EXPERIMENTALLY STUDY OF NITRATE DEGRADATION IN GROUNDWATER IN PRESENCE OF PYRITE

Saeid Sotoodehnia1, Ali Mahdavi2, Andre Banning1, Stefan Wohnlich1
1 Institute for Geology, Mineralogy, and Geophysics, Ruhr-University Bochum
2 Water Engineering Dept., Imam Khomeini International University, Visiting professor at Ruhr-University Bochum

1.13 in Wasserqualität in Grundwasser und Flusseinzugsgebieten

Agricultural activities from a global perspective visibly show a major role in declination of the quantity and quality of groundwater resources (Burri et al., 2019). Agricultural fertilizers and pesticides permeate to the groundwater during irrigation and made water polluted, therefore by utilizing the nitrate as a commonly used fertilizer, we can expect an increase in nitrate concentration of the groundwater resources. To avoid the accumulation of nitrate in the soil, one we can apply is Pyrite (FeS2) as a rich sulfide mineral in nature which has a considerable effect on denitrification rate (Schweintek et al., 2008). Although much research has been done in recent years on the role of elemental sulfur in groundwater treatment, less work has been focused on the pyrite (Pu et al., 2014). A research in 2012, using a Sequencing Batch Reactor showed that autotrophic denitrification will remove 100% and 67% of sulfide and nitrogen, respectively. However, they showed that in the pH values higher than 9.0, the efficiency of sulfide oxidation into sulfate decreases to 11.3%(Fajardo et al., 2012). The result of a six-month study using two anoxic and anaerobic reactors with continuous upward flow showed that the average amount of nitrate declined by 74% (Neshat et al., 2017). In the present study, the denitrification process using pyrite from three different mines in Iran is experimentally studied. The first one originated from Sungun copper mine, located in Varzaqan county, East Azarbaijan, Iran (38°42′04″N 46°42′18″E), the second one extracted from Smalun Iron Mine, Marvast, Yazd Province, Iran(30°57'28.32"N 54° 1'40.05"E) and the third sample extracted from Sarcheshmeh copper mine, Kerman province, Iran(29° 59′ 5″ N 55° 51′ 14″ E). We used batch reactor experiments to examine the denitrification process. There were several different concentrations of pyrite and nitrate with varied time from 0 to 144 hours. The effect of pH and temperature on the denitrification process is also investigated. The results showed that among the three different samples, samples with higher pyrite content had a more effective role in nitrate uptake than other samples.



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