A rapid sand filter (gravity type) consists of the following parts: 1. Enclosure Tank: It is an open watertight rectangular tank constructed of stone or brick masonry or concrete. The depth of the tank is about 2.5 to 3.5 m. The surface area of the tank may vary from 10 to 50 m2. Thus depending on the total surface area [...]
Following are the various types of troubles which occasionally occur at the site and operation of trickling filters: 1. Odour Nuisance 2. Ponding Nuisance 3. The Fly Nuisance. Trouble # 1. Odour Nuisance: It is used due to anaerobic decomposition, sludging and undesirable growth. The odour nuisance can be eliminated by preventing the conditions responsible for it. Following are the [...]
The filters which are mostly used in sewage treatment can be classified as follows: 1. The Intermittent Sand Filters 2. The Contact Beds 3. The Trickling Filters. 1. Intermittent Sand Filters: These are the early development of sewage treatment units. These are similar in Construction to the slow-sand filter of water treatment. These require larger area, due to which these [...]
Fig 16.4 shows the section through a trickling filter. It essentially consists of a masonry or R.C.C. tank which is circular or rectangular in plan. Coarse aggregate of impervious nature is filled in this tank which acts as filtering media. The under-drainage system is provided in the bed to collect the Aggregate effluent. Fig. 16.4 (a) shows the under-drainage system [...]
In this article we will discuss about the design of trickling filters. Organic Loading Rate: Organic loading rate and the recirculation ratio are the main considerations in the design, where the organic loading rate is decided; the required filter volume is calculated. Now the depth and surface area of the filter are suitably chosen to secure hydraulic loading rates within [...]
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 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 [...]