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High Density Sludge (HDS) Process

SGS understands you need a reliable, cost effective method to treat metal contaminated wastewaters and effluents to meet local regulatory requirements.

Our High Density Sludge (HDS) experts have designed, engineered and commissioned such plants since 1998 and have delivered many quality HDS solutions. Let’s work together to ensure your site uses responsible and sustainable water treatment solutions.

HDS technology is beneficial to operations that produce solutions high in sulfate ions as a result of pressure oxidation or bio-oxidation. Our HDS process effectively removes base metals as stable precipitates by forming calcium precipitates. Iron co-precipitates on the surfaces of recycled sludge particles.

In the HDS process, limestone/lime and recycled sludge are added to the lime-sludge mix tank at the beginning of the process. This becomes the main neutralization agent. This mixture is discharged to a rapid mix tank where it is mixed with incoming solutions, thereby achieving neutralization. This mixture is fed to the main lime reactor where a combination of aggressive aeration and high shear agitation ensures optimum process chemistry and clarifier performance. The discharge from the lime reactor is then treated with flocculent. The clarifier separates the treated effluent from the sludge and a portion is recycled back to the start of the process.

The HDS process is a proven, robust technology that uses standard equipment. It has many advantages over other lime precipitation systems for metal removal.

These include:

  • A substantial reduction in sludge volume that results from an increase in sludge density. An increase from 2% to 30% solids reduces the volume of sludge by over 95%
  • Lower sludge disposal costs
  • Increased chemical and physical sludge stability. Within several days of deposition, the sludge drains so that it consists of more than 50% solids. These solids are stable enough to support the weight of people walking on the impoundment area
  • Long-term effectiveness. Following 15 years of HDS use at one facility, there has been no contamination of the surrounding groundwater
  • Production of a high quality effluent that can meet local regulatory constraints
  • Easy automation

SGS leads the industry in the application of HDS technology for a variety of mining and industrial effluents. SGS will make certain that all factors affecting your HDS project are considered, and will ensure that the design and construction of your project meets all regulatory and environmental guidelines. Our top priority is to help you affordably and effectively comply with environmental discharge limits. Partner with us and let our team of HDS experts help you manage your wastewater stream.

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  • SGS Testing & Control Services Singapore Pte Ltd

30, Boon Lay Way, #03-01,


Singapore, Singapore