Efficacy Evaluation of Two Plant Macrophytes in a Vertical Flow Constructed Wetland for Domestic Wastewater Treatment

Abstract

Constructed wetlands are engineered systems, constructed and designed to employ the natural functions of emerging macrophytes, soils, and microbial populations to remove multiple contaminants from raw wastewater to reduce environmental deterioration and increase water availability by improving the wastewater quality. To practically develop artificial wetlands in Algeria and especially in the Saharan zone with an arid climate, locally available macrophyte species (Phragmites australis and Acacia) were tested. To evaluate the treatment efficiency of each macrophyte and especially Acacia in this arid region compared to the control, the experiments were carried out for 3 months (February, March, and April) with measurements taken at the beginning of each month for untreated water and every 10 days for treated water. Therefore, the main objective of this review article is to judge the performance of two aquatic plants (Phragmites australis and Acacia) regarding the domestic wastewater pollutants removal under arid climate conditions. It was found in the work that the wastewater treatment efficacy of the two aquatic macrophytes was very remarkable. The overall results show that the pH values recorded before and after treatment are lower than the limit values of Algerian discharge standards and the World Health Organization (WHO) standards (8.5). The electrical conductivity (EC) values recorded in treated water strongly exceed those before treatment. The bed grown with Phragmite australis achieves the highest oxygen concentration (4.29 mg/L) as compared to the Acacia filter (1.97 mg/L) and even to raw wastewater (1.28 mg/L). Obtained findings also indicated that Phragmites australis donated the upmost achieving the highest removal rate for biological oxygen demand (BOD₅) (97%). Additionally, it showed superior removal efficiency for total nitrogen (TN) (89%) and total phosphorus (TP) (99.65%) in domestic wastewater samples, compared to the Acacia plant, which exhibited removal rates of 95.26, 96.79, 87.7, and 99.38% for the same parameters, respectively. The unplanted bed (no plants), on the other hand, showed lower removal efficiencies of 91.58, 95.46, 72.60, and 95.50% for the same parameters, respectively. The higher performance in removing TN after wastewater treatment may be due to the absorption of nitrates (\({\text{NO}}_{3}^{ - }\)) and ammonium (\({\text{NH}}_{4}^{ + }\)) by macrophyte plants for the growth of their tissues. On the other hand, total suspended solids (TSS) removal, the Acacia filter showed the greater removal percentage compared to that found via the Phragmite australis bed and unplanted filter respectively.