The most efficient and famous expertise to desalinate seawater along with brackish water is reverse osmosis. This results in a lower cost of water production since energy consumption is leveled to minimum ranges. Desalination occurs in the fouling membrane systems. The biofouling of seawater reverse osmosis (SWRO) membranes is widely regarded as the most important area for future research (Australia: Department of Sustainability, Environment, Water, Population, and Communities, 2013). Diverse membrane applications are yet to be tested in seawater desalination. The desalination capacity, especially in the U.S.A., for the municipal water supply ranges to two-thirds. All these procedures are carried out by the industries and more is to be done to advance the technologies. One of the processes is fouling. Membrane fouling occurs as a result of the accretion of substances on/in/or near the membrane. This accretion can lead to a decline in water production for steady pressure operations over time.
Another process linked to desalination is scaling, which occurs when dissolved materials increase salt concentration on the feedwater side of the membrane. This continues till when the solubility of the salt is exceeded in the reject water and at long last, precipitation occurs (Ettouney, 2013). Scaling also occurs in high-pressure membranes as well as nanofiltration. The desalination that occurs through scaling can be managed through feedwater monitoring, which is usually alleviated with both chemical and physical pretreatment. Another type of fouling that occurs as a desalination process is referred to as colloidal or particulate fouling. The process is a result of water permeating through membranes that have suspended materials. This finally leads to a membrane flux (Kucera, 2013). Biological fouling is also a desalination component that should be considered. It is the most challenging in RO membrane separation processes. Some of the chemicals that are introduced into the treatment process of biological fouling include impure acids and phosphate-based scale inhibitors. Organic fouling is also another membrane fouling that occurs through the adsorption of organic matter onto the membrane surface. Organic fouling leads to irreversible fouling since the removal of substances is hard once it is absorbed.
The process of desalination involves processes like antiscalants where chemicals are added before membrane separation to reduce the precipitation of sparingly soluble salts. In desalination applications, the potential for microbial growth from the application of phosphonate and carboxylate is still under research (Enayatollahi, 2013). More so, during desalination, the process is carried out in a way similar to the treatment of drinking water. The red tiles are highly destructive when marine algae rapidly increase in concentration. The blooms found in the process can adversely add to the turbidity of seawater. If this does not occur, the release of organic material could be a major problem. The harmful algal blooms are widely known for the harmful results they have on RO desalination facilities.
Desalination is also caused by some organic matters, as well as biodegradable fractions. Membrane fouling can be predicted through several measurements (Committee on Advancing Desalination Technology, 2013). For instance, the traditional fouling ability of a membrane can be estimated using a more advanced modified fouling index (MFI). Generally, seawater UV254 is usually low and it is advisable to measure it with a longer path length. This is why a specific UV absorbance (SUVA) is extensively used in drinking water treatment to measure the level of organic carbon in source waters. Liquid chromatography is also applied in the desalination process (Craig, 2013). It is used as an option for determining NOM has a lower SUVA. The separation procedure is based on size-exclusion chromatography (SEC), which, in turn, is linked to multidetection process of organic carbon. There is a major need for consistent measurement of AOC using the seawater matrix. The AOC test is a microbial assay that uses two strains of bacteria, P17 and Sprillum NOX. It controls their growth in the pasteurized water until maximum growth desalination occurs.
Models have been well known for designing RO desalination processes. They usually occur in dual areas like the mechanistic transport model and lumped parameter model. Biological fouling and modeling bacterial growth is widely known as a way of diverging biofouling on RO membranes. These processes are well known to have effects on seawater matrices such as drinking water treatment as well as distribution systems. The process also occurs in wastewater treatment (Kiefer, 2013). Therefore, high pressure membranes have been devised to know the exact cause in the RO matrices. For instance, the computational fluid dynamics (CFD) uses Navier-Stokes equation to determine the membrane systems. However, biofouling strategies should be prevented through continues or intermittent biocide application. More so, conventional desalination pretreatment involves a number of things like pre-chlorination, coagulation/flocculation, clarification as well as filtration. One of the methods of conventional desalination (filtration) presented above is carried out using granular media like sand or dual media filtration (DMF). This is due to the fact that the membranes used in the filtration process are commercially available.
References
Australia. Department of Sustainability, Environment, Water, Population, and Communities. (2013). Grants for the Construction of the Adelaide Desalination Plant Issue 32 of Audit report (Australian National Audit Office) Performance audit. Australia: Australian National Audit Office.
Committee on Advancing Desalination Technology. (2013). Desalination: A National Perspective. London: National Academies Press.
Craig, B. (2013). An investigation on biological stability of product water generated by lab-scale and pilot-scale distillation systems. London: Sage.
Enayatollahi, R. (2013). Solar Humidification Dehumidification Desalination System. Washington: LAP Lambert Academic Publishing.
Ettouney, H. (2013). Fundamentals of Salt Water Desalination. New York: Elsevier.
Kiefer, J. (2013). The desalination and Biofouling procedures. New York: Peter & Sons.
Kucera, J. (2013). Desalination: Water from Water. New York: Wiley Publishers.