Effect of varying retention times and feeding schemes on the performance of vertical constructed wetlands planted with vetiver grass in treating dairy wastewater in the Philippines

Adequate wastewater treatment from the dairy industry before disposal is still lacking in the Philippines, particularly in small-scale sectors. This limitation is due to the high cost and expertise required from conventional wastewater treatment systems. One option is using constructed wetlands, a nature-based solution with low cost, less specialized expertise and maintenance requirements and high wastewater treatment efficiency. To further evaluate the application of constructed wetlands in the Philippines, this paper studied the wastewater from the manufacturing processes of the Dairy Training Research Institute, University of the Philippines Los Banos (DTRI-UPLB). It is a small dairy farm inside the University with economic constraints in using a conventional wastewater treatment system. The main aim of this study is to determine the effect of using vertical subsurface flow constructed wetlands (VSSFCW) planted with Vetiver grass (Chrysopogon zizanioides) in sand and gravel media to treat the DTRI-UPLB effluent, using very low retention times (4 and 8 h), with daily and alternate days of wastewater feeding into the VSSFCW. The average removal efficiencies for total suspended solids (TSS), biological oxygen demand for (BOD5), total phosphorus (TP), and Total Kjeldahl Nitrogen (TKN) are 88.34%, 93.56%, 78.42%, and 94.63%, respectively. Moreover, alternate wastewater feeding provided a statistically significant increase in the performance of VSSFCW, while there is no statistical difference between the two retention times evaluated. Finally, it was observed that plant age significantly affects the performance of VSSFCW setup but should be explored further with longer operation times and additional nutrient uptake analysis.