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Sludge treatment

The liquid content of sludge from municipal and industrial wastewater treatment and waste from other operations has a high impact on disposal costs. Alfa Laval supplies equipment that cover the entire sludge treatment process, including thickening, dewatering, heating, cooling, heat recovery, digestion and pasteurization, as well as advanced control systems for optimizing plant operation and reducing manpower requirements.

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Thickening and dewatering - Reduce the amount of waste for disposal by up to 90%

On-site thickening and dewatering of sludge is a fundamental part of all current wastewater treatment options to significantly reduce the sludge volume. This has a huge impact on costs for transportation, effluent disposal, storage and drying. It is also highly relevant for sludge to be used as digester feed for biogas production, thermal processes and composting. To meet every need, Alfa Laval offers a complete spectrum of robust, well-proven technologies that effectively separate off the liquid phases and achieve a high level of dry solids content.

Mechanical thickening of sludge from primary or secondary clarifiers has replaced gravity tanks as the industry norm prior to digestion or dewatering. Alfa Laval’s sludge thickeners all have enclosed designs plus very low maintenance and odour control requirements:

  • ALDEC G3 decanters for centrifugal separation with high capacity and high cake dryness
  • ALDRUM and ALDRUM G3 drum thickeners are rotary drum filters for very gentle, small to medium capacity sludge thickening
  • AS-H Belt Thickeners with integrated polymer mixing for small to medium capacity.

For efficient dewatering of sludge and separation of liquid and products from other waste streams you can chose between several Alfa Laval  technologies –  depending  on the level of dry solids content desired, space available and other requirements:

  • AS-H belt presses for high volume and solids loading with low polymer and power use. The G3 model performs both thickening and dewatering and has up to 5x capacity on the same footprint as a conventional belt press
  • G3 decanters for centrifugal separation of very high capacities with very small footprint and low energy consumption
  • AS-H plate presses are well suited for dewatering of smaller batches where very high dry cake solids (up to 40%) and solids capture over 99% is required.
  • Screw press for smaller dewatering installations where requirements for extremely low power consumption as well as limited noise and supervision are high on the agenda.

Some of these can also be used for mud dewatering, mine tailings, pond clean-up and dredging.

Thermal sludge treatment – a short cut to cost saving, heat recovery, Class A compost and biogas

Pre-heating of wastewater sludge using Alfa Laval spiral heat exchangers and tube-in-tube heat exchangers prior to dewatering can also cut costs and provide an opportunity for heat recovery.

Our thermal equipment can also be used for sludge digestion to produce biogas and for sludge hydrolysis and pasteurization  to meet even the most stringent environmental legislation and obtain class A or B sludge quality suitable for reuse as compost or fertilizer. For some types of industrial waste, e.g. pharmaceutical, pasteurization of waste water sludge is a must.

Spiral heat exchangers can also be used for final effluent cooling to recover heat and, if it is to be discharged into the sea, river or stream, to protect the biology of the water body.

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