Colsen International BV
About
Colsen International BV, a family-owned company based in Hulst, Netherlands, has spent over 35 years developing integrated solutions at the intersection of water treatment, biogas energy, and manure valorization. The company organizes its expertise into five practice areas. In water treatment, Colsen delivers anaerobic wastewater treatment systems—including the NAS ONE installation operating in Hengelo—alongside biological nitrogen removal and recovery processes, phosphorus recovery through its proprietary UPHOS® struvite precipitation technology that produces phosphate pellets for regional circular-economy applications, and treated-water reuse schemes. The biogas division provides complete digester installation services and biogas desulfurization (gas cleaning) systems for hydrogen sulfide removal from biogas streams. On the manure side, Colsen handles chicken manure and livestock manure digestion, digestate treatment, and nitrogen stripping for nutrient recovery. Beyond technology, Colsen offers comprehensive environmental permitting services covering environmental impact assessments (MER), discharge permits, spatial planning, and nitrogen deposition calculations, as well as soil and asbestos investigation. The company's sludge-to-energy approach converts sewage sludge via anaerobic digestion into biogas, demonstrated at the STP Tiel energy factory project. Colsen serves municipal water authorities, agricultural operations, and industrial clients across the Netherlands and internationally.
Key Products
Anaerobic biological treatment systems for industrial and municipal wastewater that convert organic load to biogas while reducing pollutant concentrations.
Biological and physical-chemical processes for removing nitrogen from wastewater streams to meet discharge standards.
Technology to recover and concentrate nitrogen from wastewater and manure streams for reuse as fertilizer or industrial feedstock.
Phosphorus recovery process that precipitates struvite mineral from wastewater, producing phosphate pellets for regional circular economy applications.
Advanced treatment solutions enabling treated wastewater to be recycled and reused for industrial or agricultural applications.
Anaerobic digestion of sewage sludge to produce biogas for energy generation, reducing sludge volumes while recovering energy.
Gas cleaning technology that removes hydrogen sulfide from biogas streams to protect downstream equipment and enable energy recovery.
Specialized anaerobic digestion process for poultry waste that produces biogas and nutrient-rich digestate.
Anaerobic digestion systems for livestock manure that generate biogas while reducing environmental impact of manure management.
Post-digestion processing of anaerobic digestate to separate nutrients and reduce volumes for easier handling and resource recovery.
Physical-chemical process to strip ammonia from liquid waste streams for nitrogen recovery and discharge compliance.
Comprehensive regulatory consulting including environmental impact assessments (MER), discharge permits, spatial planning, and nitrogen deposition calculations.
Environmental site assessment services for soil contamination and asbestos surveys to support permitting and remediation decisions.
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