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I. I. GLUKHOVSKY, head, candidate of technological science; A. B. KAMENETSKY, chief engineer; V. F. TUSHINA, chief technologist (Industrial department «Zelenogradvodokanal», Moscow)
APPLICATION OF ECOPOLYMER DRAINAGE DISTRIBUTION SYSTEM IN WASTEWATER PRELIMINARY FILTERS
Picture 1. Filter flushing results with the drainage distribution systems
1 – of the “Ekopolimer” firm
2- system ¹ 4
The filters of sewage polishing of sewage treatment facilities of the city of Zelenograd are similar to fast water supply filters as to their construction and are designed for the suspended matter concentration reduction in the sewage liquid after secondary settlers and drum grids. The exploitation of these filters has testified to the fact that the construction of the drainage distribution system influences the effectiveness of their functioning considerably.
There have been tested 5 kinds of drainage systems at the Zelenograd aeration station: 1 - cast-iron pipes with the diameter of 150 mm and the mouth diameter of 10 mm (design system); 2 – aperture polyethylene pipes with the aperture of 0,8-1 mm and the distance between the apertures of 20 ± 2 mm; 3 — polyethylene aperture plates with the aperture of 0,3 mm; 4 – slick polyethylene perforated pipes with pneumo-extrusion evaporation; 5 –ribbed polyethylene perforated pipes with the complex coating of the “Ekopolimer” firm. These systems characteristics are given in the following table:
| Drainage type
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Filtration speed, m per hour
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Filtering cycle,h
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Density of flushing, l/(second-m2)
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Lifting of the suspended matter, mg/l
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| 1
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5,8
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5,1
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10,8
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3
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| 2
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7,7
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5,4
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11,2
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3,2
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| 3
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6
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5,9
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11
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-
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| 4
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9,5
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5,6
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9
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1,6
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| 5
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11,8
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6
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12
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1,4
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As is seen from the table, the fifth drainage type (of the “Ekopolimer” firm production) differs favorably from the rest: it allows maintaining the highest filtering speed, the filtering cycle has the longest duration and the quality of treatment for the suspended matter is high, which testifies to the increase of the contaminant capacity of the filter; low drainage resistance allows carrying out the flushing at a high speed.
The flushing density and the quantity of the flushed water is limited by the reservoir volume (360m2) at the Zelenograd aeration station, which is only sufficient for just one flushing in the course of 6-7 minutes with the density of 10-12 l/( second-m2). A technological method of the charge flushing improvement is the introduction of supplementary preventive flushings, carried out straight after the main one. The mass of the suspended matter flushed out during the second flushing may reach more than 60% of the first flushing mass. Preventive flushings make up 20-30% of the sum total of flushings.
The results of the two consecutive filter flushings with the drainage system of the “Ekopolimer” firm (¹ 5) and system ¹ 4 are given in the picture 1. As is seen from the picture 1 the concentration of the suspended matter is considerably lower than in the analogous filter flushing with the drainage system ¹ 4. At that in the first case the mass of the second flushing makes up only 10% of the first flushing, in the second case – 60%. This makes it possible to considerably decrease the number of prevention flushings and exploitation costs.
The distinctive peculiarities of the drainage distribution system of the “Ekopolimer” firm are as follows: application of ribbed polyethylene perforated pipes with complex coating; availability of adapter duct connecting the collector to the drainage pipes and allowing increasing their number. (65 instead of 35 according to the design)
The constructive differences of the drainage components of the system ¹ 4 and the “Ekopolimer” firm (¹ 5) are shown in the picture 2.
 Picture 2. Drainage components design
à – of the system ¹ 4;
1 – perforated tubular hull;
2 – macroporous protective-filtering coating;
3 – finely porous protective-filtering coating;
4 – water-distributing and drainage holes;
á – systems of the “Ekopolimer” firm;
1 – dispersive coating;
2 – ribbed hull;
3 - holes
The ribbed polyethylene pipes with a complex coating enjoy sufficient mechanical reliability due to their thickness, capable of enduring the charge mass and liquid above it in the process of filtering as well as pressure surge in the process of flushing. The adapter duct ensures the calculated values of speed and pressure required for flushing and ensures the connection of the required number of wavepaths.
Special research has testified to the fact, that the infiltration quality remains high in the course of 10 hour filtering, however, it is more convenient to do an 8-hour cycle and one preventive flushing per day and night in the everyday practice.
At the present time 6 out of the 15 filters of sewage polishing, installed at the Zelenograd aeration station have been equipped with the drainage system of the “Ekopolimer” firm. This allowed improving the sewage treatment and reducing exploitation costs. The filter rehabilitation works are being further implemented.
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