In this article we will discuss about the various operations involved in water treatment. 1. Sedimentation: Sedimentation is a process of separating from water by gravitational settling the suspended particles that are heavier than water. In water there are mainly two types of suspended solids: (i) Inorganic solids having specific gravity of about 2.65, and (ii) Organic solids having specific [...]
The priliminary treatment of sewage involves the use of only physical unit operations such as screening, comminution, grit removal, skimming, floatation, etc. The physical unit operations involved in preliminary treatment of seawge are accomplished by employing various units or appurtenances which include screens, comminutors, grit chambers or detritus tanks, skimming tanks, floatation units, etc. 1. Screening—Screens: Screening is the first [...]
The various considerations involved in the design of screens and screen channels are as follows: 1. Velocity of Flow: The velocity of flow ahead of and through a screen varies materially and affects its operation. The lower the velocity of flow through the screen, the greater is the amount of screenings that would be removed from sewage. However, the lower [...]
The various considerations involved in the design of grit chambers are as follows: 1. Settling Velocity 2. Surface Overflow Rate (SOR) 3. Detention Period 4. Bottom Scour and Flow through Velocity 5. Velocity Control Devices 6. Number of Units 7. Dimensions of Each Unit 8. Loss of Head. 1. Settling Velocity: Grit chamber may be designed on a rational basis [...]
The sewage filters that are commonly employed are of the following types: 1. Intermittent Sand Filters 2. Contact Beds 3. Trickling Filters 4. Dunbar Filters 5. Magnetite Filters 6. Rapid Sand Filters Type # 1. Intermittent Sand Filters: The intermittent sand filter is the earliest type of sewage filter used in the biological treatment of sewage. It consists of a [...]
The important considerations in the design of high-rate trickling filters are the organic loading rate and the recirculation ratio. The efficiency of a high-rate trickling filter depends on both organic loading rate and recirculation ratio. A number of equations are available for the determination of plant efficiency based on organic loading rate and recirculation ratio. The sizing of the trickling [...]
In this article we will discuss about:- 1. Features of High-Rate Trickling Filters 2. Comparison with Conventional or Standard Trickling Filter 3. Proprietary Types 4. Merits and Demerits. Features of High-Rate Trickling Filters: High-rate trickling filters are similar to conventional or standard trickling filters except that the rate of loading (both hydraulic as well as organic) for high rate filters [...]
In this article we will discuss about:- 1. Constructional Features of Conventional Trickling Filters or Standard Trickling Filters 2. Performance and Efficiency of Conventional or Standard Trickling Filters 3. Merits and Demerits. Constructional Features of Conventional Trickling Filters or Standard Trickling Filters: In general a trickling filter consists of a watertight tank having a bed of filter media, sewage distribution [...]
In this article we will discuss about:- 1. Introduction to Activated Sludge Process 2. Oxygen Requirements and Transfer 3. Secondary Settling 4. Advantages and Disadvantages of Activated Sludge Process. Introduction to Activated Sludge Process: The activated sludge process was developed in England in 1914 by Ardern and Lockett and was so named because it involved the production of an activated [...]
In this article we will discuss about:- 1. Operations and Units of an Activated Sludge Plant 2. Operational Difficulties in Activated Sludge Plant. Operations and Units of an Activated Sludge Plant: Fig. 13.2 shows a typical flow diagram for an activated sludge plant. The activated sludge process is usually preceded by preliminary and primary treatments of sewage for which screening [...]