American Journal of Environmental Protection, 2013, Vol. 1, No. 1, 14-16 Available online at http://pubs.sciepub.com/env/1/1/3 © Science and Education Publishing DOI:10.12691/env-1-1-3 Chromium Removal by Using Chosen Pseudomonads T. Raghuraman 1 , C. Jerome Geoffrey 1 , S. Suriyanarayanan 1 , A. J. Thatheyus 2,* 1 Department of Immunology and Microbiology, The American College, Madurai, India 2 PG and Research Department of Zoology, The American College, M adurai, India *Corresponding author: jthatheyus@yahoo.co.in Received December 26, 2012; Revised January 18, 2013; Accepted March 03, 2013 Abstract Tannery effluent is a major source of aquatic pollution in India. Hexavalent chromium compounds are being used in a wide variety of commercial processes and unregulated disposal of the chromium containing effluent has led to the contamination of soil, sediment, surface and ground waters. In trace amounts, chromium is considered an essential nutrient for numerous organisms, but at higher level, it is toxic and mutagenic. Therefore in the present study three strains of Pseudomonas such as Pseudomonas aeruginosa , P. fluorescens strain 1 and 2 were isolated from the collected tannery effluent samples. All the three strains showed more than 60 percentage of reduction for all chromium concentrations (500, 1000, 1500 and 2000ppm) tested. Keywords: chromium, tannery, effluent, pseudomonas 1. Introduction Nearly 80% of the tanneries in India are engaged in the chrome tanning processes. Heavy metals, the major constituents of industrial effluents are not usually eliminated from the aquatic systems by natural processes in contrast to most organic substances. Heavy metals, such as mercury, lead, chromium, nickel, copper, cadmium and zinc, are of considerable concern because they are non- biodegradable, highly toxic and probably carcinogen. They tend to accumulate in bottom sediments from which they may be released by various processes of remobilization and in changing form can move up the food chain and cause various chronic and acute ailments [1]. Wastewater of industries like coil coating, ferroalloys, inorganic chemicals, iron and steel, leather tanning and finishing (including electroplating), petroleum refining, porcelain enameling, textile manufacturing and timber products contain chromium [2]. The toxicology of chromium compounds has been reviewed by USNAS, IARC and Taylor [3,4,5] . Chromium (Cr) reacts with nucleic acids and other cell components to produce mutagenic and carcinogenic effects on biological systems [6]. Conventional methods of Cr removal include chemical reduction followed by ion exchange, precipitation and adsorption on activated coal, alum, kaolinite and ash. But they require large quantities of chemical reagents and high amount of energy [7]. Several treatment processes have been suggested for the removal of heavy metals from aqueous waste streams: adsorption, biosorption, ion exchange, chemical precipitation and electrochemical methods: electrowinning, electrodialysis, electrodeionization, membrane-less electrostatic shielding, electrodialysis and electrocoagulation which are highly expensive. But microbial methods are cost effective and efficient [8]. In the present work, an attempt has been made to employ chosen bacteria Pseudomonas aeruginosa and Pseudomonas fluorescens in the bioremediation of tannery effluents. 2. Materials and Methods The tannery effluent samples were collected from the leather industries at Tiruchirapalli and Dindigul in sterile containers. They were brought to the laboratory immediately and analysed for the concentration of chromium using Atomic Absorption Spectrophotometer (AAS). The effluent samples were serially diluted with sterile distilled water and plated on to nutrient agar (Himedia, Bombay) medium. The plates were incubated at 37°C for 24 hours. Among the bacterial colonies grown, three dominant colonies were selected and cultivated in nutrient broth for eight hours. This three isolated organisms were subjected to biochemical tests for tentative identification following Bergy‟s ma nual of Systematic Bacteriology [9]. After testing the resistance of the chosen bacterial strains to different concentrations of chromium prepared by dissolving required amount of potassium chromate (K 2 Cr 2 O 7 ), 500, 1000, 1500 and 2000 ppm concentrations were selected for the experiment. Minimal broth (Dipotassium hydrogen phosphate 7g; Potassium dihydrogen phosphate 2g; Ammonium sulphate 1g; Glucose 1g; Sodium citrate 0.5g; Magnesium sulphate 0.1g made upto 1litre.) was prepared and autoclaved at 115°C for 15 minutes and was cooled in a water bath at 45-50°C. In 250ml Erlenmeyer flasks, 100ml minimal broth was taken along with the above mentioned concentration of chromium. Under aseptic conditions, the three chosen organisms were inoculated individually into these flasks with 10 9 cells (0.1ml). The flasks were incubated at room temperature. Uninoculated control flasks were also maintained in the same manner. After