Wednesday, May 22, 2013

Sedimentation Units and their various processes

Sedimentation Units
Sedimentation Units are used for the application of sedimentation or water treatment processes. The process of physical water treatment to remove the suspended solids using gravity from water is sedimentation. In still water of oceans or lakes, in the turbulence of moving water the solid particles are entertained which is removed by the process of sedimentation naturally. Ponds are settling basins which are constructed with the aim of sedimentation to remove the entwined solids. Settling basins are clarifiers built mechanically for removing solids continuously which are deposited by sedimentation.

The mass of a given porosity of dry solid particles which are associated with the water sample volume is retained by a filter and are known as suspended solids. These suspended solid particles are not lower than 10 micrometer in size. The particles of size ranging between 0.001 micrometer and 1 micrometer based on the process of quantification are colloids. These particles do not settle naturally because of the electrostatic forces and Brownian motion balancing the gravity.

The suspended particles are removed by the process of sedimentation depending upon the specific gravity and size of the particles. If the suspended solids have specific gravity similar to the water then these solids remain in suspension on a filter while the dense particles settle down after passing through the filter. The sedimentation processes are of 4 types which include type 1 in which all the particles settle independently. These particles are free setting, non flocculent and dilutes in the liquid.  In type 2 particles are flocculent and dilute which settle down as flocculate. In type 3 particles settle in zones, have concentrated suspensions and sludge thickening. In Type 4 the particles have compression, concentrated suspensions and sludge thickening.

Sedimentation Units have wide applications in portable water treatment and waste water treatment. In portable water treatment, sedimentation is followed by a step of flocculation and coagulation which allows the particles to group together into a collection of larger size. This allows settling colloids and speed of settling of suspended solids is increased.

To treat wastewater, sedimentation tanks have been used for years. Removal of settleable and floating solids thorough the process of sedimentation is the primary treatment of sewage. The content of the suspended solids is reduced by the primary clarifiers. The clarifiers also reduce the pollutants that are implanted in the suspended solids. Flocculation and coagulation are used for building a package treatment plant or compact treatment plant for treated water’s further polishing. Primary clarifiers or primary sedimentation tanks or pre settling basins are used in the primary sedimentation stage of sewage treatment. These tanks are utilized for settling the sludge and the oils and grease from the surface of the tanks are skimmed off. Mechanically driven scrappers are present in these settling tanks which continuously move the sludge to the base of the tank which is towards a hopper and from there the sludge treatment facilities are pumped.

Secondary clarifiers are sedimentation tanks which are used for removing collection of biological growth in many processes of secondary treatment which includes trickling filters, activated sludge and rotating biological contractors.

All types of units used for sedimentation are available online. Organizations interested can browse the internet and get the information and the products directly from the manufacturers.