Thiopaq – Chemical/Biological H2S Scrubber

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Thiopaq – Chemical/Biological H2S Scrubber

Leading in biological wastewater and gas treatment

Company Description:

For over 30 years, Paques has helped industries to reduce water and carbon footprints and reclaim valuable resources. Paques’ anaerobic water purification systems produce energy (biogas) from wastewater, while purifying the water and facilitating water reuse. After the introduction of the first BIOPAQ® reactor in 1981 Paques developed a broad portfolio for integrated water and gas treatment in close cooperation with partners. All the solutions proved to be cost-effective and highly reliable. Leading companies from a variety of industries worldwide select Paques as their partner for meeting their purification and sustainability obligations.


In more than three decades, Dutch second-generation family owned business Paques became one of the leading players in water and gas treatment and currently Paques has offices and/or production facilities in the Netherlands, China, Brazil, the United States of America and India and a network of professional partners worldwide. 


With a large number of installed references (over 1800 in more than 60 countries), Paques has proven to be a reliable partner in business. Solutions for water and gas treatment require an integrated approach. Paques’ strength lies in devising solutions that meet even the most far-reaching requirements of customers.


Paques has a high focus on innovation, and continuously develops new treatment systems for new challenges. Over the past decades, the company has converted many innovative ideas into successful solutions for clients. With dedicated R&D centers in the Netherlands and China, Paques remains a leading company in the field of the development of water and gas treatment. The combination of knowhow, experience, decisiveness and our multidisciplinary approach, guarantees an accelerated implementation. 

 A Paques technology that is currently in high demand for RNG projects is the THIOPAQ® scrubber. Paques has also built many anaerobic reactors in North America for treatment of brewery, pulp and paper, food processing and other effluents, as well as an Anammox reactor for ammonia removal.

Technology Description:

The THIOPAQ® was developed by Paques, in cooperation with universities, research institutes and customers. It can be applied to a wide range of biogas streams containing H2S and can be combined with all biological anaerobic systems. The ‘caustic’ solution in the THIOPAQ® scrubber is continuously biologically regenerated. In the scrubber, the gas containing H2S is brought into contact with the washing water in counter currently. Absorption of H2S under slightly alkaline conditions (pH 8-9) enables a chemical reaction with hydroxide ions. The hydroxide used in the scrubber is regenerated in the bioreactor. The system obtains a very high H2S removal efficiency, exceeding 99.5%. Both the small bleed stream (consisting of sodium salts) and the produced sulphur are free of sulphide, so discharge is no problem. After treatment in the THIOPAQ® scrubber, the biogas can be used in a gas engine or boiler of can be transported in a local micro gas grid. Upgrading to biomethane, which can be brought into the gas distribution network of use as fuel for vehicles is another possibility. The elemental sulphur, produced by the THIOPAQ® can be used as a high-quality fertilizer.

Currently approximately 35 THIOPAQ® scrubbers are in operation in the USA and Canada.  The first one was installed in 2001 in Iowa.  These systems treat flows from a few hundred to 10,000 scfm and sulfur loads from < 100 lbs/d sulfur to several tons/day

Paques- Thiopaq 2400 District Ave., Suit 330 Burlington, MA USA (781) 362-4636 Visit Company Website

Technology Type

  • AD Support


  • Equipment Vendor


  • Energy


  • GHG
  • Odor
  • Pathogens

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Technology Strengths, Weaknesses and Critical Indicators

Anaerobic Digester Associated Technology:

NOTE: There are several technology types that are used as part of an integrated manure management system that includes an anaerobic digester and are not applicable to manure management in other cases. The impact of these technologies on the critical indicators are represented as those of an entire anaerobic digester system.


  • Long usable life and can be run reliably
  • Creates energy and generates environmental credits
  • Requires proper preparation of the feedstock
  • Requires other technologies for energy utilization
  • Requires other technologies for digestate handling
  • Proper feeding & system monitoring is required to avoid system downtime
  • Proven technology for odor control, GHG reduction and pathogen reduction

Newtrient Comments/Opinions:

H2S scrubbing represents one of the biggest technological challenges for anaerobic digester systems. This technology is required before most internal combustion engine generator sets as well as for systems that are upgrading biogas to Renewable Natural Gas (RNG) for injection into the national gas grid.

The Thiopaq system offers a unique opportunity to utilize a technology that can be used in both of these types of systems, because it does not directly inject air or oxygen into the biogas, yet offers effective H2S removal. Claiming a very high removal rate with low operating cost, paired with worldwide experience with H2S removal in a verity of industries including dairy this technology is worth considering for any digester project.

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