Challenges of insufficient freshwater for domestic and industrial uses in different parts of the world necessitate the development of desalination technology. However, brine wastes and CO2 emitted from the desalination process are of detrimental effects to the environments and living beings, owing to high-level of alkalinity and presence of toxic levels of various chemicals. This study acknowledged efforts being made by scientists to integrate carbon mineralization of brine wastes with desalination system to generate various carbonates: nesquehonite, ragonite, calcite, dolomite, etc. However, the carbonation process behaves differently under the effects of impurities in the CO2 stream. Studying and analyzing the process using PHREQC simulation software, the carbonation of brine using pure CO2 shows high drop in pH of the solution, thereby increasing the level of the acidity. The presence of impurity in the CO2 further worsens the acidity problem in the presence of N2 and O2.
TopDesalination Processes And Challenges
Water is essential to the survival of man, yet a very significant proportion of the world’s population is still experiencing scarcity of water (World Bank, 2017). Increase in world’s population, perennial water scarcity, extreme conditions of weather and uncertainties about hydrological cycles (drought, precipitation and flood) are presently exerting tremendous pressures on water resources world-wide. The availability or non-availability of water is closely linked to quality of life, public health and the extent of burden of diseases world-wide (World Bank, 2017). It is for these reasons that several efforts are being undertaken by governments all over the world to ensure its availability and safety. The availability of safe drinking water is one of the principal pillars of the Sustainable Development Goals (SDGs); and this is captured in the 6th goal as Clean Water and Sanitation. A further dissection of the sixth pivotal goal of the SDGs shows that targets aimed at ensuring that the goal is attained, are set for attainment by 2030. The strengthening of international cooperation and capacity building support to developing countries in water and sanitation- related programmes stood out among the eight targets. Among other programmes, desalination is seen as one of the key activities to be pursued for the attainment of this mission as it is presently playing leading roles in clean water supply in Maldives, Malta, Saudi Arabia and the Bahamas (UNEP, 2019).
Simply put, desalination is a technique that is deployed to remove salt from water. While the idea of water desalination is not entirely new as it is dated back to the time of the 2nd World War, its potential in the solution to the global water supply has not been fully explored. The seas and the oceans around the world constitute inexhaustible endowments of water resources that could help in the attainment of the SDGs. The issues of drought, climate change and global population increase are currently putting pressure on the available water resources. In the same vein, poverty and arid nature of some nations especially in the developing countries have further deepened the need for investment in desalination of seawater for safe global water availability.
The approaches in the desalination of water are either by thermal or membrane separation although; there are sub-classifications of these methods. The thermal techniques could be by vapour compression, multiple effect distillation or multi-stage flash distillation while the popular membrane technologies include electro-dialysis, reverse electro-dialysis and reverse osmosis. The products of a desalination process for treatment of saline water are usually two; one part that is very low in salt concentration and the other with higher salt concentration than the original saline water (brine concentrate). According to Liyanaarachchi (2014), desalination efforts are presently tilting towards the development of membrane technologies which are believed to require lesser energy compared to the thermal process.
Notwithstanding, the major breakthroughs in the development of seawater desalination techniques, quite a number of challenges still exist and the attainment of the SDG in the area of clean water availability is closely associated with overcoming these drawbacks. One such drawback is the handling of the brine concentrate that is left after fresh water has been separated from the saline seawater feed. Brine effluents (wastes) have tremendous deleterious effects on the environment (Ariono et al., 2016; UNEP, 2019). A major feature of brine waste is its richness in salt concentration which makes it highly corrosive and detrimental to coastal structures and ecosystems. There could also be other pollutants depending on other chemicals used in the treatment process. As much as one and half litres of liquid effluents containing chlorine and copper are produced per litre yield of drinking water in majority of the existing desalination processes (UNEP, 2019). Most modern techniques employed for desalination now favour the recovery of salt from the brine concentrate in order to address the environmental challenges posed by its disposal. Another challenge is the high energy requirement of the process. This chapter therefore focuses on the prospects and challenges of various desalination techniques and the characteristics of the resulting brine wastes.