Achieving a sustainable and economical supply of healthy, clean, and adequate water is a major global challenge. The membrane separation technique is an affordable and commonly used approach to water purification. Several filtering technologies are employed to remove emerging contaminants, including ultrafiltration, microfiltration, nanofiltration, and reverse osmosis. As microfiltration and ultrafiltration have limitations for the removal of contaminants nowadays, reverse osmosis and nanofiltration methods are utilized to overcome these obstacles. The amount of pressure, temperature, viscosity, flow rate, concentration polarization, pore size of membrane, and fouling are the most important factors influencing nanofiltration and reverse osmosis. Nanofiltration is a pressure-driven membrane separation technology intermediate between ultrafiltration and reverse osmosis (RO) that is commonly used for water softening. NF membranes have slightly greater pores than RO membranes, with sizes ranging from 1 to 10 nanometres (nm). However, RO membranes have the smallest pore sizes among membrane filtration technologies, typically less than 1 (nm). This chapter focuses on the use of nanofiltration and reverse osmosis to eradicate different toxins. This chapter will highlight the nanofiltration and reverse osmosis playing crucial roles in water purification, desalination, and wastewater treatment.