A Controllable Molecular Sieve for Na+ and K+ Ions

Both brackish water desalination and seawater desalination processes are well established and in common use around the globe to create new water supply sources. The farther the location of the source water from the ocean or seashore, the lower the salinity (TDS) of the water and the lower the osmotic pressure that needs to be overcome when desalinated water is produced. This is one of the major reasons that brackish desalination is often considered less costly than seawater desalination. A number of project considerations, however, indicate that seawater desalination can be beneficial and more cost-effective than brackish water desalination. To make a fair comparison, we need to properly compare all major aspects of both types of projects to define the best and most appropriate desalination technology. While brackish water has less feed water TDS, it is more challenging to dispose of the produced concentrate. Also, although brackish water desalination needs less energy to overcome osmotic pressure, it usually requires more energy to draw the water from the well than it takes to pump seawater from the open ocean intake. Another factor is that the temperature of the brackish well water may be lower than the temperature of ocean water, giving seawater desalination an advantage in energy demand. In comparing brackish to seawater desalination, these major aspects should be evaluated: (1) Locations of seawater and brackish water plants, relative to the major consumers of the desalinated water, (2) Transportation (pumping and disposal) costs of the feed water and produced water, (3) Potential colocation of a seawater plant with a large industrial user (e.g., power plant) of the seawater for cooling or other purposes, (4) Produced quality of brackish water and seawater desalination in terms of major minerals and emerging contaminants, (5) Sustainability of the water source: capacity and depth of the brackish water wells, as well as the type of soil. (6) Technical and economic aspects of produced concentrate disposal, (7) Permitting process costs for brackish and seawater desalination, and (8) The economics of both brackish and seawater desalination treatment processes: capital costs, operational and maintenance (O&M) costs, lifetime water cost, and total water cost (TWC). This paper discusses the major evaluation criteria and considerations involved in properly comparing the economic and technical aspects of brackish and seawater desalination to determine the more favorable desalination technology for a given desalination project.

Multi-effect still for hybrid solar/fossil desalination of sea- and brackish water

Potassium channels ubiquitously exist in nearly all kingdoms of life and perform diverse but important functions. Since the first atomic structure of a prokaryotic potassium channel (KcsA, a channel from Streptomyces lividans) was determined, tremendous progress has been made in understanding the mechanism of potassium channels and channels conducting other ions. In this review, we discuss the structure of various kinds of potassium channels, including the potassium channel with the pore-forming domain only (KcsA), voltage-gated, inwardly rectifying, tandem pore domain, and ligand-gated ones. The general properties shared by all potassium channels are introduced first, followed by specific features in each class. Our purpose is to help readers to grasp the basic concepts, to be familiar with the property of the different domains, and to understand the structure and function of the potassium channels better.

Brackish water desalination using reverse osmosis and capacitive deionization at the water-energy nexus

Brackish and seawater pretreatment processes: A systematic literature review

A novel technique to construct a nanofluidic device that consists of a single wall carbon nanotube (SWCNT) and a polydimethylsiloxane (PDMS) microchannel is presented. The nanofluidic device was made using dielectrophoretic (DEP) trapping of SWCNT followed by soft lithography technique. A SWCNT can be seamlessly embedded in a PDMS microfluidic channel using this technique. Moreover, controlling PDMS curing condition allowed us to make both devices with and without SWCNT (the device without SWCNT has a PDMS nanochannel instead of SWCNT nanochannel). Simple flow pass tests were performed for the fabricated nanofluidic devices with and without SWCNT. An immediate fluid flow was observed in the device with SWCNT while significant flow resistance in the device without SWCNT.

Desalination of high salinity brackish water by an NF-RO hybrid system

Preparation of ion-exchange materials and membranes

Access to fresh water is a major human right as mankind existence depends on it. The balance between fresh water supply and actual water demand for agricultural purposes (irrigation) relies on the availability of fresh water in the underground aquifers or surface water resources. Water resources are under great pressure due to the high demand for irrigation to sustain crop productivity and cover domestic use as a result of demographic growth. Desalination of sea or brackish water is one of the solutions to provide water for irrigation in remote areas of limited freshwater reserves. In such areas, if desalination is powered by renewable energy sources, then it can become a lot more sustainable. This paper presents the development of an innovative computational tool for the optimal (economically and technically) design of seawater reverse osmosis desalination systems for sustainable water production for crop irrigation. In order to further reduce the cost of water produced, an energy management and control system was also designed and included in the computational tool to ensure the optimal operation of the desalination plant. This system allows the seawater reverse osmosis unit to operate at variable load and determines its optimal operation point using computational intelligence techniques based on fuzzy cognitive maps. According to the results, the implementation of the computational tool for the design of PV-SWRO system presents the lowest cost as compared to the system designed with the conventional methodology.

Desalination of Sea and Brackish Waters

§ 1 - Hollow fiber modules; fabrication thereof

Water stress is an important issue throughout India today, and ways to augment water are needed urgently. One of the methods is the desalination of sea and brackish water. There are various desalination techniques, and both thermal and membrane systems have been addressed in this chapter. The negative impact of the desalination system is discussed. National Institute of Ocean Technology (NIOT) under Ministry of Earth Sciences (MoES) has developed a technology called Low Temperature Thermal Desalination (LTTD), which has been successfully operating in the Lakshadweep islands for several years with no visible environmental impact. An offshore barge-mounted plant and one in a power plant using the condenser reject heat have also been demonstrated successfully. To reduce the usage of fossil fuels for powering desalination systems, it may be prudent to use renewable energies. Lastly, the ecological and environmental costs should be considered to arrive at the cost of any technology. MoES through its institute NIOT thus has made a tremendous societal impact through this technology developed for the first time in the world and implemented in Indian waters.

§ 1 - Production of potable and industrial water

Electrodialysis related processes are effectively applied in desalination of sea and brackish water, waste water treatment, chemical process industry, and food and pharmaceutical industry. In this process, fundamental component is the ion exchange membrane (IEM), which allows the selective transport of ions. The evolvement of an IEM not only makes the process cleaner and energy-efficient but also recovers useful effluents that are now going to wastes. However ion-exchange membranes with better selectivity, less electrical resistance, good chemical, mechanical and thermal stability are appropriate for these processes. For the development of new IEMs, a lot of tactics have been applied in the last two decades. The intention of this paper is to briefly review synthetic aspects in the development of new ion-exchange membranes and their applications for electrodialysis related processes.

Historic background of desalination and renewable energies