Dynamics and influencing factors of heterotrophic bacterial utilization of acetate in constructed wetlands treating woodwaste leachate

14C-acetate was used as a tracer of substrates for heterotrophic bacteria to investigate the dynamics and influencing factors of bacterial activity in surface flow wetlands treating woodwaste leachate. Epiphytic assimilation and mineralization of acetate increased considerably over three weeks of microbial colonization. No significant longitudinal variation in acetate uptake was found. The temporal variation of bacterial activity was neither correlated to water temperature nor acetic acid concentration. Mineralization percentage varied significantly with acetate uptake rate. Acetate uptake rates of bacterioplankton (408±258 μg L−1 h−1), epiphyton (67.7±41.7 mg m−2 h−1) and sedimentary bacteria (26.7±25.6 μg g−1 h−1) were influenced by the concentrations of organic substrates and inorganic nutrients. Sedimentary bacteria contributed to the majority (55–73%) of the total heterotrophic acetate uptake, while epiphytic bacteria played only a minor role (1–3%). The acetate mineralization percentage of sediment (16%) was much lower than that of water (55%) and epiphyton (64%). Addition of ammonium nitrate fertilizer increased acetate uptake rates significantly, especially for sediment. No remarkable changes in mineralization percentage and the relative importance of water, sediment and epiphyton were found due to fertilization.