About Aquest Colsen

Aquest provides specialised, comprehensive water treatment solutions across Africa. Our presence in the Netherlands and South Africa allows us to offer you the best of Dutch water knowledge and engineering services, combined with local sector expertise and service.

Our Group

The Colsen group, founded by Joop Colsen in 1989, has grown into an international specialist in the field of water, sustainable energy and the environment. With offices in the Netherlands, Italy, Spain and South Africa, and a global partner network, we provide knowledgeable local support. Short lines of communication, flexibility and innovation come first in all the branches of this family-owned business. A leading developer of innovative technologies, the Colsen group remains at the cutting edge of environmental sustainability.

Our Expertise

We design customised client solutions that minimise costs and ecological impact, while maximising environmental efficiency and profit. Our experienced multidisciplinary engineers deliver the most effective products and services to meet and exceed clients’ needs.

Our expertise is defined in the following fields:



We design, build and commission a variety of filtration technologies – from media filtration to standard membrane applications (UF/NF/RO) and more advanced membrane applications for ion selective and chemical recovery.


Waste Water Treatment
and Re-use

We excel in advanced biological treatment systems. Experts in the application of anaerobic technologies, our strength lies in the design of the overall treatment solution – from pre-treatment to final polishment or re-use of effluent.



We have an extensive track record in the design and construction of biogas plants, specialising in anaerobic digestion of combined waste streams, manure and municipal sludge streams. Our knowledge of auxillary requirements, such as dewatering, desulphurisation and centrate treatment, makes us the preferred tech and EPC partner.


Nutrient Recovery
and Removal

We have a selection of technologies for the recovery of nutrients, such as nitrogen and phosphorous. Converting these nutrients into a valuable fertiliser product enhances your business case and contributes to a circular economy.