The deterioration of natural sources of fresh water supply is linked to an increase in worldwide social economic growth and activities, which produces wastewater with high pollution levels. Water-related technologies and materials development have been a top focus in most wastewater industries due to the negative consequences of pollution in wastewater. Integrating coagulation and filtration is one of the many purification processes available. In water and wastewater environments where water quality is critical, sedimentation or flotation are well-known pre-treatment procedures. However, variations in inflow water quality and a lack of well-designed treatment facilities reduce treatability efficiency while increasing production costs. Even though the chemical purification process, also known as coagulation, is necessary in wastewater treatment, it is sometimes perceived as an expensive technology due to the cost of chemicals used. Coagulants are used to precipitate the soluble metal ions in this approach. As a result, long-term use of metal-based coagulants (aluminium and iron) has prompted concerns about sludge development and heavy metal residuals that could be hazardous to the ecosystem. As a result, most wastewater does not meet the strict Environmental Protection Agency regulations for regulating effluent plant quality.
A heterocoagulation approach is commonly used in a normal wastewater treatment facility, and it consists of a blend of inorganic and organic polymer additions. This is done to speed up the agglomeration and coalescence of weighted particles so that they can be removed from the water using sedimentation or flotation procedures. Most industrial wastewaters from the oil refinery, food, and agricultural processing industries, on the other hand, contain organics, suspended and emulsified oil and grease, which prefer to float rather than settle. In addition, the use of polymers to improve dewatering and improved sewage treatment, which includes the removal of phosphorus, has become quite widespread.
Although coagulant chemicals and their derivatives are extremely useful in wastewater treatment, they have the potential to change the physicochemical properties of effluents. In addition, the challenge of disposing of large amounts of sludge and metals in effluents, such as when using hydroxide precipitation, necessitates the development of a process to recover valuable or harmful metals from the sludge. As a result, Donnan membrane technology, which requires a lower operating pressure than other membrane technologies, has been one of the most widely explored techniques in wastewater treatment. However, one of the drawbacks is the cost of the membrane.
Applications
Process of chemical purification
Chemical treatment using metal salts of iron and aluminium is commonly used as a primary treatment in numerous wastewater treatment businesses to successfully remove particle and organic debris. Coagulation is a crucial mechanism that promotes the aggregation of suspended solids, which are primarily responsible for removing turbidity, colour, and odour. The flocculation helps the coagulated particles agglomerate into larger flocs, which speeds up the gravitational settling or flotation process for removing pollutants. Flocculation is the spontaneous formation of flocs in suspension. This is commonly used in the purification of water and the treatment of sewage. The most effective flocculants have been cationic polyelectrolytes. Because of their low charge density, they are less likely to promote instability by reversing the surface charge.
Other Applications
- When coagulation or clotting occurs in the blood, it occurs quickly after the damage to the blood vessels. There are two procedures that take place. Platelets undergo a transformation, and the subendothelial tissue factor is exposed to plasma Factor VII, which eventually results in the formation of fibrin. When platelets plug an injury, this is known as primary hemostasis. Secondary hemostasis occurs as a result of the interaction of clotting factors and fibrin factors in the platelet plug.
- Yogurt is formed when milk proteins coagulate and thicken a liquid combination. Blood platelets coagulate blood, allowing it to be sealed around a wound. Pectin is responsible for the gelling (coagulation) of jam. As the gravy cools, it begins to coagulate.
Conclusion
Coagulation is a common occurrence in most traditional water and wastewater treatment systems. This happens in a physical purification unit, where transport processes and the addition of coagulants for chemical reactions, charge neutralisation, and the production of smaller flocs that agglomerate into bigger flocs are all involved. This improves downstream processes’ ability to effectively remove recalcitrant pollutants.
This chapter aims to overcome the drawbacks of using inorganic coagulants by assessing the efficacy of organic coagulants and investigating the factors and mechanisms that influence coagulation in a physicochemical treatment process for water and wastewater. The impact of pH, coagulant type, and dosage on high sludge development and residual metals discharge into downstream streams is investigated. It has been proposed that organic coagulants and technologies be developed to reduce the performance and recovery of mineral coagulants from wastewater treatment residuals.