Clarifier

Clarifier equipment is suitable for all sewage settlement applications and for the treatment of trade effluents and process liquors. It has, however, been designed with particular reference to the the need for rapid collection and withdrawal of activated sludge, which is accomplished by means of diametrically-opposed, continuous helical scrapers.

Description

Clarifier equipment is suitable for all sewage settlement applications and for the treatment of trade effluents and process liquors. It has, however, been designed with particular reference to the the need for rapid collection and withdrawal of activated sludge, which is accomplished by means of diametrically-opposed, continuous helical scrapers.

Clarifier Setting Tank employs a fixed bridge which is made in a range to suit tanks from 4mtr to 35mtr.in diameter, with a recommended floor slope of (1:12) or 71/2°.

In the standard arrangement, an inlet pipe passes under the tank floor and turns upwards at the centre to discharge the incoming liquid through a dispersion pipe into a deflector drum from which an even radial flow emerges. The settled effluent passes over a peripheral weir. Continuous helical scrapers sweep the accumulating sludge into a central well from which it is withdrawn through a sludge draw-off pipe. The scrapers are mounted on framework attached to the rotating dispersion pipe, the drive unit for which is mounted on the bridge structure.

Bridge

For tanks up to 55 ft. in diameter, the bridge is fabricated from channel sections. For tanks of greater diameter, a lattice girder bridge is provided. Steel bridges may be grit-blasted and zinc sprayed before painting if required. Aluminum alloy may be used as an alternative. Where dissimilar metals would otherwise be in contact, insulation strips prevent galvanic and electrolytic action. A walkway is provided on one side of the bridge to give access to the drive unit. Double-row tubular handrailing is supplied in all cases. For steel structures, both handrails and solid pillars are galvanised as standard without extra charge, in view of their susceptibility to corrosion, irrespective of the protection specified for the rest of the plant.

Drive

The drive unit, mounted on the bridge at the centre of the tank, comprises a fractional horsepower electric motor and reduction gearing, the output shaft being attached to the upper end of the dispersion pipe or driving shaft. This output shaft is carried in a robust housing incorporating journal and thrust bearings.

Scrapers and Sludge removal

Scraper arms are attached to the central dispersion pipe or driving shaft, and braced and stayed to prevent distortion. The cross members of each pair of scraper arms are extended as necessary toprovide mountings for a continuous helical scraper blade, fitted with a wearing edge of abrasion re-sistant synthetic rubber, which spans the radius of the tank. Sludge is conveyed by the scrapers to the central well.

Peripheral weir

The most economical type of weir plate is of steel with a machined, plain edge, adjustable for accurate setting. Vee- notched or castellated plates can also be provided, with aluminum alloy or plastic offered as alternative material in each case.

Side-wall scraper

This is available as an optional item and constitutes a framework, fitted with a renewable synthetic rubber wearing edge, mounted on the outer end of the scraper arm.

Scum-skimming device

Where provision for the removal of surface scum is required, a continuous scum-baffle is supported on brackets attached to the tank wall. A radial scum-blade which breaks the water surface is carried from the top of the deflector drum and supported from one scraper arm. A retractable, radial scum-barrier is mounted on the bridge structure. When it is desired to remove scum from the tank, this barrier is lowered to break the water surface immediately after the rotating blade has passed beneath the bridge, it forms an enclosed channel and, in this position, the mechanism is stopped. The collected scum is then withdrawn by operating a flap valve mounted in the scum-removal trough which connects with the outer sludge well.

Lubrication

Care has been taken to ensure that adequate lubrication is achieved with the minimum of attention and no part of the equipment requires lubrication more frequently than twice per year.

GA Drawing of Clarifier

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