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Section F

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Section F

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  1. Section F Alternate Technologies

  2. Bio-medical waste and technology • Technology is only a fraction of the solution. • Major components of waste management are: • Segregation of waste • Waste minimisation • Reducing use of hazardous substances or processes • Waste Audit F1

  3. Treatment technologies Treatment technology for bio-medical waste should: • Disinfect waste • Make waste non-reusable • Be environmentally safe • Should consider worker safety F2

  4. Approved treatment methods • Autoclave • Chemical disinfection • Hydroclave • Microwave • Incineration • Any other technology after CPCB approval F3

  5. Technologies for bio-medical waste treatment • Thermal processes • Low heat • Medium heat • High heat • Chemical processes • Irradiative processes • Biological processes F4

  6. Biological indicators Suspensions of resistant endospores are used as biological indicators for microbial inactivation: • Bacillus stearothermophilus: thermal • Bacillus subtilis: chemical • Bacillus pumilus: irradiation F5

  7. Autoclaves • Saturated steam acts as the disinfecting agent • Pressure, temperature, time combinations • for gravity flow 121oC, 15psi, 60’/135oC, 31psi,45’/149oC,52psi, 30’ • for pre- vacuum type (121oC, 15psi, 45’/135oC, 31psi, 30`) F6

  8. Types of autoclaves Air is an effective insulator, thus complete disinfection demands removal of air from the chamber. Two methods of removing air are: • Gravity displacement • Pre-vacuum F7

  9. Components of an autoclave Major components • A metal chamber that can withstand high pressure • A steam jacket surrounding the chamber • A steam generator • A capillary thermometer and 2 pressure gauges to monitor temperatures and pressures respectively • Recording mechanism F8

  10. Stages in autoclave operation • Pre-heating • Loading of waste with an indicator • Air evacuation • Steam treatment • Steam discharge • Unloading • Mechanical treatment F9

  11. Types of waste allowed/ disallowed Type of waste allowed category (3,4,6,7): • Microbiological and biotechnological waste • Sharps, soiled waste, solid waste Not to be treated: • Volatile and semi-volatile organic compounds • Chemotherapeutic wastes, mercury and other hazardous chemical waste • Radiological waste, Sealed heat resistant containers • Huge and bulky bedding material Poorly segregated waste can lead to emission of alcohols, phenols, aldehydes, mercury and other toxic contaminants F10

  12. Advantages • Proven technology, with disinfection parameters well established • Minimal emissions (with properly segregated waste) • Relatively lower capital costs • Automated systems F11

  13. Disadvantages • Waste recognisable after treatment • No volume reduction (till a shredder is attached) • Odours • Emissions (with unsegregated waste) • Process gives wet waste, if not subjected to drying • Barriers to direct steam exchange may compromise efficiency. F12

  14. Points to ponder • Segregated waste is a must • Air evacuation is necessary • Place bags in multi-load trays • Proper ventilation to avoid odors • Thermocouples and pressure gauges should be checked frequently F13

  15. Hydroclave • Hydroclave is steam treatment with fragmentation and drying of waste • It has a double walled chamber with an agitator inside • Steam is injected into this wall (jacket) and waste is loaded in the inner chamber • The agitator fragments and turns waste F14

  16. Hydroclave: treatment mechanism • The moisture in the waste turns to steam and exerts pressure on the inner walls. If this pressure is not sufficient, additional steam may be injected inside. • Cycle runs at 132oC for 15’/ 121oC for 30’ • Finally the steam is vented through a condenser while maintaining heat input, causing the waste to dry • Steam is shut off, discharge door is opened and agitator runs in reverse rotation to place the waste on a conveyor belt/ container. F15

  17. Hydroclave • Advantages • Shredded, dry waste • Internal mixing improves transfer of heat • Disadvantages • Clogging of agitator blades with waste • Mixed shredded waste makes recycling difficult F16

  18. Microwave: action mechanism • Disinfection by moist heat and steam generated by microwave energy • Magnetrons convert high voltage electrical energy into microwave energy • The microwaves create an electromagnetic field • Water and other molecules in waste try to align in the field and in the process they vibrate • Vibration of the molecules produces heat F17

  19. Microwave: action mechanism Microwave kills by two mechanisms: • By heat energy from the steam generated • Changing the biological molecular structure of proteins F18

  20. Microwave: operating parameters • Microwaves are high frequency (2450+50mhz) radio waves capable of creating electromagnetic field • Temperatures reached are around 97-100oC. In some new systems, steam under pressure is passed, to achieve temperatures>135oC. • Cycle time is around 25’ • Typically, around 2-6 magnetrons are used with an output of about 1.2KW each F19

  21. Stages in microwave operations • Waste loading • Steam injection in the hopper • Internal shredding • Microwave treatment • Disinfection cycle • Optional secondary shredding • Discharge Category of waste that can be and cannot be treated is similar to the autoclave. Emission parameters are also similar F20

  22. Advantages and disadvantages Advantages • In use for more than a decade • Minimal emissions if no hazardous waste fed • Automated system • No liquid effluent Disadvantages • Relatively high capital cost • Toxic emissions if hazardous waste fed • Any large metal item can damage shredders • Odour problems • Probability of microwave energy leakage F21

  23. Points to ponder • Properly segregated waste is a must. It becomes necessary to ensure: • absence of large metal blocks • absence of hazardous or radiological waste: • Workers to be trained for monitoring leakage of microwave energy and handle it F22

  24. Other thermal technologies • Low heat (dry) technologies (<350oF) • high velocity heated air • Medium heat (350oF-700oF) • reverse polymerization or thermal depolymerisation • High heat technologies (1,000oF-15,000oF) • pyrolysis Medium and high heat technologies also produce dioxins and furans and other toxic pollutants, require pollution control devices, and are fairly expensive. F23

  25. Chemical methods • (NaOH/ KOH: For treatment of pathological and cytotoxic waste): • Sodium hypochlorite • Glutarladehyde • Peracetic acid • Ozone gas • Calcium oxide • Sodium hydroxide: alkaline hydrolysis F24

  26. Evolving technologies Irradiation (ionising radiation): • X rays/gamma rays • Electron beam Biological: • Enzymes • Composting, vermiculture F25

  27. Choosing an alternate technology • Throughput capacity • Types of waste treated/not suited • Microbial inactivation efficiency • Environmental emissions and water residues • Regulatory acceptance • Space requirements • Utility and other installation requirements F26

  28. Choosing an alternate technology • Reduction of waste volume and mass • Occupational safety and health • Noise and odour • Automation • Reliability • Manufacturer background • Cost • Recurring cost and maintenance • After sales service • Level of operator training, other manpower requirement F27

  29. Centralised facilities Guidelines on common facilities • Treatment facilities: 90% non-burn, 10% burn • Limits incineration to Categories 1&2 • At least 1 Km from residential areas. Acceptable in industrial area • One operator allowed to cater upto 10,000 beds, situated within 150 km radius • Segregation is the role of generator; operator can report mixing of waste to the prescribed authority F28

  30. Chemical Disinfection

  31. Hydroclave

  32. Microwave

  33. Autoclave

  34. Incinerator