Methylene blue is one of the most commonly used dyes in several industries. This causes an alarming rate of dye-containing effluents discharged into the environment, affecting humans and the aquatic ecosystem that comes in contact with these pollutants. This study investigated P. stratiotes L. and S. molesta D.S. Mitch. in decolorizing methylene blue (MB). The plants were exposed to four treatments: 10 mg/L, 25 mg/L, 50 mg/L, 100 mg/L for 48 hours. The dye decolorization, pH, and the final relative growth rate of the plants were observed. Samples were extracted at 0, 0.5, 1, 2, 3, 4, 5, 6, 24, and 48 hours to determine its absorbance value at 670 nm. After 48 hours, it was determined that S. molesta D.S. Mitch. decolorized 97.8% of MB at pH 6.4 in a ten mg/L MB solution than P. stratiotes L., removing 80.9% at pH 6.5 of MB in the same treatment solution. However, neither plant sample can grow under increasing concentrations of MB, substantiating the damaging attributes of MB to the environment. Furthermore, S. molesta D.S. Mitch. was used to determine its dye decolorization potential when subjected to MB-contaminated synthetic wastewater (SWW). Results showed that S. molesta D.S. Mitch. decolorized 58.5% of MB at pH 8.5 in ten mg/L of SWW. In addition, its COD was also determined in all SWW samples of S. molesta D.S. Mitch., which was found to exceed the required value of 60-100 mg/L for wastewater discharge pursuant to the DENR DAO 2016-08. This study determined that P. stratiotes L. and S. molesta D.S. Mitch. have phytoremediation potential in decolorizing MB, which works best under low concentrations and suitable conditions.

Keywords: Wastewater, Relative Growth Rate, Absorbance, Chemical Oxygen Demand ---

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Mark Andrei L. Arjona

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Marianne Dawn C. Dionson

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Wissel Sam Brondial

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