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Biofilm based microalgal cultivation has recently received great attention because of its low water requirement and harvesting cost. However, the contradiction between microalgal attachment and harvesting still hinders the development of this technology. Therefore, in this study the most readily available and inexpensive shifting sand was used as attached substrate for microalgal (Microcoleus vaginatus) biofilm cultivation under different water conditions. After the inoculation, a stable and easily peeled microalgal biofilm formed through filamentous binding and exopolysaccharide cementing. In general, microalgal biomass, photosynthetic activity and exopolysaccharide accumulation were all significantly affected by the cultivation time, water content and their interaction (P < 0.001). According to the maximal photosynthetic activity and microalgal productivity, cultivation time of microalgal biofilm on sand surface should be controlled around 15-25 days, with water content at 10%. Based on the biofilm cultivation system, microalgal biomass yield reached up to 11 g m(-2) eventually on the sand surface. (C) 2017 Published by Elsevier Ltd.