The real solutions for wastewater treatment of settlements and towns

Kolesnikov V.P.¹, Vilson Е.V.², Chernikova L.Y.<sup>3

1</sup> Rostov Scientific Research Institute of the Academy of Public Services, Head of the Sewage Purification Department, Russia, Rostov-on-Don, st. Tekucheva, 207. (E-mail: ekosistema@rniiakh.com).
² Rostov State Architectural University, Ph.D., Russia, Rostov-on-Don, st. Socialisticheskaya, 162 (E-mail: ekosistema@rniiakh.com).
³ Rostov Scientific Research Institute of the Academy of Public Services, research scientist of the Sewage Purification Department, Russia, Rostov-on-Don, st. Tekucheva, 207. (E-mail: ekosistema@rniiakh.com).

Abstract
We consider the improvement of the wastewater quality after its treatment in the combined works with power consumption in 2-3 times lower than the existing ones.

Keywords
Sewage treatment facilities, wastewater treatment, combined facilities.

Over 80% of sewage treatment facilities in Russia do not work or do not provide the necessary quality of treatment because of the unreliability of long-term operation of aeration equipment, deterioration and complete cessation of biological treatment in cold weather, rapid death of activated sludge during power outage and emergency conditions. Almost all old buildings with biological filters belong to this group. Limited opportunities of budget financing are not sufficient to fully normalize the functioning of drainage systems. Orders for treatment facilities design and construction are carried out mainly at the expense of budgetary funds, leaving billions of rubles for the construction of expensive, inefficient and inadequate sewage treatment facilities. Improving the well-known structures can reduce energy consumption by no more than 15%.
To solve the pressing problem of public services industry, it would seem possible with the participation of the corporate, banking and private capital. However it is impossible to do using traditional domestic and foreign technologies of wastewater treatment because of low profitability of capital investments, as payback period of investment is more than 20 years.
To stabilize the situation in ecology at the current rate of housing construction is possible only by active introduction of new technologies of wastewater treatment that reduces the payback period of investment of up to 5 years.
Since 1982, in Rostov Scientific Research Institute of APS named after K.D Pamfilov commissioned by Housing and Utilities of the RSFSR, a system of new types of sewage treatment facilities [1], which ensures the reliability of technological modes of treatment, high and reliable quality cleaning during the winter, reducing capital and operating costs has been developed. New types of compact and environmentally friendly sewage treatment plants can be installed directly in neighborhoods. In 1988, State Building and the Ministry of Agriculture of Russia took part in developing this system.
In the basis of combined works (CW) was the idea of combining the positive properties of biological filters (high oxidative and mass transfer properties of the attached microflora, vitality and low power consumption for oxidation of pollutants), aerotanks (high cleaning effect, the possibility of deep mineralization of exceed sludge and the possibility of creating a high concentration of sludge in the reaction volume) and water jet aeration.
In 1997, the Ministry of Construction of Russia recommended that the subjects of the Russian Federation used in the construction and operation of waste water treatment facilities technologies developed by RSRI APS (letter No. BE-23-184/28). In 2005 the book "Modern development processes of sewage treatment in combined works" [2] was sent by Rosstroy (letters No. 03-3/599, No. 03-3/600 dtd 30.05.2005), to the territorial administration of housing and public utilities and water treatment plants of Russia.
As a result, a system of new types of facilities for sewage treatment for cities, towns and industries on a range of performance 50-100000 m³/day was developed. Power consumption of this system is 2-3 times lower than power consumption of the best existing types of treatment facilities. The circulation of sludge fluid through the biofilter - aerotank (picture 1) allows to solve simultaneously two problems: the first - ensuring sufficient oxygen level to sludge mixture in a reaction volume of aerotank and the second - the initial dilution of wastewater, which in turn allows facilities to operate without primary sedimentation tanks and to ensure equal load of organic substances on organic biofilter complex.

Last factor contributes to the development of nitrification processes (the middle layer of the attached biofilter biomass) and denitrification - the lower layer of biomass. Empirically, it was found that the processes of biodegradation of organic matter, transformation processes of nitrogen (nitro-and denitrification) and phosphorus take place in biofilter. In aerotank reaction volume the process of the extended aeration in small sludge loads on organic substances takes place and provides the development of nitrification process. An important element of the combined works is blocking of the aeration and sediment zones, which allows to maintain high doses of activated sludge (4-8 g/l of ash-free substance)in the aeration zone. Activated sludge has a high mineral content (ash content 35%) and has a low specific resistivety to filtering (33...45)x10^-10 cm/g. Tertiary treatment of waste water is realized in bioreactors loaded with the material with a developed surface of blocks of biological loading (BBZ 45 and 65). Oxygen saturation is carried out in bioreactor aeration zone using water-jet aeration.
Compactness of constructions can produce them in the enclosed design that provides environmentally friendly mode of operation of new facilities, which in turn makes it possible to place them in residential neighborhoods. Purified on basic indicators (BOD, suspended solids, N and P) and disinfected water can be used in different industries, for watering plants and for replenishment of internal waters. The simplicity and reliability of new technological processes allows for almost complete automation of buildings and to minimize the number of support personnel (50%). In the climatic conditions of Northern part of Russia the most stable structures that can constantly work are structures of only RSRI APS - their constructive device allows to reduce to 3-4 times the required amount of outside cold air for biochemical processes.
The main task now is to normalize the work of existing treatment facilities. Their reconstruction in accordance with RSRI APS Technology with full use of previously built structures will provide high quality of wastewater treatment.
The cost of cleaning of 1 m³ of domestic sewage in the traditional aeration plants, depending on the geographical location and local conditions vary currently between 7-18 USD. Construction and reconstruction of existing treatment facilities in accordance with proposed technology allows to reduce capital and operating costs. The real cost of cleaning of 1 m³ of waste water will be 2-3 rubles that ensures the net profit of 5 to 10 rubles. Waste water treatment facilities become highly profitable enterprises that guarantee the receipt of significant revenues for investing in wastewater systems.
At the moment, more than 20 sewage treatment plants with capacity 50-1500 m³/day are built and operate successively. Governor support is one of the main conditions of early implementation of construction sewage treatment facilities in practice. It will allow us to complete the construction of demonstration sites. After completion of their construction, Waste water Treatment Plant in Aksai, Rostov region with capacity 12000 m³/day and Waste Water Treatment Plant in Kalacha, Voronezh region with capacity 3000 m³/day can become demonstration sites designed by technology of RSRI APS. The construction of Waste Water Treatment Plant in town Volsk, Saratov region with capacity 25000 m³/day and Waste Water Treatment Plant of Darasun, Chita region with capacity 1000 m³/day is in process. It is necessary to build Waste Water Treatment Plants in town Dolinsk (7000 m³/day), village. Tymovskoye (4200 m³/day) in Southern Sakhalin, as well as finish the reconstruction according to biofilter treatment works technology of RSRI APS in village Starodub, Bryansk region (5000 m³/day). and aerotank treatment works technology in town Kineshma (20000 m³/day). Demonstrative Waste Water Treatment Plant in village Kushchevskaya is already functioning (2700 m³/day).
Nowadays most municipal sewage treatment facilities are part of the village and urban water utilities, where they don’t attract real attention, ie, priority in financing and development is drinking water facilities. Residential sewage system gets what is left. In this regard, many drainage systems are in poor condition, technological solutions inherent in them can not provide modern quality of cleaning required. Normalization of the situation of wastewater treatment in the country can be implemented by organization of regional companies engaged in long-term lease with an option to purchase of medium-sized sewage treatment plants in major towns and cities.
One of the sources of income should be the utilization of mineralized sewage sludge as fertilizer soil. In accordance with [3, 4], precipitation can be used as organic fertilizers in agriculture, floriculture industry, green construction, forestry, as well as for biological reclamation of disturbed land and landfills.
Carbon, nitrogen, phosphorus and micronutrients are in an optimum ratio in sewage sludge. When dry sludge was put into the soil of village Severino, Krasnodar region yield of vegetable crops sharply increased. But the possibility of widespread introduction of sludge as fertilizer was hampered because of helminthes viability. The use of microwave systems provides 100% of sediment deworming. With high degree of mineralization of sludge odors disappear. Sludge,mineralized under aerobic conditions, does not contain foul-smelling substances. Technology of the company «Engineering & ecological technologies engineer» (Israel) was taken as a basis for process of sludge utilization. Technological process of utilization is a multi-processing system, which results in atomic nitrogen, steam and process water ejection to the environment. Solid by-products are packaged in hermetically environmentally-friendly sealed containers which are ready to use as organic fertilizer.
Conclusions: To solve environmental problems in Russia it is suggested:
-to use the processes of wastewater treatment, providing a high return on investment;
-to organize research centers with modern experimental and laboratory equipment;
-to transfer water disposal systems on a rental basis;
-to recycle mineralized sludge as fertilizer.

References
[1] V.P Kolesnikov, E.V Vilson, V.K Gordeev-Gavrikov “Combined works with biofilters and aerotanks”, magazine “ZHKH” No. 12, Part I., Moscow, Russia, 2003.
[2] V.P Kolesnikov, E.V Vilson “Modern development processes of sewage treatment plants in combined works” publishing house "South", Rostov-on-Don, Russia, 2005.
[3] GOST 17.4.3.07-2001 Nature Conservancy. Soils. Requirements for the properties of sewage sludge when used as fertilizer, GosStandart, 2001.
[4] SanPiN 2.1.7.573-96 Hygienic requirements for the use of wastewater and rainfall for irrigation and fertilizers, Moscow, Russia, 1996.