English abstract
Increasing population and extensive use of ground water resources lead to intrusion of sea water in aquifers adjacent to most coastal areas resulting in an increase in water salinity and bacterial contamination. Highly contaminated brackish water is not suitable for human, animals and plants consumption. There is a big demand to search for a suitable method to treat saline and contaminated ground waters. Capacitive deionization (CDI) technology deionizes sea water by application an electrical potential across two electrodes. During desalination process (treatment) the ions leave the water and absorbed by the charged electrodes resulted in low outlet ionized water. The absorbed ions released back to the water during the regeneration process when the electrical potential equals, resulting in highly ionized outlet water. This project was aimed to study the efficiency of CDI in reducing densities of microorganisms in contaminated brackish water samples. The total bacterial number, densities and percentages of dead and live cells were compared before and after desalination of artificial (made from distilled water and NaCl) and natural (collected from Mussanah) contaminated brackish water with CDI operated at 1.6V, 130mA and flow rate 3ml/min, The CDI bacterial removing efficiency and cleaning of saturated electrodes also have be tested in this project. The results showed that CDI reduced by 20-70% the total number of bacteria, number of pathogens, as well as numbers of viable cells in natural and artificial contaminated brackish water. The efficiency of CDI in removing bacteria was higher for artificial water than for natural one due to the different nature of the water samples. Initial salinity, concentration of bacteria, solid substances and ions in the water, as well as the CDI cell size, flow rate, current and voltage affect the removing efficiency of the CDI. At the end of each treatment cycle CDI was regenerated, which increased the number of bacteria in water. After five treatment cycles the efficiency of CDI in removing bacteria decreased and washing with Citric Acid solution and NaOH solution restored the antimicrobial properties of the CDI cell. In conclusion, this study suggested that CDI technology can be used for removal of microorganisms from contaminated brackish water.
