Study On Treatment Of Paper Making Wastewater By Integrated Membrane Process

Wastewater from paper mill contained hard-decomposed organic compound with high concentration.Nowadays it was mainly treated by activated sludge techniques. But the discharged water treated by this way was hard to satisfy the discharge standards.In most part of china,the paper-making industry consumed large amount of water and discharged large amount of wastewater.So to find an economical and efficient treatment was instancy.The treatment and reuse of paper making wastewater was studied on in this paper.Membrane technologies as the key treatment method included membrane bio-reactor(MBR),continuous membrane filtration(CMF),and reverse osmosis(RO)was used in this experiment.CMF was used to treat with the secondary sedimentation tank effluent.The permeate quality was as followed:COD_Crwas 87.7mg/L,turbidity was 0.17NTU, chroma was 23.4PCU on average.The removal rate was high to 39%,98.3%,and 48.2%respectively.As a pretreatment unit of RO system,CMF permeate satisfies all the requirements of RO influent.The system runs steadily during all the experiment time.The trans-membrane pressure was no more than 0.02 MPa;the hydrophilic polythersulfone(H-PES)membrane module has good antifouling property.The COD_Crof RO permeate was 3.2 mg/L on average,while the concentrated was 171mg/L,which can not meet the standard of discharge requirement.To solve this issue Bio-treatment was needed to be improved.The integrated technology of anaerobiotic/aerobiotic MBR and RO (A/O/MBR+RO)was used to deal with the effluent of first sedimention tank.COD_Cr of the effluent quality of MBR was 50 mg/L at lowest,66.4mg/L on average,and the total removal was up to 94.6%when the test running in the condition of 9000mg/L MLSS and 22 hour HRT.The average chroma was 55.9PCU,of which the retentate rate of membrane was 62.7%.The quality of MBR permeate meet the standard of discharge and the requirements of RO system influent.The conductivity of RO influent was 2031μS/cm while the effluent less than 71μS/cm and the conductivity high to 3473 on average,with the condition of 60%recovery rate and 0.3MPa operation pressure.The effect of RO system desalination was perfect;the desalination rate was high to 97%on average.Concentration of RO retentate COD_Crsatisfied the standard of discharging.