A Study of Microfiber Phytoremediation in Vertical Hydroponics

Abstract

Microfibers (MFs) are one of the most prevalent microplastic (MP) sub-groups found in the aquatic environment released from many sources, including household laundry. MPs pose risks to the growth rate of terrestrial/aquatic biota and through biomagnification. Although MFs can be ingested by humans, their toxic effects and potential impact on public health are not yet clearly understood. Moreover, the removal of MPs, including MFs, during wastewater treatment is a challenge, since treatment plants are not designed to collect them. Therefore, this work aims to study the potential of the in situ phytoremediation of microfibers from a domestic washing machine effluent by growing barley in a vertical hydroponic system. The temporal variation in barley growth, water quality parameters, length distribution of MFs, and their removal were evaluated over 4 weeks. We investigated the MFs’ interaction with two systems: without barley (System NP) (used as a control) and with barley (System P). The results show the barley growth is negatively affected at the end of 4 weeks, mainly by the accumulation of phosphate and the presence of fungi. However, the level of dissolved oxygen in System P is satisfactory and the presence of MFs decreases considerably (mainly for MFs > 600 µm) from different interactions with the barley roots. These interactions were corroborated by microscopy images. The total removal of MFs through the hydroponic system was 52% in week 2, decreasing to 42%. This is the first time that the removal of MFs has been evaluated using vertical hydroponics, which demonstrates that this phytoremediation system can be used at the household level. It also shows that vertical hydroponics, as an experimental methodology, for the analyses of MFs’ impacts on plant health has merit. It is expected that this study will contribute to new investigations of MF removal by green technologies.