This fully funded PhD position at Wageningen University & Research focuses on the sorption and biodegradation of surface-active chemicals (SACs) in anaerobic granule-based bioreactors, specifically within the recycled cardboard industry. The project aims to understand how commonly used SACs behave at the solid-liquid interface of microbial biofilms, such as anaerobic granular sludge, and to identify which chemicals contribute to process instabilities. By combining expertise in surface rheology, material science, food physics, and environmental process engineering, the research will systematically screen SACs through batch sorption-biodegradation experiments and continuous expanded granular sludge bed (EGSB) investigations. The goal is to assess the accumulation potential and impact of these chemicals on process performance under continuous flow conditions. Key activities include investigating sorption kinetics and isotherms of SACs in solution and when attached to colloids, studying biodegradation kinetics, analyzing sorption and biodegradation in EGSB reactors, and performing particle image velocimetry in shear-controlled experiments. The project will also develop guidelines for controlling negative effects of SACs in anaerobic wastewater treatment. The research is embedded within the chair of Environmental Technology and the group of reusable water, led by Prof. Adriaan Mels, with co-supervision from Dr. Dainis Sudmalis and collaboration with Dr. Mehdi Habibi and Dr. Leonard Sagis. The project is funded by an NWO Open Technology Programme grant and involves close collaboration with industry partners such as Kemira, Paques B.V., DS Smith Kemsley, and Smurfit Westrock Roermond. Candidates should have an MSc in a relevant field, strong background in rheology, fluid dynamics, or bioprocess engineering, and be fluent in English at C1 level. Experience with programming (Python), sorption behavior of surfactants/polymers, and anaerobic bioreactors is a plus. The position offers excellent employment terms, including a competitive salary, pension scheme, year-end bonus, and tailored training opportunities. Wageningen University & Research provides a supportive international environment, assistance with immigration procedures, and a focus on diversity and inclusion. Applications are open until November 25, 2025, with interviews scheduled for December 2, 2025. Applicants must submit a CV, motivation letter, and complete a mandatory qualification form via the university's vacancy page.

This fully funded PhD position at Wageningen University & Research focuses on the mechanisms of surface-active chemical (SAC) film formation and their mechanical properties, particularly in the context of recycled cardboard industry and microbial biofilms (anaerobic granular sludge). The project integrates expertise from surface rheology, material science, food physics, and environmental process engineering to investigate how SACs interact with biofilm surfaces, their rheological properties, and the implications for process stability in water treatment. The research aims to identify problematic chemicals, understand their biodegradability and accumulation, and redesign biological processes to avoid instabilities. Key activities include preparation and rheological characterization of SAC films, development of surface rheology protocols, use of colloidal probe atomic force microscopy (AFM) and super resolution microscopy to visualize and quantify film structure, and assessment of mass transfer of biogas through these films using microfluidics. The project is embedded within the chair of Physics and Physical Chemistry of Foods, led by Prof. Erik van der Linden, and co-supervised by Dr. Dainis Sudmalis, Dr. Mehdi Habibi, and Dr. Leonard Sagis. Collaboration with industry partners and another PhD project at Environmental Technology is central. Candidates should have an MSc in a relevant field, strong background in rheology, fluid dynamics, or bioprocess engineering, and be fluent in English (C1 level). Experience with Python, rheology, and AFM is a plus. The position offers a competitive salary, excellent benefits, and a supportive, international research environment. Applications are open until November 25, 2025, and must include a CV and motivation letter (max 3 pages), plus a mandatory information form. Wageningen University & Research provides assistance for international staff, including visa support and integration services.