Removal efficiencies of seven frequently detected antibiotics and related physiological responses in three microalgae species.

The main objective of this study is to investigate the effect of mixtures of seven widely used human antibiotics (ciprofloxacin, clarithromycin, erythromycin, metronidazole, ofloxacin, sulfamethoxazole, and trimethoprim) on the growth, pH, pigment production, and antibiotics removal of three microalgal species (Auxenochlorella protothecoides, Tetradesmus obliquus, and Chlamydomonas acidophila). Batch assays were conducted with media with antibiotic mixtures at 10, 50, and 100 µg L-1 for each antibiotic. The three microalgae species effectively removed the antibiotics without any growth inhibition, even when exposed to the highest antibiotic concentrations. Biosorption was reported as the primary mechanism for ciprofloxacin, clarithromycin, metronidazole, and ofloxacin, with up to 70% removal, especially in A. protothecoides and C. acidophila. A. protothecoides, a species never investigated for antibiotic removal, was the only microalgae exhibiting bioaccumulation and biodegradation of specific antibiotics, including sulfamethoxazole. Furthermore, in media with the highest antibiotic concentration, all three species exhibited increased chlorophyll (up to 37%) and carotenoid (up to 32%) production, accompanied by a pH decrease of 3 units. Generally, in the present study, it has been observed that physiological responses and the removal of antibiotics by microalgae are interlinked and contingent on the antibiotic levels and types.

Pharmaceuticals effect and removal, at environmentally relevant concentrations, from sewage sludge during anaerobic digestion.

This paper investigates the performance of AD in the presence of high-risk pharmaceuticals found in sewage sludge and its removal capacity. The digestion process of synthetic sewage sludge was observed in two 7L glass reactors (D1 and D2) at 38 °C (OLR 1.3 gVS L-1 d-1 and HRT 43 d). Environmentally relevant pharmaceuticals (clarithromycin, clotrimazole, erythromycin, fluoxetine, ibuprofen, sertraline, simvastatin and tamoxifen) were added in D2 at predicted environmental (sludge) conditions. The results demonstrated that long-term presence of pharmaceuticals can affect AD and induce instability resulting in an accumulation of VFAs. This study showed a concurrent effect on AD microbial composition, increasing the percentage of Firmicutes (>70%) and decreasing the percentages of Bacteroidetes and Euryarchaeota (<5%), which seems to be the cause of VFA accumulation and resultant the decrease in the biogas production. However, it seems that anaerobic microorganisms offer enhanced removal of the antibiotics clarithromycin and erythromycin over aerobic techniques.

Mechanistic and ecotoxicological studies of amoxicillin removal through anaerobic degradation systems.

Many studies have been conducted on the evaluation and monitoring of micropollutants and by-products in wastewater treatment plants. Considering the increase in the production and consumption of emerging contaminants, such as drugs, personal care products, and plasticisers, it is necessary to conduct studies that support the elaboration of laws and regulations that promote the environmentally sustainable use of sludge and effluents. In this work, the biological degradation of amoxicillin was studied under two anaerobic conditions: i) using a 6 L reactor operated under semi-continuous flow; and ii) a batch system with 100 mL sealed glass syringes. According to the statistical analysis, amoxicillin was completely removed from the systems, but biogas production inhibition was observed (p < 0.05). Liquid chromatography-high-resolution mass spectrometry analysis identified amoxicillin penicilloic acid, amoxilloic acid, amoxicillin diketopiperazine and phenol hydroxypyrazine as by-products under anaerobic conditions. Ecotoxicity tests on effluent treated under the batch conditions showed that the addition of higher amounts of amoxicillin inhibited the target species Aliivibrio fischeri and Raphidocelis subcaptata, causing functional decreases of 28.5% and 22.2% when the antibiotic concentration was 2500 µg L-1. A. fischeri was the most sensitive organism to effluent treated under semi-continuous flow conditions; a continuous reduction in bioluminescence of up to 88.8% was observed after 39 days of feeding, which was associated with by-products accumulation due to unbalanced conditions during anaerobic digestion. Changes in the physico-chemical characteristics of the effluent caused the accumulation and removal of AMX-DKP IV and modified the toxicity to Lactuca sativa and R. subcapitata.

Ammonium removal from anaerobically treated effluent by Chlamydomonas acidophila.

Several batch culture studies were carried out to evaluate an anaerobically treated effluent as a low-cost growth medium for the microalga Chlamydomonas acidophila and to study the effectiveness of the microalga in removing NH4-N from the effluent. An initial decrease in the effluent pH to 3 was required for adequate growth of C. acidophila and removal of NH4-N. Growth of the microalgae was inhibited at high light intensity (224µmolphotonsm(-2)s(-1) at the surface of the vessels). However, the growth was not greatly affected by the high solid content and turbidity of the effluent. The microalga was able to grow in media containing NH4-N at concentrations of up to 1000mgL(-1) (50% of effluent) and to remove 88mg of NH4-NL(-1) in 10days. C. acidophila therefore appears a promising agent for the removal of NH4-N from anaerobically treated effluents.

Nitrogen dynamics in soil amended with manures composted in dynamic and static systems.

The main objectives of this study were to evaluate the stability of three different composts and to study the N dynamics in soil incubated with the composts under laboratory conditions. The composts were produced from sheep manure processed by static pile composting (C1) and from cattle and sheep manure processed by dynamic pile composting (C2 and C3 respectively). Laboratory incubation assays were carried out at 28 °C to determine the amount of N mineralized and N leached under extreme rainfall conditions in the first 30 days after application of doses of each compost equivalent to 170 and 450 kg ha(-1) of N. There were no differences in the values of these parameters in samples of the composts produced by the static (C1) and dynamic (C3) systems, and both composts behaved in the same way when applied to soil. The chemical characteristics of the three final composts, the respiration rates and the lack of stimulation of total microbial biomass indicated that the composts were stable. However, the final C/N ratio was slightly higher in C2 than in C1 and C3 (14 compared with 10 and 11) as was the respiration rate of the high dose of C2 indicating that C2 was more labile, and thus less stable than C1 and C3. Compost C2 generated the highest N mineralization rates after application of different doses (6.5 and 13.1%), as well as the highest N supplying potential (54.7 and 36.2%), and thus the highest rate of mineral N leaching (16.8 and 16.5 mg L(-1) of NO(3)-N), probably as a result of the slight difference in lability. The N release after compost application was very low and thus the leaching potential was also low, indicating that high doses of mature compost (>170 kg ha(-1) of N) could be applied to soil.