Genetic algorithms (GA) is a stochastic search method which imitates the natural biological evolution process. The GA methodology provides one of the best tools for finding optimal solutions for several industrial problems such as seawater desalination and wastewater treatment, and this is due to its consistency, speed, and flexibility for quickly reaching a global solution. This chapter discuses examples of successful applications of the GA methodology on seawater desalination studies. In particular, it also discusses the application of GA for maximising the removal of organic compounds from wastewater in an RO process.