Paper sensor-based method using a portable 3D-printed platform and smartphone-assisted colorimetric detection for ammonia and sulfide monitoring in anaerobic digesters and wastewater

•Field deployable platform to monitor inhibitory compounds in anaerobic digesters.•Paper sensors in a well-microplate prevent cross-contamination during gas pervaporation/diffusion.•Simultaneous ammonia and sulfide determination without sample treatment.•Fast and semi-automated processing of digital colorimetric images.•Good recoveries are obtained in anaerobic supernatants and wastewater.