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| Clogging of vertical subsurface flow constructed wetland and its effects on purifying efficiency |
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Abstract The clogging of vertical subsurface flow constructed wetland (VSSF) and its effects on purifying efficiency were investigated during treating digested swine wastewater. The results suggest that accumulation of non-filterable material in substratum layer was the main cause resulting clogging in the VSSF, and the non-filterable material consists of both organic substances and inorganic substances, which sizes of the most part of granular non-filterable material were larger than 5.00 micrometers. Porosity and hydraulic conductivity of the substratum layer decreased, and the content of the non-filterable material in the substratum layer increased correspondingly with the operation of the VSSF. The spatial variation profiles of them alone the vertical direction depended on vertical flow state of the wastewater fed onto the substratum layer. As the hydraulic loading rate was kept at 0.02m3/(m2·d), the purification effect of the VSSF deteriorated after operations of 1380 days, which the removal efficiencies of COD, TSS, TN, ammonium nitrogen and TP declined to 37.31%, 57.82%, 20.80%, 32.13% and 51.18%, respectively.
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Received: 10 December 2014
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