Photothermal Floats for Evaporation Enhancement and Waterfowl Deterrence

Abstract

Many industries store hazardous liquid waste in open ponds prior to treatment or as a means of disposal. In some cases, these ponds may present a hazard to migrating waterfowl. Present methods of deterring birds, such as plastic ‘shade balls’, reduce evaporation, making them ineffective where evaporation is desirable. To combat this effect, we applied photothermal materials to high-density polyethylene (HDPE) containers to create “photothermal floats”, which absorb solar irradiation and promote, rather than deter, evaporation. In this study, inexpensive materials (granular activated carbon, fiberglass, and carbon air filters) were coated onto HDPE containers. Carbon foam, a buoyant material, was used alone. These materials were tested for their effects on evaporation rates in a laboratory environment at low light intensities (150 W∙m−2). Granular activated carbon (GAC) displayed the largest improvement in evaporative performance, increasing the evaporation rate by 64 ± 7% compared to a control with standing water and 199 ± 7% compared to uncoated HDPE. Materials were characterized using scanning electron microscopy, specific surface area analysis, water retention analysis, contact angle goniometry, and reflectance. We observed significant and unexpected differences between materials in all parameters and their connections to measured evaporation rates. These novel and inexpensive material combinations may provide a new tool for water managers who need to maintain or improve evaporation rates while deterring waterfowl.