**3. Sludge irradiation dosimetry**

subsidiary of Johnson and Johnson) together with High Voltage Engineering Corp. (a manu‐ facturer of accelerators) in order to sterilize single-use medical devices such as gloves, hypo‐ dermic needles, sutures, surgical drapes. Nowadays, it is worldwide used, not only for medical devices, but also for cosmetics. The exact mechanism by which radiation kills microorgan‐ isms isnotverywellunderstood,butitis certainlyrelatedto thedamage causedbythe radiation to the DNA molecule of the microorganisms. Also it is generally accepted that the smaller the microorganism the larger the dose of radiation needed to kill it. So, the radiation dose needed to kill bacteria will be larger than the dose needed to kill human cells, and it will be smaller than

Sterilization is not the only area in which radiation can be used in biotechnological applica‐ tions. Radiation is being used to develop new implant materials which are biocompatible. An example of this is the irradiation of water-soluble polymers in aqueous solutions, with or without the addition of another monomer which gives rise to a variety of cross-linked gels which can be used in the biomedical field. Some of these hydrogels can be used to hydrate the

Radiation is also used in the area of food preservation. Depending on the dose used on a food commodity, the radiation can either sterilize (e.g., in meat products), kill bacteria including *Salmonella* and *Streptococcus* species, disinfest (e.g., in fruits and grains), kill insects in adult, larvae, or pupae stages, or delay maturation (e.g., in some fruits and vegetables) by

The commercial use of irradiation to disinfect sludge started in 1973 when an industrial gamma ray facility from Geiselbullach near Munich (Germany) used Co-60 and Cs-137 sources [1]. The

More recently, a new technology using electron beam accelerators was developed in Miami,

where a 1.5 MeV 37.5 kW accelerator, with a maximum throughput of 45 l/min were described [2]. However, these two studies only addressed the engineering aspects of the facilities and the possibilities to use electron beam irradiation for environmental applications. The radiation effects on the bacterial load and removal of noxious chemical compounds have been performed mostly in small samples of sludge irradiated under laboratory conditions and mainly address either only the microbiological or the chemical effect of radiation in a sample of sludge [3–5]. Processing and disposal of wastewater sludge are a critical problem worldwide [5]; therefore,

Sludge is commonly used as a soil amendment and fertilizer but must be treated in order to remove various bacteria, toxic compounds, parasites, and viruses. Many researchers have shown that exposing sludge to high-energy radiation successfully removes all the bacteria and other organisms from the sludge. Thus, the right dose of radiation will ensure proper sludge

/day of sludge.

/day, and in Brazil

facility used 90,000 Ci of Co-60 and 570,000 Ci of Cs-137 and treated up to 180 m3

Florida where a 1.5 MeV 50 mA accelerator with a throughput of 645 m3

new technologies to solve this problem are constantly being sought.

the dose needed to kill a virus.

232 Radiation Effects in Materials

skin of patients with severe burns.

decomposing the enzymes responsible for ripening.

**2. Application of electron beam technology**
