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This study evaluated the individual and interactive effect of phenol and thiocyanate (SCN) on partial nitritation (PN) activity using batch test and response surface methodology. The IC of phenol and SCN on PN sludge were 5.6 and 351 mg L, respectively. The PN sludge was insensitive to phenol and SCN at levels lower than 1.77 and 43.3 mg L, respectively. A regression model equation was developed and validated to predict the relative specific respiration rate (RSRR) of PN sludge exposed to different phenol and SCN concentrations. In the range of independent variables, the most severe inhibition was observed with a valley value (17%) for RSRR, when the phenol and SCN concentrations were 4.08 and 198 mg L, respectively. An isobole plot was used to judge the combined toxicity of phenol and SCN, and the joint inhibitory effect was variable depending on the composition and concentration of the toxic components. Furthermore, the toxic compounds showed independent effects, which is the most common type of combined toxicity. [ABSTRACT FROM AUTHOR]

The feasibility of the anaerobic ammonium oxidation (anammox) process to treat synthetic swine wastewater containing antibiotics and heavy metals was studied in this work. Nitrogen removal performance and granule characteristics were tracked by continuous-flow monitoring to evaluate the long-term joint effects of Cu and Zn and of Cu and oxytetracycline (OTC). Cu and Zn with a joint loading rate (JLR) of 0.04 kg m day did not affect the performance, while a JLR of 0.12 kg m day caused a rapid collapse in performance. Cu and OTC addition with a JLR of 0.04 kg m day for approximately 2 weeks induced significant nitrite accumulation. Granule characteristic analysis elucidated the disparate inhibition mechanisms of heavy metals and antibiotics: the internalization of heavy metals caused metabolic disorders, whereas OTC functioned as a growth retarder. However, anammox reactors could adapt to a JLR of 0.04 kg m day via self-regulation during the acclimatization to subinhibitory concentrations, which had a stable nitrogen removal rate (>8.5 kg m day) and removal rate efficiency (>75 %) for reactors with Cu-OTC addition. Therefore, this study supports the great potential of using anammox granules to treat swine wastewater. [ABSTRACT FROM AUTHOR]