Study On Flax Retting Wastewater Treatment Using Upflow Anaerobic Sludge Blanket And Membrane Bioreactor Method

By theoretical analysis, this paper offers such opinion that Upflow Anaerobic Sludge Blanket Process and Membrane Bioreactor (UASB-MBR) can treat refractory wastewater efficiently and experiments were conducted as complexity of the refractory organic substances basically. The experimental study of treating flax retting wastewater was conducted by the process of UASB firstly, the aim is to improve the biodegradation performance for creating a good condition for the following aerobic biodegradation process, then utilizing MBR reactor to advanced treating flax retting wastewater and at the same time the results show that:(1) The average removal efficiency was higher than 64%, BOD5ou(BOD5 in the effluent)= 1698.55-2123.19 mg/L and the average removal efficiency was higher than 67%, and water quality is steady, when flax retting wastewater was treated in the UASB under the condition of CODin (COD in the influent)=6000-6800mg/L, BOD5in(BOD5 in the influent)= 3000-3500 mg/L, organic matter degradation by anaerobic biological treatment, CODou(COD in the effluent)= 1698.55-2123.19mg/L.(2) pBou(the lignin concentration in the effluent)= 83.38-129.12mg/L and the removal efficiency was 7.8-48.6%, when flax retting wastewater was treated in the UASB under the condition of pBin (the lignin concentration in the influent)=100-180mg/L, lignin matter degradation by anaerobic biological treatment,(3) The average removal efficiency was higher than 92%, BOD5ou= 16.86-28.32mg/L mg/L and the average removal efficiency was higher than 97% and the water quality is steady, when flax retting wastewater was treated in the MBR under the condition of CODin =1698.55-2123.19mg/L, BOD5in=713.14-987.52mg/L, after the aerobic digestion, the organic matter is relatively lower in outflow, CODou= 74.15-99.37 mg/L. It is indicate that the membranes are very important to keep the water quality.(4) A better removal effect of lignin can be gotten using the MBR to treat flax retting wastewater, the ps(the lignin concentration in the influent) decreases from 83.38-129.12mg/L to11.06-21.04mg/L and the average removal efficiency was higher than 74%.(5) By analysis of the data obtained from the experiment, the calculated kinetics parameters of the wastewater treated in MBR is: Yg=0.6054kgVSS/kgCOD, Kd =0.1039 d-1, vmax=0.536 kgVSS/kgCOD.d-1, KS =426.6 mg/L.(6) The loading capacity of sludge is no more than 0.21kgCOD/kg VSS.d when flax retting wastewater was treated in the MBR.(7) During the experiments of treating the flax retting wastewater, the shortest solidsretention time is 43.04d, the optimal solids retention time is 86.08-172.16d, which can be realized perfectly in MBR.(8) When studying membrane fouling, the increasing rate of suction pressure of membrane was used to evaluating the membrane filtration characteristics of membrane bioreactor process. Through a group of test by means of orthogonal table, influence of suction time, suction suspended time and aeration rate on membrane filtration was investigated. Shorter suction time, longer suction suspended time and larger aeration rate could alleviate membrane fouling, which influenced accumulation and back transportation of pollutants and from membrane surface. The optimum operation parameters were 12 minutes of suction time,6 minutes of suction suspended time and aeration rate of 0.13m3/h under the condition of the flux of membrane 5L/(m2h). Suction time was the key factor among these three factors, and aeration rate had the least impact on membrane fouling.(9) In order to optimizing the hydraulic condition in the reactor, constant aeration and intermittent pumping was conducted and optimal aeration quantity, pumping period and pause period were identified which could slow down cake layer accumulation and flux decline. Hydraulic rinse through constant aeration could hold the convection transfer from the sludge mixture to membrane surface and boost up the counter-diffusion and transfer along the membrane surface so that flux could be recovered to a certain degree. To control the microbe contamination, chemical cleaning using sodium hypochlonte had satisfactory result for eliminating organic and bacteria contamination.