Application of vacuum membrane distillation for small scale drinking water production Gayathri Naidu a , Sanghyun Jeong a , Yongjun Choi b , Eunkyung Jang c , Tae-Mun Hwang d , Saravanamuthu Vigneswaran a, ⁎ a Faculty of Engineering, University of Technology, Sydney, P.O. Box 123, Broadway, NSW 2007 Australia b Civil Engineering Department, Kyungnam University, 631–701 Masan, Republic of Korea c Korea University of Science & Technology, 217 Gajeongro, Uuseong-Gu, Daejeon 305–333, Republic of Korea d Korea Institute of Construction Technology, Gyeonggi-do 411–712, Republic of Korea HIGHLIGHTS • Loose crystal deposition (scaling) was observed in the V-MEMD module. • Permeate vacuum pressure and feed flow velocity influenced the crystal formation. • Periodic water flushing was effective to remove the deposits in V-MEMD. • V-MEMD is suitable for small scale application with a projected 70% recovery. abstract article info Article history: Received 9 July 2014 Received in revised form 18 September 2014 Accepted 20 September 2014 Available online xxxx Keywords: Cleaning cycle Saline groundwater Scaling V-MEMD This study evaluated the applicability of a modified design vacuum enhanced-multi effect membrane distillation (V-MEMD) for drinking water production with feed solution containing NaCl and CaSO 4 . The applicability was studied in terms of flux, scale formation and ease of cleaning. A slight flux decline (18–20%) was observed with loosely deposited crystals in the membrane module during the 920 min of the operation. Larger formation of crystal (volume weighted mean size, D[4,3]) was observed in the final feed brine (D[4,3] brine feed = 455.96 μm) compared to that inside the module (D[4,3] brine module = 62.68 μm). The loose crystal deposition was attributed to the absence of hydraulic pressure, low feed temperature, high turbulence (Re = 5665.6) and short membrane retention time (21.6 s). The crystal formation in the membrane module, D[4,3] brine module increased with reduced permeate side vacuum and lower feed velocity. Periodic DI water flushing was found to be efficient to remove the scaling. The feed component mass balance showed that most of the components were able to be removed with 2 L DI water flushing. A 70% recovery ratio was projected for a scaled-up unit, highlighting the suitability of the V-MEMD as a small scale system for drinking water production. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Around 40% of the world's population lives in arid and semi-arid regions with low rainfall. Globally, these regions are facing challenges of falling water tables and increasing ground water salinity, resulting in water scarcity [1]. In Australia, these inland arid and semi-arid areas are mostly populated by indigenous people that rely on the brackish groundwater as drinking water source [2]. The brackish groundwater in Australia is highly saline, with total dissolved solids (TDS) ranging from 15,000–30,000 mg L -1 [3]. That apart, some of this brackish ground water contains high ion concentrations such as ferrous. The consumption of low quality drinking water has been linked to the poor health rate within these indigenous communities [4]. The challenge of applying pressure driven membrane desalination process such as reverse osmosis (RO) for treating saline inland brackish ground water is the osmotic pressure constraint, high electric energy requirement and low recovery rate at high salinity [5]. This results in a high volume of brine waste, requiring inland brine management [6]. Further, RO operations are built as large centralized desalination plants due to the energy recovery capacity in large plants [7]. As such, RO sys- tems are mainly suitable for areas of high population density. Presently, membrane distillation (MD) technology, a thermal inte- grated membrane process, is an imminent technology for the produc- tion of drinking water from high saline water. As a vapor pressure operated system, MD is not restricted by salt concentration in saline feed solutions and therefore can achieve good quality distillate with Desalination 354 (2014) 53–61 ⁎ Corresponding author. Tel.: +61 2 9514 2641; fax: +61 2 9514 2633. E-mail address: Saravanamuth.Vigneswaran@uts.edu.au (S. Vigneswaran). http://dx.doi.org/10.1016/j.desal.2014.09.026 0011-9164/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal