Studies On Characteristics Of Adsorption And Biodegradation Of Typical PPCPs Oxtetracycline In The Activated Sludge Treatment System

Series experiments were conducted to investigate the adsorption and degradation of Oxtetracycline(OTC) in synthetic municipal wastewater by aerobic,anoxic and anaerobic sludge. Effect rules of some possible factors in the environment of municipal wastewater to the removal of OTC by aerobic,anoxic and anaerobic sludge were investigated.The High Performance Liquid Chromatography(HPLC) method was adopted for the determination of OTC,and a set of detection methods was established on the basis of the reference literature including detection conditions,sample pre-treatment,the method accuracy and drawing the standard curve.The result was,using Solid Phase Extraction,with the detection conditions:Agilent1100 HPLC;ZORBAX Eclipse XDB-C18 column(250 mm×4.6 mm,5μm);column temperature 25℃;mobile phase-acetonitrile and water(adjust pH to 2.5 using phosphoric acid)(30:70,V/V);flow rate(constant)-1.5 mL/min;detection wavelength-350nm; sample volume-20μL,the recovery of standard addition of the method was above 82%and the linear correlation coefficient of standard curve was 0.9994.Adsorption performance of aerobic,anoxic and anaerobic inactivated sludge to OTC was then studied separately.Adsorption equilibrium time of OTC on three kinds of inactivated sludge was first researched.Effects of temperature,pH value,metal ions and polysaccharide and protein to the adsorption were also investigated.The adsorption characteristics of aerobic,anoxic and anaerobic inactivated sludge for OTC were similar.The adsorption equilibrium was established in 30min.The experimental data of equilibrium concentrations were well correlated by both Freundlich and linear adsorption isothermal models.The adsorption capacities decreased with the increasing temperature.The Langmuir adsorption coefficient Q and maximum adsorption quantity b of three kinds of inactivated sludge for OTC also decreased with the increasing temperature. Adsorption of OTC by three kinds of inactivated sludge fits Pseudo Second-order adsorption kinetics better than Pseudo First-order adsorption kinetics.Decreased adsorption capacities with increasing pH value was observed in the pH range of 6～10.Both polysaccharide and protein have inhibitory effects to the adsorption of oxytetracycline,the inhibition of protein to the absorption is comparatively weak.Fe³⁺,Mn²⁺ and Cu²⁺ improved the decrease of OTC concentration while Ca²⁺ was opposite.Batch experiments were conducted to investigate the removal of OTC by aerobic,anoxic and anaerobic activated sludge.The first-order degradation kinetics fitting of OTC by aerobic, anoxic and anaerobic activated sludge was performed.Effects of pH value,coexistent organic contaminants in wastewater and solid retention time(SRT) on the removal of OTC in the activated sludge process were studied.As a result,the degradation of OTC by aerobic,anoxic and anaerobic activated sludge was well confirmed to the first-order degradation kinetics,the biodegradation property of OTC is poor;decreased biodegradation capacities with increasing pH value was observed in the pH range of 6～9;effects of degradation capability of three kinds of activated sludge for OTC was different when there exist different carbon or/and nitrogen resource in the wastewater environment;improved removal rate of oxtetracycline by three types of activated sludge was observed as a result of increasing SRT.