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I. K. FAZLETDINOV, deputy chief specialist of the environment protection (Public Joint-Stock Company «Ufaneftkhim»)
OPERATION OF AERATION SYSTEM AT BIOLOGICAL TREATMENT FACILITIES OF PUBLIC JOINT-STOCK COMPANY "UFANEFTKHIM"
The biological treatment facilities (BTF) of the public Joint-Stock Company “Ufaneftkhim” with the design productivity of 144 ths. m3 per day and night (in practice 100 ths. m3per day and night) implement full biological treatment of the sewage of the entire group of the oil refinery Joint-Stock Company “Bashnrftekhim” (oil-refinery of the city of Novokuznetsk, oil-refinery of the city of Ufa, “Ufaneftekhim”, “Ufaorgsintez”) as well as Cogeneration plant-4, the Line Enterprise of Road-building “Cherkasy” and a number of other enterprises of the north zone of the city of Ufa. Main construct if the BTF are the aerotank of the I and II level.
The aerotank-mixer ¹1 of the I level (put into operation in 1958) has the dimensions of 160õ36 m and consists of 3 sections: regenerator, mixer and the aerotank itself. In 1998 the major repairs of the aerotank ¹1 were carried out with the replacement of worn-out reinforced concrete structures. During the repairs the old aeration system was completely replaced by the new one of the “Ekopolimer” firm. In 1999 when carrying out routine repairs of the aerotank-mixer ¹2 of the I level (similar to the aerotank ¹1) the aeration system was replaced by the new one of the “Ekopolimer” firm of tubular polyethylene aerators. Aeration system of filtering ceramic plates used to function on the aerotanks before and in the beginning of the 80s the air-distributing system with titanium attachments of filtering type was introduced. Air-distribution network was made of steel pipes of the diameter of 300 and 50 mm. Mounting of the titanium attachments to the pipe was carried out by way of clamping of the titanium attachment between the rectangular disks with a 650 mm long locking pin to the pipe with the diameter of 57 mm. In the course of exploitation the locking pins would break off at the welding point, the pipe, due to intensive corrosion would weaken and break off too, the titanium pores would get clogged with dust in the course of 5-6 years. All the above mentioned design defects resulted in the swashing in the aerotank, large air overexpenditure and low efficiency of oxygen transfer to the sewage water.
If contaminating agents, especially sulfides, increased, there was a shortage of oxygen in the aerotank at the water course inlet in spite of large air supply. The oxygen shortage resulted in appearance of filamentous bacteria and, consequently, in the active sludge index increase and its “swelling”. All these adversely affected the mode of sewage biological treatment.
The new aeration system has made it possible to obtain uniformity of air distribution, to completely eliminate the aerotank swash, to considerably lower the air supply to the aerotanks (with the introduction of the new aeration system there left 3 air pumps supplying the air to the two aerotank-mixers of the I level, seven aerotank-displacers of the II level, air lifts of the II level, mixers ¹ 1-3, blenders of acid and alkaline flows ¹ 1-4 instead of 4 air pumps of 800 kilowatt capacity) and to concurrently increase the oxygen content in the aerotanks ¹ 1, 2, of the I level. The oxidation capacity with respect to BOD has increased approximately by 20 %, the processes of nitrification started in the aerotanks of the I level (conversion NH4 to NO2 and NO3), which used to be only the characteristic of the II level aerotanks. Particular attention should be paid to the fact that the new aeration system has made it possible to increase the threshold concentration of the sulfides at the inlets of the of the I level aerotanks from 1 mg/l up to 5,0 mg/l, which is of particular importance for our oil refineries, refining large amounts of the Arlan sour oil.
There have been no reprimands to the aeration system for the period of exploitation on the aerotanks of the first level. At the present time it is planned to replace the aeration system of titanium attachments for the new one of the “Ekopolimer” firm production in the course of routine repairs during 2000-2002.
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