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| Long term performance of pilot-scale vertical flow constructed wetland using different substrates |
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Abstract In order to investigate the long-term performance of pilot-scale vertical-flow constructed wetland (CW), different substrates, including zeolite, anthracite, shale, vermiculite, ceramic filter media, gravel, blast furnace steel slag and bio-ceramic were used. Column experiments were carried out in a greenhouse, and their purification performance at a high hydraulic loading rate of 2400~3400 mm/d was assessed. The whole experiment lasted for 25 months. With the operation of the systems, COD removal rates by all the substrates increased gradually in varying degrees; nitrogen removal by zeolite maintained at a high and stable efficiency, among which the removal rates of total nitrogen (TN) and ammonia nitrogen (NH4+-N) were up to 82.03% and 91.32%, respectively. The removal rates of total phosphorus (TP) and soluble reactive phosphate (SRP) by steel slag reached 89.61% and 96.77%, respectively. Removal efficiency of phosphorus by anthracite was lower than that by steel slag during the second stage, whereas no significant differences between them during the following stages. Proper selection of long-term high-efficiency substrates (e.g., zeolite, anthracite and bio-ceramic) based on the characteristic of wastewater was a guarantee of better performance at a high hydraulic loading rate.
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Received: 21 September 2009
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