Leading the biotech revolution
in wastewater and biogas.


Why let valuable dissolved metals go to waste? Why mix toxic metal with a pile of gypsum? THIOTEQ Metal technology recovers dissolved metals from liquids by the formation of high purity metal sulfides. These can either be marketed or disposed of in a very compact form. The required sulfide for this process is generated on-site in a bioreactor from a low cost sulfur source at ambient temperature and pressure. Customers collect ROI on THIOTEQ Metal installation as fast as three years.

Typical application range for economically attractive metal recovery

Application Range
Dissolved metal concentration 50 to 5,000 mg/l
pH range 0 to 10
Temperature range 0 to 80ºC
Typical sulfide demand 100 kg to > 20 tonne per day

For the simultaneous removal of sulfate and the recovery of metals please refer to SULFATEQ

Better than metal hydroxide precipitation

Compared to precipitation as metal hydroxides, THIOTEQ offers

  • Lower metal effluent concentrations
  • Revenue from metal sulfides: attractive ROI at metal concentrations > 0.1 g/l
  • Capability to deal with complexes and most chelating agents
  • Better settling and dewatering characteristics of the metal sulfide sludge

Sulfide precipitation would be applied widely if the high cost of transport, storage or production of sulfide on-site (as NaSH or H2S) did not hinder its practical application.

The THIOTEQ Metal technology solves this problem with a biogenic sulfide generator that generates sulfide on-site and on demand under ambient conditions. All that is needed to enable production is elemental sulfur, a food source like alcohol and some fertilizer-like nutrients. The sulfide is transported from the generator to one or more contactors via a closed gas recycle.

Advantages of THIOTEQ Metal compared to NaSH or ‘chemical H2S’

  • Cost-effective sulfide source: lower cost per tonne of metal sulfide produced
  • Safe process at ambient conditions
  • On-site sulfide production: no transport and storage of hazardous sulfide
  • Better selectivity of metals, higher product quality
  • Flexible process: production naturally adjusts to demand
  • Robust and proven process

Working principle

The patented Paques THIOTEQ Metal process consists of two stages: a chemical and a biological. The water to be processed only passes through the chemical stage. Sulfide is produced in the biological stage and transported to the chemical (precipitation) stage via a gas recycle.

Biological stage

A biocatalyst produces sulfide from elemental sulfur and an organic feedstock like ethanol or hydrogen. The biocatalyst grows in a bioreactor with a very long hydraulic retention time and is unaffected by the characteristics of the process stream. The conditions in the bioreactor are ambient, which makes it safe to operate.

Chemical stage - contactor

Sulfide is transported via a gas recycle to the chemical stage that consists of a gas-liquid contactor. The H2S dissolves in the process liquid and reacts virtually instantaneously with the dissolved metal. The metal sulfide that is formed is separated via gravity settling and dewatered. The lean gas is recycled back to the biological stage.

More information

For more information on Metal & Mining please contact us and/or download our business case leaflet on how we recover copper at the Pueblo Viejo goldmine in the Dominican Republic.


At Paques, we believe in a cleaner, more sustainable world where innovation in biotechnology plays a crucial role in managing our planet's resources wisely.

If you have any questions or wish to explore what Paques technologies can do for your operations, we encourage you to connect with our team of experts. Our knowledgeable professionals are ready to assist you, offering insights and guidance tailored to your specific needs.

Leading the biotech revolution in wastewater and biogas

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Thank you for reaching out to Paques

Your inquiry is important to us, and we are eager to assist you in exploring our innovative solutions for biological wastewater and gas treatment.

A member of our expert team will be in touch shortly to discuss your specific needs and how Paques can help you achieve your environmental and operational goals.

We look forward to collaborating with you and hope to build a cleaner, more sustainable world together.

Warm regards,
The Paques Team