**5. Discussion**

Sixth of the world's population, on average, lacks access to clean drinking water. The availability of freshwater supplies is limited, making it difficult for the world to meet growing demands for clean water. Depletion as a result of (i) protracted droughts, (ii) rising population, (iii) stricter health-based laws, (iv) conflicting demands from various users, and (v) water contamination. Therefore, it is vital to take action to create an inventive technology that can supply clean, affordable water to suit human needs. A healthy existence requires access to clean drinking water. 80% of diseases in nations like India are caused by water, especially drinking water. The World Health Organization (WHO) advises that any water meant for drinking should have zero fecal and total coliform levels in each 100 mL sample. Today, a variety of methods, including chemical and physical processes, are employed to clean water. These methods include the treatment of chlorine and its derivatives, ultraviolet light, boiling, low-frequency ultrasonic irradiation, distillation, reverse osmosis, and water sediment filters [61].

The three primary categories of wastewater treatment techniques are physical, chemical, and biological. Filtration is a key component of solid-liquid separations, which are the main focus of physical wastewater treatment. There are two broad categories that conventional and unconventional filtration methods fall under. Applications involving water purification rely on this technique. The treatment process is just one component of a conventional water treatment system, which offers a variety of technology and equipment alternatives based on the treatment's objectives. Understanding the function of filtration in water purification in comparison to other technologies and the goals of various unit processes is crucial. This cost-effective method can eliminate wastewater microorganisms and suspended particulates in specific circumstances, such as when membranes are used. However, it is unable to reduce the wastewater's organic pollution and heavy metal levels on its own, which are dangerous when reused in the home or industrial settings. One of the most

#### *Sewage Treatment Using Nanoparticles DOI: http://dx.doi.org/10.5772/intechopen.109407*

prevalent instances of this technique is membrane filtration, whose structure may be easily adjusted utilizing cutting-edge technology like nanoparticles as well as used with other types of treatment.

Chemical techniques of treatment depend on chemical reactions between the contaminants and the person using the chemical agent, and they help either completely remove contaminants from water or neutralize any negative effects they may have. Chemical treatment techniques can be used both alone and in conjunction with physical processes to treat a variety of problems. By using this pricey process, the wastewater's organics will be removed, but new compounds, some of which may be dangerous, will be introduced. For instance, activated carbon adsorption is frequently used in home and industrial treatments to eliminate turbidity and the smell of water without causing any negative side effects.

Although the biological treatment of wastewater appears straightforward because it depends on natural processes to aid in the breakdown of organic chemicals, it is actually complicated, poorly understood, and occurs where biology and biochemistry meet. Organic materials, such as rubbish, organic wastes, partially digested foods, heavy metals, and poisons, can be found in wastewater. Organic debris is typically broken down by bacteria, nematodes, and other tiny organisms in biological treatments. Worldwide application of biological treatment is possible due to its adaptability, affordability, and environmental friendliness. Many mechanical or chemical techniques fall short of biological treatments in terms of effectiveness or efficiency. A notable example of this is the conventional activated sludge (CAS) procedure. These systems frequently consist of an aeration tank that serves as a biological degrading agent and a secondary clarifier to separate treated wastewater sludge [62].

The primary purpose of a wastewater treatment system is to remove primary pollutants such as suspended particles, biochemical oxygen demand (BOD), nutrients (organic and inorganic), toxicity, and coliform bacteria. The sedimentation process is used in a traditional wastewater system to remove dissolved organic matter and suspended particulates. Sewage preliminary treatment removes 60% of large solid materials through a well-designed sedimentation tank and approximately 35% of BOD delivered by sewers responsible for obstructing flow through the plant or damaging equipment. Heavy grit particles, rags, fecal materials, and wood can be removed from sewage by passing it through screen bars. The secondary treatment method seeks to minimize suspended particles and BOD by lowering organic matter by 85 percent. This is mostly accomplished by a diverse population of heterotrophic bacteria capable of exploiting the organic ingredient for energy and development. Some of the secondary wastewater treatment operating systems include fixed film and suspended growth reactors. Tertiary treatment techniques strive to eliminate 95% of organic ions. It can be done either biologically or chemically, but it is a costly process. Chemical precipitation, reverse osmosis, carbon adsorption, and ozonation are examples of advanced treatment methods based on technologically complex techniques. These methods remove nutrients like phosphorus and nitrogen, which can cause eutrophication in surface water. To remove tiny particles on a small scale, technologies such as land application, filtration, and lagoon storage are utilized. Several primary and secondary treatment plants have been installed in a variety of locations to remove settled materials and oxidize organic material from wastewater. Furthermore, even after tertiary treatment, complete removal of the incoming waste load is not possible, and as a result, many organisms remain in the water bodies.
