| With the development of the society and the level of industrialization, water demands become bigger and bigger. At the same time, due to the unreasonable utilization of water resources, serious water waste and water pollution phenomenon is aggravating. There are many different kinds of water pollutants in water, we select the nitrate in groundwater and antibacterial agent ciprofloxacin were studied in this paper.Firstly, nitrate reduction by Fe2+ and Fe0 were discussed. It found that nitrate reduction by Fe0 or Fe2+ alone, under neutral condition, is not ideal. Reduction efficiency improved significantly once combining Fe2+ and Fe0. The intermediate of nitrate reduction was NO2- and NH4+ were produced after reaction. Furthermore, electronic mainly comes from Fe0 in the reaction. With the increase of initial concentration of Fe2+ and NO3-, nitrate degradation accelerated significantly; the depletion of Fe2+ have a connection with nitrate reduction. Fe2+ was consumed, NO3-reduction significantly decreased; Once NO3- reduction stopped, Fe2+ was no longer changed. Nitrate reduction by Fe2+ and Fe0 occurred on the surface of the iron powder; Zero-order dynamic model can match the process properly; Fe3O4 generated rapidly when Fe2+ was added to the system of Fe0 and nitrate. In addition, factors influencing nitrate reduction was conducted. Results showed that appropriate iron powder, ferrous ions and near neutral condition were benefit to NO3- degradation.Secondly, degradation of nitrate was studied by microbial and zero-valent iron in the following experiment. At the beginning, microorganism separation experiments were conducted from pipe scales, which were collected in drinking water distribution system. And then DNA extraction and PCR amplification were carried. Finally, sequencings were determined to verdict the type of bacteria. Nitrate reduction was researched using separated three kinds of bacteria(SYQ---6, GSM---8, LF---7), together with iron powder. Results demonstrated that compared with SYQ---6 and GSM---8, LF---7 had a better nitrate reduction; NO2- were produced on the NO3-degradation. Combined with iron powder. NH4+ was not detected. What's more, total nitrogen was always decreasing during the reaction, which probably converted to nitrogen gas. Acetic was not changed in the process of reaction. LF---7 may be an autotrophic bacteria, Which fed on iron during nitrate reduction. It needs to be confirmed. pH maintains at around 10 after nitrate denitrification.Finally, ciprofloxacin degradation was conducted, which taking simulated pipe network as reaction vessel. First of all, taking chlorination of ultrapure water as inlet was carried. Results showed that ciprofloxacin was degraded in simulated pipe network. Hypochlorous acid fell in the reaction. Corrosion production of iron, microbial or hypochlorite at work need to be confirmed.Since simulated pipe network had a good degradation on ciprofloxacin, choosing water after carbon in water plant substitude ultrapure water to research. High performance liquid chromatography was used to analyze Ciprofloxacin degradation products.Results showed that in the same ciprofloxacin initial content, the pollutant in water after carbon was slightly higher than that in ultrapure water; It was probably due to water after carbon contained a spot of ciprofloxacin precursors. In two group of pipe network, the production was the same. Structure of it remains to be further confirmed. Liquid Chromatogram- mass spectrometry demonstrated that taking ultrapure water as inlet and that in water after carbon mainly generated the product of 263 and 306(m/z). Also, the latter produced 334( m/z) substance and changed obviously than the former; DOC and three-dimensional fluorescence were determined in the reaction; Reaction system was gradually stable with the reaction processing; The composition of pipe scale and resistant microbe were also monitored. XRD showed that the simulation pipe using water after carbon Fe3O4 was less in outer scale, while it was no change inner; 16 s rRNA and resistant microbe demonstrated that total microorganism reduce during the process of reaction, resistant microbe decreased in the biological membrane and increased in pipe scale. |
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