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V. V. BULGAKOV, head (Biological Purification Complex “Bezlyudovsky” of the city of Kharkiv); L. Ĺ. ŇÎRBINA, chief engineer of the project (“UkrkommunNIIproekt”city of Kharkiv); Ĺ. I. TYRIN, senior staff scientist (research and production firm “Ekopolimer”);
SLUDGE BED RECONSTRUCTION AT "BEZLYUDOVSKY" BIOLOGICAL TREATMENT COMPLEX OF THE CITY OF KHARKIV
Dewatering of the sediment, resulting from the sewage biological purification has always been a challenging problem up to the present moment. The methods of mechanical sediment dewatering have not yet been properly developed. Due to this fact sludge beds are often used as the main sediment dewatering facilities.
At the present time there have been appropriated 126 hectares of agricultural land, including 84 hectares of man-made ground at the Biological Purification Complex “Bezlyudovsky” of the city of Kharkiv.
The sludge beds are equipped with the special devices, the so-called “nods”, for water withdrawal from both surface and from under the surface. Due to rather a high level of the underground water the sludge beds run extremely low.
Neither function satisfactory the natural beds in dry ground. The stress does not exceed 0,5 m3/m2 per year. As a result of continuous exploitation an indentation down to clay retainer happens when the sludge beds are cleared. In fact, these beds serve as compactors dewaterating only because of evaporation. In total 2620 m3 per day and night is supplied to the sludge beds, including 1770 m3 per day and night of the sludge of the Biological Purification Complex “Dikanevsky”
Due to the low productive capacity the beds are overloaded and major difficulties appear for their further exploitation.
According to the calculations carried out by the professionals of the “UkrkommunNIIprogress” the required sludge bed territory of the city of Kharkiv would make up 372 hectares in prospect with the calculated load of 1,32 m3/m2 per year.
With the purpose of sludge beds productivity enhancement the professionals of the research and productive firm “Ekopolimer” and “UkrkommunNIIprogress” have developed a joint project of reconstruction of six natural beds with horizontal and vertical drainage with the area total of 2,2 hectares.
The “Ekopolimer” drainage components placed in rows every six meters were used for the horizontal drainage.
The distinctive peculiarity of the “Ekopolimer” drainage components is their high water intake capacity (more than 100 times higher than those of the drain lines of the perforated pipes). The “Ekopolimer” drainage components are easy to mount, connected by threaded collar joint and meet the strength and antirust requirements.
The sludge bed drainage channels are made of ferroconcrete chutes.
The drainage components are stacked at a pitch of 0,002 on sand foundation with the subsequent crushed rock, gravel and river sand backfilling. Argillaceous admixture did not exceed 5 %.
The vertical drainage components are mounted directly onto the horizontal drainage with the step of 12 m and designed as a pipe in pipe with the height of 1250 mm with the longitudinal slot of 5 mm width for the entire height. The inner pipe is filled with gravel. The drainage components connected to the portal of asbestos-cement pipes and brought out to the sewer manholes.
Sludge water flows through the drainage system to the receiving tank and then the pump station feeds it to the “head” of the treatment facilities.
Six sludge beds have been built by the present time. One of these beds has been filled with the mixture of the primary settler sediment and the excess compacted sludge from June, 2000. The mixture moisture is 96,3 %. The sludge bed dimensions are 64ő64 m. Overall height, – 1,5 m. Loading is executed once a day and night for the height of no more than 30 sm. The duration of the loading is 14 days. The overall loading height made up 75 sm. Then the bed had been working in the sediment predrying mode for 19 days. The moisture of the dried sediment made up 78 % allowing commencement of the sediment unloading. There has been unloaded around 4000 m3 of the sediment.
The analysis of the sludge bed functioning shows that the expected load is going to considerably exceed the calculated one (5 m3/m2 per year). After loading of the rest of sludge beds the ultimate technological regulations of their exploitation are going to be developed.
Picture. Subimage of a sludge bed at the Biological Purification Complex “Bezlyudovsky”
of the city of Kharkiv
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