Modelling the non-biogenic steps of arsenic retention in horizontal subsurface flow constructed wetlands

•Two As retention processes in constructed wetlands were implemented in RCB–ARSENIC.•Aqueous complexation, and As precipitation and sorption in the media were included.•Five theoretical case studies and data from a prototype were used to test the model.•The simulated data closely matched the data measured in most evaluated cases.•At this stage the RCB–ARSENIC model has provided reasonably good response values.