Study On The Treatment Process Of Coal-based Polyoxymethylene Wastewater

Coal-based polyoxymethylene (POM) wastewater is mainly generated by the POMproduction unit and domestic wastewater, and also a portion of floor washingwastewater and initial rainwater. The Coal-POM wastewater is classified asintractable industrial wastewater due to its characteristics, such as high concentrationof formaldehyde, large fluctuations in water quality and quantity, containingrefractory pollutants, etc. So far, there are no mature treatment processes or successfultreatment cases in the world.In this thesis, the research objects are in three parts pretreatment, biological treatmentand deep treatment of Coal-POM wastewater. In the pretreatment section, the originalSaccharification method is replaced by Fenton reagent oxidation process. Bychanging the dosage of hydrogen peroxide, the COD and formaldehyde removal aremeasured at different concentrations of hydrogen peroxide. In the biological treatmentsection, the MBBR reactor is used for biochemical reactions instead of UASB reactor.Through on-site pilot commissioning MBBR reactor, choose the best filling ratio ofthe fillers, the most appropriate amount of dissolved oxygen and the best HRTaccording to the inflow water quality. In the deep treatment section, WDM membranefilter is used instead of dissolved air flotation machine and the activated carbon filter.The removal efficiency of WDM membrane filter for TDS and COD are measuredunder both vibration and non-vibration operational conditions.1. When H2O2dosage was245mmol/L, COD removal efficiency reached amaximum peak of90.1%, the formaldehyde removal rate reached92.6%.Considering the removal efficiency and economic factors, taking H2O2dosage200mmol/L. Under this condition, the formaldehyde removal efficiency was86.1%, COD removal rate was81.2%; The optimum reaction time is2h; Theoptimum pH value is3; n(H2O2):n(Fe2+)=4;2. When MBBR reactor fillers ratio was40%, the COD removal efficiency reached89.2%, formaldehyde removal efficiency was about95.0%; Dissolved oxygenshould be controlled within2mg/L to3mg/L; Hydraulic retention time is40h; The optimum reaction temperature is25℃to30℃; The optimum pH value is7;3. Under the vibration mode, WDM membrane filter had a stable TDS removal rateat around96.9%, COD removal remained at87.6%after removing special points.Under the non-vibration mode, WDM membrane filter had a stable TDS removalrate at around96.2%, COD removal remained at83.7%after removing specialpoints. Compare two sets of experimental data, it can be seen that vibration hasenhanced the processing capabilities of WDM membrane filters, especially for theCOD removal efficiency. Since the internal pressure is very large when the WDMmembrane filter is operating, it must be ensured that the sealing portion of thefilter should be sealed to prevent the occurrence of leaks. The TDS removal of redRO membrane is better than white RO membrane, but its flux and physicalstrength are poor. EDTMPS is selected as corrosion inhibitor; polyacrylateHB-901is selected as scale inhibitor.According to the data, the final effluent COD concentration was13mg/L,formaldehyde concentrations was0mg/L, TDS was62mg/L, temperature was35.5℃,pH value was7. Meet the "Integrated Wastewater Discharge Standard"(GB8978-1996)in the secondary petrochemical industrial wastewater discharge standards.