In this article we will discuss about:- 1. Characteristics of Settleable Solids 2. Types of Settling 3. Analysis of Settling of Discrete Particles-Type 1 Settling 4. Performance of Settling Tanks. Characteristics of Settleable Solids: The settleable solids to be removed from sewage in primary and secondary settling tanks after grit removal are mainly organic and flocculent in nature, either dispersed [...]
Chemical-aided sedimentation of sewage is analogous to chemical coagulation, flocculation and sedimentation in water treatment. The colloidal and finely dispersed solids which cannot be removed by plain primary sedimentation alone, as they possess extremely low settling velocities, are aggregated into settleable particles by addition of chemicals known as coagulants in chemical-aided sedimentation. Chemical-aided sedimentation involves the unit processes and operations [...]
The settling tanks are generally made of reinforced cement concrete and may be rectangular or circular in shape. The settling tanks can be classified in the following two ways: 1. Classification based on method of operation: (a) Fill and draw type settling tanks (b) Continuous flow type settling tanks 2. Classification based on location: (a) Preliminary settling tanks (grit chambers) [...]
In order to get a fairly high percentage of removal of the suspended material in a continuous flow type settling tank, it is desirable that the tank is properly designed. For this it is essential to study the various design considerations for these tanks which are as follows: (i) Velocity of flow (ii) Surface overflow rate and solids loading rate [...]