Degradation Of Organic Pollutants In Water By Ultraviolet/Hydrogen Peroxide And Activated Carbon Process

Advanced oxidation process（AOPs）based on ultraviolet（UV）can be used as a means of degrading dissolved organic matter（DOM）in water.However,the large molecule DOM is broken into small molecules,Therefore the removal efficiency of DOM is limited,which is easy to generate more precursors of disinfection by-products（DBPs）.Activated carbon process also has its own disadvantages in the treatment of the part DOM that are difficult to degrade.In order to achieve a better treatment effect,UV-AOPs combined activated carbon process can get the good removal efficiency of organic matter and DBPs.Therefore,different of removal effect of organic pollutants by different UV-AOPs were studied,concluded that UV/H₂O₂ process was more suitable for pollutant removal efficiency and economic benefit.The quenching kinetics of Granular activated carbon（GAC）for H₂O₂ in the presence of a large amount of DOM was studied.Finally,different water samples in Ganjiang River Basin were extracted by solid phase extraction（SPE）.The effect of GAC and H₂O₂/GAC process on DBPs-FP in rapid small carbon column（RSSCT）were studied.The main conclusions are as follows:The ability of UV-AOPs to remove DOM from water samples was obviously better than that of direct UV photolysis and oxidation treatment.COD decreased significantly and BOD₅ increased.UV-AOPs treatment will not produce obvious biologically toxic intermediate products,and the water sample has changed from being difficult to biodegrade to good biodegradability.Through COD removal efficiency,oxidant dosage,economic analysis and comparison,it is obtained that the UV/H₂O₂ process has high organic degradation ability under low energy consumption.The reaction of H₂O₂ quenched by GAC conforms to the first-order kinetics.The normalized rate constant（k_n）does not change with the dosage of GAC and the initial concentration of H₂O₂.k_n is constant(1.6×10^-3 L g^-1 min^-1).With the solution temperature increasing from 5°C to 25°C,the kn value gradually increased and the activation energy was 31.6 k J mol^-1.The effect of solution temperature on GAC quenching H₂O₂ was relatively small.With the p H of the solution increases from 4.5 to9.5,the kn value increases.The kn value decreased with the addition of Cl^-,SO₄^2-,NO₃^-and DOM,and increased with the addition of HCO₃^-.The addition of HCO₃^-significantly increased the hydroxyl radical（HO·）concentration between GAC surface and solution.Electron paramagnetic resonance spectroscopy spectra showed the presence of Persistent free radical（PFRs）in the target GAC.HCO₃^-significantly increased PFRs,thus improving the quenching rate of H₂O₂.By optimizing the polarity of the eluent,it was found that the elution effect of methanol+acetone of four kinds water samples was better,and the target recovery rate was higher.The dissolved organic carbon and UV₂₅₄ recoveries of four kinds of water samples were more than 91.08%and 75.47%,respectively.Liquid phase organic carbon analysis,Fourier ion cyclotron mass spectrometry analysis and toxicity test analysis were carried out on the enriched water samples.The results showed that hydrophobic organics were only detected in Ganjiang River water sample（GW）,and low molecular weight organic acid was not detected in any water samples.The four water samples all belong to Ganjiang River basin.Although the analysis of each component of water source in different regions is different,the relative abundance is similar.All the water samples showed high concentrations of CHO and CHNO substances.Specifically,they may represent fatty acids or alcohols（unsaturated substances,aromatic compounds）,carbohydrates and their decomposition products,lignin-derived compounds.The risk entropy（RQ）was calculated based on the acute toxicity test of luminescent bacteria.Baita Sewage Treatment Plant（BW）was the highest risk,and Jiuqu River（NW）was the lowest risk.In the SOS genotoxicity test,it was found that no genotoxicity was detected in all the samples.The DBPs produced by chlorination of the four water samples were different,and the content of dibromochloromethane was the cause of the difference.GAC adsorption could control the generation of some DBPs,but there still may be a risk of increasing DBPs content for different water samples.Compared with GAC treatment,H₂O₂ and GAC generated PFRs.Through the role of free radicals to promote the transformation of organic matter,to achieve better DBPs control,reduce the risk of toxicity.For water samples with different water quality,H₂O₂/GAC process for DBPs and its toxicity control is more stable than GAC process alone.UV-AOPs combined with activated carbon process can effectively reduce the cost investment and operation.It is reducing the risk of generating DBPs,and has a good development prospect.We look forward to subsequent research and development and put into practical application.