One of the biggest problems at present century that we face with, are wastes and how to use them correctly. Chlorobenzoates are the big xenobiotics that are mediator in making of insecticides, dyes and drugs. They are entered into environment through residue destruction and analysis of PCBs by human. The purpose of this research is isolation and identification of 2,5-dichlorobenzoic acid (DCBA) degrading bacteria and examining the growth of them in presence of this compound and also evaluating and justifying biodegradation of mentioned compound in landfill. Sampling was done from different places of landfill in spring and summer of 2010. Amount of 4.0g of sample was added to inorganic medium containing 2,5 -DCBA, then aeration was done every day for one minute. For identifying bacteria, the common biochemical tests were used. The amount of released colure was measured with UV. The measurement of the organic material 2,5-DCBA in samples of culture of 50 days was then examined by HPLC. The number of bacteria in medium containing 2,5-DCBA and the medium without this compound was accounted. In medium without 2,5-DCBA, the number of bacteria was more than the mineral medium containing this material. In spring, most of degrading bacteria was gram negative while in summer was gram positive. Resistant bacteria to 2,5-DCBA was identified and isolated as: Bacillus sp., Corynebacterium, Enterobacter, Klebsiella, Citrobacter, Neisseria. The most quantity of degradation of 2,5-DCBA was belonged to Entrobacter 62% and Corynebacterium 48% and least quantity determined by Bacillus sp.14% bacterium. The results of the research also showed the advantage of primary enriching method for better isolation of bacteria in compare with direct culture of them.
