Bio-hazardous waste treatment

Some solid and liquid wastes may contain bio-hazardous or infectious ma­terials. Further to radiological protection, other precautions for handling these wastes should be respected. When processing bio-hazardous wastes, their infectious features, and tendency to putrefaction, to insect attacks and to microbial degradation must be controlled. Clearance of bio-hazardous waste from radiation regulatory control is unlikely to mean that this waste is also exempt from bio-hazardous waste regulatory control. The goals of treatment of bio-hazardous waste are the following: (a) biologic detoxifica­tion; (b) prevention of biological degradation; (c) volume reduction.

An important step in the treatment of bio-hazardous waste is neutraliza­tion of biological hazard. It can be done by sterilization. A number of steri­lization methods are regularly used in hospitals and they can be applied for treating bio-hazardous RAW with some adaptation. Some other methods are aimed at volume reduction of the waste. Available treatment methods for bio-hazardous and medical radioactive waste have been described in detail [24]. Lidded containers lined with plastic bags are used for collection of wastes displaying biological hazards. Special consideration should be given to sharp objects. When possible, these items should be collected in puncture-resistant packages, properly labelled and treated separately. Most microbiologically contaminated laboratory wastes are suitable for steam autoclaving, but this method should not be used where the radioactive content of the waste is volatile during steam treatment. This method is not considered appropriate for most non-microbial pathogens, animal carcasses or parts. Chemical disinfection is useful for laboratory ware or similar ma­terials, but it is not suitable for pathological waste and animal carcasses or parts. Gamma irradiation is an attractive option for sterilization since it is appropriate for pathological waste, animal carcasses and parts. After deacti­vation or procedures aimed at preventing decomposition of its biological components, bio-hazardous waste can usually be treated using the same methods applied to non-biological radioactive materials in order to meet the waste acceptance criteria. Incineration is the preferred method for treating bio-hazardous RAW of animal or human origin, as well as organic chemical waste [11,21]. Incineration provides complete combustion of waste, produc­ing totally sterile residues, with any emissions from the stack being kept to acceptable environmental standards. Thermochemical treatment has been proven to be an effective method to treat animal carcasses producing totally sterile slag residue, with minimal off-gas emissions, the composition of which can be kept in line with acceptable environmental standards [11, 22, 23].

In cases where incineration is not available or the volumes of human and animal wastes are so low that it is desirable to treat them as they are pro­duced, it may be feasible to use maceration/pulverization to render these

materials liquid, so that they can be discharged via a liquid RAW route, including any necessary chemical deactivation to treat the biological hazard. Compaction and shredding are not considered viable for treatment of bio­hazardous solid waste. The primary reason for this restriction is that any microorganisms contained within the waste may be spilled or released during these processes and contamination may be widely dispersed.

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