Following factors influence to a great extent the above mentioned three stages of sludge digestion: 1. Temperature 2. Sludge Seeding 3. Mixing 4. pH- Value 5. Miscellaneous Conditions. Factor # 1. Temperature: An aerobic decomposition of organic matters in sewage is greatly influenced by temperature at which it takes place. The above mentioned three stages are based at a temperature [...]
In modern sewage works, the sludge digestion tanks are circular in plan with flat or hopper-shaped bottom. These are usually covered from the top to retain the heat and odours and for collecting the sludge gas. If the sludge contains some grit the bottom is given a slope of 1 in 2 (vertical to horizontal). Sufficient space is provided in [...]
While designing the digestion tanks, the required capacity of the sludge digestion units depends on the following: (i) The quantity of the sludge to be digested. (ii) The quantity of the sludge remained after digestion. (iii) The detention time or the period required for the digestion. The quantity of the raw sludge produced in the various sewage treatment units are [...]
In this article we will discuss about the determination of sludge volume. If Ww be the weight of the water in the sludge, W8 be the weight of the dry solids, ps be the specific gravity of the dry solids and p be the specific gravity of the sludge, mathematical the specific gravity of the sludge can be expressed as, [...]
In this article we will discuss about the design of Imhoff tanks, explained with suitable diagram. Imhoff tanks are the improvements over the septic tanks. These tanks derive the name ' Imhoff tank' after its inventor Karl Imhoff of Germany. Imhoff tanks are two-storeyed tanks which have large settling tanks and below it are sludge digestion chambers. Fig. 18.6 shows [...]
The design of some of the treatment units have also been illustrated by means of suitable solved example. Example: For a city having population of 2.75 lacs, design a suitable sewage treatment plant, with the following data: (i) Sewage flow = 200 litres/capita/day (average). (ii) Hourly variation Max. Flow/Average flow = 1.40 and Minimum flow/Average flow = 0.65 (iii) Suspended [...]