The aim was to investigate microbial removal from the liquid fraction of anaerobically digested pig manure in mesa-scale integrated constructed wetlands (ICW's) over a 13 month period. Four treatments were investigated: T1 (standard), T2 (effluent recycling), T3 (high nutrient loading), and 14 (high flow rate). Mean counts of yeasts and moulds and spore-forming bacteria were higher in T3 and 14 than in T and T2 (P < 0.05). Flow through the cells reduced mean counts of coliform, yeasts and moulds and spore-forming bacteria across all treatments (P < 0.01). Counts varied with season; coliform were highest in the Summer (P < 0.001), with yeasts and moulds highest in the Summer and Autumn (P < 0.01) and spore-formers lowest in the Autumn (P < 0.001). As Salmonella was undetectable in the influent and Escherichia colt and Enterococcus were rarely detected it is difficult to make conclusions regarding pathogen removal. Further investigations using marked strains would allow pathogen tracking within the ICW's. (C) 2011 Elsevier Ltd. All rights reserved.