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Experimental Study on Seepage and Purification of Modified Fly Ash as the Substrate of Constructed Wetlands

An experiment on seepage and purification by modified mixtures of power plant fly ash and soil at different mass ratios was studied for developing a novel high efficient substrate of constructed wetland. The results showed that the soil’s osmotic coefficient can be improved by mixing fly ash and soil. The different mass mixing ratios of ash and soil had little effects on the removal of total nitrogen in wastewater, comparatively they had positive effects on the removal of total phosphorus and ammonia nitrogen. The phosphorus’s removal efficiencies were maintained at 81.94%~89.68%. The average removal efficiency of ammonia nitrogen was 85%, and the 4:6 level obtained the best removal efficiency, which was 93.41%. The different mass mixing ratios of ash and soil had obvious effects on COD removal of wastewater. The 1:9 and 0:10 levels gained higher removal efficiencies than others, whose removal efficiencies were 95.16% and 95.39%, respectively.