| Fly ash is a solid waste produced from coal-fired power plant and smelting, by combusting coal at high temperature. Currently, fly ash has become one of the major industrial solid wastes in China. Fly ash is applied to wastewater treatment, because of its porous structure and specific surface area. In recent years, urban non-point source pollution is serious, having affected human life production. In this paper, the infiltration system is constructed with fly ash infiltration system to deal with urban non-point source pollution. It not only can reduce the fly ash of excessive accumulation of effects on the environment, but also can achieve the result of using waste treat waste. Based on statistical analysis of storm runoff rainwater load both at home and abroad, rain runoff pollutants and the load is determined. Through researching on the indoor artificial soil infiltration system treat artificial compound water, verified the possibility using fly ash as infiltration substrate to treat the urban non-point source pollution, discussing the main pollutants removal performance. The main contents are as follows:1. The physical and chemical properties of fly ash are analyzed. The results showed that the fly ash mainly composing SiO2 and Al6Si2O13 had a pH of 8.10, density of 1.7-2.2g/cm3, diameter of 0.01-0.1mm and specific surface area of 0.3-0.6m2/g, respectively.2. The adsorption dynamics of the fly ash is studied, results show that the adsorption of phosphate by fly ash followed a linear curve and could be described by the secondary kinetic equation while the adsorption of ammonia did not performed with any curve but also could be described by the secondary kinetic equation. By using the fitting equation, we obtained fly ash adsorption equilibrium time of phosphate and ammonia nitrogen was 6 h and 3 h, respectively. Fly ash can ensure finished in shorter time of ammonia nitrogen and phosphorus removal.3. Filtration device was simulated indoor. Using artificial rain researched on the removal efficiency and mechanism. And the early running results show that the TOC, TN, ammonia and TP concentration was reduced by 90%,40%,90% and 90%, respectively, which is in accordance with the requirement by stormwater control practices. Therefore, even though this study was only operated with around 70 days, during which the biological effect did not work while only the adsorption effect worked, the result has proved that the fly ash can be used as infiltration media.In the studied infiltration system, the removal of organic mater、 ammonia and phosphorus mainly took place in the initial 10 cm fly ash of the top while the reduction of TN in the 0-40cm. This result indicates that the height of infiltration can decreased to some degree to reduce the construction cost. On the other hand, considering that the adsorption of phosphate and ammonia by fly ash reached balance within very short time (6 hr for phosphate and 3 hr ammonia, respectively), the HRT of infiltration can be modified form 2 days to 1 day. However, the effect of microorganisms and plants should be investigated in the future study. Because as the extension of running time and the embodiment of the microbial effect, its removal efficiency of pollutants, especially the improvement of nitrogen removal have larger space, on the basis of this can be further optimized design and reasonable operation parameters were determined. |
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