Abstract
Oxytetracycline (OTC) is a commonly used antibiotic in livestock farming for controlling intestinal and respiratory infections in farm animals. However, the absorption of antibiotics by animals is limited, and most antibiotics are excreted in the original form with manure, which will have an impact on the environment. The removal of antibiotics from swine manure could generally be performed via anaerobic digestion (AD). In this study, the effect of oxytetracycline (OTC) at doses of 0.1, 0.5, and 1.0 mg/L on the thermophilic anaerobic digestion of swine manure (55 °C) in batch digesters was studied. The methane production, volatile fatty acid (VFA) levels, and dissolved organic matter (DOM) were determined and compared with the control (0 mg/L of OTC). The results indicate that (1) OTC at 0.1 mg/L had no inhibitory effect on methane production or on the accumulation of VFAs, while 0.5 mg/L and 1.0 mg/L inhibited methane production, with inhibition rates of 4.03% and 14.12% (p < 0.05), respectively; (2) the VFAs of each reactor peaked on the first day of the reaction, and as the OTC dose increased from 0 to 1.0 mg/L, the maximum VFA accumulation increased from 1346.94 mg/g to 2370 mg/g of volatile solids (VS); and (3) oxytetracycline (0.5 and 1.0 mg/L) could promote the temporary accumulation of propionic acid, which did, however, not result in significant VFA accumulation. Further, OTC at 1.0 mg/L can promote DOM production, and therefore, VFA accumulation.
Highlights
Published: 4 April 2021Oxytetracycline (OTC) is a commonly used antibiotic in livestock farming for controlling intestinal and respiratory infections in farm animals [1]
Few studies have focused on thermophilic anaerobic digestion, compared with digestion at moderate temperatures, thermophilic anaerobic digestion has the advantages of a shorter residence time, a more comprehensive range of organic matter loading, and a smaller digestion tank volume
We investigated the impacts of low-concentration OTC on the dynamic changes of volatile fatty acid (VFA) in anaerobic fermentation at a higher temperature (55 ◦ C) and the underlying mechanisms
Summary
Published: 4 April 2021Oxytetracycline (OTC) is a commonly used antibiotic in livestock farming for controlling intestinal and respiratory infections in farm animals [1]. The OTC concentrations in manure samples can be in the range of 0.006–136 mg/L [2]. The absorption of antibiotics by animals is limited, and more than 85% of antibiotics are excreted in their original forms with manure [3]. Mesophilic temperature anaerobic digestion and thermophilic anaerobic digestion are two commonly used processes, both with their own sets of advantages and disadvantages. Few studies have focused on thermophilic anaerobic digestion, compared with digestion at moderate temperatures, thermophilic anaerobic digestion has the advantages of a shorter residence time, a more comprehensive range of organic matter loading, and a smaller digestion tank volume. The degradation rate of organic matter is higher, resulting in the production of larger amounts of biogas [6,7].
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