**2. Seawater utilization**

Seawater utilization can be divided in three primary use areas: the use for agriculture, for the home, and for industry [19]. While the principal portion is used for agriculture in developing countries, a significantly increased proportion for use in households and industry can be seen in industrialized countries. Advancing industrialization also causes increased water consumption. Over the last century, the world population has quadrupled, while the water demand has increased sevenfold.

In general, usable water comes from surface water, groundwater, or fossil aquifers. In order to increase the supply of usable water, processes such as the desalination of seawater have been moving into focus for some time [20]. Seawater has most commonly been used as a coolant in energy generation and in industrial processes so far. It is also used in mining to extract minerals as well as for the hydraulic fracturing of gas and oil. It is additionally applied in production processes, such as sea salt extraction, aquaculture, algal cultivation as well as food manufacturing [21]. It is also used for temperature moderation in buildings and areas as well as for cold water fishery (**Figure 3**).

Two characteristic economic seawater application sectors are seawater desalination and sea salt extraction. For sea salt extraction, seawater is diverted into large basins. Over time, the water evaporates by the heat of the sun and wind and the previously dissolved salt remains [22]. The media currently reports again and again about the contamination of sea salt with high quantities of microplastics. Thus, 50–280 microplastic particles/kg of salt were detected in Spanish sea salt and in Chinese sea salt 550–681 microplastic particles/kg of salt [23, 24].

 Seawater desalination is the production of drinking water and process water for industrial facilities or power plants from seawater through the reduction of the salt content. The desalination can be based on various processes, which remove the salts and minerals from the water. To some extent, usable ancillary products like table salt accrue. In addition to the already present burden from anthropogenic stressors, the chemicals added to the seawater against fouling and scaling as well as the metals dissolved by corrosion threaten marine ecosystems, e.g., in the Red Sea. An

**Figure 3.** 

*Overview of the different seawater applications [21].* 

*Technological Approaches for the Reduction of Microplastic Pollution in Seawater… DOI: http://dx.doi.org/10.5772/intechopen.81180* 

investigation of 21 plants, which together produce 1.5 million m3 /day, accounted for 2.7 kg of chlorides, 3.6 kg of copper, and 9.5 kg antiscaling agents piped into the sea per day of seawater desalination [25].

 Seawater desalination is practiced in numerous coastal semiarid regions [20]. In addition to small plants in areas with insufficient infrastructure with only a few hundred cubic meters of water a day, there are also large desalination plants, e.g., in southern Europe (Barcelona Seawater, 200,000 m3 /day), the USA (Claude Bud Lewis Carlsbad, 204,000 m3 /day), Israel (Sorek, 624,000 m3 /day), Australia (Kurnell, 250,000 m3 /day), and the Unites Arab Emirates (Dschabal Ali Block M, >2,000,000 m3 /day). Significant expansion of production capacities for seawater desalination is, for example, planned in the Persian Gulf. Due to the development of the steel, petrochemical, cement, aluminum, and energy industry, there will be a demand of roughly 940,000 m3 /day only for use in these sectors until 2030 in Iran alone [26].
