Degradation Of Typical Ppcps By UV/NaClO And UV/K₂S₂O₈ Advanced Oxidation Processes

In recent years,pharmaceutical and personal care products?PPCPs?have received extensive attention due to continuous input,food chain enrichment,and potential threats to the ecological environment and human health.As the“second city water source”,the reuse of recycled water is a main way for the undegraded PPCPs in the wastewater treatment plant to return to the people's life circle,therefore,studies about the efficient and feasible PPCPs reduction technology are of great significance to the improvment of reclaimed water quality and the implementation of recycled water use.Conventional water treatment processes?including flocculation,sedimentation,filtration?and advanced treatment?including chlorination,ozonation,active adsorption,membrane filtration?cannot completely remove PPCPs.Advanced Oxidation?AOPs?can produce active free radicals to completely oxidize and decompose PPCPs.Compared with the traditional oxidant H₂O₂,NaCl O and K₂S₂O₈possess higher molar absorption coefficient and quantum yield under UV irradiation to rapidly generate active free radicals with strong oxidizing power to degrade PPCPs,which conduct to effectively improve the quality of recycled water.In this paper,Sulfamethoxazole?SMX?and Ciprofloxacin?CIP?were used as degradation targets to evaluate the ablity of PPCPs removal in recycled water by both UV/NaCl O method and UV/K₂S₂O₈ method.UV/NaClO method can effectively remove more than 98.5%of SMX and CIP.The reaction process accorded with the pseudo-first-order reaction kinetics model and the rate constant was obviously higher than UV/H₂O₂,UV and NaClO alone.At initial concentrations of 1?mol/L SMX and CIP,the degradation rate constant increased first and then decreased with increasing NaCl O dosage and the optimal NaClO dosage was0.1 mmol/L and 1 mmol/L,respectively.The initial pH value of the solution affected the degradation effect of SMX and CIP,the SMX and CIP degradation rate constants peaked at pH 3 and pH 5,respectively.The degradation got better at pH 3⁸ as a whole which indicated UV/NaClO can adapt to the conventional reclaimed water ranging from 6 to 8.The five common anions(CO₃^2-?HCO₃^-?Cl^-?NO₃^-?SO₄^2-)and humic acid in water all showed obvious inhibitation on the degradation of SMX and CIP.The amount of trichloromethane generated in UV/NaClO method was significantly lower than that of chlorine alone.UV/NaClO method can effectively control the generation of disinfection byproducts.The EE/O values of UV/NaClO method to degrade SMX and CIP were influenced by the chlorine consumption,pH value and humification,that energy conservation can be arrived by optimization of process parameters.The EE/O value of UV/NaClO was lower than UV and UV/H₂O₂,which indicated UV/NaCl O is a relatively economical process.UV/K₂S₂O₈ method can effectively remove more than 99.5%of SMX and CIP.The reaction process accorded with the pseudo first-order reaction kinetics model and the rate constant was obviously higher than UV/H₂O₂,UV and K₂S₂O₈ alone.The degradation effect of CIP was slightly higher than that of UV/NaClO.At the initial concentrations of 1?mol/L SMX and CIP,the degradation rate constant first increased and then decreased with the increase of K₂S₂O₈ dosage and the optimal K₂S₂O₈dosage was respectively 0.1 mmol/L and 1 mmol/L.The pH value of the solution affected the degradation effect of SMX and CIP and the degradation rate constants of SMX and CIP increased first and then decreased with the pH value increased from 3to 11.The degradation was respectively best at pH 9 and 7 and the degradation effect was better in the pH range of 4 to 10,which is wider than that of the UV/NaClO method.UV/K₂S₂O₈ degradation of SMX and CIP is also affected by anions and humic acids.The electricity consumption of SMX and CIP degradation by UV/K₂S₂O₈ method were affected by chlorine dosage,pH value and humic acid.The EE/O value of UV/K₂S₂O₈ method was lower than NaClO method.UV/NaClO and UV/K₂S₂O₈ can effectively remove SMX and CIP in both W and B actual reclaimed water while the UV/K₂S₂O₈ method had a slightly higher degradation effect than UV/NaClO method.With the influence of anion(HCO₃^-/CO₃^2-),natural organic matter and color in the water,the degradation rate constants was significantly reduced.Compared with hydroxyl radical-based UV/H₂O₂mothed and UV mothed,chlorine radical-based UV/NaClO method and sulfate radical-based UV/K₂S₂O₈ method aer less affected by background water quality.On the whole,the degradation of SMX and CIP in B reclaimed water were better than those in W reclaimed water,which was mainly conducted by TOC and alkalinity.The EE/O value of SMX and CIP degradation by UV/NaClO method was higher than that of UV/K₂S₂O₈ method in actual reclaimed water.Comprehensive consideration about the degradation effect and power consumption,the UV/K₂S₂O₈ method is more suitable for the treatment of residual low-concentration PPCPs in the reclaimed water than the UV/NaClO method.However,taking into account the current status of application,UV/NaClO method is easier to implement and has greater application value.In this study,UV/NaClO and UV/K2S2O8 advanced oxidation methods can effectively remove SMX and CIP both in laboratory water and actual reclaimed water.Compared to UV/H₂O₂ and UV,UV/NaClO and UV/K₂S₂O₈ method arrived better degradation rate and lower power consumption although the amount of oxidant dosing and background water quality parameters?pH,alkalinity,HA?,which indicates good development prospects and practical application value of UV/NaClO and UV/K₂S₂O₈method.The experimental data and conclusions of the study can provide reference and theoretical basis for the practical application of UV/NaClO and UV/K₂S₂O₈ to reclaimed water treatment.