Study On PVA-bearing Desizing Wastewater Treatment By Hydrolytic Acidification-submerged MBR

The Combined Hydrolytic Acidification-Submerged Membrane Bioreactor Process made the treatment for PVA-bearing Desizing Wastewater according to the characteristics of the wastewater. The method reduced the organic matter of dyeing wastewater and decreased the stay time and the building cost.By comparison with MBR in presence of polymeric aluminum ferric sulfate (PAFS) (PMBR) and MBR in absence of PAFS(PMBR) when, their removal effect, mixed liquor characteristic and membrane fouling were systematically investigated, and the following results have been obtained:(1) When the hydraulic stay time (HRT) of the hydrolysis-acidification and the SMBR were 20h and 10h, respectively, and influent COD was about 1000mg/l, the total removal efficiency of COD achieved more than 95 %, and the COD removal of hydrolysis-acidification and SMBR accounted for 75% and 20%, respectively, which indicated that SMBR was crucial to remove the COD.(2) The aim of hydrolysis-acidification was to change the molecular structure of PVA and the value of BOD/COD. The HRT of hydrolysis-acidification were 20h, 16h and 10h, the maximum of COD-VSS loading, respectively, was 0.33 kgCOD/(kgVSS.d), 0.29 kgCOD/(kgVSS.d) and 0.20 kgCOD/(kgVSS.d) in the PMBR and the maximum of COD-VSS loading, respectively, was 0.31 kgCOD/(kgVSS.d), 0.24 kgCOD/(kgVSS.d) and 0.15 kgCOD/(kgVSS.d) in the MBR when the HRT of SMBR was 10h, which indicated that hydrolysis-acidification were essential for the Combined Hydrolytic Acidification-Membrane Bioreactor Process.(3) The maximum of COD-VSS loading was 0.33 kgCOD/(kgVSS·d) in the PMBR while the value 0.31 kgCOD/(kgVSS·d) in the MBR although the reactor and the permeate COD were low and stable. If the value of the COD-VSS loading in the PMBR and MBR were higher than 0.33 kgCOD/(kgVSS·d) and 0.31 kgCOD/(kgVSS·d), respectively, there being much PVA coagulating sludge and a lot of foams in the aeration tank, activated sludge stuck together and decreased the COD removal rate.(4) The maximum of COD-VSS loading in the PMBR was higher than that in the MBR, indicating that PAFS were favorable to degrade the organic matter.(5) The rising rate of suction pressure was significantly reduced and the total resistance, were the quarter of that in the PMBR, which were due to more kinds of microorganism and bigger particle in the PMBR, indicating that PAFS explored to MBR was favorable to control Membrane fouling.(6) Water and NaOH were the effective ways in the PMBR while HCl and NaOH were the effective ways to cleaning the fouled membrane in the PMBR. Moreover, the Water/HCl/ NaOH were the best methods of cleaning the fouled membrane in the both MBRs. However, the more flux of the clean membrane was recovered in the PMBR, which indicated the different fouled membrane.