Study Of The Advanced Treatment On Flax Wastewater By Fluidized-bed Fenton

Flax wastewater is produced during the production of flax scouring and degumming process including cellulose,hemicellulose and its degradation products(such as lignin,tannin,etc.).Thus,this kind of wastewater often has a high salinity,high color(brown-black),and poor biodegradability characteristics.After the secondary biological treatment process,the colority and organic matter content of the flax wastewater is still high and cannot meet the PAPER INDUSTRY WASTEWATER POLLUTANT EMISSION STANDARDS.The main objective of this paper is to investigate the advanced treatment of the flax wastewater by using Fenton fluidized-bed process.Then preparation of a kind of iron oxide loaded quartz sand(iron oxide/SiO2)as fluidized catalytic carrier with further experiments was carried out.Finally,a Fenton composite bed reactor was designed which was coupled with tubular ceramic for advanced treatment of flax wastewater.The application of Fenton fluidized-bed along with coagulation process was discussed in a treatment project.Main results of this paper are as follows:(1)The flax wastewater effluent taken from the secondary sedimentation tank effluent after A/O treatment was degraded effectively under Fenton fluidized bed reaction.Traditional Fenton reaction experiments were carried out to determine the operation parameters of flax wastewater treatment.After comparing different carriers,inorganic material was chosen as the carrier of FBR carrier.Within a fluidized bed reactor,experiment was carried out using three inorganic carrier particles including quartz sand,alumina and iron ore carrier under different concentration of ferrous ions at room temperature.Color and TOC removal rate in SiO2 or Fe2O3 Fenton-FBR system was higher than that of alumina system.With similar pollutant removal rate,iron concentration in effluent of Fe2O3 Fenton-FBR system was higher than that of quartz sand system.Considering the above results,quartz sand was chosen as a preferable carrier in reactor.At the same time,hydrogen peroxide,ferrous dosage,bed expansion was regarded as a fluidized bed Fenton important factor.At room temperature,pH=3,quartz sand dosage of 74.07 g/L,300mg/L of ferrous and 600mg/L of hydrogen peroxide,the highest removal rate(color and TOC removal were 92.4%and 89.1%,respectively)of flax wastewater was obtained at 50%bed expansion.Based on the above,second order kinetic model was carried out to calculate the reaction kinetic constant of Fenton fluidized bed degradation process,for further study of the reaction process.Rate constant of TOC degradation was 18.43×10-2 L/(mg·min)under 300 mg/L of Fe2+ and 600 mg/L of H2O2 in Fenton fludized bed reator.The color degradation mechanism was inferred additionally.(2)In this study,quartz sand(QS)was chosen as optimized carrier for preparing iron loaded quartz sand carrier.Iron loaded SiO2(ILQS)were used in the reactor and the discoloration and mineralization of flax wastewater in fluidized-bed Fenton reaction weas investigated,compared QS and ILQS.Fenton reagent dose and reaction pH range were studied and the fluidized-bed Fenton system with iron oxide/SiO2 saved a third of iron dosage compared with SiO2.The acceptable pH value range was broadened to 5 in iron oxide/SiO2 system.At room temperature,pH=5,ferrous and hydrogen peroxide dosage was 200 mg/L and 600 mg/L,color and TOC removal rates of flax wastewater were 92.1%and 85.3%.Concentration of iron ions in effluent was then compared between Fenton fluidized-bed with QS and ILQS.The experimental results showed that the concentration of iron ions in the effluent was slightly higher than Fenton-FBR system with unloaded SiO2.Finally,second-order kinetic model was utilized to analyze the TOC degradation rate constant of flax wastewater with ILQS in the system.The calculation shows that the reaction rate constant higher than the unload carrier system.And a greater advantage was shown in conditions of low iron dosage.(3)Independent design and manufacture of composite bed reactor coupled with tubular ceramic membrane was made in further,with the addition of polyacrylamide sedimentation tank conditions.Experiment was carried out using a continuous flow pattern flax wastewater treatment.On the basis of the results of the previous experiment,an excess iron dose of ferrous sulfate was added to replace the pH adjustment steps.With 800 mg/L of ferrous,500 mg/L of hydrogen peroxide and 15 mg/L of polyacrylamide(PAM)combined with the ceramic membrane,colority and TOC removal efficiencies of flax wastewater were 92.7%and 90.2%,respectively.In this new device,flax wastewater treatment and operation processing can be simplified,and the effluent can meet PAPER INDUSTRY WASTEWATER POLLUTANT EMISSION STANDARDS,The color degradation and carbon pollutants reduction of flax wastewater can be obtained.(4)Based on the previous experiments,flax wastewater treatment engineering test was carried out via Fenton-FBR reaction.With 25%FeSO4 flow 160 L/h,30%H2O2 flow 20 L/h,0.25%PAM flow 60 L/h,HRT is 120 min,COD and color removal rate was 80.0%and 92.1%.In the process of continuous and stable operation of the Fenton-FBR process after 2h,color was degradated from 250 to 20 with the removal rate higher than 92%;COD was degradated from 1000 mg/L to 200 mg/L with removal higher than 80%.Economic cost was calculated with Fenton-FBR reaction combined with PAM coagulation process.Unit operating cost of raw water oxidation treatment was 4.29 RMB/m3 and per unit of the total processing cost was 4.99 RMB/m3.Meanwhile,cost of treatment for unit COD removal was 6.23 RMB/(kg COD).