a number of attendant and difficult of calculation factors. Most of filters available on the market are not suitable for systematic regeneration, which increases operating expenses in  connection with the necessity of replacement of all kinds of cartridges. But a price  fixed at systems with the automated regeneration is unjustifiably high.

     As to the bottled ("spring") water or water purified in a special way, then there are a lot of problems in this, connected with unconfirmed or not completely attested production quality. And random inspections of the bottled water quality send alarm signals informing about available violations of products sanitary standards.

     It seems as though the prospects of radical improvement in water supplying of historic towns and areas are connected with modernization of centralized water treatment plants on the basis of well-known technologies, but, first and foremost, pipeline nets. However it is clear that programs of contemporary development or restoration of historic and cultural objects with necessary improving of water supply dwellers would be postponed for an uncertain period because of exceeding expensiveness. On the other hand, everybody conceives no sustainable development of historic cities is impossible without real improvement in people’s health and an increase in average length of human life.

      Nowadays economic and engineering solution of the pure-water problem evidently might be found only on the road of creation of high-effective, decentralized water treatment systems of various capacity and of their arrangement right in the places of water consumption (including large housing blocks, individual buildings and even enterprises of social infrastructure).

     Thus life itself has brought up on the agenda of creation of a new class of high-effective, compact, economical and easy in exploitation equipment for decentralized water treatment. Development of such kind of technology and equipment (being mobile in a number of cases) is required as well to solve diverse problems connected with liquidation of the consequences of emergencies at large water treatment works, in sewerage net- works, at industrial plants, on transport, at oil exploration and production fields, in pipelines, under field conditions and in various extraordinary situations.

     The most realistic, at first sight, way of an increase in capacity of individual water purifiers of well-known types was evaluated from the very beginning as having few prospects for the above-mentioned reasons. It was necessary to search for new, more efficient technologies of decentralized water purification, which would enable to combine the advantages of most of well-known water purification methods with the absence of their drawbacks. It proved to be quite a real task. We had managed to develop systematic approaches to creation of a new generation of local water purification means with application of electrosorption technology. The first models of apparatuses for electrosorption, or water electroconditioners (WEC) named  "Cascade"® and "Elecon" were created on the basis of new technology. These models (unlike chemical-sorption devices) excellently retain bacteria, viruses and other microorganisms with allergens of microbe origin which are formed at oxidizing destruction of microorganisms, any kinds of foreign particles, ions of heavy metals and many other deleterious components. Unlike filtration and sorption devices for drinking water purification, which are available in the market, WECs do not require periodical replacement of any components (cartridges, filling) in the course of operation having practically unlimited service life owing to their ability for a complete regeneration. WECs advantageously differ from well-known electrochemical systems and may purify water from natural sources (rivers, lakes, wells, holes). They do as well not need in preliminary filtration of mechanical impurities or petroleum products which initial water contains and can be used for cleaning both cold and hot water.

      It is necessary to emphasize, that not only drinking and domestic water used by population should be subjected to thorough purification, but also waste water discharged into natural reservoirs by industrial and agricultural plants and by inhabitants of individual houses. This should be done for prevention of further pollution of drinking water sources.

      For an increase in efficiency of water purification processes it was offered to apply a principle of filtration of fluids through the filled-up diaphragms with the use of phenomenon of electrosorption of polluting components.

     At electrosorption  a considerable increase in sorption ability of neutral materials (used as filtering packing of "electrocolumns") takes place as a result of their polarization with the aid of external electrical field. After removal of the field sorption ability of the packing goes down to initial level providing for an opportunity of the filter regeneration which realizes itself with particular efficiency in the suspended layer of the filter.

     A number of well-known water treatment devices release in flowing water bactericidal ions of iodine, bromine or silver being harmful for health at systematic use. WECs are free from this defect in full.

      Filtration and sorption purification units which are widespread at present, in the course of operation are overgrown with microflora and practically turn into microbiological reactors worsening (poisoning) water more and more, which results in the necessity of its purification. Owing to simple and reliable preventive measures (convenience of washing and "self-disinfection") WECs exclude this phenomenon in full.

Service life of all components of electroconditioners is rated at long operation.

     Owing to opportunity of simple and regular preventive measures, electroconditioneres for water purification are always in proper working order and ready for efficient functioning, whereas in cases with apparatus of other types a user is not able to determine the time of exportation of their service life (apropos rather insignificant under real loads conditions).

     Availability of electrodes and the fact that they fulfil active electrochemical function, provide for carrying out by electroconditioner the water purification from components being undesirable in excess concentration, such as ions of iron, manganese, chlorine, as well as nitrate, nitrite, phosphate ions and a number of other ones, multiple decrease in the indices of oxygen chemical and biological consumption.

     Finally, there is one more important merit of electrosorption technology consisting in a complete exclusion of formation of toxic chlororganic compounds at purification of water from microflora, which becomes its decisive advantage as compared with such widespread and far from being harmless way of water disinfection, as chlorinating.

     On the basis of the above-mentioned and consideration of accumulated data on operation of the first production lots, it is possible to conclude that the offered development and wide spreading of electrosorption equipment presents itself not only real but optimal way for today to solution of problems of decentralized high quality water supply of citizens without replacement old pipelines between old buildings.

      Low-rise buildings demand installation of 1-2 units only, but buildings having from 6 to 20 floors need several parallel electroconditioners (in practice - from 3 - 8 units and even more).

This requires an area from 1 to 15 m2 in technical premises, typically used for installation of   water-meters and gauges.

     We have implemented practical approbation advanced electric treatment of tap water, exposed to secondary pollution in the city pipes, in the buildings in the historical center of St.Petreburg and the suburban palaces.

      If WECs are begun to install in the low-rise houses since 2000, since 2005 they are mounting in multistory buildings.Some real examples from construction practice in St. Petersburg are indicated below (see slides).
     Today, our electroconditioners work at the central area in hotels, residential buildings on the Vasilevsky Island, near Smolny, in the buildings of the Marine residence of the President in Strelna (The Palace of Congresses) and in the palace and park ensemble of Petrodvorets.

     In addition to St.Petersburg WECs already are successfully operating in Moscow and Moscow Region, Omsk, Perm, Khanty-Mansiysk, Surgut, Khabarovsk. The positive experience of using of electroconditioners took place in Finland and Germany as well.