Toxicity assessment of textile wastewater treated by constructed wetland augmented consortium endophytic bacteria using <i>Daphnia magna</i>

Constructed wetlands (CWs) augmented endophyte bacteria, well known as a sustainable and low-cost technological approach, have been widely applied to treat textile wastewater. However, the remaining dyes and other pollutants in treated textile wastewater are not guaranteed to impact the biotic environment negatively. Validating the toxicity level of treated textile wastewater is critical to ensuring aquatic environmental safety. Therefore, this study evaluates the acute toxicity of treated textile wastewater from CWs reactor integrated with Vetiveria zizanioides and consortium endophytic bacteria. Acute toxicity (LC50) represents the concentration causing 50% mortality in the aquatic organism population within 96 hours. Whole effluent toxicity (WET) testing using Daphnia magna as a standardized bioassay was conducted to determine LC50. Three variations of treatments, untreated wastewater (K), constructed wetland without bacteria (C1), and constructed wetland with bacteria (C2), were monitored for treating three loading concentrations (25%, 50%, and 100%) of textile wastewater. As a result, the untreated wastewater had LC50 1.52 – 200% and TUa 0.50 – 65.62, indicating slight to high acute toxicity. On the contrary, CWs with and without consortium bacteria exhibited LC50 > 100% and TUa < 1, indicating that both treatments raised effluent quality and became non-acute toxicity. Moreover, the survived D. magna in treated textile wastewater from CWs with and without bacteria exhibited less morphological and physiological impact on the organs, particularly heart rate and thoracic limb movement. These findings demonstrate that CWs augmented endophytic bacteria can eliminate acute toxic risks in textile wastewater and reduce its hazardous potential to the aquatic environment.