Veterinary antibiotic removal in a two step nitrification process treating manure digestate

Short-cut biological nitrogen removal is considered a reliable and cost effective technology to treat effluent from anaerobic digestion compared to conventional activated sludge treatment; however there is a lack of knowledge concerning removal of antibiotics in via-nitrite systems. The aim of this study was to clarify the role of nitrifier populations in the removal of veterinary antibiotics compounds. Fate and removal of two antibiotics, oxitetracycline and chlorotetracycline, were assessed in two-sludge activated sludge systems treating manure digestate and enriched with nitrifiers. Partial nitritation of influent nitrogen was accomplished in the first stage, while the second reactor completed the nitrification to nitrate. Results showed that higher degree of tetracycline degradation was observed in enriched nitrifying system compared to a conventional activated sludge. CTC disappeared at a higher extent but its removal was affected by its low stability under the temperature of operation. On the contrary, OTC was more stable and its removal was influenced by the variation in the activity of the nitrite oxidizing bacteria.