Microbial Analysis of Phytoremediation Wastewater Treatment in Rwanda

This study confirms that the phytoremediation-based wastewater treatment system at the National Police College in Rwamagana, Rwanda, is highly effective in reducing both physicochemical pollutants and harmful microorganisms. The treatment process, which includes anaerobic baffled reactors, blackstone flotation chambers, shallow aeration basins, phytoremediation beds, and maturation basins, significantly improved wastewater quality from influent to final effluent.

The results showed a steady decrease in pH, total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total nitrogen (TN), and total phosphorus (TP) across the treatment stages. This indicates efficient removal of organic matter, suspended particles, and excess nutrients that could otherwise cause environmental pollution and eutrophication.

The phytoremediation bed played a major role in nutrient removal through plant uptake and microbial activity in the root zone. Vetiver grass helped absorb pollutants and supported nitrification and denitrification processes. The shallow aeration basin improved oxygen transfer, enhancing aerobic microbial breakdown of organic waste.

Microbial indicators such as total coliforms, fecal coliforms, E. coli, heterotrophic bacteria, and helminth eggs also showed significant reduction. This demonstrates strong pathogen removal efficiency and reduced public health risks associated with wastewater discharge or reuse.

The final maturation basin provided additional polishing and natural disinfection through solar exposure, helping the treated wastewater meet Rwanda’s environmental compliance standards. The final effluent was within acceptable limits set by the Rwanda Standards Board (RSB) and REMA.

Overall, the study proves that nature-based solutions like phytoremediation are sustainable, cost-effective, and environmentally friendly alternatives to conventional wastewater treatment systems. The NPC system serves as a strong model for improving sanitation, protecting water resources, and supporting Sustainable Development Goal 6 in Rwanda.