ORIGINAL ARTICLE Effects of gamma radiation on wastewater microbiota Sandra Cabo Verde 1 • Telma Silva 1 • Paula Matos 2 Received: 26 February 2015 / Accepted: 5 September 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract Wastewater treatment by gamma radiation is a promising technology, with the capacity to reduce the impact of chemical and biological pollution of effluents in the environment. The aim of this study was to find out the effect of gamma radiation on the inactivation response of wastewater microorganisms. Wastewater samples were irradiated at a Co-60 facility, at different dose rates and at sublethal doses. The D10-values of total coliforms and mesophilic microbiota were determined for each sample and dose rate. Radio-resistant microorganisms in wastew- ater samples were isolated and their growth and inactiva- tion kinetics in different composition substrates were determined, to find out the capacity of these bacteria to biodegrade the organic content of the wastewater. The results obtained suggest that irradiation substrate and dose rate influence the response of microorganisms to gamma radiation and could be also important factors for bioremediation. Keywords Wastewater Á Gamma irradiation Á Microbial inactivation Á Coliforms Á Dose rate effect Á Substrate effect Introduction The contamination of water resources by pollutants from industry, municipal and agriculture discharges is increasing worldwide. This may lead to health risks and even jeop- ardize human survival (e.g., contaminants in water, air, soil, etc.). Control and remediation of these pollutants are necessary to prevent us harming ourselves and future generations. Moreover, the increasing demand for drinking water in many countries often faces two main problems: the scarcity of drinking water and the proper processing and disposal of increasing amounts of wastewater. One solution to these problems is to process wastewater for reuse. The purification of wastewater has been and con- tinues to be a prime environmental issue. Although con- ventional wastewater treatment systems such as shallow maturation ponds have the capacity to improve effluent quality, they are not sufficient to remove all contaminants (Von Sperling and Mascarenhas 2005). In contrast, disin- fectant agents act by inducing biochemical changes in both pathogenic agents and the effluent (Blatchley et al. 1997). Wastewater disinfection methods include chlorination, ozonation and ultraviolet (UV) radiation. The International Atomic Energy Agency (IAEA) has published many documents, which draw attention to the considerable potential of radiation technology to clean up waste discharges from various industrial and municipal activities (IAEA 2001). Irradiation treatment has proven to be a powerful tool in inactivating human pathogenic microorganisms in water, wastewater and sludge, as well as in food and medical products (Farooq et al. 1993; Lagunas- Solar 1995; Rawat et al. 1998; Basfar and Abdel Rehim 2002; IAEA 2004; Wang and Wang 2007). One of the main advantages of such treatment is the fact that because irradiation is a physical process, no chemicals & Sandra Cabo Verde sandracv@ctn.ist.utl.pt 1 Centro de Cie ˆncias e Tecnologias Nucleares, Instituto Superior Te ´cnico, Universidade de Lisboa, Estrada Nacional 10, km 139, 7, 2695-066 Bobadela LRS, Portugal 2 Laborato ´rio de Aceleradores e Tecnologias de Radiac ¸a ˜o, Instituto Superior Te ´cnico, Universidade Te ´cnica de Lisboa, Estrada Nacional 10 km 139, 7, 2695-066 Bobadela LRS, Portugal 123 Radiat Environ Biophys DOI 10.1007/s00411-015-0617-2