Hybrid constructed wetlands for tertiary treatment of poultry slaughter wastewater to meet quality standards of discharge and reuse: a full-scale case study in Vietnam

The construction and operation of a small-scale hybrid constructed wetland (HCW) system for tertiary wastewater treatment was presented. The HCW system includes a vertical sub-surface flow CW (VFCW), a horizontal sub-surface flow CW (HFCW), and a free water surface flow CW (FWSCW). Operated in series, it had a total area of 150 m2. It received 7.5 m3day of secondary effluent wastewater from the existing treatment system of a poultry slaughter enterprise at the production capacity of 500 ducks per day in an on-site experiment of 12 months. The results showed that the removal efficiencies of biological oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total nitrogen (TN), orthophosphate (PO43--P), total phosphorus (TP), Escherichia coli (E. coli), and total coliforms (T. coli) reached average values of 76.2, 78.7, 77.1, 83.9, 86.3, 84.9, 72.3, 73.9, 98.9, and 96.4%, respectively, while the effluent concentrations of the study system complied with the most difficult limits not only for discharge into the receiving water source but also for reusing wastewater to water plants. The function made by various configurations such as a VFCW, a HFCW, and a FWSCW placed sequentially in the HCW system proved crucial to treat wastewater and make it reusable.