Wastewater Treatment Process by Physico Chemical Methods

Contaminated water contains particles of different sizes which can be classified as dissolved 0.08 µm , colloidal 0.08 1 µm , supracolloidal 100 100 mm and settleable 100 µm . The type of treatment selected depends on the size of particles present in the wastewater. In practice, treatment efficiency also depends on particle size. Solids of the size that are visible to the naked eye can be separated either by settling under the influence of gravity or by flotation, depending on the relative densities of solids and water. They may also be easily separated by filtration. However, very fine particles of a colloidal nature called colloids, size 1 µm which have high stability are significant pollutants. The reason for this stability is that these particles have electrostatic surface charges of the same sign usually negative . This means that repulsive forces are created between them, preventing their aggregation and subsequent settling. It has therefore proved impossible to separate them by settling or flotation. It is not possible to separate these solids by filtration because they pass through any filter. However, separation by physico chemical treatments is possible. Physico chemical treatment of wastewater focuses primarily on the separation of colloidal particles. This is achieved through the addition of chemicals called coagulants and flocculants . These change the physical state of the colloids allowing them to remain in an indefinitely stable form and therefore form into particles or flocs with settling properties. Dr. Bhoopendra Singh "Wastewater Treatment Process by Physico-Chemical Methods" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-6 | Issue-6 , October 2022, URL: https://www.ijtsrd.com/papers/ijtsrd51862.pdf Paper URL: https://www.ijtsrd.com/chemistry/other/51862/wastewater-treatment-process-by-physicochemical-methods/dr-bhoopendra-singh