Comparison of membrane distillation and freeze crystallizer as alternatives for reverse osmosis concentrate treatment

Abstract

Membrane distillation (MD) and freeze crystallizer (FC) were evaluated as alternative reverse osmosis concentrate (ROC) treatment options. A direct contact MD (DCMD) was capable of obtaining 60% water recovery with chemically pretreated ROC. Nevertheless, in repeated cycles, DCMD displayed a trend of reduced water recovery and declining permeate quality. At elevated concentrations, ROC caused scaling and membrane hydrophobicity reduction, indicating reduced membrane life span. On the other hand, FC in three-stage freeze/thaw approach was able to concentrate ROC by 2.3 time, achieving a 57% water recovery with no scaling issues. The fresh ice water quality (total dissolved solids) obtained from FC was within the range of 0.08-0.37 g/L. A brief techno-economic evaluation highlighted advantages and limitations of both options. The efficiency of DCMD as a compact, low thermal process for ROC treatment was compromised by membrane scaling, indicating the necessity for a scaling mitigation pretreatment. This invariably incurs an additional cost. FC was advantageous as a scaling and chemical free process. The high freezing requirement of FC could be met by coupling with refrigerant coolant from liquefied natural gas. Nevertheless, the practical industrial application of FC is inherently restricted due to complex scaling up issues.

Slippery for scaling resistance in membrane distillation: A novel porous micropillared superhydrophobic surface

“…MVR and ED not only require high energy but also suffer from corrosion. Membrane distillation (MD) has attracted wide attention for desalinating highly concentrated brine with concentrations up to crystallization (Ji, Curcio et al 2010, Nghiem, Hildinger et al 2011, Edwie and Chung 2013, Chen, Lu et al 2014, Hickenbottom and Cath 2014, Naidu, Jeong et al 2014, Bouchrit, Boubakri et al 2015, Chen, Wang et al 2015, Eykens, Hitsov et al 2016, Gryta 2016, Shin and Sohn 2016, Bouchrit, Boubakri et al 2017, Chen, Tian et al 2017, Chen, Zheng et al 2017, Duong, Hai et al 2017, Junghyun, Heejung et al 2017, Choi, Naidu et al 2018 2018, Kim, Kim et al 2018, Naidu, Zhong et al 2018.…”

Comparative Study of Denitrifying-MBBRs with Different Polyethylene Carriers for Advanced Nitrogen Removal of Real Reverse Osmosis Concentrate

“…At present, the methods for treating reverse osmosis concentrate mainly include the Fenton reaction [4], advanced oxidation-nanofiltration [5], coagulation and ozone [6], coagulation sedimentation [7], membrane distillation and freeze crystallizer [8], electrodialysis with bipolar membranes [9], ultrasonic method [10], and biological treatment, which include the sequencing batch reactor (SBR) process [11], fluidized bed reactor (FBR) process [12], and anammox and moving bed biofilm reactor (MBBR) process [13]. Among the biological treatment processes, MBBR is an ideal wastewater treatment technique, combining the advantages of the activated sludge process and biofilm process.…”

A Review on Recent Progress in Membrane Distillation Crystallization

“…As mentioned in the previous subsection, membrane fouling is the biggest limitation for standalone MD. Hence, it has been found out that many studies highlighted the use of non-membrane-based technology such as freeze crystallization (FC) to overcome that limitation [69]. FC is solid-liquid separation involving separation of ice and highly soluble dissolved salts concentrate [70,71].…”