Polishing Domestic Wastewater on a Subsurface Flow Constructed Wetland: Organic Matter Removal and Microbial Monitoring
2011
Mina, I Aguiar-Pinto | Costa, M. | Matos, A. | Calheiros, C Sousa Coutinho | Castro, P. M. L.
Microbial monitoring of constructed wetlands (CWs) treating domestic wastewater is generally scarce, despite the need of more knowledge about its biocenosis. The sanitation quality of a wastewater treated in a CW is a crucial aspect, mainly when the receiving water body is used as a swimming and/or recreation area. The present study was carried out in a horizontal subsurface flow CW planted with Phragmites australis receiving pre-treated domestic wastewater (mean flow 50 m³ day⁻¹), from a population of about 300 inhabitants. The monitoring programme undertaken during the first year operation, revealed removal efficiencies of 61% BOD₅, 44% COD, and 65% TSS for inlet water with ca. 90 mg L⁻¹ BOD₅, 157 mg L⁻¹ COD, and 17 mg L⁻¹ TSS. Total Coliform (TC) and Faecal Coliform (FC) bacteria were removed from wastewater (mean inlet values of 5 × 10⁶ CFU 100 mL⁻¹ TC and of 9 × 10⁵CFU 100 mL⁻¹ FC), with efficiencies of 92 and 97%, respectively. The dynamics of microbial communities established in the system assessed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), had revealed a high bacterial diversity within the system, with no relevant differences in composition at the CW inlet and outlet but exhibiting temporal differences in bacterial communities.
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