Microbial quality and compliance of phytoremediated wastewater in Rwanda

This research evaluated the microbial status and compliance level of wastewater treated through a nature-based phytoremediation system in Rwanda. Physicochemical parameters such as pH, temperature, total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were measured and analyzed. The microbial contents, such as total heterotrophic bacteria count, fecal coliform bacteria, total coliform bacteria, E. coli, and helminth eggs, were also investigated. Morphological identification and biochemical tests were conducted via standard techniques. After water treatment in different chambers, the physicochemical parameters were analyzed, and the mean values of the microbial indicators were all within the compliant limits of the Rwanda established water quality standards. The results revealed a decrease in the pH, TSS, BOD₅, COD, TP, HE and microbial counts as the wastewater passed through the initial and middle stages. However, there was a statistically significant decrease in the physicochemical parameters and microbial indicators as the water passed through the final stages of water treatment. These relative and logarithmic decreases indicate polishing and pathogen removal efficiency at the end of the treatment. However, the reduction in microbial counts was limited, indicating areas for process improvement. Therefore, the National Police College phytoremediation system is effective at removing both organic pollutants and pathogenic microorganisms.