Pilot study of constructed wetlands for tertiary wastewater treatment using duckweed and immobilized microalgae

Duckweed-microalgae constructed wetland (DM-CW) was a continuous flow pilot wetland used in wastewater phytoremediation assays. This study investigated the microbial and chemical wastewater quality before and after treatment in order to evaluate the DM-CW efficiency. Results indicated that with 3 days as hydraulic residence time, the hydraulic efficiency was high and allowed significant removal for chemical and microbial parameters. COD, BOD and ammoniacal nitrogen removals were the highest with a percentage of 67.5 +/- 8.2, 70.6 +/- 9.5 and 65.9%, respectively. Total phosphorus removal was acceptable (21.5%) but was closely related to the algal growth. Total and faecal coliforms percentage removals were respectively 68.5 and 47.16%. The quality of the treated wastewater issued from the DM-CW was approved and can be reused in the agriculture domain.