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| Wastewater treatment performance of a pilot-scale airlift oxidation ditch. |
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Abstract The wastewater treatment performance of a pilot-scale airlift oxidation ditch (AOD) was studied in a wastewater treatment plant near the Taihu Lake. The main process parameters that can satisfy the current discharge standard were obtained. It was possible to achieve a COD effluent concentration <50mg/L at the maximum loading rate of 0.88kg/(m3·d). The ammonium nitrogen concentration of the effluent could be lower than 5 mg/L with a loading rate less than 0.06kg/(kg·d). After the dissolved oxygen in the straight part was maintained between 0.6~1.0mg/L, total nitrogen (TN) concentration in the effluent was less than 15mg/L and kept steadily for over 14 days. The average TN concentrations of the influent and effluent were 30.7mg/L and 11.3mg/L, respectively. When air flow rate was 30m3/h, a velocity of 0.19m/s in the bottom of straight part was sufficient to prevent the settling of activated sludge. Liquid velocity in the top of straight part was only 0.03m/s, but it did not interfere with the removal of organic pollutants. Technical and economic evaluation showed that a large-scale AOD will save at least 25% land area compared with the conventional oxidation ditch.
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Received: 17 November 2008
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