Treatment and disposal technologies for health-care waste ...

1 Treatment and disposal technologies for health-care waste778 Treatment and disposaltechnologies for health-carewasteIncineration used to be the method of choice for most hazardous health-care wastes and is still widely used. However, recently developed alterna-tive Treatment methods are becoming increasingly popular. The finalchoice of Treatment system should be made carefully, on the basis ofvarious factors, many of which depend on local conditions: disinfection efficiency; health and environmental considerations; volume and mass reduction; occupational health and safety considerations; quantity of wastes for Treatment and disposal /capacity of the system; types of waste for Treatment and disposal ; infrastructure requirements; locally available Treatment options and technologies ; options available for final disposal .

2 Training requirements for operation of the method; operation and maintenance considerations; available space; location and surroundings of the Treatment site and disposal facility; investment and operating costs; public acceptability; regulatory Treatment options presented in this chapter may effectively re-duce the infectious hazards of health-care waste and prevent scavengingbut, at the same time, give rise to other health and environmentalhazards. For example, incineration of certain types of health-care waste ,particularly those containing chlorine or heavy metals, may under cer-tain conditions (such as insufficiently high incineration temperatures,inadequate control of emissions) release toxic material into the atmo-sphere.

3 Land disposal may result in groundwater pollution if the landfillsite is inadequately designed and/or operated. In choosing a Treatment ordisposal method for health-care waste , particularly if there is a risk oftoxic emissions or other hazardous consequences, the relative risks, aswell as the integration into the overall framework of comprehensivewaste strategy, should therefore be carefully evaluated in the light oflocal and drawbacks of the various Treatment and disposal tech-nologies discussed in this chapter are summarized in Table (page 110).

4 Principles of incinerationIncineration is a high-temperature dry oxidation process that reducesorganic and combustible waste to inorganic, incombustible matter andSafe management of wastes from health-care activities78results in a very significant reduction of waste volume and weight. Thisprocess is usually selected to treat wastes that cannot be recycled,reused, or disposed of in a landfill site. The process flow is illustratedschematically in Fig. combustion of organic compounds produces mainly gaseous emis-sions, including steam, carbon dioxide, nitrogen oxides, and certain toxicsubstances ( metals, halogenic acids), and particulate matter, plussolid residues in the form of ashes.

5 If the conditions of combustion are notproperly controlled, toxic carbon monoxide will also be produced. The ashand wastewater produced by the process also contain toxic compounds,which have to be treated to avoid adverse effects on health and large, modern incinerators include energy-recovery facilities. Incold climates, steam and/or hot water from incinerators can be used tofeed urban district-heating systems, and in warmer climates the steamfrom incinerators is used to generate electricity. The heat recovered fromsmall hospital incinerators is used for preheating of waste to be waste characteristicsIncineration of waste is affordable and feasible only if the heating value of the waste reaches at least 2000kcal/kg (8370kJ/kg).

6 The value forinfectious waste , for instance, exceeds 4000kcal/kg. The characteristicsthat make waste suitable for incineration are listed in Box flow scheme of incineratorTreatment and disposal technologies for health-care waste79 Box Characteristics of waste suitable for incineration Low heating value: above 2000 kcal/kg (8370 kJ/kg) for single-chamber incinera-tors, and above 3500 kcal/kg (14 640 kJ/kg) for pyrolytic double-chamberincinerators. Content of combustible matter above 60%. Content of non-combustible solids below 5%.

7 Content of non-combustible fines below 20%. Moisture content below 30%.An input of appropriate fuel may overcome a slightly deficient heatingvalue or a slightly excessive moisture requires no pretreatment, provided that certain waste typesare not included in the matter to be incinerated. Wastes that should notbe incinerated are listed in Box of incineratorIncinerators can range from extremely sophisticated, high-temperatureoperating plants to very basic combustion units that operate at muchlower temperatures. All types of incinerator, if operated properly, elimi-nate pathogens from waste and reduce the waste to ashes.

8 However,certain types of health-care wastes, pharmaceutical or chemicalwastes, require higher temperatures for complete destruction. Higheroperating temperatures and cleaning of exhaust gases limit the atmo-spheric pollution and odours produced by the incineration equipment should be carefully chosen on the basis of theavailable resources and the local situation, and of risk benefit consider-ations balancing the public health benefits of pathogen eliminationBox waste types not to be incinerated Pressurized gas containers.

9 Large amounts of reactive chemical waste . Silver salts and photographic or radiographic wastes. Halogenated plastics such as polyvinyl chloride (PVC). waste with high mercury or cadmium content, such as broken thermometers,used batteries, and lead-lined wooden panels. Sealed ampoules or ampoules containing heavy management of wastes from health-care activities80before waste disposal against the potential risks of air or groundwaterpollution caused by inadequate destruction of certain basic kinds of incineration technology are of interest for treatinghealth-care waste : double-chamber pyrolytic incinerators, which may be especially de-signed to burn infectious health-care waste ; single-chamber furnaces with static grate, which should be used onlyif pyrolytic incinerators are not affordable.

10 Rotary kilns operating at high temperature, capable of causing decom-position of genotoxic substances and heat-resistant designed especially for Treatment of health-care wasteshould operate at temperatures between 900 and 1200 C. Low-cost,high-temperature incinerators of simple design are currently beingdeveloped, and a system designed specifically for health-care and phar-maceutical waste in low-income countries is currently under test inEngland, at De Montfort incinerators for health-care waste have been tested in units permit on-site Treatment in hospitals and clinics, thus avoid-ing the need to transport infectious waste through city streets.