Applications of Bacterial Biotechnology in the Bioremediation of Water Contaminated with Heavy Metals

Heavy metals contaminated soil and water samples were collected from the Tigris River Power Plant, Baghdad. The bacterial isolation was performed by using the culturing technique on proper nutrient media prepared with low a concentration of heavy metals such as lead and mercury. The isolated strains were tested for their growth capability in heavy metal-polluted media by the polymerase chain reaction method for the identification of genes that provide resistance or degradation of heavy metals. Isolation and determination of heavy metal-resistant bacterial strains from genera like Pseudomonas, Bacillus and Streptomyces, which showed high tolerance to lead and cadmium.

The aim to analyze environmental factors like pH, temperature, carbon sources and nitrate that would affect bacterial growth. Efficiency of bacteria in the removal of heavy metals from contaminated water was also determined by atomic absorption spectroscopy by comparing the concentration of metals before and after treatment.

The study showed that significant soil and water contamination was present around the power plant area, emanating from industrial activity: lead concentration ranged from 100-500 ppm and cadmium from 5-30 ppm in soil. Water concentrations were above the safety limits set by WHO for lead and cadmium, ranging between 0.1-1 ppm and 0.01-0.1 ppm, respectively, showing slight decreases after discharge into the Tigris River but remaining above natural levels. Some of the bacterial strains, like Pseudomonas, Bacillus and Streptomyces, which are resistant to heavy metals (Pb: 50-100 ppm and Cd: 5-20 ppm), were isolated. Genetic detection identified genes that code for resistance, including czcA and merA; however, it lacked the gene pbrT. Thus, the capability for lead removal is very limited.