Bioaugmentation enabled simultaneous biodegradation of sulfadiazine and nitrification

Antibiotics are detected in surface waters in part because classical wastewater-treatment processes are ineffective for biodegrading them. Furthermore, the presence of antibiotics can inhibit the performance of biological treatment, particularly for nitrification, but an effective strategy for simultaneous antibiotics and nitrogen removals was not reported so far. This work targeted biodegradation of the common sulfanilamide antibiotic sulfadiazine (SDZ) and its inhibition of nitrification. The experimental results showed that nitrification rate decreased to 3.4 mg/(L·h) and 1.9 mg/(L·h) (from 19 mg/(L·h)) when normal nitrifying biomass (NNB) was exposed to SDZ at 10 mg/L and 20 mg/L due to inhibition by SDZ. Bioaugmentation of NNB with a SDZ-acclimated biomass (SDAB) enabled biodegradation of SDZ, which relieved its inhibition of nitrification. In the presence of 20 mg/L of SDZ, the NH₄⁺-N removal rate reached at 7.8 mg/(L·h), which was more than 4-fold faster with SDAB bioaugmentation. Metagenomic analysis supported that NNB was responsible for nitrification, while bioaugmented SDAB was responsible for SDZ biodegradation that allowed simultaneous removal of NH₄⁺-N and SDZ. For example, metagenomic analysis further showed that SDAB contained 4 genes for monooxygenations critical to initiating SDZ biodegradation, but NNB was enriched in genes for oxidations of NH₄⁺ and NO₂^-.