Phosphorus and biologically active nitrogen are valuable nutrient resources. Bioremediation with macroalgae is a potential means for recovering nutrients from waste streams. In this study, reject water from anaerobically digested sewage sludge was successfully tested as nutrient source for cultivation of the green macroalgae Ulva lactuca. Maximal growth rates of 54.57 +/- 2.16% FW d(-1) were achieved at reject water concentrations equivalent to 50 mu M NH4+. Based on the results, the growth and nutrient removal was parameterised as function of NH4+ concentration a tool for optimisation of any similar phycoremediation system. Maximal nutrient removal rates of 22.7 mg N g DW-1 d(-1) and 2.7 mg P g DW-1 d(-1) were achieved at reject water concentrations equivalent to 80 and 89 mu M NH4+ respectively. A combined and integrated use of the produced biomass in a biorefinery is thought to improve the feasibility of using Ulva for bioremediation of reject water. (c) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.