Application of a constructed wetland for industrial wastewater treatment: A pilot-scale study

The main objective of this study was to examine the efficacy and capacity of using constructed wetlands on industrial pollutant removal. Four parallel pilot-scale modified free water surface (FWS) constructed wetland systems [dimension for each system: 4-m (L) × 1-m (W) × 1-m (D)] were installed inside an industrial park for conducting the proposed treatability study. The averaged influent contains approximately 170 mg l−1 chemical oxygen demand (COD), 80 mg l−1 biochemical oxygen demand (BOD), 90 mg l−1 suspend solid (SS), and 32 mg l−1 NH3–N. In the plant-selection study, four different wetland plant species including floating plants [Pistia stratiotes L. (P. stratiotes) and Ipomoea aquatica (I. aquatica)] and emergent plants [Phragmites communis L. (P. communis) and Typha orientalis Presl. (T. orientalis)] were evaluated. Results show that only the emergent plant (P. communis) could survive and reproduce with a continuous feed of 0.4 m3 d−1 of the raw wastewater. Thus, P. communis was used in the subsequent treatment study. Two different control parameters including hydraulic retention time (HRT) (3, 5, and 7 d) and media [vesicles ceramic bioballs and small gravels, 1 cm in diameter] were examined in the treatment study. Results indicate that the system with a 5-d HRT (feed rate of 0.4 m3 d−1) and vesicles ceramic bioballs as the media had the acceptable and optimal pollutant removal efficiency. If operated under conditions of the above parameters, the pilot-plant wetland system can achieve removal of 61% COD, 89% BOD, 81% SS, 35% TP, and 56% NH3–N. The treated wastewater meets the current industrial wastewater discharge standards in Taiwan.