General description

Sludge De-watering equipment

In General

The sludge from the thickening tanks should be discharged by positive displacement progressive cavity pumping units (or gravity) to a mechanical de-watering system.

The sludge de-watering equipment shall include the following:

× Centrifuge decanter.

× Polymer preparation and dosing system.

The thickened sludge from thickening tanks shall be conveyed by gravity (or pumps) to the suction nozzles of the thickened sludge transfer pumps, which shall discharge the sludge to the de-watering centrifuge decanter. 

The Decanter

The centrifuge decanter consists of a horizontal conical cylindrical rotor containing a screw conveyor, rotating in the same direction as the rotor but at a slightly deferent speed. The thickened sludge shall be fed using the thickened sludge feed pumps, to the decanter at the narrow end of the rotor through a central inlet in the hollow conveyor shaft. The sludge will be propelled by centrifugal force into the rotor cavity.

The conveyor shall transport the solids towards the narrow end where they will be discharged by centrifugal force through outlet ports situated around the rotor.

The supernatant shall overflow through the weirs at the wide end. Both the supernatant and solids shall be collected in a certain cover surrounding the rotor and discharge from the decanter by gravity.

The liquid wetted parts of the decanter shall be made of stainless steel. Extra erosion protection shall also be added to sensitive spots.

Strips of hard wearing metal shall be welded to bowl wall. Also replaceable bushings shall be provided at solids discharge ports. The decanter shall be driven by a three phase squirrel cage induction motor 380 V, 50Hz

The decanter shall be of suitable capacity to deal with thickened sludge.

Polymer Preparation and Dosing System

A package system for batch preparation and continuous metering of polymer solution shall be provided. The unit shall comprise vacuum-fed hopper with dissolver, maturing tank with agitator and supply tank with two metering pumps (one as standby) complete with automatic replacement.