Radiation Treatment of Wastes: Applications for Hygienization ofBiosolids

Tae Hyun Kim; Seung Joo Lim

doi:10.4172/2155-6199.1000e121

ISSN: 2155-6199

Journal of Bioremediation & Biodegradation

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Radiation Treatment of Wastes: Applications for Hygienization ofBiosolids

Tae Hyun Kim and Seung Joo Lim^*
Research Division for Industry & Environment, Korea Atomic Energy Research Institute, 1266 Sinjeong, Jeongeup, Jeollabuk-do, 580-185 Republic of Korea
Corresponding Author :	Seung Joo Lim Research Division for Industry & Environment Korea Atomic Energy Research Institute 1266 Sinjeong, Jeongeup Jeollabuk-do, 580-185 Republic of Korea Tel: +82-63-570-3357 Fax: +82-63-570-3348 E-mail: seungjoolim@gmail.com
Received August 22, 2012; Accepted August 27, 2012; Published August 29, 2012
Citation: Kim TH, Lim SJ (2012) Radiation Treatment of Wastes: Applications for Hygienization of Biosolids. J Bioremed Biodeg 3:e121. doi: 10.4172/2155-6199.1000e121
Copyright: ©2012 Kim TH, et al. This is an open-a ccess article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Abstract

As a naturally occurring element, the abundance of uranium in the environment is very low. Anthropogenic activities, including fossil fuel combustion, uranium ores mining and enrichment for nuclear weapon manufacturing, and electricity generation in nuclear fueled power plants, has released significant amount of uranium into the environment. As a result, uranium contamination is a worldwide phenomenon. According to the US Department of Energy (DOE), there are about 2, 000,000 acres in 30 states that are contaminated with uranium.

High energy radiation has the unique capability of producing highly reactive ions or radical species that can inactivate pathogens in a simple and effective manner. The most important mechanism of waste treatment by radiation is the action of radiation on water. It produces the hydroxyl radical (•OH), the hydrogen radical (H•) and the solvated electron (e_aq ), all of which are highly reactive radical species. The radicals are capable of producing a variety of chemical lesions in nucleic acid and proteins. The OH radical seems to be mainly responsible for producing biological damage in the nucleic acid that results in inactivation. The first study on the radiation treatment of wastes (mainly for the purpose of disinfection) was carried out in the 1950s. Work carried out showed consistently that radiation is effective in degrading organic matter in wastes, destroying pathogenic organisms, and enhancing the sedimentation and filterability of sludge. In situ reactivation of carbon used as an adsorbent for wastewater has been observed. Full scale plant for complete sterilization of sewage sludge, for use as a fertilizer is in operation.

Sewage sludge is generated from wastewater treatment plant. Sewage sludge is typically organic in nature. Sludge is also a rich source of many macro (N, P, K) and micronutrients essential for soil. As sewage sludge still contains microbes, viruses and worm eggs, which under certain circumstances can be dangerous for human beings and animals, it must be disinfected before it is deposited on to agricultural areas. Mann, reporting the performance of a commercially operating sewage treatment plant in Florida, USA, stated that Coliform bacteria were reduced in number by at least a factor of 10⁴ at a total dose of 500 Gy. This 1000 gal/d plant, which operated for about 1 year, as per the report generated and consisted of an extended aeration plant, the ⁶⁰CO irradiator, a primary filtration system and an optional activated charcoal polishing filter. Etzel, Born, Stein, Helbuig and Baney, Purdue University, have found that a dose of 2 kGy in activated sludge killed 99.99% microorganisms. A positive step has now been taken by the Federal Republic of Germany, which has largely financed the construction of the first sewage sludge sterilization experimental facility, near Munich. In Switzerland, the sanitary effect of gamma irradiation on sewage sludge was implemented. There were less than 10 Enterobacteriaceae per gram in 97.2% of the samples irradiated with 3 kGy. The results of these model experiments could be completely confirmed under practical conditions in the irradiation plant of Geiselbullach. Sludge Hygienization Facility at Vadodara, India, was set up in 1992 in collaboration with State Government of Gujarat, Vadodara Municipal Corporation, and BARC (Bhabha Atomic Research Centre, India). Utilization of enriched hygienized sewage sludge and water were effectively applied for growing grapes in Gujarat where most of the land has very low fertility. The hygienized sludge is an ideal medium for nitrogen fixing bacteria like Rhizobium to grow and hence can be converted easily into a bio-fertilizer. Many crops have been tested in actual fields with excellent results. Soil condition improves considerably after application of hygienized sludge. At Baja in southern Hungary, there is a large state farm producing 100,000 swine yearly. The amount of liquid manure produced by the farm daily was 800-1000 m³. They tested gamma ray to determine those radiation doses which are completely lethal to microbes that cause various food infections. The irradiation of samples was carried out with NORATOM-type gamma-cell equipment with a ⁶⁰CO source. The results showed that the anaerobic bacteria are more radio resistant than aerobic bacteria. In this respect, spores play a subsidiary role, because the vegetative Clostridia are much more resistant than the aerobic spores. It seems reassuring that to destroy Salmonellae, a relatively low dose of 4 kGy is sufficient. Disinfection of liquid manure by gamma irradiation enables it to be reused for its nutritive value.

A method of dealing with solid waste is compaction and polymer impregnation, followed by curing, to produce structural materials which may be used to replace wood, aluminum or concrete. Polymerimpregnated concrete is well known to be stronger than conventional Portland cement concrete. The strength of radiation-polymerized material is improved up to 38% greater than the thermally polymerized ones. The strengths of 11,300 lbf/in² for sewage-cement-polymer concrete and 4000 lbf/in² for refuse-cement-polymer were made with several kinds of paper, sawdust, straw, cloth, hair, solid waste and sludge, cured with a total absorbed dose of 8 to 10-60 kGy. Strength and hardness were comparable with or superior to standard structural materials such as concrete, wood or aluminum.

Korea Atomic Energy Research Institute (KAERI) developed the radiation treatment technology of sewage sludge. Poly Aliphatic Hydrocarbons (PAHs) such as naphthalene, acenaphthylene, acenaphthene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene and benzo(b)fluoranthene contained in sludge were effectively reduced by less than 10 kGy radiation, and their toxicities could be also reduced. The mixture of sewage sludge and starfish were irradiated by electron beam for the preparation of fertilizer, named “green soil”. The effectiveness of green soil as a fertilizer was investigated for some vegetables and trees. KAERI also studied the recycling technology of sewage sludge. The organic carbon source was recovered from sewage sludge by radiation. It was effectively used for biological wastewater treatment.