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Phytoremediation Performance of Dominant Aquatic Macrophytes and Riparian Vegetation of Balili River, Benguet, Philippines in a Pilot-Scale Constructed Wetland
Dissertation Abstract:
Amidst more than a decade of rehabilitation efforts, Balili River remains polluted thus alternative clean-up method such as phytoremediation is timely and worth investigating. This study documented the phytoremediation potential of selected local dominant aquatic macrophytes of the river namely Amaranthus spinosus, Eichhornia crassipes, Eleusine indica, and Pennisetum purpureum which were planted in pilot scale constructed wetlands and subjected to varying hydraulic retention time (HRT) treatments. Also, the effects of the phytoremediation treatment to the macrophytes were documented. Results showed significant improvement of the wastewater in almost all water quality parameters. At optimal HRT, total suspended solid (TSS), dissolved oxygen (DO), nitrate (NO3-), and mercury (Hg) were significantly lowered at values passing the water quality standard while biological oxygen demand (BOD), phosphate (PO43-) and lead (Pb) were slightly above. But total and fecal coliform, amidst the high reduction rate, were still not passing the water quality standard for Class A water. The pollution reduction efficiencies of the aquatic macrophytes were significantly affected by HRT. Significant pollution reduction (p=0.00) was observed as early as Day 1 but optimal reduction was recorded at 3 - 4 days HRT. The response of the aquatic macrophytes toward phytoremediation treatments was species-specific where Eleusine indica and P. purpureum were the ones significantly affected. Eleusine indica suffered significantly lower growth rate under phytoremediation which could be attributed to the inability of its relatively short root system to tap into the water and nutrients. On the other hand, P. purpureum exhibited higher biomass and growth rate under phytoremediation treatment which is primarily due to the water pollutants absorbed as nutrients by the plant. This shows that, indeed, phytoremediation treatments significantly affected (p=0.00) some aquatic macrophytes should be taken in consideration when planning and designing constructed wetlands. These also showed that the solution to the pollution Balili River is within our grasp. We just need to tap the documented phytoremediation potential of our local macrophytes, particularly Pennisetum purpureum, in a full-scale constructed wetlands (CW).