Nanofiltration (NF) is a promising technique since it can reclaim the concentrated nutrients from the biogas digestion slurry from swine farms, and produce reusable permeates. However, a lack of efficient and reasonable pretreatment processes to alleviate membrane fouling has become one of the main obstacles for practical NF applications. In this study, an electrocoagulation (EC) process was developed to pretreat biogas digestion slurry prior to NF. It was found that current density had the most significant effect on turbidity removal and electric energy consumption of the EC process, and the optimal combination for a high turbidity removal (65.6%) with low electric energy (0.73 W h L-1) consumption was determined by the response surface method as current density of 35.7 A m(-2), reaction time of 24 min, and A/V of 20.7 m(2) m(-3). Finally, the EC was proved to be able to alleviate NF membrane fouling by 22.2% for treating biogas digestion slurry. (C) 2015 Elsevier B.V. All rights reserved.