The increase in the population has caused a drastic scarcity of natural resources and a burden on the natural environment. Although a number of different technologies and methods are available for wastewater treatment. However, growth in industrial sector is associated with a diverse range of wastewater from agricultural to industrial and household wastewater .
Table of Contents
What Are Polymers
Polymers are composed of smaller units called monomers arranged in the form of a chain. Depending upon the number of monomer subunits, the polymer chain differs. It is a common practice that specific polymers can act as flocking agents (form flocs or colloids), precipitators, and dewatering agents against various ranges of organic and inorganic waste and microbial contaminants. Not only waste is handled, but also the chemicals themselves should be cost-effective, biocompatible, and easy to degrade. Polymers, especially natural polymers, provide the promising potential to be explored for multiple aspects(1).
Fundamentals of Polymer Water Treatment
Two types of polymers are utilized in wastewater treatment: emulsions made of surfactants and emulsifying agents made of liquified polymers; and dry polymers. Polymers are used for wastewater treatment that can be divided into two categories: liquified polymers as emulsions composed of emulsifying agents and surfactant; polymers dry polymers (1). Due to the functional groups attached to the natural polymers, it is used in wastewater treatment (2). Some specific types of polymers used for particular niches include Polyacrylamide, Polyamines, Poly (Diallyl Dimethyl Ammonium Chloride) Polymers, and Cationic Starches (Figure 1).
Advantages of Polymers in wastewater treatment
Polymers are essential in treating wastewater. They help reduce waste variety by removing suspended particles, compacting solids, and decreasing sludge volume. Saves money on transportation costs and is cost-effective. Different types of polymers are used.
Importance of Coagulants and Flocculants in Wastewater Treatment
Coagulants and flocculants separate unwanted, unnecessary components from the contaminated water, typically removal from sludge. These substances carry out a variety of activities, from facilitating the process to being the most critical component in separation—in some situations, it would be impossible without them. Most people think wastewater is anionic, meaning it has a negative charge. However, polymers have a positive charge (called a cationic charge), which helps the liquid-solid separation process called flocculation (Figure 2).
In the world of material, chemicals in both inorganic and organic flocculants are employed. In the class of inorganic flocculants, where the salts of multivalent metals like iron and aluminum are most frequently employed commercially in high concentrations with vast quantities, pH variations have a significant impact on how well these flocculants work. Polymeric organic flocculants are also found in nature, contrary to the inorganic ones, which are only effective at low concentrations of parts per million (ppm). Both synthetic and natural water-soluble polymers are used as flocculants.
Flocculants: Dewatering
A polymer chain serves as a bridge between particles during flocculation, promoting the growth of larger flocs or aggregates. Consequently, there are two options: either flocs float (flotation) or sedimentation, which refers to the settling of particles at the base and facilitates their removal from the system.
Essentially, sludge dewatering alludes to the course of expulsion of water from slop. As a result, there is a noticeable decrease in its volume, bringing down pulling costs, likewise causing the muck simple to consume as fuel, also causing a decrease in fuel costs (3). Cationic polyacrylamide copolymers (PAMs) are a large group of water-soluble polymers that have numerous applications, such as industrial waste treatment and agricultural waste. One of the most vital uses is the usage of PAM in sludge dewatering for municipal wastewater treatment plants (MWWTPs) (4).
Biopolymers as Eco-Friendly materials in wastewater treatment
Environmental conditions have deteriorated dramatically and alarmingly as a result of the introduction of natural or manmade contaminants. There are many different kinds of environmental contaminants that are bad for both the ecosystem and people’s health. Due to its saving time and money, and ease of use, the solid suspended particles approach, such as chemical ways to remove solid suspended particles, has historically been used to remove pollutants. Its capacity to cure environments with high pollution concentrations, however, restricts its economical application. When not renewed, ion exchange systems that produce resins might result in secondary pollutants. They are also not cost-effective for treating huge amounts of wastewater (5).
Due to their unique properties, biopolymers—polymeric materials created by organisms— have piqued the scientific community’s curiosity. These biopolymers are composed of repeating, biodegradable monomer units. These biopolymers are created by cells as the sum of the chemical reactions that take place within each cell of a living organism and that provide energy for important functions during the microbial growth cycle. The bulk of biopolymers are made from biological materials, including plant biomass, agro-waste, and microorganisms. Proteins, nucleotides, lipids, and polysaccharides make up biopolymers(6) .
Biopolymers have a greater economic value and are more readily biodegradable since they are derived organically from ecosystems. Biopolymers naturally have well-defined structural characteristics. They appear as uniformly sized, long-chain molecules. Recent competition between biopolymers and other materials has risen due to rising global interest in cleaning up environmental damage. This ultimately resulted in the commercialization of biopolymers and the goods they are associated with in a variety of environmental fields (5).
Applications for wastewater treatment have come into focus due to the characteristics of biopolymers and their composites. The cost of the clean-up procedure is decreased with the use of economical polymers as an adsorbent. Pollutant adsorption has often used composites. Increased tensile strength, processing flexibility, high functionality, and a large surface area are just a few of the distinguishing characteristics of biopolymer-based composites that improve adsorption and the removal of impurities and pollutants from various ecosystems, including water, air, and soil (5).
Some of the aspects of composites made of hydroxyapatite and hydrogel have been studied recently for their potential to absorb dyes and heavy metals. In order to address membrane fouling difficulties, biopolymers have recently been employed as membrane modifiers in waste removal procedures (6).
The utilization of biopolymers with extra functional moieties in membrane-based treatment procedures is made possible by both their intrinsic qualities and their environmental ability to be maintained at a certain rate or level. Some of the most popular polymers utilized in membrane changes are chitosan, chitin, alginate, and carrageenan. Biopolymer-based membranes, therefore, offer promise for the adsorption process(6) .
Conclusion
Wastewater is increasing due to the increase in population as the water resource is limited, so wastewater treatment is important for the survival of life on earth. Recently, advanced technologies used for wastewater treatment are time and cost-effective. There are a number of advantages to selecting the appropriate wastewater treatment method, including a reduction in the spread of diseases through polluted water.
FAQs
Polymers are used in water purification as flocculants, substances that promote the clumping of particles. They help to remove suspended solids, organic matter, and other impurities from water, making it safer for consumption and use.
In wastewater treatment, polymers are used to aggregate and settle out suspended solids, reducing the turbidity of the water. They can also be used to precipitate dissolved contaminants, making them easier to remove.
The advantages of using polymers in wastewater treatment include their effectiveness in removing a wide range of contaminants and their ability to improve the clarity of the treated water. However, challenges include the need for precise dosing and the potential environmental impact of residual polymers in the treated water.
Polymers have significant potential in transforming water purification technologies due to their versatility and effectiveness. They can be engineered to target specific contaminants, and new polymer-based technologies are being developed that could offer more efficient and sustainable solutions for water purification.
Current research is exploring a variety of new applications for polymers in wastewater treatment, including the development of more efficient flocculants, the use of biodegradable polymers, and the creation of polymer-based nanomaterials for advanced contaminant removal.
References
- Sher, F., Malik, A., & Liu, H. (2013). Industrial polymer effluent treatment by chemical coagulation and flocculation. Journal of Environmental Chemical Engineering, 1(4), 684-689.
- Huang, D.L., Wang, R.Z., Liu, Y.G., Zeng, G.M., Lai, C., Xu, P., Lu, B.A., Xu, J.J., Wang, C. & Huang, C. (2015). Application of molecularly imprinted polymers in wastewater treatment: a review. Environmental Science and Pollution Research, 22, pp.963-977.
- Nath, A., Mishra, A., & Pande, P. P. (2021). A review of natural polymeric coagulants in wastewater treatment. Materials Today: Proceedings, 46, 6113-6117.
- Hennecke, D., Bauer, A., Herrchen, M., Wischerhoff, E., & Gores, F. (2018). Cationic polyacrylamide copolymers (PAMs): environmental half-life determination in sludge-treated soil. Environmental Sciences Europe, 30(1), 1-13.
- Grzebyk, K. (2019). Modifying Interfacial Polymerization Reaction Conditions in High-Pressure Membrane Fabrication for Enhanced Organic Micropollutant Removal.
- Yaashikaa, P. R., Kumar, P. S., & Karishma, S. (2022). Review on biopolymers and composites–evolving material as adsorbents in removal of environmental pollutants. Environmental Research, 212, 113114.
