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UNIT 5.pptx
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- 2. SLUDGE • Sludge isan odious, semisolid residual that resembles thick soft mud produced from the solid–liquid separation processes in wastewater treatment. • It is usually very inconsistent in its composition and most often unmanageable. • The final destination of treated sewage sludge usually is the land. • Dewatered sludge can be buried underground in a sanitary landfill. • It also may be spread on agricultural land in order to make use of its value as a soil conditioner and fertilizer.
- 3. OBJECTIVES OF THESLUDGE TREATMENT • To decrease moisture content in the sludge (Volume reduction) • To remove organic matters • To destroy microorganisms • To eliminate toxic materials..
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- 5. Primary sludge • Primarysludge is produced following primary treatment. • This step consists of physical or chemical treatments to remove matter in suspension (e.g. solids, grease and scum). • The most common physical treatment is sedimentation. • Sedimentation is the removal of suspended solids from liquids by gravitational settling. SLUDGE DISPOSAL METHOD
- 6. Primary sludge • Chemicaltreatments are coagulation and flocculation. • Coagulation is the addition and rapid mixing of a coagulant to neutralize charges and collapse the colloidal particles so they can agglomerate and settle. • The flocculation is the agglomeration of the colloidal particles that have been subjected to coagulation treatment. SLUDGE DISPOSAL METHOD
- 7. Secondary sludge • Secondarysludge is generated from the use of specially provided decomposers to break down remaining organic materials in wastewater after primary treatment. • The active agents in these systems are micro- organisms, mostly bacteria, which need the available organic matter to grow. • There are various techniques such as lagooning, bacterial beds, activated sludge as well as filtration or biofiltration processes. SLUDGE DISPOSAL METHOD
- 8. Tertiary sludge • Tertiarysludge is generated when carrying out tertiary treatment. • It is an additional process to secondary treatment and is designed to remove remaining unwanted nutrients (mainly nitrogen and phosphorus) through high performance bacterial or chemical processes. SLUDGE DISPOSAL METHOD
- 9. Screening • Screening grindersare beneficial for medium- size plants. • Reduced-size solids are returned to raw sewage or mixed with sewage sludge depending on grinder location related to the treatment units • It contains both organic and inorganic matter. SLUDGE CHARACTERISTICS
- 10. Grit • Final gritdisposal is by burial. • It may be in either a sanitary landfill or other accepted landfill operation. • The grit must be having a minimum of 6 inches (15 cm) of soil covering. • This is to prevent vector attraction and odors. • It involves organic and inorganic matter, especially fats and grease.. SLUDGE CHARACTERISTICS
- 11. Scum/Grease • It consistsof the floatable materials, oil and grease, animal fats, food wastes, vegetable and fruit skins, paper and cotton, cigarette tips, and plastic materials. Sludge from chemical • Industrial wastewater treatment plants produce solids that are also referred to as sludge. • This can be generated from biological or physical- chemical processes. • In the activated sludge process for wastewater treatment, the terms "waste activated sludge“ and "return activated sludge" are used. • It contains much iron SLUDGE CHARACTERISTICS
- 12. Scum/Grease • It consistsof the floatable materials, oil and grease, animal fats, food wastes, vegetable and fruit skins, paper and cotton, cigarette tips, and plastic materials. Sludge from chemical • Industrial wastewater treatment plants produce solids that are also referred to as sludge. • This can be generated from biological or physical- chemical processes. • In the activated sludge process for wastewater treatment, the terms "waste activated sludge“ and "return activated sludge" are used. • It contains much iron SLUDGE CHARACTERISTICS
- 13. Scum/Grease • It consistsof the floatable materials, oil and grease, animal fats, food wastes, vegetable and fruit skins, paper and cotton, cigarette tips, and plastic materials. Sludge from chemical • Industrial wastewater treatment plants produce solids that are also referred to as sludge. • This can be generated from biological or physical- chemical processes. • In the activated sludge process for wastewater treatment, the terms "waste activated sludge“ and "return activated sludge" are used. • It contains much iron SLUDGE CHARACTERISTICS
- 14. • Aerobic DigestionWorks • Aerobic digestion is the degradation of the organic sludge solids in the presence of oxygen. • The oxygen is introduced as fine bubbles of air into the reactor. • The microorganisms in the sludge convert the organic material to carbon dioxide and water, and the ammonia and amino species to nitrate. METHODS OF SLUDGE TREATMENT
- 15. METHODS OF SLUDGETREATMENT
- 16. THICKENING Gravity thickening • Gravitythickening is a widespread technique, performed in tanks usually fitted with a rotating ploughing system. • The gravitational forces bring the thickened sludge at the base of the tank from where it is extracted. • Gravity thickening is the process by which bio- solids are condensed to produce a concentrated solids product and a relatively solids-free supernatant.
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- 18. Gravity thickening Advantages • Gravitythickening equipment is simple to operate and maintain. • Gravity thickening has lower operating costs than other thickening methods such as DAF, gravity belt or centrifuge thickening. • Truck traffic at the plant and the farm site can be reduced; • Trucking costs can be reduced; • Existing storage facilities can hold more days of biosolids production;
- 19. Gravity thickening Disadvantages • Scumbuild-up can cause odors. This buildup, which can occur because of long retention times, can also increase the torque required in the thickener. Finally, scum build-up is unsightly. • Grease may build up in the lines and cause a blockage. This can be prevented by quick disposal or a back flush. • Septic conditions will generate sulfur-based odors. This can be mitigated by minimizing detention times in the collection system and at the plant, or by using oxidizing agents.
- 20. Gravity thickening Disadvantages • Scumbuild-up can cause odors. This buildup, which can occur because of long retention times, can also increase the torque required in the thickener. Finally, scum build-up is unsightly. • Grease may build up in the lines and cause a blockage. This can be prevented by quick disposal or a back flush. • Septic conditions will generate sulfur-based odors. This can be mitigated by minimizing detention times in the collection system and at the plant, or by using oxidizing agents.
- 21. Rotary drum filtering •Rotary drum thickening increases the sludge solids concentration (i.e. Thickens the sludge) by agitating the solids in a slowly-rotating vessel with porous walls though which the water (or filtrate) drains the sample of rotary drum filtering for sludge disposal. • A rotary drum thickener (RDT) is based on the same principle as a gravity belt thickener (GBT), in that water drains from the sludge through a retaining porous medium. • For an RDT the porous medium is the cylindrical wall of a 0.5−1.5 m diameter drum which rotates at speeds between 5 and 20 RPM while the sludge continually passes through it.
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- 23. Rotary drum filtering Applications •The rotary filter is most suitable for continuous operation on large quantities of slurry. • If the slurry contains considerable amount of solids, that is, in the range of 15-30%. Advantages • The rotary vacuum drum filter is a continuous and automatic operation, so the operating cost is low. • The variation of the drum speed rotating can be used to control the cake thickness. Disadvantages • Due to the structure, the pressure difference is theoretically limited to atmospheric pressure (1 bar), and in practice somewhat lower. • Besides the drum, other accessories, for example, agitators and vacuum pump,vacuum receivers, slurry pumps are required.
- 24. Gravity Belt Thickening •Gravity belt thickening (GBT) increases the sludge solids concentration (i.e. thickens the sludge) by allowing the water (or filtrate) to drain from the sludge under gravity through a permeable medium (a moving belt) on which the sludge sits. • Gravity thickening is the process by which biosolids are condensed to produce a concentrated solids product and a relatively solids-free supernatant. • The bio solids technology fact sheet for gravity thickening provides: A description of gravity thickening. • Applicability to wastewater treatment plants. • There are two types of belt-based processes for increasing sludge solids concentration. GBT is a low-pressure process which operates by allowing the water to drain from the sludge under gravity.
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- 31. SLUDGE SAND DRYINGBED FILTER
- 32. FACTOR AFFECTING DEWATERING PERFORMANCE Underland disposal the following methods may be included • Burial • Fill • Application as fertilizer or soil conditioner
- 33. INCINERATION • Incineration −or combustion of sewage sludge is the most widely-accepted alternative end disposal method after land spreading. • It is an oxidative method, converting the organic carbon, nitrogen, sulphur, nitrogen and phosphorus into gaseous and predominantly mineral (i.e. inorganic) solid products.
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- 35. Incineration of SewageSludge in Coal-Fired Power Plants