Comparison of sand-based water filters for point-of-use arsenic removal in China Kate Smith a, b , Zhenyu Li b , Bohan Chen c , Honggang Liang d , Xinyi Zhang a, b , Ruifei Xu a, e , Zhilin Li f , Huanfang Dai a, b , Caijie Wei a, b , Shuming Liu b, * a RISE, Tsinghua University, Beijing 100084, China b School of Environment, Tsinghua University, Beijing 100084, China c College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China d College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China e School of Social Sciences, Tsinghua University, Beijing 100084, China f College of Computer Science and Technology, Taiyuan University of Technology, Taiyuan 030024, China highlights graphical abstract  5 filters were compared to find the most effective for an As-affected village.  Iron-based filters can remove As, but removal is affected by filter design.  Nails placed in biosand filter sand were more effective than those placed above.  The arsenic biosand filter (nails above sand) rarely removed arsenic to <50 mg/L.  The biosand filter with embedded nails removed arsenic to <50 mg/L for six months. article info Article history: Received 20 March 2016 Received in revised form 26 September 2016 Accepted 7 October 2016 Handling Editor: X. Cao Keywords: Biosand filter Contamination Drinking water Iron SONO filter abstract Contamination of groundwater wells by arsenic is a major problem in China. This study compared arsenic removal efficiency of five sand-based point-of-use filters with the aim of selecting the most effective filter for use in a village in Shanxi province, where the main groundwater source had arsenic concen- tration >200 mg/L. A biosand filter, two arsenic biosand filters, a SONO-style filter and a version of the biosand filter with nails embedded in the sand were tested. The biosand filter with embedded nails was the most consistent and effective under the study conditions, likely due to increased contact time be- tween water and nails and sustained corrosion. Effluent arsenic was below China's standard of 50 mg/L for more than six months after construction. The removal rate averaged 92% and was never below 86%. In comparison, arsenic removal for the nail-free biosand filter was never higher than 53% and declined with time. The arsenic biosand filter, in which nails sit in a diffuser basin above the sand, performed better but effluent arsenic almost always exceeded the standard. This highlights the positive impact on arsenic removal of embedding nails within the top layer of biosand filter sand and the promise of this low-cost filtration method for rural areas affected by arsenic contamination. © 2016 Elsevier Ltd. All rights reserved. * Corresponding author. E-mail address: shumingliu@tsinghua.edu.cn (S. Liu). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.10.021 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 168 (2017) 155e162