Sludge thickening and Sludge dewatering

The excess activated sludge from the industrial water treatment plant, also called excess sludge, can be partially thickened by a special thickening process. This is necessary for subsequent transport. This is done gravitationally, mechanically via a thickening table or via Dissolved Air Flotation (DAF).

Sludge dewatering is then done by one of a variety of technologies: screw presses, centrifuges, sieve belt presses or filter presses.

All these technologies save costs by reducing sludge transport mileage.

Gravity or mechanical sludge thickening

Excess sludge needs to be thickened for transportation. Sludge needs to be concentrated for cheaper and faster processing. There are several methods for this:

  • The excess sludge sediments. The top layer of water can be returned to the treatment plant and the sludge on the bottom is removed.
  • Mechanically:
    • Options are:
      • The thickening table. This is a type of sieve that places sludge onto a table with a sieve belt. With the belt rotating continuously, the water seeps through while the sludge remains on the belt.
      • DAF technology, while used mainly at the primary waste water treatment stage, can also be used at a later stage for sludge thickening.

Sludge drying using a variety of technologies

To minimize transport costs and in some cases the sludge processing costs, the sludge from the industrial water treatment plant can be dewatered locally. Depending on the sludge type and the final processing requirements, the most appropriate technology can be chosen: screw press, centrifuge, sieve belt press or filter press. Aquaplus has the advantage of not being tied to sales routes or sludge processors and is always looking for the lowest total cost as a function of fluctuating market prices.

The following variables determine the cost:

  • chemicals
  • energy consumption of dewatering apparatus
  • personnel
  • sludge transport
  • final processing of the sludge

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