GPS-Guided Focal-Point Identification and Hydraulic Optimization of a Submersible Floating-Waste Collector in Matab-Ang River, Philippines

Abstract

Floating solid waste in rivers is transported by spatially variable surface flows, making collector placement a critical design decision. This study developed a low-cost GPS-based floating profiler to identify probable waste-transport focal points in Matab-ang River, Talisay City, Philippines, and evaluated a hydraulically modified inner basket for a submersible floating-waste collector. A 3D-printed polylactic acid enclosure containing a GPS tracking module was deployed through 31 trials in each of three river sections. Trajectory frequency was analyzed using a gridded spatial framework. Four focal cells were identified: E11 in the left section (25/31 trajectories; 80.65%), H5 and I4 in the middle section (19/31 each; 61.29%), and N6 in the right section (22/31; 70.97%). The collector was evaluated using computational fluid dynamics (CFD) and controlled physical testing. Three basket geometries were considered in the CFD comparison: straight, varying-diameter, and varying-diameter with a bell-shaped inlet. The latter produced the highest average simulated velocity (0.4859 m/s), compared with 0.3914 m/s for the straight geometry. In 30 physical trials per configuration, mean intake velocity increased from 0.14799 to 0.19769 ft/s, equivalent to a 33.5% improvement. A two-sample t-test assuming unequal variances indicated a statistically significant difference between the designs (t = −26.41, df = 49, p < 0.001). Average turbulent kinetic energy increased from 0.001443 to 0.002196 m²/s² in the CFD results. The findings support a combined trajectory-mapping and hydraulic-optimization framework for targeted river-waste interception. However, the study does not yet establish long-term field capture capacity because physical intake tests used a standardized floating object in a controlled pool environment and GPS deployment was limited primarily to low-tide conditions.