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Sludge Treatment

Sludge Treatment. CE 326 Principles of Environmental Engineering Department of Civil, Construction and Environmental Engineering Iowa State University Prof. Tim Ellis Spring 2008. Processes. Thickening Stabilization Conditioning Dewatering Volume Reduction Disposal. Thickening.

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Sludge Treatment

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  1. Sludge Treatment CE 326 Principles of Environmental Engineering Department of Civil, Construction and Environmental Engineering Iowa State University Prof. Tim Ellis Spring 2008

  2. Processes • Thickening • Stabilization • Conditioning • Dewatering • Volume Reduction • Disposal

  3. Thickening • c_______________ sludge using gravity or f____________ methods. Primary sludge can be thickened to a maximum of about 10% solids and secondary sludge to a maximum of about 6% solids.

  4. Stabilization • Converting the o____________ in the sludge to more stable (inert) forms so they can be handled more easily (more d_________________, less potential for odors) and used as soil conditioners. • Typically stabilization involves anaerobic or aerobic digestion. • During digestion considerable v___________ s________ destruction occurs

  5. Conditioning • Addition of c_____________ to allow better separation of the water and the solids. Ferric c_________and organic and inorganic p_____________ are frequently used for sludge conditioning.

  6. Dewatering • V________, pressure, or drying methods for removing w________ from the solids. • Typically about 25 to 35% solids can be achieved.

  7. Volume Reduction • Drying and p______________ for sale as a fertilizer • C_____________ • I____________________ of sludge with ash residual for ultimate disposal.

  8. Biosolids • Biosolids are t__________ s_________; • there are two different classes: • Class A: no detectable levels of p___________ and meets m_______ regulations, requires controlled treatment process involving high pH, temperature, or both; no permit required for land application • Class B: have been t_______ but may contain some pathogens and metals, requires permit for land application

  9. Processes for Class A • Processes for generating Class A biosolids: • sludge p_______________ • T____________ treatment (55̊C for 24 h) • temperature p________ anaerobic digestion (55̊C digester followed by 35̊C digester) developed at ISU

  10. Gravity thickener

  11. Dissolved Air Flotation (DAF) Thickener

  12. Dissolved Air Flotation (DAF) Thickener

  13. Anaerobic Digestion

  14. Steps in Anaerobic Digestion Hydrolysis Acidogenesis Acetogenesis Methanogenesis

  15. Fixed vs. floating cover

  16. Belt Filter Press

  17. Centrifuge

  18. Land Application

  19. Composting

  20. Characteristics • Blackish in color • 15% - 90% Solids • Mud-like to granular appearance • Mild to strong odor (musty or swamp like)

  21. Plants Grow Better with Compost

  22. Tree Rings Before and After Organic Matter Applied

  23. Typical organic matter inputs from organic manures (250kg/ha total N) Increase in arable topsoil organic matter content of 3-7% above ‘typical’ background level of c.4% (many decades to increase soil organic matter level by 1%) Environment Sensitive Farming practical advice for land managers

  24. Can you put on too much?

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