The continuous flow type of sedimentation tanks are widely adopted at present and hence, it becomes essential to study in detail some of the design aspects of these tanks. Following are the aspects of continuous flow sedimentation tanks: 1. Velocity of Flow 2. Capacity of Tank 3. Miscellaneous Considerations. 1. Velocity of Flow: The velocity of flow of water in [...]
For the purpose of designing, the continuous flow basin may be divided into following four zones: (a) An inlet zone, (b) A settling zone, (c) Sludge zone, and (d) An outlet zone. Before starting design work the following simple assumptions could be made: (i) The water in the settling zone acts as quiescent without any disturbance and the sedimentation takes [...]
The design of water softening plants will be clear from the following solved example: Design a water softening plant for a water works having the following data: (i) Hardness in the water = 450 mg/litre as CaCO3, (ii) Quantity of water to be treated = 25000 litres/hour (iii) Allowable hardness after treatment in the work = 50 mg/litre as CaCO3 [...]
The phenomena on which filtration process removes bacteria, colour, taste, odours, iron, manganese and make water sparkling can be explained on the basis of following four actions: 1. Mechanical Straining2. Sedimentation 3. Biological Action 4. Electrolytic Action. 1. Mechanical Straining: Sand consists of small pores, therefore suspended particles which are larger in size cannot pass through sand bed and are [...]
In this article we will discuss about:- 1. Properties of Sand 2. Effective Size of Sand 3. Uniformity 4. Depth and Grading of Sand Bed 5. Gravel for Filter. Properties of Sand: The sand used for filters should have the following properties: (i) It should be obtained from hard rocks such as basalt, trap and quartz. (ii) It should be [...]
The method of design of filter will be clear from the following solved examples: Example 1: Design five slow sand filter beds from the following data for the water works of a town of population 75,000; Per capita demand =135 litres/day/capita Rate of filtration = 210 litres/hour/m2 Assume maximum demand as 1.5 times the average demand. Out of five units, [...]
In this article we will discuss about:- 1. Meaning of Plain Sedimentation 2. Process of Treating Water by Plain Sedimentation 3. Principle. Meaning of Plain Sedimentation: If the water contains suspended impurities of large size, it is very economical to remove them by preliminary sedimentation. The suspended impurities make the water-turbid; therefore, when they will be removed more uniform water [...]
In practice three types of sedimentation tanks are used, which are as follows: 1. Rectangular Tanks 2. Circular Tanks 3. Hopper Bottom Tanks. Type # 1. Rectangular Tanks: These are rectangular in plan and consist of large number of baffle walls. The function of baffle walls is to reduce the velocity of incoming water to increase the effective length of [...]
In this essay we will discuss about:- 1. Standards for Quality of Treated Water 2. Objects of Treatment 3. Considerations for Public Water Supply 4. Treatment Processes. Essay # 1. Standards for Quality of Treated Water: The treatment process should be designed such that, they should treat the water up to the desired standard for which it is to be [...]
In this essay we will discuss about the classification of filters:- A. Gravity Filters B. Pressure Filters. Essay # A. Gravity Filters: 1. Slow Sand Filters: Construction of Slow Sand Filters: These are watertight shallow tanks about 2.5 m to 4 m deep and having surface area 100 sq.m to 2000 sq.m. in plan. These tanks contain 60-90 cm thick [...]