Performance evaluation of a pilot wetland system for wastewater treatment

Abstract

Wetland systems are inexpensive and easy-to-operate wastewater systems and are widely used globally at different scales for the safe treatment of wastewater. This study aims to evaluate a pilot-scale vertical flow wetland system treating wastewater under different loadings. The wetland system was constructed using indigenous plants (Imperata cylindrical) and operated using actual wastewater for twelve-months. Samples from influent and effluent of the wetland system were collected weekly. They were analyzed for parameters listed in the Kuwait Environment Public Authority standards for reuse in irrigation, such as organic matter, nutrients, heavy metals, and microorganisms. The results showed that the high hydraulic loading rate (1.67 m3/m2.d) phase was more efficient than the low hydraulic loading rate (1.04 m3/m2.d) phase in terms of organics and nutrient removal efficiency. The range of the removal efficiency of organic matter in low and high loading rates was around 48.5–49.0% and 59.1–59.1%, respectively. In addition, the range of the removal efficiency of nutrients in low and high loading rates was around 43.7–67.7% and 24.7–76.6%, respectively. Moreover, the range of the removal efficiency of heavy metals under the low and high loading rates was − 134.3–93.8% and − 1545.7–92.6%, respectively. It was evident that he metals were leaching from the soil. Moreover, it was found that the system performance was closely linked to the ambient temperature effects during the start-up (r = 0.59) and high hydraulic loading (r = 0.43) phases for example. While ambient temperature has wider effects on wetland biota, its effects on the plants are more pronounced. In conclusion, wetland systems can be constructed using indigenous plants to treat office wastewater efficiently under the harsh climate conditions of Kuwait with adjustments in capacity, loading rates, and operational conditions.