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Ecopolymer sludge exhausters – domestic equipment of European quality

07. 02. 2018

Controlling the operation of secondary sedimentation tanks is a very important task of the operating service, since the efficiency of secondary sedimentation directly affects the course of biochemical oxidation in aerotanks and determines the content of suspended solids in treated waters.

Russia and the CIS countries mainly use standard designs of secondary sedimentation tanks, which equipment has significant drawbacks, leading to a decrease in purification efficiency. To remove sludge from secondary sedimentation tanks, systems with scrapers, airlifts, and sludge exhausters are used. Let us consider the latter, as the most common solution for medium- and high-capacity treatment facilities.

Typical designs of sludge exhausters for secondary sedimentation tanks (Figure 1) are produced practically without changing the design for many decades.

Figure 1. Typical Soviet design of the sludge exhauster

The main problems of the secondary sedimentation tanks during the removal of sludge with the use of typically designed sludge exhausters are:

• formation of "dead zones", where sludge gets rotted and floats up. The reason for the formation of "dead zones" is significant construction and installation deviations between the bottom of the sedimentation tank and the sludge receiver, which are formed due to the lack of parallelity of the planes of the sedimentation tank rib and the bottom;
• uneven sludge removal associated with uneven sedimentation from the center of the sedimentation tank to its periphery, and the absence of the possibility of adjusting sludge removal along the radius of the sedimentation tank;
• excessive washout of active sludge.

In addition to the fact that typical sludge exhausters have structural defects and, as a rule, are made of materials with low corrosion resistance, physical deterioration and exhausting of equipment are observed practically at all treatment facilities (Figure 2).

Figure 2. An example of typical sludge exhausters and their physical state

The hydrodynamic mode of operation of secondary sedimentation tanks results from the cumulative impact of the following conditions:

• the mode of sludge supply to the facility, estimated by the rate of its supply and determining the intensity of interaction of the incoming stream with the flows of settling sludge and clarified water;
• the process of collecting clarified water, determined mainly by the speed of water approach to the collecting trough and its remoteness from the level of settled sludge;
• the mode of sucking of settled sludge, determined by the rate of sludge supply to the sludge exhausters, the level of the sludge stand and the remoteness of the sludge exhausters from the collecting trough.

Analysis of the existing designs of equipment for sludge removal from secondary sedimentation tanks, attempts to improve typical sludge exhausters and various developments in this field have been carried out by many domestic and foreign companies.

Specialists of Ecopolymer production enterprise have developed their own design of sludge removal systems for radial-flow sedimentation tanks.

Before the development, we analyzed the designs of similar domestic and foreign equipment and took into account the experience of installation and commissioning operations for similar equipment, as well as the experience of operating organizations.

EIRVm (Figure 3) and EIRV (Figure 4) sludge exhausters by Ecopolymer TME for radial-flow secondary sedimentation tanks meet the most modern requirements, are suitable for replacing formerly produced "typical" sludge exhausters without altering the structures of sedimentation tanks and communications. In this case, the gravity flow of the sludge mixture and the sludge drainage are provided by the difference in the hydraulic water levels between the sludge mixture distribution chamber and the sedimentation tank.

Figure 3. Appearance and basic design of the EIRVm sludge exhauster

1 - bridge; 2 - a drive cart with snowplow unit; 3 - central support; 4 - a capstan with the swing unit; 5 - rotating central bowl; 6 - directing cylinder; 7 - sludge pipe; 8 - sludge receiver; 9 - sludge manifold; 10 - connecting sludge pipeline; 11 - sludge drain pipe; 12 - individual sludge flow controller; 13 - edge cleaner (option); 14 - central annular power manifold; 15 - sludge exhauster control cabinet; 16 - EIRVm sludge exhauster control cabinet.

Figure 4. Appearance and basic design of the EIRV sludge exhauster

1 - bridge; 2 - drive cart; 3 - central support; 4 - a capstan with the swing unit; 5 - central bowl; 6 - directing cylinder; 7 - sludge pipe; 8 - sludge receiver; 9 - sludge manifold; 10 - siphon water pipeline; 11 - sludge drain pipe; 12 - individual sludge flow controller; 13 - automated siphon filling system cabinet; 14 - central annular power manifold; 15 - ShUEIRV sludge exhauster control cabinet.

The principal difference between the EIRV and EIRVm sludge exhausters is the method of sludge pouring from a sludge manifold into a central bowl (Figure 5):

1 - sludge pipe; 2 - sludge manifold; 3 - individual sludge mixture flow controller; 4 - siphon water pipeline; 5 - automated siphon filling system cabinet (conditionally shown as transparent); 6 - central bowl.	1 - sludge pipe; 2 - sludge manifold; 3 - individual sludge mixture flow controller; 4 - connecting sludge pipeline; 5 - central bowl.

Figure 5. Central part of the EIRV and EIRVm sludge exhausters

• the sludge in the EIRVm sludge exhauster flows from the sludge tank to the central bowl through a connecting sludge pipeline equipped with compensators ensuring leveling of possible displacements of the sludge receiver and central bowl. Subject to the need to operate in regions with severe winters, all pipelines are located below the water level in order to avoid their freezing.
• the sludge in the EIRV sludge exhauster flows from the sludge manifold rotating together with the bridge to the fixed central bowl via a siphon sludge pipeline equipped with an automatic filling system based on a vacuum pump. For stable operation in winter, the siphon sludge pipeline is insulated, its automatic filling system is mounted in a separate heating cabinet. This design of the sludge exhauster has proven itself in many sewage treatment facilities in Europe.

EIRV sludge exhauster is an advanced analogue of European sludge exhausters, with the design adapted to Russian operating conditions.

EIRVm sludge exhauster is a modernization of the EIRV model, the main purpose of which was to preserve all the merits of the EIRV sludge exhauster, but refuse from the siphon water pipeline.

In addition to the above-mentioned differences, the EIRV and EIRVm sludge exhausters have a number of common distinctive features:

the design of the sludge exhauster bridge is a three-dimensional truss (Figure 6). The truss rods have a curved profile shape. Such a constructive solution provided the bridge simultaneously with low sail and high strength, as well as allowed reducing the load on the tread.

Figure 6. Sludge exhauster bridge

• the bearing elements of the bridge truss are made of AMg3M aluminum alloy (optionally AISI 304, or AISI 321, or AISI 316 stainless steel). The elements of the aluminum alloy bridge are interconnected by riveting – this method has proved to be the best for connecting aluminum alloy elements in aircraft and bridge construction in terms of reliability, durability and excellent corrosion resistance;
• other elements and assemblies of the sludge exhausters are made of AISI 304 stainless steel (optionally AISI 321 or AISI 316) and other corrosion-resistant materials (rubber, plastic);

each sludge manifold has its own individual sludge pipe and sludge flow controller, which ensures its high operation efficiency (Figure 7). Controllers are arranged in such a way to make it convenient to visually control the concentration and flow of sludge and to regulate them promptly;

Figure 7. Individual sludge receivers and sludge pipes

a two-wheel drive cart with direct drive from the gear motor to the front wheel (Figure 8). The gear motor is regulated by a frequency converter. The wheels of the cart are equipped with solid tires. The choice of the front wheel of the cart as a drive is determined by the vector of loads that arise during the operation of the sludge exhauster due to its design features. as an option, a 4-wheel drive can be installed. A snowplow unit (Figure 9) is installed on the cart and consists of a rotating brush and a snow blower (option - not shown in the figure).

Figure 8. Drive cart	Figure 9. Snowplow unit

• the flooring of the bridge is made from polymer grid elements, resistant to ultraviolet radiation and low temperatures and with an anti-slip surface (Figure 10). As an option, the flooring can be made of corrosion-resistant steel.

Figure 10. Sludge exhauster bridge flooring

In 2016, Ecopolymer supplied and assembled the first in Kazakhstan EIRV-24 sludge exhauster of its own production at wastewater treatment facilities in Aktau (KOS-1), Kazakhstan.

Figures 11 and 12 show the general types of secondary sedimentation tank BEFORE and AFTER the reconstruction with the installation of the sludge equipment produced by Ecopolymer.

Figure 11. General view of the KOS-1 secondary sedimentation tank in Aktau and the condition of the equipment BEFORE reconstruction

Figure 12. KOS-1 sedimentation tank in Aktau AFTER reconstruction

During the operation of the sludge exhauster the efficiency of the secondary sedimentation tank increased, in particular, the concentration of pumped sludge increased with a decrease in the removal of suspended solids with clarified water.

The operating organization has noted the convenience of controlling the flow rate of the sludge mixture, the even running of the cart, high reliability and ease of operation.

In 2016, another sludge exhauster was successfully mounted on the secondary sedimentation tank with a diameter of 40 m in Karaganda, Kazakhstan (Figure 13).

Figure 13. Reconstruction of the secondary sedimentation tank of 40 m in diameter, Karaganda

In 2017, sludge exhausters and sludge scrapers were installed and commissioned in Zhezkazgan, Kazakhstan (Figure 14) and Gubkin, Russia (Figure 15).

Figure 14. Reconstruction of the secondary sedimentation tank of 24 m, Zhezkazgan

Figure 15. Reconstruction of the secondary sedimentation tank of 18 m, Gubkin

EIRV and EIRVm sludge exhausters (Ecopolymer TME) are a reliable, modern and economical equipment that will help increase the efficiency of secondary sedimentation tanks, pleasantly surprise by its simple operation and durability combined with an affordable price.