Comparison of the sensitivities of fish, Microtox and Daphnia-magna bioassays to amoxycillin in anaerobic/aerobic sequential reactor systems

Abstract

In this study the anaerobic treatability of amoxycillin (AMX) was investigated in a laboratory-scale anaerobic multi-chamber bed reactor (AMCBR)/aerobic continuously stirred tank reactor (CSTR) system. The chemical oxygen demand (COD) and AMX removal efficiencies were around 94% in the AMCBR reactor at hydraulic retention times (HRTs) between 2.25 and 5.5 days. Decreasing the HRT appeared not to have a significant effect on the performance of the AMCBR up to a HRT of 1.13 days. The maximum methane production rate and methane percentage were around 1,100-1,200 mL/day and 55%, respectively, at HRTs between 2.25 and 5.5 days. The decrease in HRT to 1.5 days decreased slightly the gas productions (1,000 mL/day and 500 mL for total and methane gases) and methane percentage (45%). The AMCBR recovered back to its baseline performance within a couple of days. The acute toxicity of 150 mg/L AMX was monitored with Daphnia magna, Lepistes sp., and Vibrio fischeri acute toxicity tests. The acute toxicity removals were 98, 96 and 96% for V. fischeri, D. magna and Lepistes sp. in the effluent of the sequential system treating 150 mg/L AMX at HRTs of 2.25-5.5 days. Among the trophic organisms used in the acute toxicity tests the most sensitive organism was found to be bacteria (V. fischeri) while the most resistant organism was found to be fish (Lepistes sp.).

Mechanistic and ecotoxicological studies of amoxicillin removal through anaerobic degradation systems

“…fischeri was also the most sensitive species in the study by Çelebi and Sponza (2012), who observed an increase in the toxicity when the HRT was reduced to 0.9 days, which resulted in a reduction in the biogas production and an increase in the volatile fatty acids concentration that could enhance the effluent toxicity.…”

“…Seed Germination test, Aliivibrio fischeri and Raphidocelis subcapitata were chosen due its advantages in terms of simplicity, cost effectively, reproducibility and low time to obtain the results. A. fischeri is a very sensitivity specie that has been widely used for wastewater monitoring and can be applied for a large number of compounds, including amoxicillin (Çelebi and Sponza, 2012;Di Nica et al, 2017).…”

“…The results of the ANOVA test showed that samples from the blank and the system containing 250 μg L -1 of amoxicillin exhibited the same level of toxicity to A. Fischeri (p = 0.98), while the other samples were less toxic (p = 2.41 × 10 -4 and 4.19 × 10 -6 for 2,500 and 25,000 μg L -1 of amoxicillin compared to the blank, respectively), indicating that amoxicillin by-products are less toxic to this organism. In the study conducted by Çelebi and Sponza (2012), wastewater treatment using AMCBR (anaerobic multi-chamber bed reactor) and containing 150 mg L -1 of amoxicillin led to a reduction in the EC 50 (effective concentration that causes 50% inhibition) values of A. fischeri from 143 (influent) to 215 mg L -1 (effluent) with a HRT of 5.5 days. The lower Γ than that of the raw effluent could be ascribed to dispersion of luminescent by particles or by the presence of bacteria from the inoculums used in the test.…”

“…Çelebi and Sponza (2012) observed a reduction in the removal of amoxicillin and COD when HRTs as low as 1.13 days were used. They attributed this to the insufficient time available for the mineralisation of COD, amoxicillin, and its metabolites owing to the inadequate conditions for mass transfer into the granules ofthe AMCBR.…”

“…The novelty of this work lies in the evaluation of amoxicillin degradation under anaerobic conditions and by-products formation and accumulation, whose estimated concentration were confronted to ecotoxicity analyzes performed with species from three different trophic levels. Usually studies concerning on removal of pollutants do not give attention to the formation of by-products (Çelebi and Sponza, 2012;Meng et al, 2015;Rizzo et al, 2009) which can be responsible for more pronounced toxic effects than those of the parent compound. Within this, ecotoxicological assays come as an advantageous technique in order to monitor the performance of WWTPs, providing information about trouble-shooting in case of failures in biological treatment and evaluating environmental risk regarding treated effluent discharge or even in subsequent/ tertiary treatments.…”