What is Flocculation, and Why is it Important in Water Treatment

Flocculation is the next step after coagulation and is a crucial part of water treatment. This process promotes the clumping of fine particles. It is achieved using a chemical agent called a flocculant, which invariably is a polymer. This article will discuss some important aspects of flocculation in water treatment. Also, it will give you a better understanding of what is flocculation.

Coagulation

Water treatment plant use coagulation to remove particles from the water and some dissolved matter. Coagulation effectively removes many pathogens, including bacteria and viruses, which are generally attached to dissolved substances. In the process, the coagulant bonds with these dissolved materials and settles to the bottom of the water. Coagulation is also a useful tool for removing suspended solids.

Coagulation is important in water treatment because it helps the treatment process by promoting the consolidation of particles. Larger particles are easier to separate from the liquid. The importance of coagulation in water treatment has been recognized for millennia and dates back to the Egyptians. The use of almonds as a coagulant can be traced to 2000 BC. They were widely used in the process of water purification.

The pH value of treated water affects coagulants. The pH value determines the coagulant’s form, and the impurities’ parameters are removed. To maximize the coagulant’s effectiveness, the pH value must be at the optimal level. The neutral pH value can remove turbidity caused by inorganic particles, and the slightly acidic pH value is favorable for algal and cyanobacterial cells. Acidic pH values are favorable for removing HS.

Orthokinetic flocculation

The principle of orthokinetic flocculation is simple: induced velocity gradients in a liquid induce primary particles to approach close enough to make contact and progressively form larger agglomerates. The applied velocity gradients determine the degree of flocculation and the time it takes to agglomerate. The theory has been developed by observing the flocculation of kaolin and alum using a laboratory-scale flocculator and simulating the progress of the process using a computer simulation.

Different processes can induce orthokinetic flocculation, including anaerobic selectors and a novel high-rate contact stabilization process. The feast-famine regime induces the production of EPS and can improve the quality of effluent. If the flow rate and the collision efficiency of orthokinetic flocculation are improved, effluent quality will improve.

In addition to using polymers to achieve flocculation, using cationic polymers is also a viable solution. It is a long-chain organic polymer that can bind to a surface. By adding cationic polymers to water, the particles will clump together and become bigger flocs. The resulting flocculate is removed through filtering. Flocculation and coagulation are both important parts of the modern water treatment process. 

Biopolymers

Biopolymers are organic and inorganic polymers produced by living organisms. They consist of monomeric units covalently bonded to form larger molecules. Biopolymers can be categorized into various classes based on their monomers. Some of these include polynucleotides, which are long polymers made of amino acids, and polysaccharides, which are linear or branched polymers made of carbohydrates such as starch, cellulose, alginate, and isoprene. Further, complex polyphenolic polymers like lignin are also used in water treatment.

Biopolymers are used in wastewater treatment to remove harmful pollutants and impurities from wastewater. They can reduce the concentration of pollutants in water by more than ten times compared to conventional flocculants. Further, these agents reduce wastewater’s toxicity and the risk of waterborne disease. They also improve the efficiency of biopolymer-based flocculants, which are safe for the environment and human health.

In the production process of biopolymers, nitrogen-deficient wastewater is treated with microorganisms that grow aerobically. The dissolved oxygen level in the wastewater is stabilized, encouraging the growth of necessary isolates. The biomass produced in this process is recovered. If it is successful, the process is efficient and has high levels of PHA. Soil filtration is another important process of biopolymers.

Rapid mixing

Rapid mixing is important in water treatment as it promotes flocculation. It allows for optimal flocs distribution and reduces the mixture’s residence time in the flash mix basin. The high-speed agitation produced by high-speed rapid mixers must produce violent and vigorous mixing. Depending on the application, high-speed mixing is essential for the desired results. The high-speed mixers are configured according to the required application.

The purpose of rapid mixing in water treatment is to improve the process of coagulant dispersion. In coagulation, metal coagulant hydrolysis products are formed within a few seconds of addition. The process is inefficient when too much coagulant is added, as the metal coagulant repels particles from each other. Besides, pH adjustment and post-dose of the coagulant are rarely effective.