Removal of nitrate from groundwater in situ with liquid carbon sources

Limited water resources will be available if the quality is desirable today, by entrance of extensive industrial activities and the use of fertilizers in agriculture, the most important source of human life is in dangerous. According to researchers result, groundwater contamination is often due to poisoning wastewater from industries or from wastewater reservoir resources, one of the most important pollutants is nitrate. Nitrate in nature can be exchange to nitrogen or other forms by microbial activity. There are various methods for removing nitrate from water those most commonly using denitrification substrates. It has been proposed to create a wall of denitrification as a buffer against nitrate contaminated streams as a suitable way to prevent the entering of nitrate into groundwater resources and then surface water resources. In this research, tried to study the effect of nitrification using denitrification substrates that containing a mixture of soil and four carbon sources of liquid including glucose, acetate, ethanol and methanol. In this research, a Plexiglas column was used as a pillar of Marriott and water source and a porous media column filled with soil with a loamy clay texture of 50 cm length and 10 cm in diameter. Potassium nitrate salt was used to make a concentration of 100 mg / L nitrate solution. This study was carried out in two ratios of 1.5 and 3.5 C / N, and the concentration of nitrate was measured until when the pore volume reach to 10 and also concentration of nitrate output was stabilized. This research was carried out at the research laboratory of the Water Engineering Department of Shahrekord University. After about 250 hours from the start of the biological removal process, it was observed that the concentration of output nitrate was almost constant and there is not much change. This phenomenon may be due to the growth of bacteria because of the favorable growth conditions at the beginning of the experiment and the optimal separation of nitrate in a process and, finally, the lack of one of the factors affecting growth due to the maximum growth of bacteria. It is clear that at the end of the experiments and after the concentration of nitrate output from the column was fixed, green algae were observed in parts of the absorption column due to bacterial growth and massification. The removal efficiency of nitrate by glucose, acetate, ethanol and methanol was 97.83%, 97%, 98.66% and 99% respectively, and so methanol had the most efficiency in nitrate removal. Methanol, with 99% removal efficiency, can easily remove nitrate to a concentration of 100 mg / L at groundwater reduce to 2.1 mg per liter. Methanol with 131,000 bacteria had the highest bacterial growth rate in the C / N ratio of 3.5. In fact, by increasing the concentration of carbon, the growth rate of the bacteria increased and the concentration of nitrate decreased. In statistical analysis, both carbon-to-nitrogen ratios showed significant differences in carbon-nitrogen ratios other than glucose-acetate, with a significant difference in the mean carbon concentration. Also a paired test between different concentrations of a carbon source showed that there is a significant correlation between concentrations of 1.5 and 3.5 for each carbon source.