Reverse osmosis

About: Reverse osmosis is a research topic. Over the lifetime, 20780 publications have been published within this topic receiving 299185 citations. The topic is also known as: RO.

The near-future integration of microbial desalination cells with reverse osmosis technology

Abstract: The combined negative effect of both fresh water shortage and energy depletion has encouraged the research to move forward to explore effective solutions for water desalination with less energy consumption. Reverse osmosis (RO), the most common technology for desalination today, uses much less energy than thermal processes. Several modifications and improvements have been made to RO during the last four decades in order to minimize energy consumption, and the process is now near thermodynamic limits. To further reduce energy requirements for desalination, other approaches are needed. A microbial desalination cell (MDC) is a recent technology that could be used as an alternative to RO. An MDC uses electrical current, produced by electrochemically active bacteria, to concurrently generate bioenergy, treat wastewater, and desalinate water. In an attempt to answer the question of whether this emerging technology has the ability to stand alone as an efficient replacement for RO, or it is best if used as an RO pre-treatment setup, this review addresses the recent approaches and limitations of both MDC and RO technologies in order to highlight the near-future application of MDC integration with RO operation.

The osmotic membrane bioreactor: a critical review

Abstract: The osmotic membrane bioreactor (OMBR) is a hybrid biological-physical treatment process that has been gaining interest for wastewater treatment and water reuse. The OMBR couples semi-permeable forward osmosis (FO) membranes for physiochemical separation with biological activated sludge process for organic matter and nutrient removal. The driving force for water production in OMBR is the osmotic pressure difference across the FO membrane between the activated sludge and a concentrated draw solution, which is made with inorganic or organic salts that have a high osmotic pressure at relatively low concentrations. The draw solution becomes diluted during OMBR treatment and may be reconcentrated using reverse osmosis, membrane distillation, or thermal distillation processes. The combination of processes in the OMBR presents unique opportunities but also challenges that must be addressed in order to achieve successful commercialization. These challenges include membrane fouling, elevated bioreactor salinity that hinders process performance, degradation of the draw solution by chemicals that diffuse through the FO membrane, and the potential for simultaneous water, mineral, and nutrient recovery. In this article, results from past and most recent OMBR studies are summarized and critically reviewed. Information about similar and more established technologies (e.g., traditional porous membrane bioreactors and FO) is included to help compare and contrast state-of-the-art technologies and the novel OMBR approach, and to elucidate practical configurations that should be considered in future OMBR research and development.

Exceptionally fast water desalination at complete salt rejection by pristine graphyne monolayers

Abstract: Desalination that produces clean freshwater from seawater holds the promise of solving the global water shortage for drinking, agriculture and industry. However, conventional desalination technologies such as reverse osmosis and thermal distillation involve large amounts of energy consumption, and the semipermeable membranes widely used in reverse osmosis face the challenge to provide a high throughput at high salt rejection. Here we find by comprehensive molecular dynamics simulations and first principles modeling that pristine graphyne, one of the graphene-like one-atom-thick carbon allotropes, can achieve 100% rejection of nearly all ions in seawater including Na(+), Cl(-), Mg(2+), K(+) and Ca(2+), at an exceptionally high water permeability about two orders of magnitude higher than those for commercial state-of-the-art reverse osmosis membranes at a salt rejection of ~98.5%. This complete ion rejection by graphyne, independent of the salt concentration and the operating pressure, is revealed to be originated from the significantly higher energy barriers for ions than for water. This intrinsic specialty of graphyne should provide a new possibility for the efforts to alleviate the global shortage of freshwater and other environmental problems.