Can duckweed be used for the biomonitoring of textile effluents?

Abstract

1In certain countries, poorly managed freshwaters need to be seriously controlled to not lead to ecosystems 2 degradation. This control can be achieved by a biomonitoring using living organisms as ecological alert 3 indicators. In this context, biotests were undertaken on Lemna gibba (L. gibba) to assess the toxic effect of 4 textile pollutants reaching a natural ecosystem. L. gibba were exposed to different concentrations (5-100 mg/L) 5 of two dyes, namely Direct Red 89 (DR-89) and Vat Blue 20 (VB-20), under laboratory conditions. Our findings 6 showed that at concentrations > 50 mg/L, visible damage of toxicity (chlorosis and dislocation of fronds) were 7 appeared from the third day of toxicity tests leading to serious necrosis. However, at dye concentration ≤ 50 8 mg/L, duckweed showed no visible signs of toxicity within an exposure time of 4 days. However, these 9 concentrations exhibited a significant inhibition in L. gibba growth rate with a clear abatement in the 10 photosynthetic pigments contents. The dye concentration that reduces by 50% the growth rate of the plants 11 (IC50) was 36.3 and 26.9 mg/L for DR-89 and VB-20, respectively. The concentration-dependant reduction in 12 growth and photosynthetic pigments demonstrated their sensitivity in detection of dyes in aquatic systems. The 13 current findings proving physiological alterations of L. gibba following dye exposure, suggested that the species 14 are strongly suitable for the testing of textile effluents contaminating water bodies. 15

Enzymatic Bioremediation of Dyes from Textile Industry Effluents

“…In the presence of two textile dyes, Lemna giba, an aquatic macrophyte, had its growth rate and photosynthetic pigment content decreased. The authors of the study concluded that this species can be used as a bioindicator of polluting dyes [12]. High concentrations of dyes are reported to decrease vital elements, such as P, Mg, Ca, S, and Ca in plants of Eichhornia crassipes and Salvinia natans, which also presented damaged roots, chlorosis, and necrosis in leaves [13].…”

Activated Sludge-Assisted Phytoremediation For Dye Removal

“…The activated sludge (AS) used in the biodegradation tests were taken from the aeration tank of the municipal WWTP located in the city of Annaba (East Algeria). This sludge in the form of a suspension was transported in closed plastic containers to the laboratory and was suspended in a modi ed culture medium, necessary for the development of the microorganisms; it was then aerated under a moderate stirring, at ambient temperature T = 21 ± 1 °C at pH = 6.1 ± 0.1 (Hocini et al 2019). The suspension of the activated sludge was placed in a 1 L graduated cylinder (test tube) to allow it to settle.…”

“…Furthermore, a slight reduction in the MDP was observed for the control as well as for the treatment solutions, compared with MDP of the activated sludge found in Table 1. This is probably due to the competition of the aquatic plants in the nutrient components and on the organic carbon obtained after the biodegradation of the target molecules, given that the growth of plants require different components, namely macro and micro elements that are indispensable for plant metabolism and for the complete development of their vegetative cycle (Hocini et al 2019;Kumar et al 2021).…”