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 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 [...]
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 [...]
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:- 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 [...]