Sludge handling and disposal

presentation about sludge handling and disposal of sludge in waste water treatment course of civil engineering

1. RAKESH KUMAR (2012UCE1293) DEEPAK SHERAWAT (2012UCE1280) RIJUL (2012UCE1438) 1 /35 SLUDGE HANDLING AND DISPOSAL

2. Sludge  refers to the residual, semi-solid material left from industrial wastewater, or sewage  treatment  processes. Sustainable sludge handling may be defined as a socially acceptable, cost-effective method that meets the requirement of efficient recycling of resources while ensuring that harmful substances are not transferred to humans or the environment. 2 /35

3. Primary operations Thickening Stabilization Conditioning Dewatering Heat drying Incineration Sludge handling processes 3 /35

4. This process includes Grinding -particle size reduction Screening -removal of fibrous materials Degritting -grit removal Blending -homogenization Storage -flow equalization 1.Primary operations 4 /35

5. Using higher dosage of chemical coagulant/flocculent to remove not only suspended solids but also the soluble organic matter APT will also provide persistent sulfide odor absorption Advanced Primary Treatment 1 5 /35

6. APT program requires addition of the Ferric Chloride(3 to 15ppm ferric iron)at a point just upstream of the primary clarifiers. In general the higher the dosage of coagulant the more BOD will removed, but dosage will limited by amount of alkalinity available and by economy 6 /35

7. To increase solids content percentage of sludge by removing a portion of liquid fraction volume reduction of approximately 30 – 80 % can be reached with sludge  thickening 2 METHODS :- gravity thickening flotation thickening Centrifugation Rotatary drum thickening 2. Thickening 7 /35

8. Objectives Reduce pathogens Eliminate offensive odors Reduce potential for putrefaction Production of usable gas (methane). Mechanisms Biological reduction of volatile content Application of heat to disinfect sludge 3. Stabilization 8 /35

9. Alkaline stabilization : lime is added to untreated sludge , to raise the PH to 12 or higher . Retards microbial reaction . Materials such as cement kiln dust ,fly ash are used instead of lime . Methods of stabilization 9 /35

10. A biological process that uses bacteria in an oxygen free environment. These bacteria converts volatile solids into carbon dioxide, methane and ammonia . single stage digester Anaerobic digestion 10 /35

11. Organic part decomposes in presence of oxygen by micro organisms . Mostly used in plants with average flow less than 5 MGD . Bacteria converts organic matter into carbon dioxide . Aerobic digestion 11 /35

12. Advantages and disadvantages of aerobic digestion Advantages Disadvantages Lower capital cost High power cost End product odourless and stable Digested solids have poorer dewatering characteristics Lower BOD concentrations in supernatant liquor Useful by product such as methane is not recovered More basic fertilizer values recovered 12 /35

13. In this process sludge solids are treated with chemicals or other means to prepare sludge for dewatering. It improves the drainability of digested sludge. Sludge becomes more amenable to dewatering. It can be achieved by various methods such as elutriation, chemical conditioning, heat treatment, freezing etc. 4.Conditioning 13 /35

14. A physical unit operation used to reduce the moisture content of sludge D ifficulty due to fact that particles are very fine, colloidal in nature and possess a gel-like structure due to polymeric flocculation Compared to thermal (evaporative processes) for water reduction, mechanical dewatering is often selected due to its low energy requirement 3 5 .Dewatering 14 /35

15. Centrifugation – for separating liquids of different densities, thickening slurries . Methods of dewatering 15 /35

16. Uses principle of gravity drainage and mechanically applied pressure. 2. Belt filter press 16 /35

17. It involves the application of heat to evaporate water and to reduce the moisture content of biosolids through conduction, convection or radiation . Advantage of this method is to reduce product transportation costs, improve storage capability, and marketability. 6. Heat drying 17 /35

18. Direct drying- the wastewater solids come into contact with hot gases, which cause evaporation of moisture. Dryers such as rotary dryer and fluidized bed dryer are used. Methods of heat drying 18 /35

19. Indirect drying- Moisture evaporates when the wastewater solids contact the metal surface heated by the hot medium. Dryers such as paddle dryers ,hollow flight and disc dryers are used. paddle dryer 19 /35

20. Volume reduction 20 /35

21. Involves total conversion of organic solids to oxidized end products Sludge stabilization is not necessary before incineration . Water, carbon-dioxide and ash are primarily end products . The sludge generally has calorific values ranging from11 to 17 MJ/kg (reference : Werle and Wilk,2010) 4 7.Incineration 21 /35

22. multiple hearth incinerator Dewatered sludge to dry ash. used in large plants. Methods of incineration 22 /35

23. 2. FLUIDIZED BED INCINERATION wastes are quickly and uniformly incinerated with utilizing thermal capacity of hot fluidizing sand 23 /35

24. Energy recovery potential 5 Pathogens would be reduced by a pasteurization process Waste volume reduction Destruction of combustible toxins Advantages of incineration 24 /35

25. Emission of mercury & NOx leading to air pollution High capital and operational costs Ash must be landfilled and may be hazardous 25 /35 Disadvantages

26. Sewage sludge contains both compounds of agricultural value and pollutants. Agriculture value- organic matter, nitrogen, phosphorus and potassium. Pollutants- heavy metals, organic pollutants and pathogens Sludge disposal 26 /35

27. Land fill Agricultural use Other methods Methods of Sludge disposal 27 /35

28. A site for the disposal of waste  materials by burial and is the oldest form of waste disposal. Some landfills are also used for waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling). Problem with this method is that many landfills are filling up, and towns are having trouble finding places to put new ones. Landfill 28 /35

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30. The purpose of using sludge in agriculture is partly to utilize nutrients such as phosphorus and nitrogen and partly to utilize organic substances for soil improvement. All types of sludge can be spread on farmland if they fulfill the quality requirements (heavy metals, pathogens, pre- treatment) Agricultural use 30 /35

31. Utilization of nutrients contained in the sludge, i.e. phosphorus and nitrogen. Utilization of organic substances contained in the sludge for improvement of the humus layer of the soil (i.e. soil improvement). The cheapest disposal route Advantages 31 /35

32. Major investments in storage facilities as sludge can only be spread on farmland a few times a year. Dependency on the individual farmers and considerable administration of agreements Lack of knowledge as to the content of organic micro-pollutants and pathogenic organisms in sludge and their impact on the food chains Disadvantages 32 /35

33. Ocean Disposal  – Dumping or controlled release of sewage sludge from a barge or other vessel into marine water. Distribution and Marketing  – The give-away, transfer, or sale of sewage sludge or sewage sludge product in either bagged or bulk form. Surface Disposal  – A controlled area of land where only sewage sludge is placed for a period of one year or longer. Sludge placed in this area is not provided with a daily or final cover. Other methods 33 /35

34. 1. http ://www.californiawatertechnologies.com/pdf/APTBulletin.pdf 2 .   http://www.lenntech.com/library/sludge/thickening/sludgethickening.htm#ixzz3BV2qbCFu 3 . Vaxelaire J, Bongiovanni JM, Puiggali JR (1999) Mechanical dewatering and thermal drying of residual sludge. Environ Technol 20:29–36 4. Werle and Wilk,2010 5. U. S. EPA (1985), seminar publications composting of municipal wastewater, EPA/625/4-85/014 6. Wastewater Treatment By Metcalf & Eddy, TMH References 34 /35

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