Abstract
The effect of tetracycline (TC) on nitrogen removal in wastewater treatment plants has become a new problem. This study investigated the effects of TC on nitrogen removal using a Moving Bed Biofilm Reactor system. The results showed that there was no significant effect on nitrogen removal performance when the concentration of TC was 5 mg/L, and that the total nitrogen (TN) removal efficiency could reach 75–77%. However, when the concentration of TC increased to 10 mg/L, the denitrification performance was affected and the TN removal efficiency decreased to 58%. The abundance of denitrifying bacteria such as those in the genus Thauera decreased, and TC-resistant bacteria gradually became dominant. At a TC concentration of 10 mg/L, there were also increases and decreases, respectively, in the abundance of resistance and denitrification functional genes. The inhibitory effect of TC on denitrification was achieved mainly by the inhibition of nitrite-reducing bacteria.
Highlights
The presence of residual antibiotics in water, of which tetracycline (TC) is a typical representative, are a new environmental problem
When the TC concentration rose gradually from 0 to 10 mg/L, the concentration of ammonia-N in the effluent was less than 0.5 mg/L on average, and the removal rate of the latter was stable above 98%. This result showed that there the ammonia-N removal efficiency is high in an moving bed biofilm reactor (MBBR) system when the TC concentration remained in the range of 0–10 mg/L
The nitrification of the MBBR system was not affected by TC concentrations below 10 mg/L, this could be caused by the high tolerance of nitrifying bacteria to TC below 10mg/L [11]
Summary
The presence of residual antibiotics in water, of which tetracycline (TC) is a typical representative, are a new environmental problem. Traditional wastewater treatment processes cannot degrade TC effectively, and its presence has become an important issue for the stable operation and maintenance of sewage treatment plants [4]. The effluent concentration of TC in a sewage treatment plant was detected in the range of μg/L to mg/L [5]. The continuous accumulation of residual TC might produce TC-resistant genes in bacterial bacteria [7]. These resistant bacteria spread to humans through the food chain [8]. An increasing number of researchers are paying attention to environmental problems caused by TC [10]
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