Advanced Technologies in Water Treatment

Abstract

Advanced oxidation processes (AOPs) are chemical treatment techniques used in water and wastewater treatment. To enhance the water treatment efficiency, ultraviolet (UV), visible (Vis) or solar light irradiation and ultrasound technology (US) are frequently used. UV and Vis irradiation include bands from 100 to 400 nm and from 400 to 800 nm, respectively. Solar light at the Earth surface has a wavelength between 300 nm to 1 mm, including UV, Vis and Infrared (IR) light regions. US is a high-frequency sound, which can decompose many organic pollutants. To accelerate the AOPs, catalysts are widely used. These compounds increase the rate of the reaction without being used up. Introduction: Water TreatmentConventional water treatment and sustainability UN Sustainable development goal 6: Clean water and sanitation requires greatly improved treatment for the estimated 80% of wastewater that is released untreated, where this climbs to 95% in some developing countries (WWAP 2017). Such wastewater varies in both its source, such as from industry, urban and agriculture, and components, which may vary over time and location. There are also various emerging pollutants in water, such as antibiotics, pesticides and microplastics (Zhang et al. 2020). A key aspect to meet the sustainable development goal is for wastewater to be viewed more as a resource than as a burden to facilitate its role within a circular economy. Such an approach may become more economically sustainable if resources can also be recovered from wastewater, for instance, the recovery of valuable nutrients (Collinson and García 2013). Wastewater treatment will also become more sustainable through the use of less environmentally harmful chemicals or processes, for instance applying catalysts to reduce the use of chemicals and energy, while also finding synergies with other technologies such as renewable energy (Anastas and Zimmerman 2018; Prasannamedha and Kumar 2020). Current challengesChlorine is widely used for the disinfection of drinking water and the residual chlorine in water is important to avoid recontamination during transport and storage. The continued development of water treatment is important to avoid the possible disinfection by-products arising from disinfection using chlorine (Miklos et al. 2018). Furthermore, the efficient removal of heavy metals, persistent organic pollutants (POPs) and emerging pollutants from water provides a range of current challenges in water treatment. For instance, POPs include antibiotics, dyes and polyaromatic hydrocarbons (PAHs) which arise from a variety of sources and may not be effectively removed from water using chlorine so either an advanced oxidation process (AOP) is required or adsorption as will be discussed below. Similarly, the development of more sustainable flocculants for water treatment is also an active area