Restoration of the Balili River via Phytoremediation by Pennisetum purpureum in Constructed Wetlands and Constructed Floating Wetlands

Sitsit, Fernie D.

The Balili River is an important stream traversing Baguio City, La Trinidad, and Sablan, Benguet that stretches 23.81 kilometers. It has been declared “biologically dead” by the DENR’s Pollution Report in 2003, being the recipient of discharges and effluents from businesses and households along the river through the years. Short-term rehabilitation activities and ordinances have been conducted but there were no reports yet on biological rehabilitation done to improve its current condition. The study aimed to describe and assess the water quality parameters of the Balili River over a long-term period without any active intervention and over a short-term period utilizing an active intervention. This study used seasonal regression analysis using water quality monitoring results from years 2016-2023. Results revealed that all water quality parameters decline during the dry season in all 14 stations while the water quality improves during the rainy season due to dilution from rain. The study also determined the efficacy of Pennisetum purpureum (Napier grass) in improving the water quality of the Balili River using constructed wetlands (CW) and constructed floating wetlands (CFW) in the short-term. Results highlight the importance of hydraulic retention time (HRT) in getting the optimum results in the plant’s uptake of phosphorus, nitrogen, and chloride and in improving pH, color, dissolved oxygen while decreasing the fecal coliform load, biochemical oxygen demand and total suspended solids. The unique result of the study shows the potential of P. purpureum in improving river water quality when used in direct floating set-ups along the river and its efficacy in decreasing fecal coliform load.