PERFORMANCE OF A THREE-STAGE TOWER EARTHWORM ECOFILTER FOR SIMULTANEOUS REMOVAL OF CARBON AND NUTRIENTS FROM DOMESTIC WASTEWATER

摘要

A three-stage tower earthworm eco-filter was designed and constructed to remove carbon and nutrients simultaneously from domestic wastewater. The first and second stages provided good aerobic conditions for nitrification, while the third stage provided suitable conditions for denitrification in the presence of external carbon (glucose). The influence of temperature, hydraulic load (HL) and carbon to nitrogen (C/N) ratio of tertiary influent on the performance of tower earthworm eco-filter was investigated in this study. During stable operation period, this system performed well on various pollutants removal, with the average chemical oxygen demand (COD), total phosphorus (TP), nitrate nitrogen (NO_3-N), nitrite nitrogen (NO_2-N), ammonium nitrogen (NH_3-N), and total nitrogen (TN) in tertiary effluent at 17.59, 0.12, 2.79, 0.044, 0.76 and 4.08 mg/L, respectively. All pollutants removal showed independence on temperature. It was found that the effluent concentrations of TN, NO_3-N and COD were related to HL. With the increase of HL from 0.25 to 0.50 m/d, the average TN, NO_3-N and COD in tertiary effluent increased from 4.67 to 7.40 mg/L, from 3.05 to 6.28 mg/L, and from 15.17 to 19.75 mg/L, respectively. The variation in C/N ratio of tertiary influent affected TN and NO_3-N removal, and more than 95% of TN removal occurred at tertiary influent C/N ratio in the range of 4.76-7.41.