The pollution produced in coal based thermal power plants is a big threat to the plant employees, in particular the Coal Combustion Residues (CCRs) such as fly ash, bottom ash and others. CCRs could be useful in producing other useful products. However, their wrongly disposal to the soil or rivers is harmful to the environment. Arsenic is one of the toxicants appearing in relatively high concentrations in the residues of some coal fired power plants. The conventional chemical treatment of this toxicant is generally expensive. Therefore, a biological alternative treatment has been proposed, which is simple and less expensive. This process involves isolating two microbial species that are resistant to relatively high arsenic concentrations. The effects of temperature and ratio of biomass to substrate on the species growth have been investigation. It was observed that both species survived arsenic concentration up to 0.154 ppm in broth medium and 1.923 ppm on agar plate.